The motor theory of speech perception revised.

A motor theory of speech perception, initially proposed to account for results of early experiments with synthetic speech, is now extensively revised to accommodate recent findings, and to relate the assumptions of the theory to those that might be made about other perceptual modes. According to the revised theory, phonetic information is perceived in a biologically distinct system, a ‘module’ specialized to detect the intended gestures of the speaker that are the basis for phonetic categories. Built into the structure of this module is the unique but lawful relationship between the gestures and the acoustic patterns in which they are variously overlapped. In consequence, the module causes perception of phonetic structure without translation from preliminary auditory impressions. Thus, it is comparable to such other modules as the one that enables an animal to localize sound. Peculiar to the phonetic module are the relation between perception and production it incorporates and the fact that it must compete with other modules for the same stimulus variations. Together with some of our colleagues, we have long been identified with a view of speech perception that is often referred to as a ‘motor theory’. Not the motor theory, to be sure, because there are other theories of perception that, like ours, assign an important role to movement or its sources. But the *The writing of this paper was supported by a grant to Haskins Laboratories (NIH-NICHD HD-01994). We owe a special debt to Harriet Magen for invaluable help with the relevant literature, and to Alice Dadourian for coping with an ever-changing manuscript. For their patient responses to our frequent requests for information and criticism, we thank Franklin Coouer, Jerry Fodor, Carol Fowler, Scott Kelso. Charles Liberman, Robert Remez, Bruno Repp, Arthur Samuel, Michael Studdert-Kennedy, Michael Turvey, and Douglas Whalen. We also acknowledge the insightful comments of an anonymous reviewer. Reprint requests should be sent to: Alvin Liberman, Haskins Laboratories, 270 Crown Street, New Haven,