Subjective expectancy and inhibition of return: A dissociation in a non-spatial two-alternative forced choice task

Inhibition of Return (IOR) is conventionally defined by slow responses to targets that appear at the same location as a prior attentional cue, relative to a condition in which targets appear at a different location from a prior attentional cue (Posner & Cohen, 1984). A number of recent studies have extended the study of IOR to non-spatial orienting tasks (Law, Pratt, & Abrams, 1995; Hu, Samuel, & Chan, 2011; Spadaro, He, & Milliken, 2012), which is consistent with the view that a fundamental process that favours the perceptual encoding of new events is responsible for IOR. However, an alternative account of IOR is that participants expect uncued targets to appear more often than cued targets even when these two target types are equiprobable. The aim of the current study was to examine directly the relation between performance and subjective expectancy in a task known to produce repetition benefits under one set of conditions, and IOR-like effects under another set of conditions. The performance measure (i.e. RTs) showed either repetition benefits or IOR-like effects depending on whether or not an intervening event was introduced. Interestingly, participants reported that they expected uncued targets more often than cued targets across both conditions, a result that is inconsistent with the view that repetition effects generally, and IOR-like effects specifically, are directly related to subjective expectancy.