Abstract
In all previous studies of perceptual load, high load was shown to modulate the processing of irrelevant stimuli that were always presented concurrently with the target. Here we report results from a new paradigm used to test the effect of perceptual load on detection of peripheral stimuli that were never presented concurrently with targets. Subjects performed either a feature search (monitoring for red crosses among other colors, low load) or a conjunction search (monitoring for upright yellow or inverted green crosses, high load), on a rapid succession of crosses presented at fixation. Results showed that detection sensitivity to peripheral stimuli presented during intervals between targets was reduced under high (compared with low) perceptual load. These results suggest that the mechanism for perceptual modulation by load involves baseline shifts in levels of spatial attention, which may be related to baseline shifts of neural activity in visual cortex (Kastner et al, Neuron 1999).
This research was supported by a Wellcome Trust grant to GR.