Speech Perception

Speech perception studies how listeners recover discrete linguistic units from the continuous, variable acoustic signal of speech.

Definition

The study of the perceptual and cognitive processes by which listeners convert the acoustic speech signal into linguistic categories.

Scope

This topic examines how the auditory and cognitive systems map the speech signal onto phonemes, syllables, and words despite variability across speakers, rates, and contexts. It covers categorical perception, in which continuous acoustic differences are perceived as discrete categories; the role of context and top-down knowledge; audiovisual integration, illustrated by the McGurk effect; and competing accounts of the perceptual process, including the motor theory and auditory and general-cognition alternatives. The treatment is descriptive, surveying findings and theoretical positions.

Core questions

• How do listeners perceive discrete categories from a continuous signal?
• What is categorical perception and where does it occur?
• How do context and visual information influence perception?
• What theories explain how the speech signal is decoded?

Key theories

Motor theory of speech perception

Liberman and colleagues' proposal that listeners perceive speech by recovering the intended articulatory gestures of the speaker, advanced to explain the lack of simple invariance between acoustic cues and perceived phonemes.

Audiovisual integration

The finding, exemplified by the McGurk effect, that visual information about articulation is automatically integrated with the auditory signal, showing that speech perception is multimodal.

History

Modern speech-perception research began at Haskins Laboratories in the 1950s and 1960s, where synthesis experiments revealed categorical perception and the difficulty of finding invariant cues. The motor theory was a leading early account; the 1976 McGurk demonstration established the multimodal nature of perception, and later work proposed auditory and exemplar-based alternatives.

Debates

Motor versus auditory accounts of perception

A long-running debate concerns whether speech perception is mediated by reference to articulatory gestures, as the motor theory holds, or can be explained by general auditory and learning mechanisms.

Key figures

• Alvin Liberman
• Michael Studdert-Kennedy
• Harry McGurk
• Keith Johnson

Seminal works

• liberman1967
• mcgurk1976

Frequently asked questions

What is categorical perception?

Categorical perception is the tendency to hear a continuum of acoustic stimuli as belonging to a small number of discrete categories, with sharp boundaries, so that within-category differences are hard to detect while across-category differences are easy.

What is the McGurk effect?

The McGurk effect is an illusion in which seeing a speaker's lip movements for one sound while hearing a different sound causes listeners to perceive a third sound, demonstrating that vision influences speech perception.