Perceptual load modifies processing of unattended stimuli both in the presence and absence of attended stimuli

This study explored effects of perceptual load on stimulus processing in the presence and absence of an attended stimulus. Participants were presented with a bilateral or unilateral display and asked to perform a discrimination task at either low or high perceptual load. Electrophysiological responses to stimuli were then compared at the P100 and N100. As in previous studies, perceptual load modified processing of attended and unattended stimuli seen at occipital scalp sites. Moreover, perceptual load modulated attention effects when the attended stimulus was presented at high perceptual load for unilateral displays. However, this was not true when the attended and unattended stimulus appeared simultaneously in bilateral displays. Instead, only a main effect of perceptual load was found. Reductions in processing contralateral to the unattended stimulus at the N100 provide support for Lavie's (1995) theory of selective attention.

Research highlights▶ Perceptual load modified processing of stimuli for both unilateral and bilateral displays. ▶ Perceptual load modulated attention effects for unilateral displays (i.e., in the absence of an attended stimulus). ▶ Perceptual load did not modulate attention effects for bilateral displays (i.e., in the presence of an attended stimulus). ▶ Findings support Lavie's (1995) model of selective attention.