The motor theory of speech perception, revised, proposes that speech perception is based on the perception of intended phonetic gestures, represented as invariant motor commands in the brain. These gestures are the physical basis for traditional phonetic categories and are perceived in a specialized 'module' that detects them without translating from preliminary auditory impressions. This module is distinct from the auditory mode and is responsible for phonetic perception, similar to how the auditory system localizes sound. The theory suggests that perception of phonetic structure is automatic and does not require mediation by auditory appearances. The motor theory is distinct from other theories of perception, as it focuses specifically on speech perception and the relationship between perception and production. It is not a general theory of perception but one that applies to speech. The theory is supported by findings that show that acoustic patterns of synthetic speech must be modified to produce invariant phonetic percepts, indicating that the objects of speech perception are not at the acoustic surface but in the underlying motor processes. The theory is based on the idea that speech perception and production share the same set of invariants, and that this link is innate rather than learned. Perception of phonetic gestures occurs in a specialized mode, different from the auditory mode, and is part of the larger specialization for language. The adaptive function of this mode is to automatically convert acoustic signals into gestures, allowing listeners to perceive phonetic structures without mediation by auditory appearances. The theory also addresses the issue of context-conditioned variation in acoustic cues, which is a challenge for auditory theories. The motor theory suggests that these variations are due to the coarticulation of gestures, which influences the acoustic signal. This coarticulation means that the changing shape of the vocal tract, and hence the resulting signal, is influenced by several gestures at the same time. This relationship between gesture and signal is systematic but unique to speech. The motor theory also contrasts with auditory theories, which suggest that speech perception is based on auditory processes alone. The motor theory, however, proposes that speech perception is based on the perception of motor events, and that the relationship between signal and gesture is systematic and special to speech. This theory is supported by experimental evidence showing that phonetic categories can be perceived even when acoustic cues are not present, and that the perception of phonetic structure is based on the systematic relationship between gesture and signal. The motor theory also suggests that speech perception is different from other specialized perceiving systems, such as auditory localization or visual perception of depth. The phonetic module differs from these in that it involves a link between perception and production, and that it must compete with other modules for the same stimulus variations. The theory is supported by findings that show that phonetic categories can be perceived even when acoustic cues are not present, and that the perception of phonetic structure is based on the systematic relationship between gesture and signal.The motor theory of speech perception, revised, proposes that speech perception is based on the perception of intended phonetic gestures, represented as invariant motor commands in the brain. These gestures are the physical basis for traditional phonetic categories and are perceived in a specialized 'module' that detects them without translating from preliminary auditory impressions. This module is distinct from the auditory mode and is responsible for phonetic perception, similar to how the auditory system localizes sound. The theory suggests that perception of phonetic structure is automatic and does not require mediation by auditory appearances. The motor theory is distinct from other theories of perception, as it focuses specifically on speech perception and the relationship between perception and production. It is not a general theory of perception but one that applies to speech. The theory is supported by findings that show that acoustic patterns of synthetic speech must be modified to produce invariant phonetic percepts, indicating that the objects of speech perception are not at the acoustic surface but in the underlying motor processes. The theory is based on the idea that speech perception and production share the same set of invariants, and that this link is innate rather than learned. Perception of phonetic gestures occurs in a specialized mode, different from the auditory mode, and is part of the larger specialization for language. The adaptive function of this mode is to automatically convert acoustic signals into gestures, allowing listeners to perceive phonetic structures without mediation by auditory appearances. The theory also addresses the issue of context-conditioned variation in acoustic cues, which is a challenge for auditory theories. The motor theory suggests that these variations are due to the coarticulation of gestures, which influences the acoustic signal. This coarticulation means that the changing shape of the vocal tract, and hence the resulting signal, is influenced by several gestures at the same time. This relationship between gesture and signal is systematic but unique to speech. The motor theory also contrasts with auditory theories, which suggest that speech perception is based on auditory processes alone. The motor theory, however, proposes that speech perception is based on the perception of motor events, and that the relationship between signal and gesture is systematic and special to speech. This theory is supported by experimental evidence showing that phonetic categories can be perceived even when acoustic cues are not present, and that the perception of phonetic structure is based on the systematic relationship between gesture and signal. The motor theory also suggests that speech perception is different from other specialized perceiving systems, such as auditory localization or visual perception of depth. The phonetic module differs from these in that it involves a link between perception and production, and that it must compete with other modules for the same stimulus variations. The theory is supported by findings that show that phonetic categories can be perceived even when acoustic cues are not present, and that the perception of phonetic structure is based on the systematic relationship between gesture and signal.