Context heterogeneity has a sustained impact on attention deployment: behavioral and electrophysiological evidence

In visual search, similar nearby stimuli can be grouped and thus enhance processing of an embedded target. The aim of the present study was to examine the time course of attention deployment after a brief presentation of stimulus arrays of different heterogeneity. Targets in less heterogeneous, grouped contexts yielded higher accuracy and larger N2pc amplitudes than targets in more heterogeneous, random contexts, indicating more efficient selection in the former. Subsequently presented probes yielded shorter reaction times and a larger posterior positivity when presented at the target location. This advantage was more pronounced after grouped compared to random contexts at the shorter compared to the longer interstimulus interval. The results show that less heterogeneous contexts that allow for grouping not only enhance processing of stimuli within that context, but have a sustained effect on visual attention.