 Third, consider the processes responsible for speech perception. To what extent does perceiving speech implicate processes that are continuous with those of ordinary or general audition, and to what extent does perceiving speech involve separate, distinctive, or modular processes? While some defend general auditory accounts of speech perception (see, e.g, Holt and Lotto 2008), some argue that perceiving speech involves dedicated perceptual resources, or even an encapsulated perceptual system distinct from ordinary non-linguistic audition (see, e.g., Fodor 1983, Pinker 1994, Liberman 1996, Trout 2001b). These arguments typically are grounded in several types of phenomena, including the multimodality of speech perception—visual cues about the movements of the mouth and tongue impact the experience of speech, as demonstrated by the McGurk effect (see the section  4.3 Crossmodal Influences);  duplex perception—a particular stimulus sometimes contributes simultaneously both to the experience of an ordinary sound and to that of a speech sound (Rand 1974); and the top-down influence of linguistic knowledge upon the experience of speech. A reasonable challenge is that each of these characteristics—multimodality, duplex perception, and top-down influence—also is displayed in general audition. 