is perceived, the McGurk phenomenon is exactly what one would expect (Liberman, 1996). It can be concluded that the movement of a speaker’s face and lips can have a strong influence on perception of speech stimuli. Audiovisual integration also occurs for non-speech sounds. For example, sound localization often is influenced by vision (Moore, 1997).Models of Speech PerceptionThere are many models of speech perception. There is not one specific model that is generally accepted. Three influential models being discussed are the motor theory, the cued based approach, and the TRACE model. Motor TheoryIn the motor theory the objects of speech perception are the intended phonetic gestures of the speaker. According to Liberman (1996), “they are represented in the brain as motor commands that call for movements of the articulators through certain linguistically significant configurations.” The listener perceives the articulatory gesture the speaker is intending to make when producing the word or utterance. In the motor theory, speech perception and speech production are closely linked and innately specified. This model accounts for many speech perception characteristics. However, the model does not specify how the translation from the signal to the perceived gesture is accomplished, thus making the model incomplete (Liberman, 1996). The motor theory is in two ways motor. First, it is considered motor because it takes the proper object of phonetic perception to be a motor event. Secondly, it assumes that adaptations of the motor system for controlling the organs of the vocal tract took precedence in the evolution of speech (Liberman and Mattingly, 1985).Cue Based ApproachIn the cue based approach there is a sequence of steps of processing. The speech signal undergoes analysis in the peripheral auditory system. The next step is acoustic property detectors. This includes onset detectors, spectral change detectors, ...
