Abstract

Inhibition of return (IOR) describes a performance decrement for stimuli appearing at recently cued locations. Both attentional and motor processes have been implicated in the IOR effect. The present data reveal a double dissociation between the attentional and motor components of IOR whereby the motor-based component of IOR is present when the response is oculomotor, and the attention-based component of IOR is present when the response is manual. These 2 distinct components should be considered and studied separately, as well as in relation to each other, if a comprehensive theory of IOR is to be achieved. When attention is drawn to a location in space, the detection of targets appearing there is initially facilitated, then impaired, relative to other locations. The latter impairment at the recently attended location was first demonstrated by IOR may increase the efficiency of visual search by preventing attention from being squandered on recently visited locations, biasing it instead toward novel locations, a suggestion that has found empirical support (e.g., Strong evidence that IOR biases attention comes from the observation that IOR can exercise the same attentional influence on target processing as early facilitation. Nevertheless, doubt about IOR being a purely attentional effect arises from several findings demonstrating fundamental differences between the initial facilitation and the subsequent inhibition at the cued location. For instance, IOR is not generated indiscriminately at any location to which attention is allocated.