The effect of motion on tactile and visual temporal order judgments.

Four experiments were conducted, three with tactile stimuli and one with visual stimuli, in which subjects made temporal order judgments (TOJs). The tactile stimuli were patterns that moved laterally across the fingerpads. The subject's task was to judge which finger received the pattern first. Even though the movement was irrelevant to the task, the subjects' TOJs were greatly affected by the direction of movement of the patterns. Accuracy in judging temporal order was enhanced when the patterns moved in a direction that was consistent with the temporal order of presentation--for example, when the movement on each fingerpad was from right to left and the temporally leading site of stimulation was to the right of the temporally trailing site of stimulation. When movement was inconsistent with the temporal order of presentation, accuracy was considerably reduced, often well below chance. The bias in TOJs was unaffected by training or by presenting the stimuli to fingers on opposite hands. In a fourth experiment, subjects judged the temporal order of visual stimuli that, like the tactile stimuli, moved in a direction that was either consistent or inconsistent with the TOJ. The results were similar to those obtained with tactile stimuli. It is suggested that the bias may be affected by attentional mechanisms and by apparent motion generated between the two sites on the skin.