Abstract:
In four experiments using a feature singleton search, the present manuscript tests whether hand proximity results in differential processing of a magnocellular feature such as motion and a parvocellular feature such as color. Importantly, the study manipulates the relevance or irrelevance of the feature singletons. When the feature was task-irrelevant, relatively shallower search slope was obtained for motion feature near the hand compared to a ‘Far’ and a baseline ‘No-hand’ condition. The search slope of color singleton appearing far from the hand was found relatively steeper than other conditions. However, when the feature singleton was made task-relevant, no such hand-specific changes in processing were found; indicated by an overall shallower search slope for singleton targets compared to the non-singleton targets. The results highlight how proximity of the hands to specific features interacts with the task requirements. When task involves tuning out distractor features that are dependent on the magnocellular stream for processing, the presence of the hand makes it difficult to accomplish. On the other hand, when the feature is dependent on the parvocellular stream, the tuning out is so successful in the periphery that it is almost inhibited. Also, the finding highlights that featural difference in itself is not sufficient for hand-related effects to occur; the relative distance of the hand from the feature singleton seemed critical for the feature specificity of the effect to be observed clearly. Overall, the results suggest that the attentional effect of hand-proximity may be driven by attentional selectivity involving active distractor rejection.
