Cognitive load modulates early visual perceptual processing
33.541, Sunday, 18-May, 8:30 am - 12:30 pm, Pavilion
Virginia Liu1, Jason Forte1, Luca Cocchi2, David Sewell1, Olivia Carter1; 1Melbourne School of Psychological Sciences, University of Melbourne, 2Queensland Brain Institute, University of Queensland
In the current dual-task literature, it seems accepted that cognitive load does not affect early perceptual processing but this issue has not been systematically evaluated. Recent studies show that when observers held information in working memory, performance on an unrelated visual perceptual task (i.e., grouping-by-proximity) was improved (increased accuracy and reduced reaction time)(Cocchi et al, 2011). Thus, cognitive control mechanisms supporting working memory may modulate concurrent but independent visual perceptual processing. Four experiments were conducted to further explore the nature of cognitive load modulation on early visual processing. In experiment 1, a contrast detection task was employed to explore whether contrast sensitivity varies under different cognitive loads. Participants judged the orientation of a small Gabor of various contrasts located in parafovea. In experiment 2 to 4, three tasks that are thought to elicit surround-suppression i.e., a motion discrimination task (Tadin et al., 2003), the Chubb illusion and a contrast detection task under surround suppression in periphery (Petrov & Mackee, 2006) were employed to investigate whether cognitive load modulates surround suppression. In all experiments, the perceptual tasks were performed during a concurrent no-, low- and high-working memory load task. Results of experiment 1 show that under high cognitive load, there is a rightward shift of the psychometric function suggesting cognitive load influences early visual processing. No effects of cognitive load on surround inhibition were found in experiments 2 to 4. According to the contrast-normalization model, the balance between excitation and suppression determines contrast response. The results of this study suggest that under high cognitive load excitatory drive is diminished whereas surround suppression remains unchanged. Taken together, cognitive load effects do penetrate to the early visual perceptual processing stage, however, these effects appear limited to excitatory responses.