The relationship of speech perception and speech production: It's complicated.

A widely held belief is that speech perception and speech production are tightly linked, with each modality available to help with learning in the other modality. This positive relationship is often summarized as perception and production being "two sides of the same coin." There are, indeed, many situations that have shown this mutually supportive relationship. However, there is a growing body of research showing very different results, with the modalities operating independently, or even in opposition to each other. We review the now-sizeable literature demonstrating the negative effect that speech production can have on perceptual learning of speech, at multiple levels (particularly at the lexical and sublexical levels). By comparing the situations that show this pattern with ones in which more positive interactions occur, we provide an initial account of why the different outcomes are found, identifying factors that lead to either positive or negative effects of production on perception. The review clarifies the complex relationship that exists between the two modalities: They are indeed linked, but their relationship is more complicated than is suggested by the notion that they are two sides of the same coin.