Final answer:
Effective adult response to infants' cooing and babbling is to reinforce these sounds with a verbal response, using an adapted form of speech known as 'motherese'. This interaction supports their language acquisition process.
Step-by-step explanation:
When infants begin to coo and babble, effective adults should reinforce these sounds by some kind of verbal response. The early stages of language development in infants involve not just hearing and processing sounds, but also practicing vocalizations and linking them to social interactions. During the cooing phase, babies produce combinations of consonants and vowels that begin to echo the sounds of the languages spoken around them. As they progress to the babbling phase, they start to form syllable patterns, which sets the groundwork for more complex speech development. It's during this time that responsive verbal interaction from adults is crucial. Gesturing and facial expressions are also significant nonverbal cues that babies learn to associate with communication.
Adults engaging in motherese, a high-pitched and sing-song pattern of speech, can support the baby's language acquisition. While some cultures might view oversimplified baby talk as detrimental, the adaptation of adult speech to be more accessible to infants has been recognized as beneficial. This modified speech includes slower tempo, exaggerated intonation, and simplified vocabulary, which could help infants in making linguistic connections.