Abstract
Thirty-two younger adults (mean age was 20.8 years) participated in a solid shape recognition task. In an initial study phase, participants were either visually or haptically familiarized with either 4 (or 6) randomly chosen replicas of naturally-shaped objects (bell peppers, Capsicum annuum). In this familiarization phase, the study objects were presented 4 separate times for 15 seconds each time. Following familiarization, 8 (or 12) bell peppers were presented to either the same or opposite modality. The participants’ task for each object was to indicate whether it was “old” (presented during the familiarization phase) or “new” (not previously presented). For the condition where the participants were familiarized with 6 objects (and tested with 12), the participants’ unimodal visual recognition performance was significantly higher than both unimodal haptic (34.5 percent higher) and cross-modal recognition performance (38.1 percent higher). When the memory demand was reduced (participants only needed to remember 4 study objects), however, performance for unimodal vision and unimodal haptics became much more comparable (87.5 versus 81.3 percent correct, respectively). In this later condition (4 study objects), an asymmetry emerged between haptic-visual and visual-haptic shape recognition, such that visual-haptic performance was superior. The current results demonstrate that visual shape memory capacity is higher than that of haptics. When the number of objects to be remembered does not exceed either modality’s storage capacity, however, human participants’ visual and haptic shape recognition performance is comparable. When recognizing the shape of objects across the sensory modalities of vision and touch, accurate performance only occurs when the objects are familiarized using vision and the resulting object recognition is tested haptically.