Semantic priming and stimulus degradation: Implications for the role of the N400 in language processing

TLDR

The study aimed to investigate how stimulus degradation affects behavioral and ERP measures of semantic priming to clarify the psychological processes underlying the N400 component. Participants performed speeded lexical decisions to target words or pseudowords preceded by related or unrelated primes, with targets presented either intact or degraded by 33 % letter removal (Experiment 1) or dot overlay (Experiment 2). Behavioral priming was stronger for degraded targets, but the N400 ERP difference between related and unrelated targets did not increase with degradation, suggesting behavioral and ERP measures tap distinct components of semantic priming.

Abstract

Abstract Two experiments explored the effects of stimulus degradation on behavioral and event‐related potential (ERP) measures of semantic priming. The primary goal was to help elucidate the psychological processes that underlie the N400 component. In both experiments, subjects made speeded lexical decisions to words and pseudowords preceded by either semantically related or unrelated prime words. In one block of trials, the target stimuli were intact, and in a second block they were degraded by removing a random 33% of the elements making up each letter of the target (Experiment 1) or by overlaying a matrix of dots on the target (Experiment 2). In both experiments, subjects responded faster and more accurately to related targets than to unrelated targets (behavioral semantic priming effect), and this priming effect was greater when the target was degraded. However, although the N400 component was larger for unrelated than related targets (ERP semantic priming effect), there was no evidence that this difference was larger in the degraded block of either experiment. These results indicate that the behavioral and ERP measures reported here appear to be tapping into different components of the process(es) involved in semantic priming. The implication of the results for the linguistic processes underlying the N400 are discussed.