What term describes the manipulation of sounds by infants from six weeks old?

The manipulation of sounds by infants from six weeks old is best described as cooing. At this developmental stage, infants begin to produce soft vowel sounds, typically consisting of sounds like "oo" and "aa," as they experiment with their vocal cords. This cooing phase is an essential part of language development, as it represents early attempts at vocalization and communication. It lays the groundwork for later speech patterns and the development of more complex sounds.

In contrast, the other terms pertain to different stages or aspects of language development. Babbling occurs later, usually around four to six months, when infants start to produce consonant-vowel combinations like "ba," "da," and "ma." Telegraphic speech refers to two or three-word sentences that convey meaning, typically developing around age two. Phonological retrieval relates to the ability to access and produce the sounds of known words, a skill that develops further in later childhood. Thus, cooing specifically aligns with the sounds infants make around six weeks.