What do "hum"-type syllables indicate about an infant's development?

"Hum"-type syllables indicate that the infant is developing their vocal skills. At this stage, infants begin to experiment with their vocalizations, producing sounds that reflect the early development of their ability to control their voice and manipulate pitch and volume. This stage is crucial for infants as they learn how to produce different sounds, which sets the foundation for future speech and language development.

In the context of vocal development, "hum"-type sounds demonstrate an exploration of sound production and indicate that infants are beginning to gain more control over their vocal apparatus, thus progressing in their overall communication skills. This also shows that the infant is engaged in a form of vocal play, which plays a significant role in the development of language.

The other options may reference stages of vocal development but do not accurately describe what "hum"-type syllables specifically indicate. For example, the cooing stage primarily involves softer vowel-like sounds rather than the more varied and controlled sounds represented by "hum"-type syllables, and babbling involves combining consonant and vowel sounds rather than just humming. Thus, the focus on developing vocal skills aligns most closely with what "hum"-type syllables reflect in an infant's development.