Electrophysiological correlates of meaning-based attentional guidance mechanism as a function of cognitive loads in visual search for words

This study investigates the impact of foveal and task-related cognitive loads on meaning-based attentional guidance during visual search for words. Participants searched for words through successive three-words displays while their electroencephalogram was recorded. In target-absent trials, displays contained a central word and two parafoveal words: one distractor semantically-related to the target and one unrelated distractor. To manipulate the task-related cognitive load, participants either searched for specific words either provided beforehand (literal task) or defined only by their semantic category (categorical task). The foveal load was manipulated by varying both the lexical frequency and the semantic-relatedness with the targets of the centered word in the three-words displays. Results indicated that in the literal task, when cognitive load was low, parafoveal distractor words semantically-related to the target triggered faster attentional responses as reflected in increased P2a amplitude, while increasing foveal load delayed parafoveal semantic processing, as shown by N3 and N400 modulations. In contrast, the categorical task, characterized by higher task-related cognitive demands, showed limited evidence of parafoveal semantic processing. Rather, word processing seemed to be focused on deeper processing of central words, as evidenced by N400 variations. Altogether, this work contributes to understanding the interplay between semantic and attentional mechanisms in visual search, highlighting the influence of cognitive resources on visual word processing. Moreover, the findings suggest that covert and overt attention may follow distinct temporal dynamics in parafoveal semantic processing, underscoring the importance of considering task demands and spatial factors when comparing visual search and reading.