Assessing the frames of references involved in the crossed hands temporal order judgments deficit: The role of response demands
Single Paper Presentation

David I. Shore
Department of Psychology, Neuroscience & Behaviour, McMaster University

Alberto Gallace
Department of Experimental Psychology, University of Oxford

Keely Mimnagh
Department of Psychology, Neuroscience & Behaviour, McMaster University

Charles Spence
Department of Experimental Psychology, University of Oxford

     Abstract ID Number: 186
     Full text: Not available
     Last modified: June 11, 2006
     Presentation date: 06/18/2006 10:30 AM in Hamilton Building, McNeil Theatre
     (View Schedule)

Abstract
Judging the order of two tactile stimuli delivered to the index finger of each hand produces Just Noticeable Differences (JNDs) in the nominal range of 20-40 ms. Placing the hands in a crossed posture drastically degrades performance (JNDs = 100-200 ms). Previous researchers have typically only required a spatial response in environmental coordinates (i.e., a ‘left first’ or ‘right first’ response). Here we examine the impact varying the response demands. When asked to respond to the limb (i.e., hand) stimulated rather than the location of that limb (i.e., on the right side of space), the deficit was significantly reduced, but not eliminated entirely. When asked to use an up-down response that was orthogonal to the left-right direction of hand crossing, the deficit was again reduced significantly. Finally, when making an entirely non-spatial stimulus-intensity discrimination response, no deficit was observed. These results are discussed in terms of processing stages involved in remapping the tactile stimulation from a somatotopic representation (on the body surface) into a more environmental (or body-centred) one.