Context homogeneity facilitates both distractor inhibition and target enhancement

Homogeneous contexts were shown to result in prioritized processing of embedded targets compared to heterogeneous contexts (Duncan & Humphreys, 1989). The present experiment used behavioral and ERP measures to examine whether context homogeneity affects both enhancing relevant information and inhibiting irrelevant in contexts of varying homogeneity. Targets and distractors were presented laterally or on the vertical midline which allowed disentangling target- and distractor-related activity in the lateralized ERP (Hickey, diLollo, & McDonald, 2009). In homogeneous contexts, targets elicited an N-T component from 150 ms on and a P-D component from 200 ms on, showing early attention deployment at target locations and active suppression of distractors. In heterogeneous contexts, an NT component was also found from 150 ms on and PD was found from 250 ms on, suggesting delayed suppression of the distractor. Before 250 ms, distractors in heterogeneous contexts elicited a contralateral negativity, indicating attentional capture of the distractor prior to active suppression. In sum the present results suggest that top-down control of attention is more pronounced in homogeneous than in heterogeneous contexts.