Crossmodal identification Gemma

senses, each tuned to a distinct form of energy and providing a unique window through which to experience the environment. The possession of multiple sensory systems provides considerable behavioural flexibility since input from one modality can substitute for another under circumstances of specific sensory deprivation. In darkness, for example, auditory and tactile cues might supplant visual information. Such polysensory capability also permits the integration of different sensory streams. Combining sensory inputs is clearly advantageous since it supplies information about the environment that is unavailable from any single modality, influencing the perception of events in the surroundings and our subsequent responses. The many behavioural consequences of multimodal integration have been investigated extensively with respect to orienting and attentive behaviours, primarily concerned with the determination of stimulus location (for reviews, see Stein and Meredith1; Driver and Spence2, this issue). In addition to facilitating the detection of, and orientation to, stimuli in the environment3,4, the integration of different sensory cues has also been shown to influence localization judgements. Specifically, when two or more sensory events are in close temporal proximity, albeit in slightly distinct spatial locations, they are generally perceived as emanating from a common source5–7. Typically, the modality with the best spatial resolution (e.g. vision’s superiority over audition) has the greatest influence on the location of the fused percept. Such crossmodal influences on localization are perhaps best typified by the ventriloquist’s illusion. The ventriloquist speaks without moving his lips but it is his puppet that seems to be talking.