Is Influence of Substratum's phonology biological? [closed]

Question

As a follow up to a recent question (1) where it is argued that the effect of substrate on the second language is most remarkable in phonology:

Do you know if this has biological reasons in production (bones, muscles, innervation, etc.) and perception (cognition), or what?

I have heard that children's ability to learn phonemes drops off after the first six months, but the causes and implications were left unexplained (Lingthusiasm Episode 12 [2], refering us for the age claim to Non-native phonemes in adult word learning: evidence from the N400m [2]).

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Update, now that I reviewed the source:

Gretchen McMuloch (Lingthusiasm) explains:

So, there are pairs – so in English, for example, English babies retain the ability to hear the difference between “ba ba ba,” “pa pa pa,” but they don’t retain the ability to hear the difference between “ta ta ta” and “ʈa ʈa ʈa” and –

[...] the second ones were produced with my tongue curled back so that the bottom of my tongue was touching the roof of my mouth.

[...] I can produce them because I know where to put my tongue, but I can’t actually hear the difference.

[Transcript]

I have listened to enough English speaking podcasters mentioning comparanda from German to know that Gretchen has with a relatively high degree of probabability not produced those sounds in a manner that would be unmarked to any Nepali speaker. This agrees with the premise of the related question (1), which is after all not in doubt.

It is arguable that the perception is relied on in practice. The language learner practicing a given realization has no way to reinforce their progress in training if they cannot perceive the sound. This does not answer the question to satisfaction, because it denies the purpose of practice. Even if they reach an acceptable stage where most of all minimal pairs could be distinguished, the vast majority of late second-language learners have a ''thick accent'', effectively creating allophones. Some idiolects can be close to incomprehensible, despite a certain degree of fluency.

Infants babble, progressing through a series of phonemes which are typologically common. I know I do when reading the description of a phoneme.

I expect that baby talk develops a representation of the sounds which may be rather abstract, and that the production conditions the cognition as well. It is no coincident that /m/ is among the simpler and most common phonemes (as has been argued for mama).

Answer 1

Discovering that a language has a particular syntactic peculiarity requires that you have a relatively deep knowledge of the language, thus you won’t know about syntactic V2 in a Germanic language unless you can speak the language moderately well. You will not know the word order of Hindi unless you learn some Hindi. You will not know the structure of a Turkish word with one root and 7 suffixes, unless you know Turkish to some degree. But, you can discern “what a language sounds like” with rather superficial exposure. You may be wrong in the specific identification (Mandarin rather than Shanghainese; Lushootseed rather than Kwakwala). Relying on superficial phonetic patterns, you can notice implosives in some Asian languages, and some vowel-quality properties, that allow you to say “He speaks Vietnamese” (or a similar language). Superficial phonetic knowledge is the easiest thing to learn from speech (when you say it that way, it seems rather obvious). This is not to say that in the future, “language contact” might not be predominantly in written form (thanks to the internet), but at least classically, the foundation of language contact is spoken language. Syntactic parsing logically depends on converting the speech stream into segments – phonetic knowledge. This also means that phonetic patterns are easily transmissible, and true phonological patterns (abstract alternations such as the phonology of glides in Arabic verb conjugation) are also difficult to pick up from superficial exposure.

Answer 2

Supposedly, children gradually stop paying attention to sound distinctions that aren't relevant to the language they hear as infants, so I would say perception.