The gap effect reduces both manual and saccadic inhibition of return (IOR)

Abstract

Inhibition of return (IOR) is the effect of slower responses to validly than invalidly cued targets. The discovery of IOR raised controversy as to whether it has two “flavors”, i.e., attentional/perceptual and motoric, or whether it is a homogeneous visual-motor phenomenon that should be understood in terms of the preparation of different effectors (mainly eye movement). Since manipulation of fixation offset (0 and 200 ms gap) is believed to affect the latency of saccades, we measured its influence on saccadic and manual IOR with a simple keypress response when eye movements were forbidden. In the two experiments which we carried out, the fixation offset decreased IOR in both the saccadic and the manual conditions. The results suggest the limitations of the attentional hypothesis, which assumes that manual IOR is independent of the motoric component; they are also in line with the tenets of the oculomotor hypothesis of IOR.

Inhibition of return: An information processing theory of its natures and significance

“…Hunt and Kingstone (2003) asked their participants to make manual or saccadic localization responses to targets in alternate blocks while orthogonally manipulating target luminance and whether or not the fixation stimulus was removed at the time of the target. Their experiment revealed a double-dissociation: when saccadic responses were required IOR interacted with fixation removal but not with luminance, and when manual responses were required IOR interacted with luminance but not with fixation removal (but see, Michalczyk & Bielas, 2019).…”