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Marisa Ferrara BostonCornell University
John HaleCornell University
Reinhold KlieglUniversity of Potsdam
Umesh PatilUniversity of Potsdam
Shravan VasishthUniversity of Potsdam


The surprisal of a word on a probabilistic grammar constitutes a promising complexity metric for human sentence comprehension difficulty. Using two different grammar types, surprisal is shown to have an effect on fixation durations and regression probabilities in a sample of German readers’ eye movements, the Potsdam Sentence Corpus. A linear mixed-effects model was used to quantify the effect of surprisal while taking into account unigram frequency and bigram frequency (transitional probability), word length, and empirically-derived word predictability; the socalled “early” and “late” measures of processing difficulty both showed an effect of surprisal. Surprisal is also shown to have a small but statistically non-significant effect on empirically-derived predictability itself. This work thus demonstrates the importance of including parsing costs as a predictor of comprehension difficulty in models of reading, and suggests that a simple identification of syntactic parsing costs with early measures and late measures with durations of post-syntactic events may be difficult to uphold.

About this article


Received: February 29, 2008
Published: September 08, 2008


Boston, M. F., Hale, J., Kliegl, R., Patil, U. & Vasishth, S. (2008). Parsing costs as predictors of reading difficulty: An evaluation using the Potsdam Sentence Corpus. Journal of Eye Movement Research, 2(1):1, 1-12.



Parsing costs

Potsdam Sentence Corpus

Parsing difficulty