Inhibition of return

Inhibition of return (IOR) refers to an orientation mechanism that briefly enhances (for approximately 100–300 milliseconds (ms)) the speed and accuracy with which an object is detected after the object is attended, but then impairs detection speed and accuracy (for approximately 500–3000 milliseconds).

In order to explain the IOR mechanism, Anne Treisman and Gary Gelade's theory of visual search was expounded.

Because one's attention is shifted to the stimulus without much thought or effort, these cues are seen as a form of reflex that the person has low control over.

Both cues play an equally important role of directing attention in Inhibition of Return, however the way in which they do so differs on a neurological level as well.

Researchers found that top-down signals, coming from endogenous cues, are processed predominately in the frontal cortex and offer longer lasting effects, while exogenous bottom-up cues have faster occurring effects that appear in the lateral intraparietal area.

Support for this suggestion comes from work with a patient who suffered injury to one of the superior colliculi[11] and experiments with the archer fish.

[12] Moreover, IOR is commonly triggered by an exogenous sensory signal presented in the visual periphery when the eyes are fixed.

This conclusion has been questioned by researchers who have found in their studies that endogenous saccade activation is not efficient to produce IOR.

Thus, IOR is a mechanism that allows a person not to re-search in previously searched visual fields as a function of "inhibitory tags".

Pratt and Abrams[15] suggested that IOR was not a foraging assistant because inhibition only occurred at the most recently attended stimulus.