An event-related brain potential analysis of visual word priming effects

Abstract

Two experiments are reported that provide evidence on task-induced effects in a visual semantic priming paradigm. The research focuses on target expectancy effects, by manipulating the proportion of related and unrelated word pairs. In Experiment 1, a lexical decision task was used and reaction times (RTs) and Event- Related Potentials (ERPs) were obtained. In Experiment 2, subjects silently read the stimuli, without any additional task demands, and ERPs were recorded. The RT and ERP results of Experiment 1 demonstrate that an expectancy mechanism contributed to the priming effect when the proportion of related word pairs was high. The ERP results of Experiment 2 suggest that in the absence of extraneous task requirements, an expectancy mechanism is not active. However, an ERP priming effect was obtained in Experiment 2. The results are taken to suggest that priming effects due to relatedness proportion are induced by task demands and are not a standard aspect of on-line lexical processing