A discrepancy between two modes of haptic length perception.

This study investigated the possibility that systematic differences exist between the perceptions resulting from the use of two different heptic modes to know the same object. In each of three experiments 24 male and female college students chose visual comparison stimuli to match the length of haptically presented standard stimuli. In each experiment significantly smaller visual matches were made when the length of the haptic standard was perceived by holding it between the thumb and index finger than when the haptic standard was perceived by stroking it from end to end with the index finger. Experiment 1 established a significant difference (p less than .05) using a horizontal visual comparison. Experiment 2 replicated this effect (p less than .001) using vertical visual comparisons. Experiment 3 again replicated the effect (p less than .001) with visual comparisons and ruled out the possibility that the effect was due to the orientation of the haptic stimuli.