Attentional guidance from unique faster/slower discrete and smooth feature changes in visual search

Abstract

ABSTRACT Two studies examine the circumstances in which singletons, defined by unique feature-change rate, guide attention in visual search. Participants searched for a static vertical/horizontal white target bar amidst tilted distractors. Bars were contained inside surround shapes with periodically oscillating features. In Experiment 1, displays consisted of surrounds with abrupt (discrete) or continuous (smooth) changes between two values (red–blue, square–diamond). For discrete displays, target surrounds did not guide attention when uniquely faster-oscillating than distractor surrounds, but did in smooth displays. For unique-slow oscillating target surrounds, the opposite guidance pattern was found across discrete and smooth displays. In Experiment 2, displays had a mixture of discrete and smooth surrounds. Here, only unique slow-oscillating discrete surrounds guided attention. No guidance was found for smooth surrounds. Findings suggest that faster oscillations are masked by higher-frequency harmonic signals from slower changing discrete items, and there is attentional prioritization of discrete over smooth changes.