Sensory and motor systems have critical or sensitive periods early in life and then the neural network is pruned and the critical period closes. This is why sec

Sensory and motor systems have critical or sensitive periods early in life and then the neural network is pruned and the critical period closes. This is why second language acquisition is much easier at younger ages. There are some drugs that may reopen the critical period although not much can be done about the pruning. So basically all the early neural circuits for interpreting sounds are not organized correctly and it's unclear if they can be post critical period.