Haptic form perception: Relative salience of local and global features

Abstract

When we examine objects haptically, do we weight their local and global features as we do visually, or do we place relatively greater emphasis on local shape? In Experiment 1, subjects made either haptic or visual comparisons of pairs of geometric objects (from a set of 16) differing in local and global shape. Relative to other objects, those with comparable global shape but different local features were judged less similar by touch than by vision. Separate groups of subjects explored the same objects while wearing either thick gloves (to discourage contour-following) or splinted gloves (to prevent enclosure). Ratings of similarity were comparable in these two conditions, suggesting that neither exploratory procedure was necessary, by itself, for the extraction of either local or global shape. In Experiment 2, haptic exploration time was restricted to 1, 4, 8, or 16 sec. Limiting exploration time affected relative similarity in objects differing in their local but not their global shape. Together, the findings indicate that the haptic system initially weights local features more heavily than global ones, that this differential weighting decreases over time, and that neither contour-following nor enclosure is exclusively associated with the differential emphasis on local versus global features.In recent years, considerable effort in haptic research has been directed toward characterizing spatial processing capabilities. The haptic system combines both cutaneous and kinesthetic information to construct an internal representation of external objects and spatial configurations, using both bottom-up processes that convey topographical input concerning spatial layouts and top-down processes that optimize search procedures directed at specific types of spatial features. Two theoretical perspectives can be discerned in the literature: The first compares haptic with visual spatial processing, seeking perceptual equivalences (or nonequivalences) between touch and vision (e.g., Brown & Brumaghim, 1968;Garbin & Bernstein, 1984); the second highlights the role of non spatial cues (e.g., texture, hardness, temperature) and task-driven exploratory procedures, such as prototypical hand movements, in haptic form perception, assuming the existence of separate processing channels for touch and vision (e.g., Klatzky & Lederman, 1993).Several researchers have reported a strong equivalence between visual and haptic form perception. Brown and Brumaghim (1968) found that haptic and visual ratings of complexity of stimuli drawn from a set of 1,000 2-D

Visual and haptic influence on perception of stimulus size

“…the set of visual standards to one felt with the TDS than they could to one traced out on a monitor. Lakatos and Marks (1999) suggested that this is to be expected. People use touch to build up an impression of an object from sequentially presented information.…”

“…They generally used all fingers to select a likely match, but becursor, traveled around a pathway and, thus, matched the single haptic point of contact. Consequently, the subjects could not assess the global features of a visible square as they normally would (Lakatos & Marks, 1999;Rosch, Mervis, Grey, Johnson, & Boyes-Braem, 1976). This unusual method of presentation may have posed particular difficulty for vision, resulting in the decreased level of accuracy when this modality was used (see Loomis et al, 1991, for a similar argument).…”

Haptic perception: A tutorial

“…When haptically evaluating the relative similarity of pairs of geometric objects fairly alike in their global shape, observers initially focus more on local shape features than on global structure; with continued manual exploration, however, observers focus more on the global shape at the expense of the local features. No such switch in focus occurs for objects dissimilar in their global shapes and without notable local features (Lakatos & Marks, 1999, as depicted in Figure 8; see also Berger & Hatwell, 1993).…”

Local and global auditory processing: Behavioral and ERP evidence

“…For example, the games 'Go' and 'Chess' have been hypothesized to differentially employ local and global strategies (Chen et al, 2003). Studies of haptic processing have revealed that global shape information affects object identification at an earlier age than local features (Morrongiello, Humphrey, Timney, Choi, & Rocca, 1994), that young infants process more global information for objects explored with their left hands and more local information for explorations made with their right hands (Streri, 2002), and that the relative importance of local and global processing changes over time during object manipulation (Lakatos & Marks, 1999). However, audition has been considered to be the test-case for whether or not the local and global processing distinction applies directly to modalities other than vision (Dowling, 1978;Horváth, Czigler, Sussman, & Winkler, 2001;Justus & List, 2005;Lassonde et al, 1999;Peretz, 1990;Schiavetto, Cortese, & Alain, 1999).…”