Predictive power of word surprisal for reading times is a linear function of language model quality
Written for the Research library (claude-opus-5-5) from the paper text. Original — aclanthology.org/W18-0102.pdf
Summary
Surprisal theory links reading difficulty to a word's negative log probability in context. Researchers usually estimate these probabilities with computational language models, which predict upcoming words less well than humans do. This raises the question of whether weaker models distort conclusions about surprisal. Goodkind and Bicknell trained seven language models of varying quality on the Google One Billion Word Benchmark: n-gram models, an LSTM, and two LSTM/5-gram interpolations. They used each model's surprisal estimates to predict first-pass gaze durations in the English Dundee Corpus, fitting generalized additive mixed-effects models with both linear and nonlinear surprisal terms. As perplexity dropped, the models' gain in fit to reading times grew along a tight linear trend. Across all model types, the estimated size of the surprisal effect stayed roughly the same, and its shape looked approximately linear. These results suggest that surprisal findings based on weaker language models are not systematically biased. They also suggest that better language models yield better cognitive predictions.
Key points
- Models compared: seven in total.
- Four kenlm n-gram models (2-gram to 5-gram) with Modified Kneser-Ney smoothing; unigram counts served only as a frequency control.
- One word-level LSTM.
- Two LSTM+5-gram interpolations: one with perplexity-optimal weights of 0.71/0.29, and one with equal weights.
- Training data: the "1b corpus" (about 0.8 billion words, vocabulary of roughly 800,000).
- Perplexity on Dundee (all tokens): from 73.39 for the optimal interpolation to 290.88 for the bigram model; the LSTM scored 113.27 and the 5-gram 168.98.
- Reading data: Dundee Corpus, 10 readers of editorials from The Independent. After exclusions, 289,726 gaze durations remained, and 175 out-of-vocabulary tokens were dropped.
- Nonlinear GAMM fit: the gain in log-likelihood ranked models the same way as perplexity, from 297 for the optimal interpolation to 166 for the bigram model. The surprisal curves stayed close to linear, extending the earlier findings of Smith & Levy (2013).
Cited by
Cite
@inproceedings{goodkind2018predictive,
title = {{Predictive power of word surprisal for reading times is a linear function of language model quality}},
author = {Goodkind, Adam and Bicknell, Klinton},
booktitle = {Proceedings of the 8th Workshop on Cognitive Modeling and Computational Linguistics (CMCL 2018)},
year = {2018},
doi = {10.18653/v1/w18-0102},
url = {https://doi.org/10.18653/v1/w18-0102}
}References
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