Final answer:
At 1-year babies narrow their reporteir to the sound of their own language. Language acquisition starts with the ability to discriminate various phonemes and progresses through cooing and babbling.
Step-by-step explanation:
Babies are equipped with a remarkable ability to differentiate between a wide range of phonemes from various languages early on, but by the time they reach about 1 year old, they narrow their repertoire to the sounds of their language. This demonstrates their cognitive specialization in language acquisition and shows a preference for, and familiarity with, the linguistic sounds they are most exposed.
This loss of the ability to discriminate non-native phonemes coincides with the period where babies often begin to babble, using sounds and intonations from languages spoken in their environment.
Language acquisition in babies is influenced by their social environment and varies across cultures. Babies take cues from their caregivers and can learn a language just by being exposed to communication around them, with no need for direct 'teaching'.