Perceptual and Motor IOR: Components or Flavours?

Abstract

The most common evidence for inhibition of return (IOR) is the robust finding of increased response times to targets that appear at previously cued locations following a cue-target interval exceeding ~ 300 ms. In a variation on this paradigm, Abrams and Dobkin (1994a) observed that IOR was greater when a saccadic response was made to a peripheral than to a central arrow, leading to the conclusion that saccadic responses to peripheral targets comprise motoric and perceptual components (the two components theory for IOR) whereas saccadic responses to a central target comprise a single motoric component. In contrast to the foregoing findings, Taylor and Klein (2000) discovered that IOR for saccadic responses was equivalent for randomly intermixed central and peripheral targets, suggesting a single motoric flavor under these conditions. To resolve the apparent discrepancy, a strict replication of Abrams and Dobkin was conducted in which central and peripheral targets were either blocked or mixed. In the blocked design, peripheral targets resulted in more IOR than central targets, while in the mixed design, replicating Taylor and Klein (2000), target type had no bearing on the magnitude of IOR (i.e., equivalent IOR was obtained for both target types). This pattern of results suggests that the confound inherent in Abrams and Dobkin's blocked design generated a pattern of results that "masqueraded" as two components of IOR.