Spatial biases in inhibition of return

Inhibition of return (IOR) describes the phenomenon that reaction times (RT) to a target which appears at a previously cued location are slowed down. Spalek and Hammad ([2004]. Supporting the attentional momentum view of IOR: Is attention biased to go right? Perception & Psychophysics, 66(2), 219-233. ) reported that IOR effects were smaller at a lower or right location, compared to an upper or left location. In contrast, Snyder and Schmidt ([2014]. No evidence for directional biases in inhibition of return. Psychonomic Bulletin & Review, 21(2), 432-435. ) argued that IOR is unaffected by spatial biases and that any observed differences are better explained by general reaction time differences depending on the target's location. In two experiments (both N = 31), we aimed to test both diverging predictions by presenting cue and target at four locations along the vertical and horizontal axis. Controlling for a main effect of RTs at different target locations, we still observed a spatial bias on IOR, in that the effect was smaller at the lower than the upper target location. We also found a comparable spatial bias on the IOR-related phenomenon of early facilitation (EF). The results suggest that the magnitude and occurrence of both IOR and EF are affected by spatial configurations. Similarities with spatial biases on other visual phenomena as well as theoretical implications are discussed.