Parsing costs as predictors of reading difficulty: An evaluation using the Potsdam Sentence Corpus
Journal of Eye Movement Research, 2 (1):
1--12 (2008)Zusammenfassung
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 so-called “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.