(Klatzky, Lederman, & Reed, 1987). Most researchers report that subjects are able to discriminate textures and to a lesser extent shapes using the haptic sense only. For example, Ballesteros, Manga, and Reales (1997) reported a moderate level of accuracy for single-finger haptic detection of raised-line shapes, with asymmetric shapes being more readily discriminated. Hatwell (1995) found that recall of texture information coded haptically was successful when memorization was intentional, but not when it was incidental, indicating that haptic information processing may be effortful for subjects. Hughes and Jansson (1994) lament the inadequacy of embossed maps and other devices intended to communicate information to the visually handicapped through the sense of touch, a puzzling state of affairs insomuch as texture perception by active touch (purposeful motion of the skin surface relative to the surface of some distal object) appears to be comparatively accurate, and even more accurate than vision in apprehending certain properties, such as smoothness (Hughes & Jansson, 302). The authors note in their critical review of the literature on active-passive equivalence that active and passive touch (as when a texture is presented to the surface of the fingers, see Hollins et al., 1993, below) have repeatedly been demonstrated by Lederman and her colleagues (Lederman, 1985; Lederman, Thorne, & Jones, 1986; Loomis & Lederman, 1986) to be functionally equivalent with respect to texture perception, in that touch modality does not seem to account for a significant proportion of the variation in judgments of such basic dimensions as roughness, even though the two types of touch may lead to different sorts of attributions (respectively, about the texture object and about the cutaneous sensing surface) and motor information should clearly be useful in assessing the size and distribution of surface protrusions and retractions. Active-passive touch is ...
