BERT: Pre-training of Deep Bidirectional Transformers for Language Understanding — TEI-tagged view

Jacob Devlin, Ming-Wei Chang, Kenton Lee, Kristina Toutanova · 2018 · artificial-intelligence · arXiv:1810.04805 · full text at the source · TEI xml · tagged edition · index · concepts · authors
Where this record's text came from. faceted 2026-08 by reading the locally held text (pdftext); every evidence string verified as an exact substring of that text before merging. method is not on the suggested list; the empirical work is benchmark fine-tuning plus ablations ('In this section, we perform ablation experiments over a number of facets of BERT in order to better understand their relative importance.'), so 'computational-experiment' was used. Note the verbatim quote for the Jernite/Logeswaran relation contains the PDF-extraction artefact 'representationlearning' (no space) — it is copied exactly as it appears in the article text. The paper also implicitly disputes Peters et al. (2018b) and Melamud et al. (2016) on model-size effects, but the sentence asserting its own novelty does not name them, so no 'contradicts' relation was recorded. 2026-08-14 and 2026-08-25 schema-0.3 passes: every quote verified as an exact substring of the staged text and anchored at merge time; concept terms verified present; every edge endpoint an existing node.
Other fields define these differently the same word, defined another way in another discipline
fine-tuning 2 fields
Tags on this paper every tag the record carries, whether or not the words occur in the text below — a number is how many papers in the corpus carry that tag; a tag with no number is unique to this paper
BERT3 Transformer2 pretraining4 language model masked LM Cloze task deep bidirectional shallow concatenation GLUE system-or-tool-building173
Method, as described: computational-experiment

Our tag layer for this paper

Cross-disciplinary analysis
content-tags & facets: phenomenon · claim-type · cross-domain-transfer · mechanism · claim-relation · replication-status · limitation — grounded in the full text
phenomenonlanguage model pre-training for transfer to NLP tasks— “Language model pre-training has been shown to be effective for improving many natural language processing tasks (Dai and Le, 2015; Peters et al., 2018a; Radford et al., 2018; Howard and Ruder, 2018).”
claim-typemethod— “We introduce a new language representation model called BERT, which stands for Bidirectional Encoder Representations from Transformers.”
method — evidence— “In this section, we present BERT fine-tuning results on 11 NLP tasks.”
transferfrom psycholinguistics and reading research: the Cloze task of Taylor 1953 - delete a word from a passage and ask a reader to supply it - made the pre-training objective of a transformer language model as the masked language model— “BERT alleviates the previously mentioned unidirectionality constraint by using a “masked language model” (MLM) pre-training objective, inspired by the Cloze task (Taylor, 1953).”transfers[0]
mechanismmasked language modeling: randomly mask tokens and train the model to predict them from both left and right context, giving a deep bidirectional representation that transfers to many tasks via fine-tuning— “The masked language model randomly masks some of the tokens from the input, and the objective is to predict the original vocabulary id of the masked word based only on its context”mechanisms[0]
builds-on the Transformer architecture— “We introduce a new language representation model called BERT, which stands for Bidirectional Encoder Representations from Transformers.”claim_relations[0]
extends unidirectional pre-trained language models (e.g. GPT)— “the BERT Transformer uses bidirectional self-attention”claim_relations[1]
extends Peters et al., 2018a and Radford et al., 2018— “Unlike recent language representation models (Peters et al., 2018a; Radford et al., 2018), BERT is designed to pretrain deep bidirectional representations from unlabeled text by jointly conditioning on both left and right context in all layers.”claim_relations[2]
extends Radford et al. (2018)— “Unlike Radford et al. (2018), which uses unidirectional language models for pre-training, BERT uses masked language models to enable pretrained deep bidirectional representations.”claim_relations[3]
builds-on Vaswani et al. (2017)— “BERT’s model architecture is a multi-layer bidirectional Transformer encoder based on the original implementation described in Vaswani et al. (2017) and released in the tensor2tensor library.”claim_relations[4]
builds-on the Cloze task (Taylor, 1953)— “BERT alleviates the previously mentioned unidirectionality constraint by using a “masked language model” (MLM) pre-training objective, inspired by the Cloze task (Taylor, 1953).”claim_relations[5]
builds-on Jernite et al. (2017) and Logeswaran and Lee (2018)— “The NSP task is closely related to representationlearning objectives used in Jernite et al. (2017) and Logeswaran and Lee (2018).”claim_relations[6]
sensebidirectional - TWO ARCHITECTURES UNDER ONE WORD, SEPARATED BY THE AUTHORS: for ELMo it is the concatenation of two independently trained one-directional models, which this paper calls a shallow concatenation and elsewhere 'not deeply bidirectional'; for BERT it is a single model conditioned on both sides at once - so the adjective names a property of the training objective in one case and of the output vector in the other— “BERT uses masked language models to enable pretrained deep bidirectional representations. This is also in contrast to Peters et al. (2018a), which uses a shallow concatenation of independently trained left-to-right and right-to-left LMs”senses[0]
sensemasked LM - THE PAPER'S NAME FOR A TASK THE LITERATURE ALREADY NAMED: the authors say outright that the procedure is often referred to as a Cloze task, citing Taylor 1953, so the 2018 name and the 1953 name denote one procedure and the field kept the newer one— “We refer to this procedure as a “masked LM” (MLM), although it is often referred to as a Cloze task in the literature”senses[1]
sensethe GLUE Average - NOT THE OFFICIAL GLUE SCORE: the column excludes the WNLI set, which the caption states, so a number that carries the benchmark's name is computed over a different set of tasks than the benchmark's own average— “column is slightly different than the official GLUE score, since we exclude the problematic WNLI set”senses[2]
controlthe two pre-training approaches compared by applying them to the same CoNLL-2003 named entity recognition task — held — rules out a difference between the approaches that is really a difference in the task each was tried on— “In this section, we compare the two approaches by applying BERT to the CoNLL-2003 Named Entity Recognition (NER) task (Tjong Kim Sang and De Meulder, 2003).”controls[0]
edgemasked LM —renamed-across-fields→ Cloze task— “We refer to this procedure as a “masked LM” (MLM), although it is often referred to as a Cloze task in the literature”concept_edges[0]
edgedeep bidirectional —contrasted-with→ shallow concatenation— “BERT uses masked language models to enable pretrained deep bidirectional representations. This is also in contrast to Peters et al. (2018a), which uses a shallow concatenation of independently trained left-to-right and right-to-left LMs”concept_edges[1]
outcome (stated by the tagger, no quotation)control — heldcontrols[0]
for which uselimitation — any account of what the pre-trained model has learned to expect: WE ARE CREATING A MISMATCH BETWEEN PRE-TRAINING AND FINE-TUNING, SINCE THE [MASK] TOKEN DOES NOT APPEAR DURING FINE-TUNING— “Although this allows us to obtain a bidirectional pre-trained model, a downside is that we are creating a mismatch between pre-training and fine-tuning, since the [MASK] token does not appear during fine-tuning.”limitations[0]
for which uselimitation — any use of the [CLS] vector as a sentence embedding without fine-tuning: THE VECTOR C IS NOT A MEANINGFUL SENTENCE REPRESENTATION WITHOUT FINE-TUNING, SINCE IT WAS TRAINED WITH NSP— “The vector C is not a meaningful sentence representation without fine-tuning, since it was trained with NSP.”limitations[1]
for which uselimitation — the reported small-dataset results: FOR BERT_LARGE WE FOUND THAT FINETUNING WAS SOMETIMES UNSTABLE ON SMALL DATASETS, SO WE RAN SEVERAL RANDOM RESTARTS AND SELECTED THE BEST MODEL ON THE DEV SET— “Additionally, for BERTLARGE we found that finetuning was sometimes unstable on small datasets, so we ran several random restarts and selected the best model on the Dev set.”limitations[2]
for which uselimitation — the GLUE averages quoted from this table: the authors state the Average column is slightly different from the official GLUE score because the WNLI set is excluded, so it is not comparable with an official GLUE average— “column is slightly different than the official GLUE score, since we exclude the problematic WNLI set”limitations[3]
for which uselimitation — any claim of novelty for the masked LM objective: the authors note the same procedure is often referred to as a Cloze task in the literature, citing Taylor 1953— “We refer to this procedure as a “masked LM” (MLM), although it is often referred to as a Cloze task in the literature”limitations[4]
for which uselimitation — any comparison of bidirectional models: the authors distinguish their deep bidirectional pre-training from a shallow concatenation of independently trained left-to-right and right-to-left language models, so the word alone does not separate the architectures— “BERT uses masked language models to enable pretrained deep bidirectional representations. This is also in contrast to Peters et al. (2018a), which uses a shallow concatenation of independently trained left-to-right and right-to-left LMs”limitations[5]
replicationuntested
limitationMasking creates a mismatch between pre-training and fine-tuning because [MASK] never appears downstream.— “Although this allows us to obtain a bidirectional pre-trained model, a downside is that we are creating a mismatch between pre-training and fine-tuning, since the [MASK] token does not appear during fine-tuning.”limitations[0]
limitationThe [CLS] vector is not usable as a sentence representation without fine-tuning.— “The vector C is not a meaningful sentence representation without fine-tuning, since it was trained with NSP.”limitations[1]
limitationFine-tuning the large model was unstable on small datasets and required multiple random restarts.— “Additionally, for BERTLARGE we found that finetuning was sometimes unstable on small datasets, so we ran several random restarts and selected the best model on the Dev set.”limitations[2]
limitationThe reported average is not the official score of the benchmark it is reported on.— “column is slightly different than the official GLUE score, since we exclude the problematic WNLI set”limitations[3]
limitationThe pre-training objective is an existing task under a new name, which the authors state.— “We refer to this procedure as a “masked LM” (MLM), although it is often referred to as a Cloze task in the literature”limitations[4]
limitationThe paper's central adjective is one the systems it is compared against also use.— “BERT uses masked language models to enable pretrained deep bidirectional…limitations[5]
Content tags
content-observations: finding · quantity · variable · definition · key-term — grounded in the full text
findingbidirectional pre-training is important for language representationscontent_tags.findings[0]
findingpre-trained representations reduce the need for task-specific architecturescontent_tags.findings[1]
findinga pre-trained BERT is fine-tuned with just one added output layercontent_tags.findings[2]
findingthe major limitation of prior models is unidirectionalitycontent_tags.findings[3]
quantity80.5 percent GLUE — new GLUE score, +7.7 points absolutecontent_tags.quantities[0]
quantity86.7 percent — MultiNLI accuracy, +4.6 points absolutecontent_tags.quantities[1]
quantity93.2 F1 — SQuAD v1.1 Test F1, +1.5 pointscontent_tags.quantities[2]
quantity83.1 F1 — SQuAD v2.0 Test F1, +5.1 points
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content_tags.quantities[3]
quantity11 NLP tasks — tasks on which BERT set state of the art
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variablemasked tokens (randomly hidden inputs the model must predict)
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content_tags.variables[0]
variableleft and right context (jointly conditioned on in all layers)
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definitionBERT
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definitionmasked language model
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definitionfeature-based approach
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definitionCloze task
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content_tags.definitions[3]
key-termsBERT, pre-training, fine-tuning, bidirectional, masked language model, Transformer, language representation, next sentence prediction, word embeddings, self-attention, natural language processing
Concepts
terms this paper carries, each with the sentence it was cut from — the layer that joins one paper to another. Terms with no quote yet are on CONCEPTS.html.
conceptmasked LM
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concepts[4]
conceptCloze task
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concepts[5]
conceptdeep bidirectional
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concepts[6]
conceptshallow concatenation
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conceptGLUE
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concepts[8]
Statistics — cross-field join keys
field-invariant statistical terms, used in their statistical sense (gated on a number / symbol / test). A p-value or a standard deviation means the SAME thing in physics, biology, psychology and sociology — so these are the strongest cross-field join keys. Grounded verbatim.
correlation r as written: Spearman
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