Karin H James, Shilpi P Roy, Isabel Gauthier; Visual perception is affected by motor experience: Evidence from letter recognition. Journal of Vision 2003;3(9):812. doi: 10.1167/3.9.812.
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Motor sequences acquired through writing may be associated with letter representations, resulting in the possibility that motor sequences are invoked when we perceive a letter. Using an interference paradigm we investigated the extent that motor and visual systems interact during letter identification. Individuals identified letters presented in noise while simultaneously writing letters or shapes. Written stimuli were either visually similar to the viewed letter (high interference (HI) conditions) or visually dissimilar to the viewed letter (low interference (LI) conditions). If seeing a letter invokes a motor program associated with writing that specific letter, then in the HI condition, letter identification would suffer relative to the LI condition. Furthermore, if the motor sequences are letter specific, then less interference, leading to better identification, should result from drawing shapes while identifying letters than from writing letters. Results supported our hypotheses-writing letters interfered with letter perception more than drawing shapes. In addition, more interference resulted when the written letters were more similar to the viewed letters, than when the letters were dissimilar to the viewed letters. These data suggest that the motor systems involved in writing letters interact with processes involved in perceiving letters and that this interaction is shape specific. The idea that stored motor programs of writing interact with letter perception suggests that areas of the brain associated with motor sequencing may be active whenever we perceive a letter. We present fMRI results that suggest that, indeed, supplementary motor areas are active when we perceive letters more than when we perceive shapes. Taken together, these studies support the idea that stored information acquired through other sensory-motor systems can have an effect on visual perception.