Babies are born ready to absorb the sounds and grammar and intonation of any language, but then the brain wires itself up to only perceive and produce a specific language.
Part of the motivation for their motor theory of speech perception, against auditory theories, is to integrate explanations of speech perception and speech production (1985, 23-5, 30-1, see also Matthen 2005, ch 9, which uses the Motor Theory to support a Codependency Thesis linking the capacities to perceive and produce phonemes, 221).
Alternatively, such speech selectivity might emerge through extensive experience in perceiving and producing speech sounds.
A related conceptual question would be: What is the brain basis of negative emotions and of perceiving and producing emotional speech?
If so, with experience, are children able to perceive and produce, in a native-like way, phonemic contrasts that do not exist in their L1?
The authors suggest that the children's continued high use of their L1 influenced their ability to perceive and produce the German vowels.
The response of these regions to music in violinists suggests that the emergence of response selectivity may depend on long-term experience in perceiving and producing a given class of sounds.
The sensitivity of nonword repetition to SLI could be because it places heavier demands on processing of speech sounds than other memory tests as a result of the child's having to perceive and produce an unfamiliar sequence.
These children may have had difficulties with the English voicing contrast because they were assimilating the L2 English categories into their pre-established L1 categories and were using these categories to perceive and produce English plosives (see, e.g., Best & Tyler, 2007; Flege, 1995).
