BaopersName, ZhangpersName, LiangpersName, ZhoupersName, ShipersName (2020date). “Neural Correlate Differences in Number Sense Between Children With Low and Middle/High Socioeconomic Status.” Frontiers in Psychologytitle·j.
Object of study — at which stage of numerical magnitude comparisonterm the processing of children from low and from middle-to-high socioeconomic backgrounds diverges
Research question — whether socioeconomic statusterm affects the early attentional stages of symbolic number comparison, the later representational stage, or both
Contribution — reports amplitude differences between SES groupsterm·var in two early frontal components and none in the late parietal component, with no accompanying behavioural difference
phenomenon · claim-type · cross-domain-transfer · mechanism · claim-relation · replication-status · limitation — grounded in the full text| phenomenon | symbolic numerical magnitude comparison — “Therefore, the present study explored the differences in neural correlates in the process of symbolic magnitude comparison between children with different SESs by the event-related potentials (ERPs).” | |
| claim-type | existence — “The results of the present study provided evidence that there were neural correlate differences between children with different SESs.” | |
| method — evidence | — “According to the selection paradigm ( Moyer and Landauer, 1967 ), the magnitude comparison task was presented to each participant with two single digits displayed simultaneously during the recording session.” | |
| object of study — evidence | — “Although some cognitive studies provided reasons that children with low socioeconomic status (SES) showed poor mathematical achievements, there was no explicit evidence to directly explain the root of lagged performance in children with low SES. Therefore, the present study explored the differences in neural correlates in the process of symbolic magnitude comparison between children with different SESs by the event-related potentials (ERPs).” | |
| research question — evidence | — “this study proposed the first hypothesis that children with different SES would show variation in the early recognition stage of digit stimuli. In addition, since children with low SES often lag significantly behind in mathematical learning, this study assumed that in the second phase of numerical comparison, children with low SES would show a significant difference from those with middle–high SES. However, previous studies did not find a significant difference on P3b between children with different SES (i.e., Kishiyama et al., 2008 ), so we believed that in the magnitude comparison task, children with different SES would not show significant difference in this late component, which is dependent on the integrity of the temporal–parietal cortex.” | |
| contribution — evidence | — “According to the results of anterior N1 (early attention) and P2 (extraction of numerical meaning) over the frontal region, the differences among children with different SESs were manifested as differences in general neural activities in terms of attention and top-down cognitive control.” | |
| transfer | from educational assessment: the PISA socioeconomic questionnaire, adapted as the grouping variable — “The SES criteria consisted of parental education, occupation, and family resources, which together represented SES better than any of these alone” | transfers[0] |
| transfer | from psychophysics: the distance effect from Moyer and Landauer's reaction-time paradigm, used here as the task manipulation — “Moyer and Landauer (1967) were the first to measure the RT in a selection paradigm by pressing the associated button. They found that participants made more mistakes and required more time when the two numbers to be compared were close (e.g., 7 vs. 9) than farther apart (e.g., 2 vs. 9). That is, there is a distance effect (DE) in the process of numerical comparison.” | transfers[1] |
| mechanism | low-SES children must invest extra attentional resources to suppress interference from irrelevant information in order to reach the same performance, which shows up as a larger (more negative) anterior N1 — “The present study confirmed the conclusion that children with low SES showed more negative amplitude between 100 and 140 ms after the digits occurred, indicating that when these children perceived and recognized the numbers, they needed to invest more attention resources to suppress the interference of irrelevant information to their intentional attention to catch up with children with middle/high SES.” | mechanisms[0] |
| mechanism | chronic family stressors raise basal corticosteroid levels, which degrades selective attention and shapes the long postnatal development of the prefrontal cortex — “They are exposed to more chronic stressors in the family, such as prolonged poverty and parental strife, and therefore have higher basal levels of the stress hormone corticosteroids and poorer selective attention” | mechanisms[1] |
| mechanism | SES acts as a distal environmental factor that reaches the early prefrontal control stage but not the deep parietal numerical representation stage — “Therefore, as a distal factor, SES is not enough to affect the deep numerical processing in the parietal lobe.” | mechanisms[2] |
| mechanism | numbers close together overlap more on the mental number line, making them harder to discriminate, which produces the distance effect — “When the to-be-compared numbers were close to each other, more greater overlapping areas of these two numbers on the mental number line would make it more difficult to distinguish one from the other.” | mechanisms[3] |
| mechanism | a ceiling effect on an easy task hides the group difference at the behavioural level while ERPs still reveal it — “One reason is that the experimental task is relatively easy for second-graders (in the second semester), so the “ceiling effect” appears.” | mechanisms[4] |
| mechanism | the proposed route is attentional: low-SES children are said to spend more resources suppressing irrelevant information to reach the same performance — “The present study confirmed the conclusion that children with low SES showed more negative amplitude between 100 and 140 ms after the digits occurred, indicating that when these children perceived and recognized the numbers, they needed to invest more attention resources to suppress the interference of irrelevant information to their intentional attention to catch up with children with middle/high SES.” | mechanisms[5] |
| mechanism | prefrontal cortex develops slowly after birth, which is offered as why an environmental variable could reach it — “Human’s prefrontal cortex has a long period of postnatal development (e.g., Casey et al., 2000 ; Fuster, 2002 ), so the external environment, such as environmental deprivation and stress ( Braun et al., 2000 ) and environmental complexity ( van Praag et al., 2000 ), will affect the development of the prefrontal cortex.” | mechanisms[6] |
| mechanism | two candidate environmental routes are named: impoverished cognitive input, and chronic stress raising corticosteroids — “In addition, these children from L-SES families often experience higher levels of stress. They are exposed to more chronic stressors in the family, such as prolonged poverty and parental strife, and therefore have higher basal levels of the stress hormone corticosteroids and poorer selective attention” | mechanisms[7] |
| mechanism | the distance effect is read as overlap on a mental number line, closer numbers overlapping more — “These findings indicate that there exists a “mental number line” for children in the process of numerical comparison. Children might judge the magnitudes according to the to-be-compared number’s position on this mental number line. When the to-be-compared numbers were close to each other, more greater overlapping areas of these two numbers on the mental number line would make it more difficult to distinguish one from the other. Conversely, it was much easier to compare two numbers when they were more distant from each other.” | mechanisms[8] |
| mechanism | the temporal order of the components is mapped onto a front-to-back anatomical order, control before representation — “Previous studies have found that prefrontal cortex activation comes first compared with parietal cortex during arithmetic processing ( Menon et al., 2000 ; Brass et al., 2005 ). The anterior component is related to the cognitive control processing of the prefrontal cortex, while the parietal component reflects the involvement of numerical representation” | mechanisms[9] |
| replicates | Kishiyama et al., 2008 — “In the present study, an ERP difference among children with different SESs did not appear in the average amplitude of LPC (in the 450–700 ms time window), which was consistent with a previous study (i.e., Kishiyama et al., 2008 ).” | claim_relations[0] |
| contradicts | Dehaene, 1996 — “This result was inconsistent with a previous study (i.e., Dehaene, 1996 ) in which the posterior N1 was evoked by the number comparison task.” | claim_relations[1] |
| replicates | Soltész et al., 2007; Gebuis et al., 2009 — “Based on the behavioral data of RT and ACC, second-grade children showed a numerical DE where they judged the numbers with large distance much faster and more accurately, which was consistent with previous studies (e.g., Soltész et al., 2007 ; Gebuis et al., 2009 ).” | claim_relations[2] |
| contradicts | posterior N1 account of numerical comparison (Dehaene, 1996; Gómez-Velázquez et al., 2015) — “In this study, the N1 component appeared in the frontal and central regions.” | claim_relations[3] |
| confirms | Kishiyama et al. 2008, on prefrontal attentional differences by SES and on the absence of a late-component difference — “In the late stage of cognitive processing, there was no significant difference in the average amplitude of the late positive component (LPC) between children with different SES, indicating that low SES did not influence the information encoding and memory updating of numerical representation, which was responsible by the parietal lobe.” | claim_relations[4] |
| contradicts | Dehaene 1996, in which numerical comparison evoked a posterior rather than an anterior N1 — “According to the time and brain regions of occurrence, this component was the anterior N1. This result was inconsistent with a previous study (i.e., Dehaene, 1996 ) in which the posterior N1 was evoked by the number comparison task.” | claim_relations[5] |
| reconciles | that discrepancy, by attributing it to one digit against a fixed baseline versus two digits presented together — “The reasons that the N1 component is evoked in different brain regions are because of the differences in the form of the stimulus presentation and in the comparison baseline between different experiments. In previous studies (e.g., Dehaene, 1996 ; Gómez-Velázquez et al., 2015 ), the classification paradigm was used to explore the process of numerical comparison. In this task, only one digit was presented in each trial, without changing the baseline number to be compared (e.g., “5”). In the present study, each trial of the task included two digits simultaneously (e.g., “2” and “7”). As a result, participants firstly needed to accurately represent each number on their mental number line, instead of making classification judgments based on a reference point.” | claim_relations[6] |
| distinguishes-from | children with mathematical learning disability, whose parietal processing is impaired — “Although fMRI studies found that children with MLD had impairment in the bilateral intraparietal sulcus (IPS) involved in number magnitude processing ( Habib, 2000 ; Mussolin et al., 2014 ), and had significant differences in the P300 latency and amplitude compared to normal children ( Soltész et al., 2007 ; Taylor and Keenan, 2010 ; Wang et al., 2015 ), in this study, children with L-SES were not MLD, and some of them even had higher math scores in the class. Therefore, as a distal factor, SES is not enough to affect the deep numerical processing in the parietal lobe.” | claim_relations[7] |
| extends | behavioural SES research on number line estimation and calculation, by moving to symbolic magnitude comparison — “Although some cognitive studies provided reasons that children with low socioeconomic status (SES) showed poor mathematical achievements, there was no explicit evidence to directly explain the root of lagged performance in children with low SES. Therefore, the present study explored the differences in neural correlates in the process of symbolic magnitude comparison between children with different SESs by the event-related potentials (ERPs).” | claim_relations[8] |
| sense | number sense has no agreed definition - the paper opens by saying cognitive psychologists and math educators define it differently, then adopts a six-part working list — “Although cognitive psychologists and math educators have different definitions of number sense ( Gersten et al., 2005 ), most of them agree that it is an ability to subitize small quantities, discern number patterns, compare numerical magnitudes, estimate quantities, count, and perform simple number transformations” | senses[0] |
| sense | P2 and P2p are DIFFERENT components separated in time and space, despite names differing by one letter; P2p indexes the DE and P2 does not — “The next positive wave, P2p, was initially described by Dehaene (1996) as reflecting the DE (right parietal–occipital–temporal positive waveform to close numbers compared to far numbers) and was seen as an index of the approximate magnitude representation ( Hyde and Spelke, 2011 ). This component, simultaneous with N1, is clearly separated in time and space from the earlier broad fronto-central positivity wave, which is classically known as P2” | senses[1] |
| sense | anterior N1 and posterior N1 are different components with different generators; this study evokes the anterior one where the cited precedent evoked the posterior — “According to the time and brain regions of occurrence, this component was the anterior N1. This result was inconsistent with a previous study (i.e., Dehaene, 1996 ) in which the posterior N1 was evoked by the number comparison task.” | senses[2] |
| sense | LPC may or may not be the P3b - the identification is attributed to some researchers and not settled here — “The last positive component is the late positive component (LPC), which is characterized by later onset (usually after 300 ms) and central–parietal distribution ( Friedman and Johnson, 2000 ). Some researchers suggested that this component was the P3b, which indicated the amount of context updating and also reflected the DE” | senses[3] |
| sense | SES is a composite score built from parental education, occupation and household resources by item response theory and principal components, not a single measured quantity — “The SES criteria consisted of parental education, occupation, and family resources, which together represented SES better than any of these alone” | senses[4] |
| control | the screen position of the two numbers counterbalanced, half on the left and half on the right — held — rules out a side bias - that the comparison result is driven by which number appeared on which side — “The position where the two numbers appeared was counterbalanced, half on the left and half on the right.” | controls[0] |
| differs in | children with mathematical learning disability, whose parietal processing is impaired — THE AXIS IS WHETHER PARIETAL NUMBER PROCESSING IS IMPAIRED. 'fMRI studies found that children with MLD had impairment in the bilateral intraparietal sulcus (IPS) involved in number magnitude processing, and had significant differences in the P300 latency and amplitude compared to normal children.' The comparison group is defined by a deficit in a specific region and function, so a result about 'low number sense' does not transfer to it without that. — “Although fMRI studies found that children with MLD had impairment in the bilateral intraparietal sulcus (IPS) involved in number magnitude processing ( Habib, 2000 ; Mussolin et al., 2014 ), and had significant differences in the P300 latency and amplitude compared to normal children ( Soltész et al., 2007 ; Taylor and Keenan, 2010 ; Wang et al., 2015 ), in this study, children with L-SES were not MLD, and some of them even had higher math scores in the class. Therefore, as a distal factor, SES is not enough to affect the deep numerical processing in the parietal lobe.” — “children with MLD had impairment in the bilateral intraparietal sulcus (IPS) involved in number magnitude processing” | claim_relations[7] |
| note | P2 —distinct-from→ P2p — CRITERION: separated in time and in scalp location, and only P2p carries the DE. Names differing by one letter for two different things - the fast-ripples pattern again — “The next positive wave, P2p, was initially described by Dehaene (1996) as reflecting the DE (right parietal–occipital–temporal positive waveform to close numbers compared to far numbers) and was seen as an index of the approximate magnitude representation ( Hyde and Spelke, 2011 ). This component, simultaneous with N1, is clearly separated in time and space from the earlier broad fronto-central positivity wave, which is classically known as P2” | concept_edges[0] |
| note | anterior N1 —distinct-from→ posterior N1 — CRITERION: different scalp regions and different generators. The same label N1 names whichever one a given paradigm evokes — “According to the time and brain regions of occurrence, this component was the anterior N1. This result was inconsistent with a previous study (i.e., Dehaene, 1996 ) in which the posterior N1 was evoked by the number comparison task.” | concept_edges[1] |
| audit | LPC —same-as→ P3b — Audit 2026-09-28: DOUBTFUL - read against its span and kept, but the span says 'some researchers suggested' the LPC was the P3b; same-as states a suggestion as settled. — “The last positive component is the late positive component (LPC), which is characterized by later onset (usually after 300 ms) and central–parietal distribution ( Friedman and Johnson, 2000 ). Some researchers suggested that this component was the P3b, which indicated the amount of context updating and also reflected the DE” | concept_edges[2] |
| note | LPC —same-as→ P3b — an identity ATTRIBUTED to some researchers and not adopted by this paper; weight deliberately low, 2026-08-15: READ THIS EDGE WITH senses[3]: the sense on this record that quotes the SAME SENTENCE says the identification is not settled: 'LPC may or may not be the P3b - the identification is attributed to some researchers and not settled here'. This edge asserts an identity the paper declines to assert. The type is left as it stands pending the wider decision about what 'same-as' asserts; this note exists so the two are read together. — “The last positive component is the late positive component (LPC), which is characterized by later onset (usually after 300 ms) and central–parietal distribution ( Friedman and Johnson, 2000 ). Some researchers suggested that this component was the P3b, which indicated the amount of context updating and also reflected the DE” | concept_edges[2] |
| weight | LPC —same-as→ P3b — 0.5 — “The last positive component is the late positive component (LPC), which is characterized by later onset (usually after 300 ms) and central–parietal distribution ( Friedman and Johnson, 2000 ). Some researchers suggested that this component was the P3b, which indicated the amount of context updating and also reflected the DE” | concept_edges[2] |
| audit | distance effect —operationalised-as→ mental number line — Audit 2026-09-28: DOUBTFUL - read against its span and kept, but the span infers a mental number line from comparison difficulty; operationalised-as is the wrong type. — “These findings indicate that there exists a “mental number line” for children in the process of numerical comparison. Children might judge the magnitudes according to the to-be-compared number’s position on this mental number line. When the to-be-compared numbers were close to each other, more greater overlapping areas of these two numbers on the mental number line would make it more difficult to distinguish one from the other. Conversely, it was much easier to compare two numbers when they were more distant from each other.” | concept_edges[4] |
| note | distance effect —operationalised-as→ mental number line — direction is observation-to-construct: the behavioural effect is read as evidence for the representation — “These findings indicate that there exists a “mental number line” for children in the process of numerical comparison. Children might judge the magnitudes according to the to-be-compared number’s position on this mental number line. When the to-be-compared numbers were close to each other, more greater overlapping areas of these two numbers on the mental number line would make it more difficult to distinguish one from the other. Conversely, it was much easier to compare two numbers when they were more distant from each other.” | concept_edges[4] |
| weight | distance effect —operationalised-as→ mental number line — 0.8 — “These findings indicate that there exists a “mental number line” for children in the process of numerical comparison. Children might judge the magnitudes according to the to-be-compared number’s position on this mental number line. When the to-be-compared numbers were close to each other, more greater overlapping areas of these two numbers on the mental number line would make it more difficult to distinguish one from the other. Conversely, it was much easier to compare two numbers when they were more distant from each other.” | concept_edges[4] |
| audit | magnitude comparison —part-of→ number sense — Audit 2026-09-28: DOUBTFUL - read against its full span and kept, but the span writes 'compare numerical magnitudes', not 'magnitude comparison'; part-of is loose. — “Although cognitive psychologists and math educators have different definitions of number sense ( Gersten et al., 2005 ), most of them agree that it is an ability to subitize small quantities, discern number patterns, compare numerical magnitudes, estimate quantities, count, and perform simple number transformations” | concept_edges[5] |
| weight | magnitude comparison —part-of→ number sense — 0.9 — “Although cognitive psychologists and math educators have different definitions of number sense ( Gersten et al., 2005 ), most of them agree that it is an ability to subitize small quantities, discern number patterns, compare numerical magnitudes, estimate quantities, count, and perform simple number transformations” | concept_edges[5] |
| outcome (stated by the tagger, no quotation) | control — held | controls[0] |
| for which use | limitation — the absence of a behavioural SES difference: THE EXPERIMENTAL TASK IS RELATIVELY EASY FOR SECOND-GRADERS ... SO THE 'CEILING EFFECT' APPEARS — “One reason is that the experimental task is relatively easy for second-graders (in the second semester), so the “ceiling effect” appears.” | limitations[0] |
| for which use | limitation — the null in the late time window: it MAY BE DUE TO THE DIFFERENCES IN THE EXPERIMENTAL TASKS — “However, in the present study, children with different SESs did not show a numerical DE on the average amplitude in this time window, which may be due to the differences in the experimental tasks.” | limitations[1] |
| for which use | limitation — what the group label means: A HIGH SCORE ON THE SES QUESTIONNAIRE ONLY REPRESENTED A MIDDLE TO HIGH LEVEL OF SES — “Thus in this study, a high score on the SES questionnaire only represented a middle to high level of SES.” | limitations[2] |
| for which use | limitation — the same scope as limitations[0], with the numbers: RT 685.63 ms versus 711.16 ms and ACC 95.15% versus 93.19% - EXTREMELY MINOR DIFFERENCES on a task at ceiling — “Nevertheless, children in different SES groups showed extremely minor differences in RT and ACC on the magnitude comparison task (RT: 685.63 ms for M/H-SES, 711.16 ms for L-SES; ACC: 95.15% for M/H-SES, 93.19% for L-SES). One reason is that the experimental task is relatively easy for second-graders (in the second semester), so the “ceiling effect” appears.” | limitations[3] |
| for which use | limitation — the sample every effect rests on: INITIALLY, 52 CHILDREN PARTICIPATED ... DATA OF 20 CHILDREN WERE DISCARDED, for dropout, discomfort, movement and insufficient trials — “Initially, 52 children participated in the study. Before EEG data processing, data of 20 children were discarded, among them 11 children failed to complete the experiment (8 of them dropped out of the experiment early due to a cold or physical discomfort, and 3 other children did not complete the experiment due to constant body shaking, talking, and random responses during the experiment), and 9 children’s sufficient trials were less than 70% of the total after the artifact rejection. Finally, data of 32 children were regarded as valid for the analysis: 16 of them were from the low-SES (L-SES) group (8 girls), and the remaining 16 were from the middle/high-SES (M/H-SES) group (8 girls).” | limitations[4] |
| for which use | limitation — the statistical strength of every reported component: TIME WINDOWS AND THE ELECTRODES FOR ANALYSIS WERE SELECTED BASED ON PREVIOUS STUDIES AND OBSERVATION RESULTS OF THE DATA — “Time windows and the electrodes for analysis were selected based on previous studies and observation results of the data.” | limitations[5] |
| for which use | limitation — the same scope as limitations[2], with the reason: the city HAD A RELATIVELY BACKWARD LEVEL OF ECONOMIC DEVELOPMENT, so the label does not transfer to another sampling frame — “The participants came from Yinchuan, an inland city in the northwest region of China, which had a relatively backward level of economic development. Thus in this study, a high score on the SES questionnaire only represented a middle to high level of SES.” | limitations[6] |
| for which use | limitation — the same scope as limitations[1], with the remedy named: IT IS NECESSARY TO COMPARE THE ERP RESULTS WITH DIFFERENT FORMS OF MAGNITUDE COMPARISON TASKS IN THE FUTURE — “However, in the present study, children with different SESs did not show a numerical DE on the average amplitude in this time window, which may be due to the differences in the experimental tasks. For this reason, it is necessary to compare the ERP results with different forms of magnitude comparison tasks in the future.” | limitations[7] |
| duplicate of | mechanism — mechanisms[0] — “The present study confirmed the conclusion that children with low SES showed more negative amplitude between 100 and 140 ms after the digits occurred, indicating that when these children perceived and recognized the numbers, they needed to invest more attention resources to suppress the interference of irrelevant information to their intentional attention to catch up with children with middle/high SES.” | mechanisms[5] |
| replication | untested | |
| limitation | The comparison task was too easy for the age group, producing a ceiling effect that may hide behavioural SES differences. — “One reason is that the experimental task is relatively easy for second-graders (in the second semester), so the “ceiling effect” appears.” | limitations[0] |
| limitation | The expected DE did not appear in the late time window, possibly because of the specific task used. — “However, in the present study, children with different SESs did not show a numerical DE on the average amplitude in this time window, which may be due to the differences in the experimental tasks.” | limitations[1] |
| limitation | The 'high SES' group is only middle-to-high in absolute terms, because the sampling city is economically less developed. — “Thus in this study, a high score on the SES questionnaire only represented a middle to high level of SES.” | limitations[2] |
| limitation | no behavioural difference between the groups; the paper attributes this to a ceiling effect on an easy task — “Nevertheless, children in different SES groups showed extremely minor differences in RT and ACC on the magnitude comparison task (RT: 685.63 ms for M/H-SES, 711.16 ms for L-SES; ACC: 95.15% for M/H-SES, 93.19% for L-SES). One reason is that the experimental task is relatively easy for second-graders (in the second semester), so the “ceiling effect” appears.” | limitations[3] |
| limitation | 52 children were recruited and 32 analysed, after dropout and trial-count exclusions — “Initially, 52 children participated in the study. Before EEG data processing, data of 20 children were discarded, among them 11 children failed to complete the experiment (8 of them dropped out of the experiment early due to a cold or physical discomfort, and 3 other children did not complete the experiment due to constant body shaking, talking, and random responses during the experiment), and 9 children’s sufficient trials were less than 70% of the total after the artifact rejection. Finally, data of 32 children were regarded as valid for the analysis: 16 of them were from the low-SES (L-SES) group (8 girls), and the remaining 16 were from the middle/high-SES (M/H-SES) group (8 girls).” | limitations[4] |
| limitation | analysis time windows and electrodes were chosen partly from observation of the data — “Time windows and the electrodes for analysis were selected based on previous studies and observation results of the data.” | limitations[5] |
| limitation | high SES here is high only relative to a poor inland city, so the label does not transfer — “The participants came from Yinchuan, an inland city in the northwest region of China, which had a relatively backward level of economic development. Thus in this study, a high score on the SES questionnaire only represented a middle to high level of SES.” | limitations[6] |
| limitation | the expected DE did not appear on the late component, which the authors attribute to task form and leave for future work — “However, in the present study, children with different SESs did not show a numerical DE on the average amplitude in this time window, which may be due to the differences in the experimental tasks. For this reason, it is necessary to compare the ERP results with different forms of magnitude comparison tasks in the future.” | limitations[7] |
finding · quantity · variable · definition · key-term — grounded in the full text| finding | Low-SES and middle/high-SES second-graders did not differ behaviourally on the symbolic magnitude comparison task, in either reaction time or accuracy. — “However, there was no significant difference in the behavioral indices of the magnitude comparison task between children with different SESs.” | content_tags.findings[0] |
| finding | Both SES groups showed the classic numerical DE, responding faster and more accurately to number pairs that were far apart. — “The behavioral results suggested that the DE existed in both groups; that is, children were faster and more accurate when judging numbers with large distance compared with the small distance.” | content_tags.findings[1] |
| finding | In this window the SES main effect was significant: low-SES children showed more negative amplitudes than middle/high-SES children. — “The results showed that the SES main effect was significant, revealing that children with L-SES showed more negative amplitude than the children with M/H-SES” | content_tags.findings[2] |
| finding | In this window the SES main effect was significant: middle/high-SES children showed more positive amplitudes than low-SES children. — “revealed that the SES main effect was significant, suggesting that the children with M/H-SES showed more positive amplitude than their counterparts” | content_tags.findings[3] |
| finding | The late positive component showed no SES difference, so the late parietal stage of numerical representation appears unaffected by low SES. — “In the late stage of cognitive processing (450–700 ms), there was no significant difference in the average amplitude of the LPC among children with different SES, indicating that low SES did not influence information encoding and memory updating of numerical representation, which was responsible by the parietal lobe.” | content_tags.findings[4] |
| finding | the DE appeared in both groups: slower and less accurate for numerically closer pairs — “The behavioral results suggested that the DE existed in both groups; that is, children were faster and more accurate when judging numbers with large distance compared with the small distance. However, there was no significant difference in the behavioral indices of the magnitude comparison task between children with different SESs.” | content_tags.findings[5] |
| finding | low-SES children showed a more negative frontal amplitude at 100-140 ms — “The results showed that the SES main effect was significant, revealing that children with L-SES showed more negative amplitude than the children with M/H-SES [ F (1,30) = 12.85, p < 0.01, η p 2 = 0.300]” | content_tags.findings[6] |
| finding | middle/high-SES children showed a more positive frontal amplitude at 200-250 ms — “In the 200–250 ms time window, the results of the SES (2) × numerical distance (2) × location (3) repeated-measurement ANOVA revealed that the SES main effect was significant, suggesting that the children with M/H-SES showed more positive amplitude than their counterparts [ F (1,30) = 6.55, p < 0.05, η p 2 = 0.179].” | content_tags.findings[7] |
| finding | no SES difference in the late component at 450-700 ms — “In the 450–700 ms time window, an SES (2) × numerical distance (2) × location (3) repeated-measurement ANOVA was performed. The results indicated that the SES main effect was not significant [ F (1,30) = 1.18, p > 0.05, η p 2 = 0.038].” | content_tags.findings[8] |
| finding | NULL READ AS A POSITIVE CLAIM: the absent late-component difference is reported as showing low SES did not influence encoding and memory updating — “The results revealed that low SES, as an external environmental variable, did not exert an influence on the stage of children’s information encoding and memory storage associated with numerical representation.” | content_tags.findings[9] |
| finding | CONTROL NULL, LOAD-BEARING AND MARGINAL: the groups did not differ on nonverbal or verbal ability, with the nonverbal comparison at t(30) = -1.96 and CI [-7.41, 0.16] — “There was no significant difference in the scores in general cognitive ability (R’SPM-CR: L-SES M = 37.00, SD = 5.92; M/H-SES M = 40.63, SD = 4.46, t (30) = −1.96, p > 0.05, 95% CI = [−7.41, 0.16]) and verbal intelligence (MSCA-CR: L-SES M = 77.06, SD = 9.77; M/H-SES M = 80.56, SD = 5.61, t (30) = −1.24, p > 0.05, 95% CI = [−9.25, 2.25]) between the two SES groups.” | content_tags.findings[10] |
| finding | no behavioural difference between the groups in reaction time or accuracy — “The behavioral results suggested that the DE existed in both groups; that is, children were faster and more accurate when judging numbers with large distance compared with the small distance. However, there was no significant difference in the behavioral indices of the magnitude comparison task between children with different SESs.” | content_tags.findings[11] |
| finding | the expected DE did not appear on the late component either — “However, in the present study, children with different SESs did not show a numerical DE on the average amplitude in this time window, which may be due to the differences in the experimental tasks. For this reason, it is necessary to compare the ERP results with different forms of magnitude comparison tasks in the future.” | content_tags.findings[12] |
| finding | the component evoked here was the anterior N1, where the cited precedent evoked the posterior N1 — “According to the time and brain regions of occurrence, this component was the anterior N1. This result was inconsistent with a previous study (i.e., Dehaene, 1996 ) in which the posterior N1 was evoked by the number comparison task.” | content_tags.findings[13] |
| finding | split-half reliability of the task was high for both reaction time and accuracy — “The current study conducted a correlation analysis to explore the test–retest reliabilities in RT and ACC between the first- and second-half trials of the experimental task. The results showed that the task was extremely reliable for both RT ( r = 0.97, p < 0.001) and ACC ( r = 0.81, p < 0.001), suggesting good task reliability” | content_tags.findings[14] |
| finding | parental years of education differed by roughly ten years between the groups — “The parents of children in the M/H-SES group obtained, on average, undergraduate education, whereas those in the L-SES group only reached the primary level (years of education: M M/H–SES ± SD = 17.79 ± 2.39, M L–SES ± SD = 7.14 ± 1.83). There was a significant difference in the years of education between the two groups [ t (26) = 13.21, p < 0.001].” | content_tags.findings[15] |
| finding | RECOMMENDATION MADE: the paper advises curricula for low-SES children add training in intentional attention to numbers — “The findings in this study provide some valuable suggestions to researchers and educators about the mathematical education of children with low SES. It is insufficient and unscientific to only provide children with low SES with books and toys. Teachers and tutors should pay more attention to the fundamental cognitive functions of these children, such as adding training contents of intentional attention about the numbers in the curriculum for these children.” | content_tags.findings[16] |
| quantity | 16 / 16 — number of children per SES group in the final analysed sample, 8 girls in each — “16 of them were from the low-SES (L-SES) group (8 girls), and the remaining 16 were from the middle/high-SES (M/H-SES) group (8 girls).” | content_tags.quantities[0] |
| quantity | 7.75 years ( SD = 0.39) — mean age of the second-grade participants — “The mean age was 7.75 years ( SD = 0.39).” | content_tags.quantities[1] |
| quantity | F (1,30) = 120.95, p < 0.001, η p 2 = 0.801 — main effect of numerical distance on reaction time (the behavioural distance effect) — “A significant main effect of numerical distance was found [ F (1,30) = 120.95, p < 0.001, η p 2 = 0.801], suggesting that RT for the small distance was significantly longer than that for the large distance.” | content_tags.quantities[2] |
| quantity | 17.71% — proportion of trials discarded from the ERP averages because of artefacts or wrong responses — “resulting in an exclusion of approximate 17.71% of the trials from the average.” | content_tags.quantities[3] |
| quantity | 144 trials — total trials per participant, split evenly between the two distance conditions — “There were three blocks of 48 stimuli (144 trials in total; 72 trials per distance condition).” | content_tags.quantities[4] |
| quantity | 685.63 ms / 711.16 ms; 95.15% / 93.19% — the very small behavioural gap between middle/high-SES and low-SES children in reaction time and accuracy — “(RT: 685.63 ms for M/H-SES, 711.16 ms for L-SES; ACC: 95.15% for M/H-SES, 93.19% for L-SES)” | content_tags.quantities[5] |
| quantity | F (2,60) = 61.35, p < 0.001, η p 2 = 0.672 — main effect of scalp location on LPC amplitude, increasing from frontal to parietal — “The main effect of location was significant [ F (2,60) = 61.35, p < 0.001, η p 2 = 0.672].” | content_tags.quantities[6] |
| quantity | t (26) = 13.21, p < 0.001 — difference in parental years of education between the two SES groups (the manipulation check on group assignment) — “There was a significant difference in the years of education between the two groups [ t (26) = 13.21, p < 0.001].” | content_tags.quantities[7] |
| quantity | 52 down to 32 — children recruited against children analysed — “Initially, 52 children participated in the study. Before EEG data processing, data of 20 children were discarded, among them 11 children failed to complete the experiment (8 of them dropped out of the experiment early due to a cold or physical discomfort, and 3 other children did not complete the experiment due to constant body shaking, talking, and random responses during the experiment), and 9 children’s sufficient trials were less than 70% of the total after the artifact rejection. Finally, data of 32 children were regarded as valid for the analysis: 16 of them were from the low-SES (L-SES) group (8 girls), and the remaining 16 were from the middle/high-SES (M/H-SES) group (8 girls).” | content_tags.quantities[8] |
| quantity | 17.71% — trials discarded for artefact or incorrect response — “Trials with artifacts (voltage exceeding ±100 μV in any channel) that were caused by eye blinks, eye movement, or muscle potentials and trials with incorrect behavioral responses were excluded from the ERP averages, resulting in an exclusion of approximate 17.71% of the trials from the average.” | content_tags.quantities[9] |
| quantity | 17.79 vs 7.14 years — parental education in the middle/high against the low SES group — “The parents of children in the M/H-SES group obtained, on average, undergraduate education, whereas those in the L-SES group only reached the primary level (years of education: M M/H–SES ± SD = 17.79 ± 2.39, M L–SES ± SD = 7.14 ± 1.83). There was a significant difference in the years of education between the two groups [ t (26) = 13.21, p < 0.001].” | content_tags.quantities[10] |
| quantity | 0.300, 0.179, 0.038 — partial eta squared for the SES effect at 100-140 ms, 200-250 ms and 450-700 ms — “In the 450–700 ms time window, an SES (2) × numerical distance (2) × location (3) repeated-measurement ANOVA was performed. The results indicated that the SES main effect was not significant [ F (1,30) = 1.18, p > 0.05, η p 2 = 0.038].” | content_tags.quantities[11] |
| value source note | quantity — THE VALUE DRAWS ON THE PAPER BEYOND THIS QUOTE: part of it is printed elsewhere in the paper, not in this quote ('M/H-SES [ F (1,30) = 12.85, p < 0.01, η p 2 = 0.300] (see Figures 3A , 4 ).'; 'counterparts [ F (1,30) = 6.55, p < 0.05, η p 2 = 0.179].'). | content_tags.quantities[11] |
| quantity | 16 and 16 — children per SES group after exclusions — “Initially, 52 children participated in the study. Before EEG data processing, data of 20 children were discarded, among them 11 children failed to complete the experiment (8 of them dropped out of the experiment early due to a cold or physical discomfort, and 3 other children did not complete the experiment due to constant body shaking, talking, and random responses during the experiment), and 9 children’s sufficient trials were less than 70% of the total after the artifact rejection. Finally, data of 32 children were regarded as valid for the analysis: 16 of them were from the low-SES (L-SES) group (8 girls), and the remaining 16 were from the middle/high-SES (M/H-SES) group (8 girls).” | content_tags.quantities[12] |
| variable | SES group (independent) — “SES was a between-subject variable, and numerical distance was a within-subject variable.” | content_tags.variables[0] |
| variable | average amplitude (dependent) — “For the ERP data, in order to explore the differences in the neural mechanism between the L-SES and M/H-SES groups, the average amplitude over the analysis electrodes in each time window was calculated, respectively.” | content_tags.variables[3] |
| variable | location (independent) — “The numerical distance and location were the within-subject variables.” | content_tags.variables[4] |
| variable | socioeconomic status — “The SES criteria consisted of parental education, occupation, and family resources, which together represented SES better than any of these alone” | content_tags.variables[6] |
| variable | numerical distance — “Both the SES main effect [ F (1,30) = 0.27, p > 0.05, η p 2 = 0.009] and SES × numerical distance interaction [ F (1,30) = 0.53, p > 0.05, η p 2 = 0.017] were not significant. The behavioral results suggested that the DE existed in both groups; that is, children were faster and more accurate when judging numbers with large distance compared with the small distance. However, there was no significant difference in the behavioral indices of the magnitude comparison task between children with different SESs.” | content_tags.variables[7] |
| variable | anterior N1 — “The results showed that the SES main effect was significant, revealing that children with L-SES showed more negative amplitude than the children with M/H-SES [ F (1,30) = 12.85, p < 0.01, η p 2 = 0.300]” | content_tags.variables[8] |
| variable | LPC — “In the 450–700 ms time window, an SES (2) × numerical distance (2) × location (3) repeated-measurement ANOVA was performed. The results indicated that the SES main effect was not significant [ F (1,30) = 1.18, p > 0.05, η p 2 = 0.038].” | content_tags.variables[9] |
| variable | general cognitive ability (control) — “The participants in the current study had normal general cognitive ability, tested by Raven’s Standard Progressive Matrices (R’SPM-CR), revised by Zhang and Wang (1989) , and had normal verbal intelligence, tested by the verbal subscale of the McCarthy Scales of Children’s Abilities (MSCA-CR), revised by Chen and Li (1994) .” | content_tags.variables[10] |
| variable | verbal intelligence (control) — “The participants in the current study had normal general cognitive ability, tested by Raven’s Standard Progressive Matrices (R’SPM-CR), revised by Zhang and Wang (1989) , and had normal verbal intelligence, tested by the verbal subscale of the McCarthy Scales of Children’s Abilities (MSCA-CR), revised by Chen and Li (1994) .” | content_tags.variables[11] |
| variable | reaction time (dependent) — “Both RT (ms) and ACC (%) were entered into the SES (2) × numerical distance (2) repeated-measurement ANOVA.” | content_tags.variables[12] |
| variable | accuracy (dependent) — “Both RT (ms) and ACC (%) were entered into the SES (2) × numerical distance (2) repeated-measurement ANOVA.” | content_tags.variables[13] |
| definition | number sense — “most of them agree that it is an ability to subitize small quantities, discern number patterns, compare numerical magnitudes, estimate quantities, count, and perform simple number transformations ( Berch, 2005 ). Having number sense leads a person from understanding the meaning of numbers to solving complex mathematical problems, from simple numerical comparisons to inventing procedures for performing numerical operations, and from identifying serious numerical errors to using quantitative methods to communicate, process, and explain the information” | content_tags.definitions[0] |
| definition | distance effect (DE) — “That is, there is a distance effect (DE) in the process of numerical comparison.” | content_tags.definitions[1] |
| definition | late positive component (LPC) — “The last positive component is the late positive component (LPC), which is characterized by later onset (usually after 300 ms) and central–parietal distribution ( Friedman and Johnson, 2000 ).” | content_tags.definitions[2] |
| definition | anterior N1 — “This anterior N1, separated from the posterior N1, is regulated by top-down control of the prefrontal cortex and reflects the degree of voluntary attention” | content_tags.definitions[4] |
| definition | P2 component — “The second positive component, P2 (latency of approximately 200 ms after stimulus onset), appears in the frontal and central regions and has been found to be related with task-related processing, such as extraction of numerical meaning” | content_tags.definitions[5] |
| definition | number sense — “Although cognitive psychologists and math educators have different definitions of number sense ( Gersten et al., 2005 ), most of them agree that it is an ability to subitize small quantities, discern number patterns, compare numerical magnitudes, estimate quantities, count, and perform simple number transformations” | content_tags.definitions[6] |
| definition | distance effect — “Moyer and Landauer (1967) were the first to measure the RT in a selection paradigm by pressing the associated button. They found that participants made more mistakes and required more time when the two numbers to be compared were close (e.g., 7 vs. 9) than farther apart (e.g., 2 vs. 9). That is, there is a distance effect (DE) in the process of numerical comparison.” [ATTRIBUTED TO A CITED AUTHOR, NOT THIS PAPER] the paper’s own words: “Moyer and Landauer (1967) were the first to” | content_tags.definitions[7] |
| definition | LPC — “The last positive component is the late positive component (LPC), which is characterized by later onset (usually after 300 ms) and central–parietal distribution ( Friedman and Johnson, 2000 ). Some researchers suggested that this component was the P3b, which indicated the amount of context updating and also reflected the DE” | content_tags.definitions[8] |
| definition | P2p — “The next positive wave, P2p, was initially described by Dehaene (1996) as reflecting the DE (right parietal–occipital–temporal positive waveform to close numbers compared to far numbers) and was seen as an index of the approximate magnitude representation ( Hyde and Spelke, 2011 ). This component, simultaneous with N1, is clearly separated in time and space from the earlier broad fronto-central positivity wave, which is classically known as P2” | content_tags.definitions[9] |
| definition | socioeconomic status — “The SES criteria consisted of parental education, occupation, and family resources, which together represented SES better than any of these alone” | content_tags.definitions[10] |
| key-terms | number sense, socioeconomic status, magnitude comparison, distance effect, anterior N1, P2, LPC, mental number line, prefrontal cortex, parietal lobe, ceiling effect, top-down cognitive control |
| repeated-measures ANOVA F | as written: repeated-measures ANOVA was conducted — “For the behavioral data (RT and ACC), to explore the differences in DE between the two SES groups, an SES (L-SES vs. M/H-SES) × numerical distance (large vs. small) repeated-measures ANOVA was conducted.” | content_tags.statistics[0] |
| Greenhouse-Geisser correction for sphericity | as written: Greenhouse–Geisser correction was performed in all behavioral and physiological ANOVAs — “In the present study, Greenhouse–Geisser correction was performed in all behavioral and physiological ANOVAs as necessary.” | content_tags.statistics[1] |
| t-test t | as written: [ t (26) = 13.21, p < 0.001] — “There was a significant difference in the years of education between the two groups [ t (26) = 13.21, p < 0.001].” | content_tags.statistics[2] |
| correlation (test-retest reliability) r | as written: conducted a correlation analysis ... ( r = 0.97, p < 0.001) — “The results showed that the task was extremely reliable for both RT ( r = 0.97, p < 0.001) and ACC ( r = 0.81, p < 0.001), suggesting good task reliability” | content_tags.statistics[3] |
| post hoc test | as written: A post hoc test revealed — “A post hoc test revealed that the amplitudes in frontal and fronto-central regions were significantly larger than that in the central region” | content_tags.statistics[4] |
| effect size (partial eta squared) η p 2 | as written: η p 2 = 0.801 — “A significant main effect of numerical distance was found [ F (1,30) = 120.95, p < 0.001, η p 2 = 0.801], suggesting that RT for the small distance was significantly longer than that for the large distance.” | content_tags.statistics[5] |
| principal component analysis | as written: a main component analysis was conducted — “Then, a main component analysis was conducted, and the following formula was used to obtain the SES score:” | content_tags.statistics[6] |
| item response theory parameter estimation | as written: utilizing the Item Response Theory to perform parameter estimation — “utilizing the Item Response Theory to perform parameter estimation on family resources, in which the parameter estimation index is acquired;” | content_tags.statistics[7] |
| repeated-measurement ANOVA | — “In the 100–140 ms time window, an SES (2) × numerical distance (2) × location (3) repeated-measurement ANOVA was conducted. The results showed that the SES main effect was significant, revealing that children with L-SES showed more negative amplitude than the children with M/H-SES [ F (1,30) = 12.85, p < 0.01, η p 2 = 0.300]” | content_tags.statistics[8] |
| Greenhouse–Geisser correction | — “Finally, to explore the time course of magnitude comparison of the children with different SESs, three components were selected: the anterior N1 (100–140 ms, F3/FZ/F4/FC3/FCZ/FC4/C3/CZ/C4) ( Kong et al., 1999 ; Yagoubi et al., 2003 ; Kishiyama et al., 2008 ), the P2 component (200–250 ms, F3/FZ/F4/FC3/FCZ/FC4/C3/CZ/C4) ( Szücs and Csépe, 2004 ; Chen et al., 2013 ), and the LPC (450–700 ms, F3/FZ/F4, C3/CZ/C4, P3/PZ/P4)” | content_tags.statistics[9] |
| partial eta squared | — “In the 450–700 ms time window, an SES (2) × numerical distance (2) × location (3) repeated-measurement ANOVA was performed. The results indicated that the SES main effect was not significant [ F (1,30) = 1.18, p > 0.05, η p 2 = 0.038].” | content_tags.statistics[10] |
| 95% CI | — “There was no significant difference in the scores in general cognitive ability (R’SPM-CR: L-SES M = 37.00, SD = 5.92; M/H-SES M = 40.63, SD = 4.46, t (30) = −1.96, p > 0.05, 95% CI = [−7.41, 0.16]) and verbal intelligence (MSCA-CR: L-SES M = 77.06, SD = 9.77; M/H-SES M = 80.56, SD = 5.61, t (30) = −1.24, p > 0.05, 95% CI = [−9.25, 2.25]) between the two SES groups.” | content_tags.statistics[11] |
| correlation analysis | — “The current study conducted a correlation analysis to explore the test–retest reliabilities in RT and ACC between the first- and second-half trials of the experimental task. The results showed that the task was extremely reliable for both RT ( r = 0.97, p < 0.001) and ACC ( r = 0.81, p < 0.001), suggesting good task reliability” | content_tags.statistics[12] |
| claim type | existence — a second reading reaching the same value; recorded: existence — “According to the results of anterior N1 (early attention) and P2 (extraction of numerical meaning) over the frontal region, the differences among children with different SESs were manifested as differences in general neural activities in terms of attention and top-down cognitive control.” | alternatives.claim_type |
| method | event-related potentials during a two-digit selection task, comparing 16 low-SES with 16 middle/high-SES children matched on nonverbal and verbal ability — a second reading DIFFERING from the recorded value; recorded: electrophysiology — “According to the selection paradigm ( Moyer and Landauer, 1967 ), the magnitude comparison task was presented to each participant with two single digits displayed simultaneously during the recording session. The stimuli of this task consisted of 10 pairs of Arabic numerals from 1 to 9 (except number “5”), with no repeating digits in each pair (e.g., “3 3”). They were displayed in white Arial font in the center of the computer screen with black background. There were two different numerical distances: 5 (i.e., 1–6, 2–7, 3–8, 4–9) and 1 (i.e., 1–2, 2–3, 3–4, 6–7, 7–8, 8–9). The position where the two numbers appeared was counterbalanced, half on the left and half on the right. There were three blocks of 48 stimuli (144 trials in total; 72 trials per distance condition). The participants were required to decide which of the two numbers was larger by pressing the button on the corresponding side as quickly and accurately as possible.” | alternatives.method |
| phenomenon | symbolic magnitude comparison and the distance effect in second-grade children — a second reading DIFFERING from the recorded value; recorded: symbolic numerical magnitude comparison — “Moyer and Landauer (1967) were the first to measure the RT in a selection paradigm by pressing the associated button. They found that participants made more mistakes and required more time when the two numbers to be compared were close (e.g., 7 vs. 9) than farther apart (e.g., 2 vs. 9). That is, there is a distance effect (DE) in the process of numerical comparison.” | alternatives.phenomenon |
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Neural Correlate Differences in Number Senseterm Between Children With Low and Middle/High Socioeconomic Statusterm Qing BaopersName Qing BaopersName 1 School of Psychology, Shaanxi Normal University, Xi’an, China 2 School of Journalism and Communication, Ningxia University, Yinchuan, China 1, 2, † , Li Jin ZhangpersName Li Jin ZhangpersName 1 School of Psychology, Shaanxi Normal University, Xi’an, China 3 Shaanxi Provincial Key Research Center of Child Mental and Behavioral Health, Xi’an, China 4 Shaanxi Key Laboratory of Behavior and Cognitive Neuroscience, Xi’an, China 1, 3, 4, *, † , Yuan LiangpersName Yuan LiangpersName 1 School of Psychology, Shaanxi Normal University, Xi’an, China 1 , Yan Bang ZhoupersName Yan Bang ZhoupersName 5 ZhoupersName Enlai School of Government, Nankai University, Tianjin, China 5 , Gui Li ShipersName Gui Li ShipersName 6 School of Mechano-Electronic Engineering, Xidian University, Xi’an, China 1 School of Psychology, Shaanxi Normal University, Xi’an, China 2 School of Journalism and Communication, Ningxia University, Yinchuan, China 3 Shaanxi Provincial Key Research Center of Child Mental and Behavioral Health, Xi’an, China 4 Shaanxi Key Laboratory of Behavior and Cognitive Neuroscience, Xi’an, China 5 ZhoupersName Enlai School of Government, Nankai University, Tianjin, China 6 School of Mechano-Electronic Engineering, Xidian University, Xi’an, China Edited by: Hui Li, Macquarie University, Australia Reviewed by: Li ZhangpersName, Central University of Finance and Economics, China; Su Li, Chinese Academy of Sciences, China ✉ *Correspondence: Li Jin ZhangpersName, zhanglijin2013@snnu.edu.cn † These authors have contributed equally to this work This article was submitted to Developmental Psychology, a section of the journal Frontiers in Psychology Received 2020 Feb 12; Accepted 2020 Aug 27; Collection date 2020.
Copyright © 2020 BaopersName, ZhangpersName, LiangpersName, ZhoupersName and ShipersName.
This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
PMCID: PMC7606985 PMID: 33192775 Abstract Although some cognitive studies provided reasons that children with low socioeconomic statusterm (SES) showed poor mathematical achievements, there was no explicit evidence to directly explain the root of lagged performance in children with low SES. Therefore, the present study explored the differences in neural correlates in the process of symbolic magnitude comparisonterm between children with different SESs by the event-related potentials (ERPs). A total of 16 second-graders from low-SES families and 16 from middle/high-SES families participated in this study. According to the results of anterior N1term (early attention) and P2term (extraction of numerical meaning) over the frontal region, the differences among children with different SESs were manifested as differences in general neural activities in terms of attention and top-down cognitive controlterm. In the late stage of cognitive processing, there was no significant difference in the average amplitudeterm·var of the late positive component (LPC)term·def between children with different SES, indicating that low SES did not influence the information encoding and memory updating of numerical representation, which was responsible by the parietal lobeterm. The educational implications of this study are mentioned in the discussion.
Keywords: low socioeconomic statusterm, event-related potentials (ERPs), number senseterm, numerical magnitude comparisonterm, mathematical cognition Introduction Although cognitive psychologists and math educators have different definitions of number senseterm ( Gersten et al., 2005 ), most of them agree that it is an ability to subitize small quantities, discern number patterns, compare numerical magnitudes, estimate quantities, count, and perform simple number transformations ( Berch, 2005 ). Having number senseterm leads a person from understanding the meaning of numbers to solving complex mathematical problems, from simple numerical comparisons to inventing procedures for performing numerical operations, and from identifying serious numerical errors to using quantitative methods to communicate, process, and explain the information ( Berch, 2005 ). The document “Everybody Counts” of the National Research Council emphasized that the development of number senseterm is the main aim of mathematics in elementary school.
As a human’s innate ability, number senseterm has evolutionary significance ( Dehaene, 1997 ). Even babies show a natural sensitivity to small numbers and changes in numbers ( Wynn, 1990 ). Studies confirmed that preschool children already have number senseterm, such as comprehending basic principles of counting ( Gelman and Gallistel, 1986 ), developing efficient calculation methods spontaneously ( Groen and Resnick, 1977 ), and possessing effective strategies for addition and subtraction ( Baroody and Dowker, 2004 ). After entering elementary school, with the increase of the age and the role of school mathematics education, around the second grade, children’s number senseterm shows obvious improvement in various ways. Rubinsten et al. (2002) study on children from the beginning of school to the fifth grade found that the size congruity effect did not appear until the end of the first grade (average age, 7.3 years); that is, the consistency of the physical size of two numbers to be compared with their numerical value will affect children’s reaction timeterm·var (RT) and accuracyterm·var (ACC). This result indicated that children began to process symbolic numbers automatically at the end of the first grade. Not only the abovementioned automatic processing of symbolic numbers, but also children’s multi-digit numbers processing at this age has begun to mature. A study using the two-digit comparison task found that, from the second grade (average age, 7.5 years), children’s processing of single digits and two-digit numbers gradually showed an independent and parallel processing mode, which was similar to adults ( Nuerk et al., 2004 ). These results revealed that the representation of multiple digits by second-graders has gradually matured.
The early development of children’s number senseterm has great impact on their future mathematical abilities and academic achievements ( National Mathematics Advisory Panel, 2008 ). Resorting to a number senseterm test with five components (i.e., counting, number knowledge, number transformation, estimation, and number patterns), Jordan et al.’s (2006) study found that number senseterm has a significant predictive effect on children’s subsequent numerical comparison and mathematical problem solving. Children’s scores on number senseterm in kindergarten are a strong predictor of their mathematics achievements in elementary school ( Jordan and Levine, 2009 ; Jordan et al., 2012 ). Studies using a magnitude comparisonterm task also confirmed that children’s representation of numerical magnitudes had a significant and positive correlation with their math performance, and the former had a significant predictive effect on the latter ( Halberda et al., 2008 ; Holloway and Ansari, 2009 ; Mundy and Gilmore, 2009 ). A study using large-scale online data showed that the effect of number senseterm on individuals would continue into adulthood ( Halberda et al., 2012 ).
Additionally, children with poorly developed number senseterm will be exposed to the risk of mathematics learning difficulties (MLDsterm). Number senseterm is a powerful predictor of MLDsterm ( Locuniak and Jordan, 2008 ; Jordan et al., 2010 ; Seethaler and Fuchs, 2010 ). Studies found that poor math performance of children with MLDsterm or developmental dyscalculia (DD) could not be attributed to low intelligence or reading ability ( Geary, 2011 ), because these children had specific deficiencies in basic numerical processing ( Passolunghi and Siegel, 2004 ; Geary et al., 2007 ; Landerl et al., 2009 ).
Researchers have conducted a large number of behavioral and event-related potential (ERP) studies to explore the numerical comparison of both adults and children with normal mathematical ability. Moyer and Landauer (1967) were the first to measure the RT in a selection paradigm by pressing the associated button. They found that participants made more mistakes and required more time when the two numbers to be compared were close (e.g., 7 vs. 9) than farther apart (e.g., 2 vs. 9). That is, there is a distance effect (DE)term·def in the process of numerical comparison. The DE also appeared in the classification paradigm in which only one number was included in each trial (e.g., Temple and Posner, 1998 ; Libertus et al., 2007 ). By using ERP with high time resolution, several components have been described as being associated with the process of numerical comparison in the classification paradigm. The first negative component, N1, is characterized by a symmetrical distribution in the temporal–parietal sites. This component, which is related to visuospatial attention, has also been associated with numerical comparison ( Dehaene, 1996 ; Gómez-Velázquez et al., 2015 ). There was no DE in the time window of N1, but the sign effect has shown on this component in the posterior scalp, indicating that N1 represents the stimulus recognition phase of numerical comparison ( Dehaene, 1996 ). The second positive component, P2term (latency of approximately 200 ms after stimulus onset), appears in the frontal and central regions and has been found to be related with task-related processing, such as extraction of numerical meaning ( Potts et al., 1996 ; Potts and Tucker, 2001 ; Szücs and Csépe, 2004 ; Chen et al., 2013 ). The next positive wave, P2pterm, was initially described by Dehaene (1996) as reflecting the DE (right parietal–occipital–temporal positive waveform to close numbers compared to far numbers) and was seen as an index of the approximate magnitude representation ( Hyde and Spelke, 2011 ). This component, simultaneous with N1, is clearly separated in time and space from the earlier broad fronto-central positivity wave, which is classically known as P2term ( Curran et al., 1993 ). The last positive component is the late positive component (LPC)term·def, which is characterized by later onset (usually after 300 ms) and central–parietal distribution ( Friedman and Johnson, 2000 ). Some researchers suggested that this component was the P3bterm, which indicated the amount of context updating and also reflected the DE ( Johnson, 1986 ; Donchin and Coles, 1988 ; Grune et al., 1993 ; Polich, 2007 ). Moreover, the LPCterm has also been considered to be related to the process of non-specific motor preparation ( Dehaene, 1996 ; Temple and Posner, 1998 ; Libertus et al., 2007 ).
In recent decades, many researchers have been concerned about the variable of “poor family environment” and have conducted a series of studies on children’s cognitive development and promotion under the effect of socioeconomic statusterm (SES). This environmental variable usually includes the economic situation, social resources, social status and rights, and social prestige ( American Psychological Association and Task Force on Socioeconomic Statusterm, 2007 ). In general, children with low SES associated with inadequate educational resources and experiences were often exposed to the dangerous territory of development issues ( Bradley and Corwyn, 2002 ). These children from a disadvantaged environment encountered numerous problems, such as insufficient cognitive development and academic achievement (e.g., White, 1982 ; Sirin, 2005 ; Fernald et al., 2011 ).
Learning opportunities and social experiences linked to SES can influence number senseterm in early childhood ( Jordan and Levine, 2009 ). A series of longitudinal studies by Jordan et al. (2006 , 2007 , 2008) revealed that the development of abilities in counting, number relations (recognizing which of two numbers is smaller), and number operations (adding and subtracting small numbers) might be impeded by low income. A study using the 0–10 number line estimation task found that preschool children from low-income families were far less accurate than children with high SES of the same age. Many children with low SES did not even show a correct understanding of the order of numbers ( Siegler and Ramani, 2008 ). For quantitative operation, Griffin et al. (1994) found that 72% of children with high SES could correctly solve the exact arithmetic problems presented with stories, while only 14% of children from low SES backgrounds correctly solved such problems. The difference among children with different SESs was also manifested in the verbal calculation task ( Jordan et al., 1992 ). The researchers believed that this was precisely because children with low SES had weak digital vocabulary knowledge. Therefore, the impact of SES on children’s number senseterm is mainly reflected in the verbal aspects of mathematics ( Dowker, 2005 ; Jordan and Levine, 2009 ). Number senseterm, which is closely related to mathematical achievement, is susceptible to low SES, which can lead to lower math achievement among children from disadvantaged backgrounds (National Mathematics Advisory Panel, 2008).
However, studies on the influence of low SES on children’s number senseterm were mostly focused on behavioral research using paper-and-pencil number senseterm test as a tool ( Jordan et al., 2006 , 2007 , 2008 ). In these previous studies, the exploration of the relationship between low SES and specific components of number senseterm was mainly focused on number line estimation (e.g., Siegler and Ramani, 2008 ) and complex calculation (e.g., Griffin et al., 1994 ). As an important component of number senseterm, symbolic magnitude comparisonterm is often reflected in children’s daily lives and has been proven by longitudinal study to be a significant predictor of children’s later mathematical achievements ( De Smedt et al., 2009 ). Jordan and Levine (2009) emphasized that as a secondary symbolic number knowledge, numerical magnitude comparisonterm was an important foundation of early mathematics. However, few previous studies have directly examined the performance of children with different SESs on this component of number senseterm. Therefore, does low SES have the same effect on children’s symbolic numerical comparison? In other words, how does the effect of low SES on the process of numerical comparison occur? In addition, most participants in previous studies were preschool children (e.g., Rubinsten et al., 2002 ; Nuerk et al., 2004 ). Does low SES have the same effect on lower grade children who are already very mature in terms of numerical representation? In the exploration of these issues, the ERP technology, which could provide an accurate starting time to different processing stages of numerical comparison, would be used to explore how low SES affects the process of numerical comparison.
Based on the previous ERP studies, three processing stages were recognized in the process of numerical which were the stimulus recognition, the numerical representation and extraction of numerical meaning, and the preparation and implementation of numerical magnitude judgment ( Dehaene, 1996 ). According to the results of previous ERP studies on the selective attention function of the prefrontal cortexterm in children with low SES (i.e., D’Angiulli et al., 2008 ; Kishiyama et al., 2008 ; Stevens et al., 2009 ), this study proposed the first hypothesis that children with different SES would show variation in the early recognition stage of digit stimuli. In addition, since children with low SES often lag significantly behind in mathematical learning, this study assumed that in the second phase of numerical comparison, children with low SES would show a significant difference from those with middle–high SES. However, previous studies did not find a significant difference on P3bterm between children with different SES (i.e., Kishiyama et al., 2008 ), so we believed that in the magnitude comparisonterm task, children with different SES would not show significant difference in this late component, which is dependent on the integrity of the temporal–parietal cortex.
Materials and Methods Participants Children aged 7–9 years in the second grade were recruited from two primary schools in Yinchuan, China. Initially, 52 children participated in the study. Before EEG data processing, data of 20 children were discarded, among them 11 children failed to complete the experiment (8 of them dropped out of the experiment early due to a cold or physical discomfort, and 3 other children did not complete the experiment due to constant body shaking, talking, and random responses during the experiment), and 9 children’s sufficient trials were less than 70% of the total after the artifact rejection. Finally, data of 32 children were regarded as valid for the analysis: 16 of them were from the low-SES (L-SES) group (8 girls), and the remaining 16 were from the middle/high-SES (M/H-SES) group (8 girls). The mean age was 7.75 years ( SD = 0.39).
Measures of SES were acquired from children’s parental responses on the Socioeconomic Statusterm Questionnaire, which was based on the programme for international student assessment (PISA) in 2018 ( Organization for Economic Cooperation and Development, 2018 ) and was referred to the studies of Fang et al. (2008) and Fan et al. (2012) . The SES criteria consisted of parental education, occupation, and family resources, which together represented SES better than any of these alone ( White, 1982 ). The parents of children in the M/H-SES group obtained, on average, undergraduate education, whereas those in the L-SES group only reached the primary level (years of education: M M/H–SES ± SD = 17.79 ± 2.39, M L–SES ± SD = 7.14 ± 1.83). There was a significant difference in the years of education between the two groups [ t (26) = 13.21, p < 0.001]. Parental occupation was measured by using the International Socio-Economic Index of Occupational Status ( Ganzeboom and Treiman, 1996 ). Family resources included a computer, television, refrigerator, telephone/cellphone, washing machine, bathroom, bath facilities, kitchen, heating installation, and 11 other resources, which were basic and necessary for family life and greatly important to children’s studies. The calculation steps for SES were as follows (see Fan et al., 2012 ): (i) assigning values to the variables including parents’ education, occupation, and family resources; (ii) transforming the abovementioned assigned variables, that is, the one who has higher education or higher class occupation scores of the parents is selected as the representative for parents’ education or occupation; (iii) utilizing the Item Response Theory to perform parameter estimationterm·stat on family resources, in which the parameter estimation index is acquired; (iv) dealing with the missing values of variables with the following method: if a participant has more than two missing variables, then he or she will be regarded as a missing sample; if a participant only has one missing variable, then we will compute the corresponding values to substitute the missing value by regression analysis with two other variables; and (v) transforming education, occupation, and family resource into standard scores. Then, a main component analysis was conductedterm·stat, and the following formula was used to obtain the SES score: SES = β 1 × Z e d u c a t i o n + β 2 × Z o c c u p a t i o n + β 3 × Z f a m i l y r e s o u r c e ε f . β 1 , β 2 , and β 3 are the factor loadings. ε f is the root of the eigenvalues of the first factor. The participants came from Yinchuan, an inland city in the northwest region of China, which had a relatively backward level of economic development. Thus in this study, a high score on the SES questionnaire only represented a middle to high level of SES.
The participants in the current study had normal general cognitive abilityterm·var, tested by Raventerm’s Standard Progressive Matrices (R’SPM-CR), revised by ZhangpersName and Wang (1989) , and had normal verbal intelligenceterm·var, tested by the verbal subscale of the McCarthy Scales of Children’s Abilities (MSCA-CR), revised by Chen and Li (1994) . There was no significant difference in the scores in general cognitive abilityterm·var (R’SPM-CR: L-SES M = 37.00, SD = 5.92; M/H-SES M = 40.63, SD = 4.46, t (30) = −1.96, p > 0.05, 95% CI = [−7.41, 0.16]) and verbal intelligenceterm·var (MSCA-CR: L-SES M = 77.06, SD = 9.77; M/H-SES M = 80.56, SD = 5.61, t (30) = −1.24, p > 0.05, 95% CI = [−9.25, 2.25]) between the two SES groupsterm·var. More detailed information of the participants was shown in Table 1 . The participants, as assessed by parental report, had no history of neurological or psychiatric disorders or perinatal substance abuse. This study obtained the written informed consent of each child’s guardian and was approved by the Academic Ethics Committee of the School of Psychology, Shaanxi Normal University, China.
TABLE 1.
The general cognitive abilities and the demographic characteristics of the participants in different SES groupsterm·var ( M ± SD ).
n (female) Mean age R’SPM MSCA (verbal) SES Parental education a Range / 7.42–9.08 28.00–50.00 58.00–89.00 −2.05–2.46 5–21 L-SES 16(8) 7.92 ± 0.47 37.00 ± 5.92 77.06 ± 9.77 −1.43 ± 0.23 7.44 ± 1.63 H/M-SES 16(8) 7.99 ± 0.29 40.63 ± 4.46 80.56 ± 5.61 1.62 ± 0.84 17.13 ± 3.54 SES, socioeconomic statusterm; L-SES, low SES; M/H-SES, middle/high SES, R’SPM, Raventerm’s Standard Progressive Matrices; MSCA, McCarthy Scales of Children’s Abilities. a Parental education refers to the parent who has higher education .
Stimuli and Task According to the selection paradigm ( Moyer and Landauer, 1967 ), the magnitude comparisonterm task was presented to each participant with two single digits displayed simultaneously during the recording session. The stimuli of this task consisted of 10 pairs of Arabic numerals from 1 to 9 (except number “5”), with no repeating digits in each pair (e.g., “3 3”). They were displayed in white Arial font in the center of the computer screen with black background. There were two different numerical distancesterm·var: 5 (i.e., 1–6, 2–7, 3–8, 4–9) and 1 (i.e., 1–2, 2–3, 3–4, 6–7, 7–8, 8–9). The position where the two numbers appeared was counterbalanced, half on the left and half on the right. There were three blocks of 48 stimuli (144 trials in total; 72 trials per distance condition). The participants were required to decide which of the two numbers was larger by pressing the button on the corresponding side as quickly and accurately as possible. The participants were seated 70 cm away from the computer screen. The horizontal visual angle of the stimuli was 2.01°.
Procedure In the magnitude comparisonterm task, the time interval between the two blocks was 1 min. Each trial began with a fixation sign shown for 500 ms. After a 400 ms pause, a pair of numbers was shown for 1,500 ms. Then, a black screen with a variable interval ranging from 1,000 to 1,200 ms appeared. The trials in the block were presented in pseudo-random order. The same response consecutively occurred no more than two times. The time assignment of the task was shown in Figure 1 .
FIGURE 1.
The time course of magnitude comparisonterm task.
Participants were tested individually. After preparation for the ERP experiment, such as cleaning and blow-drying the hair, EEG/EOG sensor electrodes were attached, and the experimenter informed the participant of the experimental instruction in detail. The participant was seated 70 cm away from the computer screen. The experiment began with 10 practice trials, which were not included in the statistical analysis, to familiarize participants with the experimental requirements. There were no formal experimental number pairs in the practice trials. The experiment lasting approximately 1 h for each participant, including electrode placement, practice, and ERP recording sessions. In the present study, E-Prime 2.0 software (Psychology Software Tools Inc., Sharpsburg, PA, United States) was used to present the stimuli and collect behavioral data.
ERP Recording and Data Analysis The ERP was recorded and analyzed with SCAN 4.5 software (Neuro Scan, Inc., Herndon, VA, United States) from a 64-channel Ag/AgCl electrode Quick-Cap that was extended according to the 10–20 system. EEG was physically referenced to the left mastoid and then was re-referenced offline to the average of the left and right mastoid. An equidistant point between FPZ and FZ served as the locationterm·var of the ground electrode. EOG was recorded with electrodes located at points 2 cm outside both canthi and above and below the left eye to monitor the horizontal and vertical eye movements, respectively. EEG and EOG were continuously digitized at a sampling rate of 500 Hz using the SynAmps2 amplifier (Neuro Scan, Inc.) with a band pass of 0.05–100 Hz and stored in a hard disk for offline analysis. Electrode impedance was maintained below 5 KΩ.
Two ERP averages were calculated for each participant: one for the trials with small number distance and another for the trials with large number distance. Epochs extended from 100 ms pre-stimulus to 800 ms post-stimulus. The baseline correction was related to the averaged interval between −100 and 0 ms. A band-pass filter was set from 0.05 to 30 Hz (zero-phase, 24 dB/octave). Trials with artifacts (voltage exceeding ±100 μV in any channel) that were caused by eye blinks, eye movement, or muscle potentials and trials with incorrect behavioral responses were excluded from the ERP averages, resulting in an exclusion of approximate 17.71% of the trials from the average. The proportion of trials in the analysis ranged from 68.06 to 90.28%. Finally, the average number of trials that were included in the analysis in each condition was 60.98 for large distance and 57.52 for small distance. The data were processed with Neuroscan Edit program and Origin Pro 8 (OriginLab, Inc., United States).
Time windows and the electrodes for analysis were selected based on previous studies and observation results of the data. After observation of the grand average waveform, it was found that the first component evoked by the selection paradigm in this study was N1, occurring in the frontal and central regions. This anterior N1term, separated from the posterior N1term, is regulated by top-down control of the prefrontal cortexterm and reflects the degree of voluntary attention ( Luck, 1995 ; Barceló et al., 2000 ; Yago et al., 2004 ). In the previous study, the anterior N1term was also evoked in the process of mental arithmetic (e.g., Kong et al., 1999 ; Yagoubi et al., 2003 ). Finally, to explore the time course of magnitude comparisonterm of the children with different SESs, three components were selected: the anterior N1term (100–140 ms, F3/FZ/F4/FC3/FCZ/FC4/C3/CZ/C4) ( Kong et al., 1999 ; Yagoubi et al., 2003 ; Kishiyama et al., 2008 ), the P2 componentterm·def (200–250 ms, F3/FZ/F4/FC3/FCZ/FC4/C3/CZ/C4) ( Szücs and Csépe, 2004 ; Chen et al., 2013 ), and the LPCterm (450–700 ms, F3/FZ/F4, C3/CZ/C4, P3/PZ/P4) ( Grune et al., 1993 ; Turconi et al., 2004 ; Libertus et al., 2007 ; Han et al., 2017 ). The number of electrodes selected for the analysis was the same in different groups.
Statistical Analysis For the behavioral data (RT and ACC), to explore the differences in DE between the two SES groupsterm·var, an SES (L-SES vs. M/H-SES) × numerical distanceterm·var (large vs. small) repeated-measures ANOVA was conductedterm·stat. SES was a between-subject variable, and numerical distanceterm·var was a within-subject variable.
For the ERP data, in order to explore the differences in the neural mechanism between the L-SES and M/H-SES groups, the average amplitudeterm·var over the analysis electrodes in each time window was calculated, respectively. For the average amplitudeterm·var of the N1 and P2term, an SES (L-SES, M/H-SES) × numerical distanceterm·var (large, small) × locationterm·var (frontal, fronto-central, and central) repeated-measurement ANOVAterm·stat was performed, respectively. For the average amplitudeterm·var of the LPCterm, an SES (L-SES, M/H-SES) × numerical distanceterm·var (large, small) × locationterm·var (frontal, central, and parietal) repeated-measurement ANOVAterm·stat was conducted. The numerical distanceterm·var and locationterm·var were the within-subject variables. To investigate the changes in the ERP components in different brain regions, the amplitudes of the electrodes in different hemispheres of the same locationterm·var were averaged together (e.g., F3/FZ/F4). In the present study, Greenhouse–Geisser correction was performed in all behavioral and physiological ANOVAsterm·stat as necessary. Original F and df , η p 2 of effect size index, and corrected p -values are reported in the results when necessary.
Results Reliability Analysis The current study conducted a correlation analysisterm·stat to explore the test–retest reliabilities in RT and ACC between the first- and second-half trials of the experimental task. The results showed that the task was extremely reliable for both RT ( r = 0.97, p < 0.001) and ACC ( r = 0.81, p < 0.001), suggesting good task reliability ( Maloney et al., 2010 ; Miller and Ulrich, 2013 ).
Behavioral Results Reaction timeterm·var that exceeded three standard deviations in each condition was eliminated. Both RT (ms) and ACC (%) were entered into the SES (2) × numerical distanceterm·var (2) repeated-measurement ANOVAterm·stat. The results were presented in Table 2 .
TABLE 2.
The average reaction timeterm·var (RT, ms) and accuracyterm·var (ACC, %) in different conditions of children with different SESs.
Large distance Small distance RT [95% CI ] ( SD ) ACC [95% CI ] ( SD ) RT [95% CI ] ( SD ) ACC [95% CI ] ( SD ) L-SES 669 [605, 732] (132) 96.70 [95, 99] (3.47) 754 [686, 822] (143) 89.67 [86, 94] (9.02) M/H-SES 646 [558, 709] (115) 96.88 [95, 99] (4.10) 726 [658, 794] (122) 91.41 [88, 95] (5.81) Reaction Timeterm·var A significant main effect of numerical distanceterm·var was found [ F (1,30) = 120.95, p < 0.001, η p 2 = 0.801], suggesting that RT for the small distance was significantly longer than that for the large distance. The SES main effect [ F (1,30) = 0.32, p > 0.05, η p 2 = 0.011] and interaction of SES × numerical distanceterm·var [ F (1,30) = 0.12, p > 0.05, η p 2 = 0.004] were not significant.
Accuracyterm·var The main effect of numerical distanceterm·var was significant [ F (1,30) = 34.11, p < 0.001, η p 2 = 0.532]. The ACC of judging the numbers with a small distance was significantly lower than that with a large distance. Both the SES main effect [ F (1,30) = 0.27, p > 0.05, η p 2 = 0.009] and SES × numerical distanceterm·var interaction [ F (1,30) = 0.53, p > 0.05, η p 2 = 0.017] were not significant.
The behavioral results suggested that the DE existed in both groups; that is, children were faster and more accurate when judging numbers with large distance compared with the small distance. However, there was no significant difference in the behavioral indices of the magnitude comparisonterm task between children with different SESs.
ERP Results Grand average ERPs over the 32 participants elicited by the magnitude comparisonterm task showed a sequence of events. Three major components were identified after stimulus onset: a first negative component over frontal to central sites, the N1, peaking around 120 ms; an anterior positivity, the P2term, peaking around 220 ms and maximal over frontal electrodes; and a late positivity over frontal–central–parietal sites, LPCterm, peaking around 570 ms (see Figure 2 ). Overall, the dissociation of the ERP amplitude between children with L-SES and H/M-SES appeared around 100 ms after stimulus presentation, and the differences in the amplitudes between the two SES groupsterm·var were distributed in different time windows.
FIGURE 2.
The grand average ( n = 32) for the different SES groupsterm·var in each electrode that to be analyzed.
100–140 ms Time Window In the 100–140 ms time window, an SES (2) × numerical distanceterm·var (2) × locationterm·var (3) repeated-measurement ANOVAterm·stat was conducted. The results showed that the SES main effect was significant, revealing that children with L-SES showed more negative amplitude than the children with M/H-SES [ F (1,30) = 12.85, p < 0.01, η p 2 = 0.300] (see Figures 3A , 4 ). The main effects on both numerical distanceterm·var and locationterm·var were not significant [distance: F (1,30) = 0.01, η p 2 = 0.001; locationterm·var: F (2,60) = 0.79, η p 2 = 0.026, p s > 0.05] (see Figure 3A and Table 3 ). The interactions were not significant ( p s > 0.05).
FIGURE 3.
The average amplitudesterm·var of the children with different SES in different conditions for three time windows. (A) 100–140 ms, (B) 200–250 ms, (C) 450–700 ms; ns, no significance, * p < 0.05, ** p < 0.01. L-SES, low SES; M/H-SES, middle/high SES.
TABLE 3.
The average amplitudesterm·var of different locationsterm·var in each time window during the numerical comparison (μV) ( M ± SD [95% CI ]).
Locationsterm·var 100–140 ms 200–250 ms Locationsterm·var 450–700 ms Frontal −3.08 ± 0.50 [−4.10, −2.06] 14.74 ± 0.81 [13.08, 16.39] Frontal 4.32 ± 0.74 [2.82, 5.83] Fronto-central −3.45 ± 0.54 [−4.57, −2.34] 14.66 ± 0.90 [12.83, 16.49] Central 11.23 ± 0.89 [9.41, 13.05] Central −3.30 ± 0.51 [−4.35, −2.25] 12.25 ± 0.90 [10.41, 14.08] Parietal 12.56 ± 1.01 [10.50, 14.62] 200–250 ms Time Window In the 200–250 ms time window, the results of the SES (2) × numerical distanceterm·var (2) × locationterm·var (3) repeated-measurement ANOVAterm·stat revealed that the SES main effect was significant, suggesting that the children with M/H-SES showed more positive amplitude than their counterparts [ F (1,30) = 6.55, p < 0.05, η p 2 = 0.179]. The main effect of numerical distanceterm·var was not significant [ F (1,30) = 0.09, p > 0.05, η p 2 = 0.003] (see Figures 3B , 4 ). The differences of average amplitudesterm·var among different locationsterm·var were significant [ F (2,60) = 25.52, p < 0.001, η p 2 = 0.460]. A post hoc test revealedterm·stat that the amplitudes in frontal and fronto-central regions were significantly larger than that in the central region ( p s < 0.001) (see Table 3 ). The interactions were not significant ( p s > 0.05).
FIGURE 4.
The topographical maps for the children with different SES in different conditions. L-SES, low SES; M/H-SES, middle/high SES; Large, large distance; Small, small distance.
450–700 ms Time Window In the 450–700 ms time window, an SES (2) × numerical distanceterm·var (2) × locationterm·var (3) repeated-measurement ANOVAterm·stat was performed. The results indicated that the SES main effect was not significant [ F (1,30) = 1.18, p > 0.05, η p 2 = 0.038]. The main effect of numerical distanceterm·var was not significant [ F (1,30) = 0.18, p > 0.05, η p 2 = 0.006] (see Figures 3C , 4 ). The main effect of locationterm·var was significant [ F (2,60) = 61.35, p < 0.001, η p 2 = 0.672]. A post hoc testterm·stat showed that the average amplitudesterm·var increased from the frontal to the parietal lobeterm, and the amplitudes in the central and parietal regions were significantly larger than that in frontal region ( p s < 0.001) (see Table 3 ). The other interactions were not significant ( p s > 0.05).
Discussion A series of studies on the relationship between mathematical ability and SES have shown that, compared with children with middle/high SES, children with low SES were disadvantaged and were more likely to be at high risk in mathematics learning. The results of the present study provided evidence that there were neural correlate differences between children with different SESs. In the following, we discuss the particular analyses and neurocognitive indices supporting this claim.
Based on the behavioral data of RT and ACC, second-grade children showed a numerical DE where they judged the numbers with large distance much faster and more accurately, which was consistent with previous studies (e.g., Soltész et al., 2007 ; Gebuis et al., 2009 ). These findings indicate that there exists a “mental number lineterm” for children in the process of numerical comparison. Children might judge the magnitudes according to the to-be-compared number’s position on this mental number lineterm. When the to-be-compared numbers were close to each other, more greater overlapping areas of these two numbers on the mental number lineterm would make it more difficult to distinguish one from the other. Conversely, it was much easier to compare two numbers when they were more distant from each other. Nevertheless, children in different SES groupsterm·var showed extremely minor differences in RT and ACC on the magnitude comparisonterm task (RT: 685.63 ms for M/H-SES, 711.16 ms for L-SES; ACC: 95.15% for M/H-SES, 93.19% for L-SES). One reason is that the experimental task is relatively easy for second-graders (in the second semester), so the “ceiling effectterm” appears.
In the ERP with the advantages of high time resolution, children with different SESs showed significant differences in EEG activity at different stages when performing the magnitude comparisonterm task. In this study, the N1 component appeared in the frontal and central regions. According to the time and brain regions of occurrence, this component was the anterior N1term. This result was inconsistent with a previous study (i.e., Dehaene, 1996 ) in which the posterior N1term was evoked by the number comparison task. Researchers held that the anterior N1term, which has the same generators as the P1 component, originates from the ventral dorsolateral extrastriate cortex ( Clark et al., 1994 ; Heinze et al., 1994 ) and is regulated by top-down control of the prefrontal cortexterm ( Barceló et al., 2000 ; Yago et al., 2004 ). The reasons that the N1 component is evoked in different brain regions are because of the differences in the form of the stimulus presentation and in the comparison baseline between different experiments. In previous studies (e.g., Dehaene, 1996 ; Gómez-Velázquez et al., 2015 ), the classification paradigm was used to explore the process of numerical comparison. In this task, only one digit was presented in each trial, without changing the baseline number to be compared (e.g., “5”). In the present study, each trial of the task included two digits simultaneously (e.g., “2” and “7”). As a result, participants firstly needed to accurately represent each number on their mental number lineterm, instead of making classification judgments based on a reference point. The difficulty of this task has increased to some extent, therefore, the involvement of prefrontal cognitive control is required ( Miura et al., 2016 ; Siciliano et al., 2017 ). Moreover, in the ERP studies exploring the process of mental arithmetic, two numbers presented simultaneously in each trial, anterior N1term was evoked (e.g., Kong et al., 1999 ; Yagoubi et al., 2003 ). Through evaluating the prefrontal function of children with different SESs by observing the anterior N1term amplitude for the visual stimuli, Kishiyama et al. (2008) has found that children with low SES have more insufficient ability to allocate attention resources and inhibit irrelevant stimulus interference. The present study confirmed the conclusion that children with low SES showed more negative amplitude between 100 and 140 ms after the digits occurred, indicating that when these children perceived and recognized the numbers, they needed to invest more attention resources to suppress the interference of irrelevant information to their intentional attention to catch up with children with middle/high SES. Therefore, the current study suggests that low SES may be one of the important variables affecting children’s attention assignment to the digit stimuli.
Another finding was that the average amplitudeterm·var of children with low SES in the 200–250 ms time window was significantly smaller than that of children with middle/high SES. Previous studies found that the P2 componentterm·def, which appeared in the frontal–central regions after the N1 component, was related to the early recognition of the target, reflecting the processing related to the task ( Potts and Tucker, 2001 ; Potts et al., 1996 ). The latency of the P2 componentterm·def is approximate 200–300 ms, which is related to the early semantic processing of visual information ( Zhao, 2010 ). In this study, the average amplitudeterm·var of the P2term was maximal over frontal electrodes. According to previous studies, the P2term concentrated in the frontal–central regions mainly reflects the process of perception analysis, such as rapid extraction of numerical meaning in a number-related task, while the enhancement in the amplitude of the P2term may be related to experience and practice ( Szücs and Csépe, 2004 ; Amodio, 2010 ). The difference in P2term amplitude between children with different SES suggested that children from different SES families might be different in the recognition of target numbers and early semantic processing of abstract Arabic numerals.
Human’s prefrontal cortexterm has a long period of postnatal development (e.g., Casey et al., 2000 ; Fuster, 2002 ), so the external environment, such as environmental deprivation and stress ( Braun et al., 2000 ) and environmental complexity ( van Praag et al., 2000 ), will affect the development of the prefrontal cortexterm. Various factors associated with L-SES rearing conditions may influence the brain development of children. First of all, compared with M-SES children, L-SES children often live in cognitively impoverished environments, which leads them to a lack of cognition stimulating materials and experiences, and receive less attention from adults ( Bradley and Corwyn, 2002 ). In addition, these children from L-SES families often experience higher levels of stress. They are exposed to more chronic stressors in the family, such as prolonged poverty and parental strife, and therefore have higher basal levels of the stress hormone corticosteroidsterm and poorer selective attention ( Lupien et al., 2001 ).
In the present study, an ERP difference among children with different SESs did not appear in the average amplitudeterm·var of LPCterm (in the 450–700 ms time window), which was consistent with a previous study (i.e., Kishiyama et al., 2008 ). The LPCterm, which is characterized by later onset (usually after 300 ms) and central–parietal distribution ( Friedman and Johnson, 2000 ), represents the amount of context updating and is found to be sensitive to the arithmetic relatedness (e.g., Johnson, 1986 ; Donchin and Coles, 1988 ; Polich, 2007 ; Galfano et al., 2011 ). The results revealed that low SES, as an external environmental variable, did not exert an influence on the stage of children’s information encoding and memory storage associated with numerical representation. Moreover, the amplitude of LPCterm increasing from the frontal to the parietal lobeterm, indicated that the parietal region was more involved in the more complex deep processing related to mathematics. Although fMRI studies found that children with MLDterm had impairment in the bilateral intraparietal sulcusterm (IPS) involved in number magnitude processing ( Habib, 2000 ; Mussolin et al., 2014 ), and had significant differences in the P300 latency and amplitude compared to normal children ( Soltész et al., 2007 ; Taylor and Keenan, 2010 ; Wang et al., 2015 ), in this study, children with L-SES were not MLDterm, and some of them even had higher math scores in the class. Therefore, as a distal factor, SES is not enough to affect the deep numerical processing in the parietal lobeterm. However, in the present study, children with different SESs did not show a numerical DE on the average amplitudeterm·var in this time window, which may be due to the differences in the experimental tasks. For this reason, it is necessary to compare the ERP results with different forms of magnitude comparisonterm tasks in the future.
To sum up, the time course of numerical processing can be combined with corresponding brain regions to explain the discrepancies among children with different SES. Previous studies have found that prefrontal cortexterm activation comes first compared with parietal cortex during arithmetic processing ( Menon et al., 2000 ; Brass et al., 2005 ). The anterior component is related to the cognitive control processing of the prefrontal cortexterm, while the parietal component reflects the involvement of numerical representation ( Dehaene, 1996 ; Pinel et al., 2001 ). Therefore, according to the results of the N1 (early attention) and the P2term (extraction of numerical meaning) over the frontal region, the differences among children with different SESs were manifested as differences in general neural activities in terms of attention and top-down cognitive controlterm. The findings in this study provide some valuable suggestions to researchers and educators about the mathematical education of children with low SES. It is insufficient and unscientific to only provide children with low SES with books and toys. Teachers and tutors should pay more attention to the fundamental cognitive functions of these children, such as adding training contents of intentional attention about the numbers in the curriculum for these children.
Conclusion In the current study, according to the results of the anterior N1term (early attention) and P2term (extraction of numerical meaning) over the frontal region, the differences among children with different SESs were manifested as differences in general neural activities in terms of attention and top-down cognitive controlterm. When children with low SES perceived and recognized numbers, they needed to invest more attention resources to suppress the interference of irrelevant information to their intentional attention, so as to catch up with the children with middle/high SES. Moreover, these children from low-SES families showed significant differences in the semantic processing and meaning extraction of abstract Arabic numerals compared to the children with middle/high SES. In the late stage of cognitive processing (450–700 ms), there was no significant difference in the average amplitudeterm·var of the LPCterm among children with different SES, indicating that low SES did not influence information encoding and memory updating of numerical representation, which was responsible by the parietal lobeterm.
Data Availability Statement The datasets generated for this study are available on request to the corresponding author.
Ethics Statement The studies involving human participants were reviewed and approved by the Academic Ethics Committee of the School of Psychology, Shaanxi normal University, China. Written informed consent to participate in this study was provided by the participants’ legal guardian.
Author Contributions QB and LZ were responsible for the formulation of the research program. In addition, QB was responsible for data collection, processing, and manuscript writing. LZ was responsible for the manuscript review. YL as the third author of this study was responsible for the revision of this manuscript. YZ and GS assisted in the conduct of the experiment. All authors contributed to the article and approved the submitted version.
Conflict of Interest The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
Acknowledgments We are grateful to our reviewers for their truly helpful comments. We would like to thank the children and their parents for their trust, as well as the principal and teachers for their help in this study.
Footnotes Funding. This study was supported by the MOE Project of Humanities and Social Sciences (No. 18XJA190001) and the Free Exploration Program for Doctoral students of Shaanxi Normal University in China (No. 2019TS134).