Intramodal and cross-modal discrimination of curvature: Haptic touch versus vision.

A total of 60 subjects, 20 in each experimental condition, gave 'same-different' judgments to pairs of stimuli differing in radius of curvature. Stimuli were presented intramodally to vision, intramodally to haptic touch, and cross-modally to vision and haptic touch. Results showed that performance, quantified by the measure d', differed among the three modality conditions, being best in vision and poorest in haptics, with cross-modal performance falling roughly mid-way between. Unimodal visual performance exceeded cross-modal performance by about one d' unit, and cross-modal performance similarly exceeded unimodal haptic performance by about one d' unit. The study reveals the relative differences in the discrimination of curvatures of objects in vision and haptics.