Differential effects of one versus two hands on discriminating temporal gaps.
36.314, Sunday, May 12, 2:45 - 6:45 pm, Royal Ballroom 6-8
William Bush1, Shaun Vecera1; 1Department of Psychology, The University of Iowa
Previous research has indicated that the location of the hands relative to items in the visual field can impact visual perception, particularly when the items are within graspable space. At least two explanations have been proposed for how visual processing is impacted in near hand space. First, that spatial attention is preferentially allocated to locations near the hands (Reed, Grubb, & Steele, 2006). Second, in near hand space there is facilitation of processing in the magnocellular (M) relative to the parvocellular (P) visual pathway (Gozli, West, & Pratt, 2012). A complication in comparing these theories has been differences in the hand manipulations used. Some studies altered the distance between an item and a single hand, while others compared both hands near versus far from the display. The current study addressed these differences by directly comparing single and dual hand manipulations in the same task. A temporal gap task was used requiring discrimination of a brief (10, 20, or 30 ms) offset in laterally presented items. There were four hand conditions; left, right, both, or no hand(s) near the display. Consistent with previous studies, temporal gap discrimination was better when both hands were near compared to far from the display. However, there was no benefit to discrimination for items presented near the hand when only one hand was held near the display. These results suggest that the distribution of visual attention is altered based on the positioning of the hands. Specifically, when both hands are close to the display attention is spread broadly, facilitating temporal gap discrimination. Conversely, a single hand near the display induces a more focused attended region, resulting in reduced temporal discrimination.