Manual babbling

Manual babbling is a linguistic phenomenon that has been observed in deaf children and children born to deaf parents and appears at the early stages of language acquisition. It is characterized by repetitive movements that are confined to a limited area in front of the body similar to the sign-phonetic space used in sign languages. In their 1991 paper, Pettito and Marantette concluded that between 40% and 70% of deaf children's hand movements can be classified as manual babbling.

All infants are equipped to detect rhythmic patterns and properties of the linguistic input they receive. Where hearing children are triggered by the sound patterns they hear, deaf children are more attentive to the movement patterns they see. This, however, still leaves room for non-hearing children to piece together what these movements are and what they mean. Because of this lack of clarity, non-hearing infants explore manual gestures like a hearing child may explore phonemes. Petitto and Marentette researched the difference between the manual babbling used by hearing and non-hearing infants, and they discovered that non-hearing babies produce more different kinds of manual babbles than hearing infants do. However, there was not a significant difference between the frequency of communicative gestures between hearing and non-hearing infants. The difference between manual babbling and signed syllables is that while signed syllables are language-driven, manual babbling is centered on hand shape, location, and movement. In other words, instead of being language-driven, manual babbling is motor-driven.

When an infant is beginning to develop a means of communication, it is often also trying to get a sense of their spatial orientation and cognition. This means that there will be arm and hand movements outside of what could be categorized as manual babbling. For example, when an infant is waving their arm back and forth, they may be transitioning between uncoordinated behaviors and intentional, voluntary behaviors like reaching. The frequency of these arm and hand gestures peaks between 5 and a half months and 9 and a half months, which is the same developmental point as vocal development.

In 1995, Meier and Willerman defined the three primary manual gestures as pointing, reaching, and waving, so anything beyond those three could be categorized as manual babbles. Common babbles by this definition include arm waves, body pats, and claps. Common communicative gestures, which are different from babbles because they carry meaning, include reaches, points, conventional waves, and rituals (like patty cake). Identification of manual babbling references American Sign Language phonology. This means that the babbles have hand shapes, a general place of articulation, movement, and palm orientation.

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