Academic journal article Attention, Perception and Psychophysics

Perceptuomotor Compatibility Effects in Speech

Academic journal article Attention, Perception and Psychophysics

Perceptuomotor Compatibility Effects in Speech

Article excerpt

Kerzel and Bekkering (2000) found perceptuomotor compatibility effects between spoken syllables and visible speech gestures and interpreted them as evidence in favor of the distinctive claim of the motor theory of speech perception that the motor system is recruited for perceiving speech. We present three experiments aimed at testing this interpretation. In Experiment 1, we replicated the original findings by Kerzel and Bekkering but with audible syllables. In Experiments 2 and 3, we tested the results of Experiment 1 under more stringent conditions, with different materials and different experimental designs.

In all of our experiments, we found the same result: Perceiving syllables affects uttering syllables. The result is consistent both with the results of a number of other behavioral and neural studies related to speech and with more general findings of perceptuomotor interactions. Taken together, these studies provide evidence in support of the motor theory claim that the motor system is recruited for perceiving speech.

Throughout a number of revisions, the motor theory of speech perception (Liberman, 1957; Liberman, Cooper, Shankweiler, & Studdert-Kennedy, 1967; Liberman & Mattingly, 1985; Liberman & Whalen, 2000) has maintained its distinctive claim that the motor system is recruited for perceiving speech. (For a historical perspective on the development of the theory, see Liberman, 1996, chap. 1.) Although the claim has often been challenged by speech researchers (e.g., Sussman, 1989), in the last 15 years it has gained new credibility, thanks to evidence collected by researchers not traditionally connected to the field of speech (see Galantucci, Fowler, & Turvey, 2006, for a review).

Most notably, the discovery that some neurons in the premotor cortex of a monkey (henceforth, collectively termed the mirror neuron system) are active both when the monkey performs an action (e.g., grasping a piece of food) and when the monkey sees someone else performing that action (di Pellegrino, Fadiga, Fogassi, Gallese, & Rizzolatti, 1992) has boosted the general credibility of motor theories of perception. 1 Moreover, the link between perception and action manifest in the mirror neuron system has been explicitly proposed to be one of the key ingredients for the development of human linguistic abilities (Rizzolatti & Arbib, 1998).

The relevance of such a proposal specifically for the motor theory of speech perception has been recently enhanced by two sets of findings that more closely relate the mirror neuron system to speech.

The first set of findings connects the mirror neuron system to the vocal-auditory channel in two different species. In monkeys, Ferrari, Gallese, Rizzolatti, and Fogassi (2003) demonstrated that the mirror neuron system responds to communicative actions of the mouth (e.g., lip-smacking), whereas Kohler et al. (2002) demonstrated that some neurons in the mirror neuron system are active when the monkey hears the sound characteristic of the action coded by the neuron (e.g., the cracking noise of a peanut shell for the open-a-peanut action). In birds, Prather, Peters, Nowicki, and Mooney (2008) demonstrated that mirror-like neurons in the higher vocal center of swamp sparrows display nearly identical patterns of activity when the bird either hears a birdsong or sings it in the absence of auditory feedback.

The second set of findings connects portions of the human nervous system that are specifically motoric to speech perception. At a cortical level, two fMRI studies indicated that the same motor areas that are active during speech production are active during speech perception (Pulvermüller et al., 2006; Wilson, Saygin, Sereno, & Iacoboni, 2004). At a more peripheral level, two TMS studies demonstrated that the muscles of the tongue (Fadiga, Craighero, Buccino, & Rizzolatti, 2002) and those of the lips (Watkins, Strafella, & Paus, 2003) are active during perception of speech sequences that include lingual and labial phones, respectively. …

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