Diminished distractor exclusion for magnocellular features near the hand.

Abstract

The modulated visual pathway (MVP) hypothesis attempts to explain a range of differences observed in the processing of objects in the proximal as compared to the distal region of the hand. However, there has been no account of how 'hand proximity' interacts with task relevance within the MVP framework. In the present study, we used a visual search task to test whether the task relevance of a unique feature (motion in Expt. 1, and color in Expt. 2) influences its processing with respect to the hand. The feature was either relevant (Expt. 1a and 2a) or irrelevant (Expt. 1b and 2b) to the search task. The hand proximity effect was observed only in the experiments in which the unique feature was task irrelevant. However, the effect of hand proximity was overridden when the unique feature was predictive of the target location. We propose that it is difficult to accomplish active distractor rejection of magnocellular features near the hand. Similarly, there is improved active distractor rejection of parvocellular features in the distal region of the hand. Overall, the results suggest that processes involving active distractor rejection may drive the attentional effect of hand proximity.