Eye-centered Inhibition Of Return In Cueing And Visual Search Tasks

Inhibition of return (IOR) refers to a performance cost associated with previously attended locations. It has been suggested that this inhibitory attention mechanism evolved to maximize visual sampling (Posner & Cohen,1984), and it can facilitate visual search by decreasing the probability of attention returning to previously inspected locations (Klein & MacInnes,1999). The reference frame of IOR is one of the hotly debated theoretical questions in the field. Previous studies have shown that IOR can be coded in both retinotopic and spatiotopic coordinates, but one overlooked methodological confound of all previous studies is that the spatial gradient of IOR is not considered when selecting the baseline for estimating IOR effects. This methodological issue makes it difficult to tell whether the retinotopic IOR effects reported in previous studies were real. In addition, unattended locations will be inhibited by retinotopic IOR after each saccade in visual search task, but no studies have been investigated on this issue. To expel this doubt, in experiment 1 and 2, we address this issue with the incorporation of no-cue trials to a modified cueing paradigm in which the cue and target are always intervened by a gaze-shift. The results revealed that IOR is indeed coded in both spatiotopic and retinotopic coordinates. Experiment 3 for first time probed spatiotopic and retinotopic IOR in visual search. Spatiotopic IOR was observed while retinotopic IOR was not. Instead a facilitation of return effect that appeared to correspond to the retinal locus of previously fixated location was observed. To explore the potential sources of this facilitation effect, Experiment 4 eliminated spatiotopic IOR effect with a free viewing task. Again, we observed a facilitation effect at the retinal locus of previous fixed location. We concluded that there may be another new, facilitatory mechanism that collaborates with IOR to facilitate visual search.