The Mechanisms of Complex Visual Search: Inhibition of Return Modulates Perceptual Processing at Multiple Cued Locations

If attention is brought to a location by a cue and then leaves this location prior to the presentation of a target, performance is impaired when the target appears at the cued location relative to when it is presented at the uncued location. This phenomenon is called Inhibition of Return (IOR) and can be found at successively cued multiple locations. Although the mechanisms of IOR remain unresolved, both motor and perceptual influences have been proposed. However, there are two major limitations of the previous research investigating the mechanisms of IOR. The first has been the use of RT measures to measure changes in perceptual processing. RT measures are problematic because a reduced RT could reflect inhibition of a variety of mechanisms. The second limitation has been in the use conventional cueing paradigms, that only require a limited number of attentional shifts, which are unlikely to reflect real-life visual search. To address these limitations, the current study used a novel approach to investigate the effects of IOR on perception using a signal detection measure of perceptual sensitivity, d prime (d'). In addition, a multiple location cueing paradigm was also employed, where four out of eight possible locations were cued successively before the target appeared. Results found that IOR was associated with a significant reduction in d 'at the one-back, two-back and three-back cued locations compared with uncued locations. Consistent with the weakening of IOR over time, there was no significant difference in d' between four-back and uncued locations. Further, these effects of IOR on perceptual sensitivity were independent of whether emphasis was placed on the speed of responding. These results demonstrated a clear relationship between inhibition and perceptual processing suggesting that IOR directly affects perceptual processing.