Infant-directed speech

Baby talk, also referred to as caretaker speech, infant-directed speech (IDS), child-directed speech (CDS) or motherese, is usually delivered with a "cooing" pattern of intonation different from that of normal adult speech: high in pitch, with many glissando variations that are more pronounced than those of normal speech. It frequently displays hyperarticulation, which is an increase in the distances between peripheral vowels (such as [i], [u], and [a]). Baby talk is also characterized by the shortening and simplifying of words. Baby talk is similar to what is used by people when talking to their pets (pet-directed speech). When adults talk to each other using baby talk it is generally to either show affection by emulating the fondness shown by adults for children, or as a form of bullying or condescension.

CDS is a clear and simplified strategy for communicating to younger children, used not only by adults but also by older children. The vocabulary is limited, speech is slowed with a greater number of pauses, and the sentences are short and grammatically simplified, often repeated. Although CDS features marked auditory characteristics, other factors aid in development of language. Three types of modifications occur to adult-directed speech in the production of CDS —

The younger the child, the more exaggerated the adult's CDS is. The attention of infants is held more readily by CDS over normal speech, as with adults The more expressive CDS is, the more likely infants are to respond to this method of communication by adults.

CDS also incorporates body movements that assist visually in conveying meaning of language to infants. Due to the visual cues, infants are more highly motivated to engage in communication.

A key visual aspect of CDS is the movement of the lips. One characteristic is the wider opening of the mouth present in those using CDS versus adult-directed speech, particularly in vowels. The horizontal positioning of the lips in CDS does not differ significantly from that used in adult-directed speech. Instead, the observed difference lies in vertical lip positioning: By making the opening of the lips larger, infants are more likely to focus on the face of the speaker. Research suggests that with the larger opening of the lips during CDS, infants are better able to grasp the message being conveyed due to the heightened visual cues.

Head movements emphasize various syllables within language production. These visual cues provide infants additional information needed to perform accurate speech discrimination during language development.

Visual cues also allow infants to discriminate speech differences in environments in which they cannot rely upon their hearing (e.g., noisy environments). However, the auditory and visual aspects of CDS do not exist independently. Infants rely equally on both methods of understanding and, as development continues, infants strengthen the link between these two important categories.

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