Temporal order and tactile patterns

Abstract

Temporal orderjudgments (TOJs) were obtained for tactile stimulipresented to-subjects’ fingerpads. In one set ofmeasurements, pairs of spatial patterns were presented successivelyto a single fingerpad (same-site condition), to two fingers on the same hand-(ipsilateral condition), or to two fingers on opposite hands (bilateral condition). The subjects were instructed to report which one of the two patterns was presented first. TOJs were more accurate in the same-site conditionthan in either the ipsilateral or the bilateral conditions. In the ipsilateral and bilateral conditions, performance improved whenjudging which one oftwo locations received a stimulusfirst, although performance levels were still lower than in the same-site condition. Increasing the size of the pattern set from which the two patterns to be judged were drawn had only a slight effect on samesite performance and no effect on ipsilateral/bilateral performance; however, changing the nature of the patterns had a considerable effect on same-site performance and a smaller effect on ipsilateral/bilateral performance. Introducing an intensity imbalance between members of the pair of stimuli also had a large effect on same-site TOJ5: a less intense stimulus tended to be judged as being presented first. In the bilateral condition, however, therewas a small effect in the reverse direction: more intense stimuli tended to be judged as being presented first. The intensity imbalance had no effect in the ipsilateral condition. The results suggest that different mechanisms are responsible for TOJs for patterns presented to the same-siteand to separate sites and, furthermore, that separate sites may constitute separate channels for spatial information.