An ERP Investigation into the Influence of Spatial Relevance on Attentional Deployment

Thumbnail Image
O'Donoghue, Ellen
visual cognition , visual search , attention , scene perception
In visual search, top-down task knowledge and bottom-up stimulus salience interact to determine where observers are most likely to attend. Past research has demonstrated that during search tasks, scene regions with a high probability of containing the target (spatially relevant regions) are more likely to be attended than regions with low target-probability (spatially irrelevant regions; Chastain & Cheal, 1997; Pereira & Castelhano, 2018; Travis, Mattingley, & Dux, 2013). Pereira and Castelhano (2018) demonstrated that abrupt-onset distractors are more likely to be fixated when they appear within spatially relevant regions; however, the attentional mechanisms underlying this differential processing are not fully understood. Two hypotheses could explain the attentional mechanisms involved: firstly, information in spatially relevant regions may be enhanced, such that distractors in this area are more likely to capture attention. Secondly, information in spatially irrelevant regions may be inhibited, such that distractors in spatially irrelevant regions are actively suppressed. The present study assessed these two possibilities, which are not mutually exclusive. Here, we aimed to assess three classic ERP components – two associated with attentional capture (the P1 and the N2pc), and one with active suppression (the PD). There were two types of searches: object search, wherein scene context was relevant, and letter search, wherein context was not relevant. We found that overall task engagement was low, as reflected in both ERP data and accuracy scores. As such, we were unable to perform statistical comparisons on our ERP results; however, qualitative analyses suggest that attentional distributions did not vary depending on the spatial relevance of distractor positioning. This is more likely to reflect limitations of our paradigm than the nature of attentional deployment during visual search. We conclude with recommendations for future paradigms that concentrated on strengthening task engagement as well as distractor saliency.
External DOI