Humans have evolved to live within very complex visual environments and in order to act efficiently, need to guide action in a meaningful and productive way. One intractable result of this need for efficient goal-directed action is the need for selection; be if for a mislaid pen in the office, some ripe fruit at the supermarket, or which road to turn into whilst driving. One method of efficient selection is by withholding or suppressing a response to non-task relevant locations and objects.
Inhibition is such a mechanism and was inferred and demonstrated by a series of elegant experiments by Posner and Cohen (1984). Posner and Cohen showed that when a person had attended to a location in space, which proved to be irrelevant to
task-demands, attention was suppressed or inhibited from returning to that location.
This effect was termed 'inhibition ofreturn' (IOR) and is believed to be a marker for an underlying inhibitory mechanism.