From pre-activation to pre-updating: A threshold mechanism for commitment to strong predictions.

Abstract

Ample evidence suggests that during sentence processing comprehenders can "pre-activate" lexical/semantic knowledge stored in long-term memory. A relatively recent development suggests that in some cases a stronger form of prediction is employed, involving "pre-updating" the predicted content into the sentence's representation being built in working memory. The current study argues for an activation threshold mechanism by which pre-updating is initiated, within the routine processing stages of a word in a context. By combining a speeded cloze task with event-related potentials, we were able to analyze electrophysiological data measured prior to when participants were prompted to produce a completion, based on the participant's cloze response, reflecting their strongest prediction at that specific moment in time. A P600 effect reflecting pre-updating was observed in high (relative to low) constraint sentences, even in trials where the participant predicted a low cloze word. The results support a mechanism in which multiple predictions accumulate activations, "racing" toward a retrieval threshold. Once the activation level of a certain word passes the threshold, the word is integrated into the sentence representation in working memory. Pre-updating occurs if a certain prediction passes the retrieval threshold prior to its realization in the input.