Detection of the traversability of surfaces by crawling and walking infants.

In four studies we investigated the perception of the affordance for traversal of a supporting surface. The surface presented was either rigid or deformable, and this property was specified either optically, haptically, or both. In Experiment 1A, crawling and walking infants were presented with two surfaces in succession: a standard surface that both looked and felt rigid and a deforming surface that both looked and felt nonrigid. Latency to initiate locomotion, duration of visual and haptic exploration, and displacement activity were coded from videotapes. Compared with the standard, the deforming surface elicited longer latency, more exploratory behavior, and more displacement in walkers, but not in crawlers, suggesting that typical mode of locomotion influences perceived traversability. These findings were replicated in Experiment 1B, in which the infant was presented with a dual walkway, forcing a choice between the two surfaces. Experiments 2, 3A and B, and 4A and B investigated the use of optical and haptic information in detecting traversability of rigid and nonrigid surfaces. Patterns of exploration varied with the information presented and differed for crawlers and walkers in the case of a deformable surface, as an affordance theory would predict.