The Effects of Prediction and Speech Rate on Lexical Processing

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Listeners may predict aspects of upcoming linguistic input before it is encountered, but the specificity of information predicted can vary. It is unclear how very specific lexical predictions influence language processing, and what cognitive processes are involved with this prediction process. The goal of this study was to investigate the effect of specific lexical prediction on language processing, and how this effect varies with speech rate and individual differences in processing speed and working memory. In an active prediction paradigm, participants heard two-sentence passages at fast, medium, or slow rates while predicting the final word of the second sentence. Instead of the final word, participants were instructed to read a word aloud as quickly as possible, then indicate if this was the word they predicted. This word had about a 50% chance of matching the participant's prediction. Both correct and incorrect prediction facilitated reading time as compared with no prediction, suggesting that prediction can facilitate language processing, regardless of prediction accuracy. Additionally, slower speech rate resulted in slower reading time across prediction conditions, indicating that speed of prediction may slow to match speech rate. The effects of prediction accuracy and speech rate were not related to individual difference measures of either processing speed or working memory. In all, these results support the hypothesis that active prediction decreases language processing time, which may also be affected by speech rate.