Inhibition of return at multiple locations and its impact on visual search

Previous research has shown that when attention is directed sequentially to multiple locations, inhibition of return (IOR) can be observed at each location, with a larger magnitude of IOR at the more recently attended locations. In the present study we asked whether this “multiple IOR” effect influences search only for simple feature targets, as has been shown in the past, or whether it generalizes to more complex, attentionally demanding conjunction search situations. The results demonstrated that IOR effects (1) occur for more complex conjunction search environments, (2) are larger for the attentionally demanding conjunction search, and (3) occur at more locations for conjunction search than feature search. Together these data provide a clear demonstration of the robustness and responsiveness of the IOR effect across search situations—which is precisely what is expected of a phenomenon posited to facilitate efficient visual search of real-world environments. Nevertheless, these data do not firmly establish that IOR effects established by the cueing paradigm before search is implemented are the same as the IOR effects that are assumed to be established during search itself. We suggest that this disconnection between paradigms highlights a fundamental limitation of laboratory-based research.