Placeholders dissociate two forms of inhibition of return

Decades of research using Posner's classic spatial cueing paradigm has uncovered at least two forms of inhibition of return (IOR) in the aftermath of an exogenous, peripheral orienting cue. One prominent dissociation concerns the role of covert and overt orienting in generating IOR effects that relate to perception- and action-oriented processes, respectively. Another prominent dissociation concerns the role of covert and overt orienting in generating IOR effects that depend on object- and space-based representation, respectively. Our objective was to evaluate whether these dichotomies are functionally equivalent by manipulating placeholder object presence in the cueing paradigm. By discouraging eye movements throughout, Experiments 1A and 1B validated a perception-oriented form of IOR that depended critically on placeholders. Experiment 2A demonstrated that IOR was robust without placeholders when eye movements went to the cue and back to fixation before the manual response target. In Experiment 2B, we replicated Experiment 2A's procedures except we discouraged eye movements. IOR was observed, albeit only weakly and significantly diminished relative to when eye movements were involved. We conclude that action-oriented IOR is robust against placeholders but that the magnitude of perception-oriented IOR is critically sensitive to placeholder presence when unwanted oculomotor activity can be ruled out.