Strategic modulation of Inhibition of Return in detection and identification tasks

Subjects are faster at detecting a visual target when its position is known in advance than when they are misinformed about the targets location (Posner, 1980). These attentional orienting effects can be elicited automatically by a brief peripheral onset cue (exogenous) or voluntarily by a central symbolical cue (endogenous). However, in exogenous cueing, validly cued targets are detected slower than invalidly cued targets when the cue-target interval (CTI) exceeds approximately 250 ms (Posner and Cohen, 1984). This phenomenon is called inhibition of return (IOR). Because IOR does not occur after voluntary attentional shift, we expect IOR also to be susceptible to strategic control. In the present study, we manipulated the temporal target-onset predictability in both detection and identification cueing tasks. When target onset becomes temporally predictable, as with a fixed CTI, strategic control of the attentional shifts may be possible. Preliminary results indicate that IOR does occur in the detection task after fixed CTIs of 375ms and 500ms, but not in the identification task with fixed CTI. Results are explained in terms of different cognitive processes needed to fulfill both types of tasks.