What is the relationship between speech perception and production in bilinguals?

Sensorimotor and motor theories differ as to whether speech sounds are perceived as sounds or gestures, while bilinguals can show high individual variability in production and perception accuracy in their L2. The results from paired vowel production and categorical perception tasks in 17 Spanish-dominant bilinguals and 9 English monolingual controls show that vowel perception and production measures were significantly correlated when both groups spoke English, but not when bilinguals spoke Spanish. It is argued that this result better supports a sensorimotor framework, where motor information aids auditory processing in a less-differentiated/more vowel-dense language, and where bilinguals in their L1 rely more on auditory processing in this task.