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Deep Contextualized Word Representations

2018 · paper · Computational linguistics

Introduces ELMo, word representations drawn from the internal states of a deep bidirectional language model, so each word's vector depends on its sentence. Adding them to existing models reportedly improves the state of the art on six language tasks.

Checked: PDF from aclanthology.org, fetched 5 Oct 2026. Page numbers are those of that PDF.

2 findings

Substance Section 4 says "relative error reductions ranging from 6 - 20% over strong base models" and the Introduction says "including up to 20% relative error reductions", but Table 1 lists "4.7 / 24.9%" (SQuAD) and "2.06 / 21%" (NER), and Section 4 itself says "a 24.9% relative error reduction".
  • p. 4 Section 4 Evaluation, first paragraph
    ductions ranging from 6 - 20% over strong base
  • p. 5 Table 1, SQuAD row, Increase column
    4.7 / 24.9%
  • p. 4 Section 4, Question answering paragraph
    a 24.9% relative error reduction over the
  • p. 1 Introduction, last paragraph
    including up to 20% relative error

Judge's note: Checked on the page 1, 4 and 5 images. Table 1's relative column reads 24.9, 5.8, 17.2, 9.8, 21 and 6.8, so the maximum is 24.9%, not 20%. Recomputing from the printed scores reproduces 24.9% for SQuAD and 21% for NER. The table caption says the column is relative to the authors' baseline, which is the same quantity the text describes, and nothing in the paper explains the lower cap. The upper bound should be about 25%.

Second check: another model agreed

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Reference or label Section 5.6: "Table 7 summarizes the results for SQuAD, SNLI and SNLI." The third task in Table 7 is SRL, not a second SNLI.
  • p. 9 Section 5.6
    sults for SQuAD, SNLI and SNLI
  • p. 9 Table 7 caption
    SQuAD, SNLI and SRL comparing different choices
  • p. 9 Sec. 5.6
    Table 7 summarizes the re- sults for SQuAD, SNLI and SNLI.

Judge's note: On the page 9 image, Table 7 has rows SQuAD, SNLI and SRL, and its caption reads "SQuAD, SNLI and SRL". The body text names SNLI twice and omits SRL. The fix is evident: "SQuAD, SNLI and SRL".

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21 minor (typos and the like; most checked by the judge only)
Wording Introduction: ELMo "alone significantly improves the state of the art in every case", but for SNLI Table 1 shows previous SOTA "88.6" against ELMo + baseline "88.7 ± 0.17", a 0.1-point gain that is smaller than the reported standard deviation.
  • p. 5 Table 1 caption
    Due to the small test sizes for NER and SST-5, we report the mean
  • p. 5 Table 1, SNLI row
    88.7 ± 0.17
  • p. 1 Introduction, last paragraph (also first paragraph and abstract)
    alone significantly improves the state of the art
  • p. 5 Table 1, SNLI row, Previous SOTA
    88.6

Judge's note: Pages 1 and 5 show these values as quoted. "Significantly" is probably meant informally, and the other five tasks show clear gains, so this is a wording overstatement for one row only. The reviewer's second point, about the caption's coverage of the ± entries, is handled under C011.

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Wording Section 3.3: "regularize the ELMo weights by adding λ‖w‖₂² to the loss" uses a symbol w that is not defined; Eq. (1) calls the layer weights s^task ("softmax-normalized weights").
  • p. 4 Section 3.3, last paragraph
    weights by adding λ‖w‖
  • p. 3 Section 3.2, after Eq. (1)
    are softmax-normalized weights and

Judge's note: Page 4 shows λ‖w‖₂² in Section 3.3, and the page 3 crop shows Eq. (1) with s^task. The symbol w is not introduced anywhere, so it is unclear whether the penalty applies to the normalised weights or to the pre-softmax parameters. This is a notational ambiguity only; the intended meaning (pre-softmax weights) can be inferred. I did not verify the reviewer's separate point about Θ_e versus Θ^task.

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Wording Table 1, NER row: the absolute increase is printed as "2.06 / 21%", while the printed scores 90.15 and 92.22 differ by 2.07.
  • p. 5 Table 1, NER row
    2.06 / 21%

Judge's note: Read on the page 5 image: baseline 90.15, ELMo + baseline 92.22 ± 0.10, increase 2.06. The 0.01 gap is consistent with subtracting unrounded means, so either form could be legitimate.

Second check: another model agreed

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Wording Table 1 caption: "Due to the small test sizes for NER and SST-5, we report the mean and standard deviation across five runs", yet the SNLI entry is also given as "88.7 ± 0.17" and the text says "an average of 0.7% across five random seeds".
  • p. 5 Table 1 caption
    Due to the small test sizes for NER and SST-5, we report the mean
  • p. 5 Table 1, SNLI row
    88.7 ± 0.17
  • p. 5 Section 4, Textual entailment
    0.7% across five random seeds

Judge's note: Read on the page 5 image. The SNLI row carries a ± value that the caption does not mention, although the body text does explain that SNLI was averaged over five seeds. The caption is incomplete, not contradictory.

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Wording SQuAD development F1 for the full ELMo model is "85.2" in Table 2 (all layers, λ=0.001) but "85.6" in Table 3 (Input & Output) and Table 7 (ELMo + GloVe); Table 3's Input Only value is 85.1.
  • p. 6 Table 2, SQuAD row, All layers λ=0.001
    85.2
  • p. 6 Table 3, SQuAD row, Input & Output
    85.6
  • p. 9 Table 7, SQuAD row, ELMo + GloVe
    85.6

Only the authors can say what is right here.

Judge's note: Read on the page 6 and page 9 images. The baseline is 80.8 in both Table 2 and Table 7, and SNLI is 89.5 in all three tables, yet the SQuAD figure in Table 2 matches neither placement in Table 3. I found no statement in the text saying Table 2 used a different configuration or a separate run. A separate run is a plausible explanation, so this is a question for the authors.

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Wording SRL development F1 for the full ELMo model is "84.8" in Table 2 (all layers, λ=0.001) but "84.7" in Table 3 (Input Only) and Table 7 (ELMo + GloVe).
  • p. 6 Table 2, SRL row, All layers λ=0.001
    84.8
  • p. 6 Table 3, SRL row, Input Only
    84.7
  • p. 9 Table 7, SRL row, ELMo + GloVe
    84.7

Judge's note: Read on the page 6 and page 9 images. The baseline is 81.6 in both Table 2 and Table 7. The 0.1 difference is unexplained in the text but is consistent with a separate run or seed, so either value could be legitimate.

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Wording Figure 2 caption says "Normalized weights less then 1/3 are hatched with horizontal lines", but the hatching drawn in the figure cells and on the colour bar below 1/3 is diagonal.
  • p. 8 Figure 2 caption
    malized weights less then 1/3 are hatched with hori-
  • p. 8 Figure 2 caption
    Nor-malized weights less then 1/3 are hatched
  • p. 8 Figure 2 caption
    those greater then 2/3 are speckled

Judge's note: Viewed the page 8 image and the crop. The hatched cells (e.g. the Token row and LSTM 2 for SRL) and the lower part of the colour bar carry slanted lines, not horizontal ones. The caption misdescribes the pattern; the figure's meaning is unaffected. The "then" for "than" slips in the same caption are handled under C017.

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Typo Introduction: "allowing the learned models select the types of semi-supervision" is missing "to" before "select".
  • p. 1 Introduction, right column
    ficial, allowing the learned models select the types
  • p. 1 Introduction, third paragraph
    allowing the learned models select the types

Judge's note: Read on the page 1 image, right column, second paragraph. The word "to" is missing as printed.

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Typo Related work: "are better at predicting POS tags then second layer" should read "than the second layer".
  • p. 2 Section 2 Related work, right column
    tags then second layer. Finally, the top layer of an

Judge's note: Read on the crop of page 2. The text prints "then" for "than" and omits the article.

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Typo "then" is printed for "than" in several comparisons: "tags then second layer" (p2), "larger then the 1.8% improvement" (p4), "richer representations then CoVe" (p6), "WSD then the first layer" (p8), and "less then 1/3" / "greater then 2/3" (Figure 2 caption, p8).
  • p. 8 Figure 2 caption
    zontal lines and those greater then 2/3 are speckled
  • p. 4 Section 4, Question answering
    larger then the 1.8% improvement
  • p. 6 Section 5, overview
    tently provides richer representations then CoVe
  • p. 8 Section 5.3, WSD
    WSD then the first layer

Judge's note: Each instance was read on the page image or crop: p2 Related work, p4 Question answering, p6 Section 5 overview, p8 WSD paragraph and the Figure 2 caption. All are comparatives that need "than". The p2 instance also lacks "the" before "second layer". Cosmetic.

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Typo Section 4, Question answering: "significantly larger then the 1.8% improvement from adding CoVe" has "then" for "than".
  • p. 4 Section 4, Question answering paragraph
    larger then the 1.8% improvement from adding
  • p. 4 Question answering
    significantly larger then the 1.8% improvement

Judge's note: Read on the page 4 image, right column, last lines of the paragraph.

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Typo Section 4, Question answering: "A 11 member ensemble pushes F1 to 87.4" should read "An 11 member ensemble".
  • p. 4 Section 4, Question answering paragraph
    A 11 member ensem-

Judge's note: Read on the page 4 image. The article "A" is printed before "11".

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Typo Section 4: "a very general result across a diverse set model architectures and language understanding tasks" is missing "of" after "set".
  • p. 4 Section 4 Evaluation, first paragraph
    verse set model architectures and language under-

Judge's note: Read on the page 4 image, Section 4, first paragraph. The first sentence of the same paragraph has the correct form, "diverse set of six benchmark NLP tasks".

Second check: none (judge only)

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Typo Section 5: "semantic information is captured a higher layers" should read "at higher layers".
  • p. 6 Section 5 Analysis, intro paragraph
    mation is captured a higher layers, consistent with
  • p. 6 Section 5, overview paragraph
    mation is captured a higher layers
  • p. 6 Sec 5 intro
    semantic information is captured a higher layers

Judge's note: Read on the page 6 image, Section 5 introductory paragraph. The same sentence has the correct form, "at lower layers".

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Typo Section 5: "our biLM consistently provides richer representations then CoVe" has "then" for "than".
  • p. 6 Section 5 Analysis, intro paragraph
    tently provides richer representations then CoVe.
  • p. 6 Sec 5 intro
    richer representations then CoVe

Judge's note: Read on the page 6 image, Section 5 introductory paragraph.

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Typo Section 5.5: "For coreference and SQuAD, the this is strongly favored" contains a stray "the".
  • p. 8 Section 5.5
    coreference and SQuAD, the this is strongly
  • p. 8 Sec 5.5
    For coreference and SQuAD, the this is strongly
  • p. 8 Sec. 5.5
    the this is strongly
  • p. 8
    For coreference and SQuAD, the this is strongly favored

Judge's note: Read on the page 8 image, right column, Section 5.5. The words "the this" are printed as quoted; it is not an extraction artefact.

Second check: none (judge only)

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Typo Section 5.3: "this is direct test of the biLM's representations" lacks the article "a"; Section 5.4: "performance of baselines models with and without ELMo" should read "baseline models".
  • p. 8 Section 5.3, POS tagging paragraph
    of model capacity, this is direct test of the biLM
  • p. 8 Section 5.3, POS tagging
    this is direct test of the biLM
  • p. 8 Section 5.4
    formance of baselines models with and without
  • p. 8 POS tagging
    this is direct test of the biLM’s

Judge's note: Both phrases were read on the page 8 image (POS tagging paragraph in the left column; Section 5.4 continuation in the right column). Cosmetic grammar slips.

Second check: none (judge only)

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Typo Section 5.7: "All of the results presented in Sec.4 include" lacks the space after "Sec." that is used everywhere else ("Sec. 4", "Sec. 5.1" and so on).
  • p. 9 Sec 5.7
    results presented in Sec.4 include

Judge's note: The crop of page 9 shows "Sec.4" with no space. A text search shows every other section reference is printed as "Sec. N". Purely typographic.

Second check: none (judge only)

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Typo Reference Kumar et al. 2016: "Mohit Iyyer, Ishaan Gulrajani James Bradbury, Victor Zhong" has no comma between "Gulrajani" and "James".
  • p. 10 References, Kumar et al. 2016
    Iyyer, Ishaan Gulrajani James Bradbury, Victor
  • p. 10 References, Kumar et al.
    Ishaan Gulrajani James Bradbury

Only the authors can say what is right here.

Judge's note: Rests on outside knowledge: that Ishaan Gulrajani and James Bradbury are two separate authors of the cited work. The crop shows the text as quoted, with no comma between the two names while every other author in the entry is comma-separated, so a missing separator is very likely.

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Typo Reference "Yoon Kim, Yacine Jernite, David Sontag, and Alexander M Rush. 2015. Character-aware neural language models. In AAAI 2016." gives the year as 2015 and the venue as AAAI 2016.
  • p. 10 References, Kim et al.
    models. In AAAI 2016.

Judge's note: The crop shows the entry as quoted, and it is cited in the text as Kim et al. (2015). The two years disagree within the entry. Either could be legitimate (a preprint year beside the conference year), so this is a consistency point only.

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Typo Reference Rajpurkar et al. 2016: "Squad: 100, 000+ questions for machine comprehension of text" has a stray space inside the number and prints "Squad" where the article itself writes "SQuAD".
  • p. 11 References
    Squad: 100, 000+ questions

Judge's note: The crop of page 11 shows "Squad: 100, 000+" as quoted. The article body uses "SQuAD" throughout, so the lower-casing looks like a bibliography-style artefact, as with "lstm" in other entries. Cosmetic.

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