What is cooing primarily characterized by?

Cooing is primarily characterized by vowel-based noises, typically produced by infants between the ages of 6 to 8 weeks up to about 6 months. During this stage, babies experiment with vocalizations that focus on elongated vowel sounds such as "oo" and "ah," often in a relaxed and joyful manner. This vocal play is essential for language development as it allows infants to practice the sounds they will later use in speech.

The other choices do not accurately represent the cooing stage. Complex sentence structures are far too advanced for infants in this stage, as they have not yet developed the ability to form sentences. Single consonant sounds are more characteristic of the babbling stage that follows cooing, where infants begin combining consonants and vowels. Gestures and body language play an important role in communication, but they do not define the vocal experimentation seen in cooing. Thus, vowel-based noises are the hallmark of this early stage of language development.