Multimodal Interactions: Visual-Haptic

Dominance

Traditionally, philosophers believed that touch dominated over, and even educated, vision. However, over the last 75 years or so, psychologists have conducted many studies showing that vision frequently dominates over touch. For example, J. J. Gibson reported that when people ran their fingers up and down a straight rod, they [Page 598]perceived it as being curved if they simultaneously looked through lenses that made the rod look curved. As soon as the participants closed their eyes, however, the rod felt straight again. Similar results were reported by Irvin Rock and his colleagues in a now-classic series of experiments in which participants rated their impression of the size of a small object that they could either see (through a distorting lens) or feel, or both see and feel at the same time. This kind of visual dominance over the perceived size and shape of the haptically explored objects is so strong (and automatic) that it cannot easily be overridden by instruction. In fact, Irvin Rock and Charles Harris went so far as to state that vision completely dominates touch and even shapes it.

Taken together, these and many other published results subsequently showed that vision typically dominates over the haptic perception of both the substance and structural properties of objects when the senses are put into some kind of intersensory conflict. Researchers have also demonstrated that visual dominance effects tend to be more pronounced when the stimuli presented in the two modalities originate (or at least are perceived to originate) from the same spatial location at more or less the same time. For example, Sergei Gepshtein and colleagues showed in 2005 that visual and haptic cues were combined more effectively when they originated from the same spatial location (rather than from different locations), whereas other researchers have shown that people can still integrate visual and haptic information in a near-optimal manner when they come from different locations, just as long as participants believe that what they are seeing and feeling refers to the same object (as when one looks in a mirror in one location in order to see an object that is being haptically explored at a different location). Epp Miller also reported in 1972 that an observer's beliefs concerning whether visual and haptic sensory impressions belonged together, a phenomenon known as the unity assumption, also modulate the extent to which the visual cues influence haptic form perception.

...