Recognising familiar objects by hand and foot: haptic shape perception generalises to inputs from unusual locations and untrained body parts.
The limits of generalisation of our 3D shape recognition system to identify objects by touch was investigated by testing exploration at unusual locations and using untrained effectors. In Experiments 1 and 2 people found identification by hand of real objects, plastic 3D models of objects and raised line drawings placed in front of themselves no easier than when exploration was behind their back. Experiment 3 compared one handed, two handed, one footed and two footed haptic object recognition of familiar objects. Recognition by foot was slower (7s versus 13s) and much less accurate (9% versus 47% errors) than recognition by either one or both hands. Nevertheless, item difficulty was similar across hand and foot exploration and there was a strong correlation between an individual's hand and foot performance. Furthermore, foot recognition was better with the largest 20 of the 80 items (32% errors) suggesting that physical limitations hampered exploration by foot. Thus object recognition by hand generalised efficiently across the spatial location of stimuli whilst object recognition by foot seemed surprisingly good given that no prior training was provided. Active touch (haptics) thus efficiently extracts 3D shape information and accesses stored representations of familiar objects from novel modes of input.
Attention, Perception and Psychophysics (2014), 76, 541-558.