Effects of speech rate, preview time of visual context, and participant instructions reveal strong limits on prediction in language processing

Abstract

There is a consensus among language researchers that people can predict upcoming language. But do people always predict when comprehending language? Notions that “brains … are essentially prediction machines” certainly suggest so. In three eye-tracking experiments we tested this view. Participants listened to simple Dutch sentences (‘Look at the displayed bicycle’) while viewing four objects (a target, e.g. a bicycle, and three unrelated distractors). We used the identical visual stimuli and the same spoken sentences but varied speech rates, preview time, and participant instructions. Target nouns were preceded by definite gender-marked determiners, which allowed participants to predict the target object because only the targets but not the distractors agreed in gender with the determiner. In Experiment 1, participants had four seconds preview and sentences were presented either in a slow or a normal speech rate. Participants predicted the targets as soon as they heard the determiner in both conditions. Experiment 2 was identical except that participants were given only a one second preview. Participants predicted the targets only in the slow speech condition. Experiment 3 was identical to Experiment 2 except that participants were explicitly told to predict. This led only to a small prediction effect in the normal speech condition. Thus, a normal speech rate only afforded prediction if participants had an extensive preview. Even the explicit instruction to predict the target resulted in only a small anticipation effect with a normal speech rate and a short preview. These findings are problematic for theoretical proposals that assume that prediction pervades cognition.