Inhibition of Return

Characteristics of the IOR Effect

Several characteristics of the IOR effect have been recognized by using variants of the standard cue-target paradigm. When the task involves either target detection or target localization, the IOR effect is observable at cue-target time intervals of around 300 milliseconds. When the task involves target identification, IOR appears at longer cue-target intervals of 500 milliseconds or longer. The IOR effect is relatively long lasting, and only begins to diminish when the cue-target interval is approximately 3 seconds or longer. It has been established that IOR can be environmentally coded, such that the IOR is observed [Page 411]at the environmental location where a cue was presented rather than at the location stimulated on the retina. The IOR effect also appears to operate on both moving and stationary objects and can co-occur at up to five locations when multiple cues are presented sequentially.

Whereas the IOR effect is typically observed using peripheral cues and targets while having participants fixate a central cross, IOR is also observed when eye movements are involved. For example, when participants are required to move their eyes to the cue and then return them back to the center before the target appears, both manual responses and eye movements to a target are slower if the target is presented at the previously inspected location. IOR is also measured for consecutive responses in a so-called target-target paradigm. When participants have to respond to successive targets presented in the periphery, their response times are slower to detect targets presented at the same location than the previous one. The IOR effect can be cross-modal—people are slower to respond to a target at a previously cued location, even when the cues and targets are presented in different sensory modalities.

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