Explicit semantic tasks are necessary to study semantic priming effects with high rates of repetition

ObjectiveThe purpose of the present study was to clarify in which experimental conditions the semantic processing of repeated words is preserved.MethodsWe contrasted a short (250 ms) and a long (1000 ms) stimulus onset asynchrony (SOA) in two different experiments, using a relatively low proportion of related words (30%). One group of participants performed a lexical decision task (LDT) and a second group performed an explicit semantic matching task with the same words (except for pseudowords) and the same task parameters. In both tasks, word stimuli consisted solely of two prime and two target words repeated throughout the experiment.ResultsThe effects of semantic priming on reaction time (RT) and the amplitude of the N400 ERP were absent for both the short and the long SOA in the LDT. In contrast, in the explicit semantic task, these effects were significant. In this task, the activity of N400 generators in the left superior temporal gyrus and the inferior parietal cortex significantly differentiated primed and unprimed trials but this effect did not interact with SOA.ConclusionsOur results indicate that task instruction is critical to preserve semantic processing with repeated presentations.SignificanceUsing explicit semantic designs, it may be possible to study associative or categorical relations between individual concepts.

► Associative priming decreases N400 amplitude and reaction time (RT) to highly repeated target words.
► N400 generators in the left superior temporal gyrus and inferior parietal cortex are involved in priming effects across stimulus onset asynchronies (SOAs).
► Task used, rather than SOA or the proportion of related words, is crucial for the maintenance of semantic processing with high rates of repetition.