Part II: How do Homo sapiens sapiens children acquire speech?

From an evolutionary perspective, especially in a highly social species, communication of information seems to be intrinsic to the survival of the organism. Individuals within a social group need to be aware of individuals, relationships, objects and actions. In general, species which care for dependent young, the primary caregiver, usually the mother, must be able to identify the vocalizations of its offspring. Additionally, the offspring must be able to identify the sounds of its primary caregivers, members of its own species (allies and rivals), other species and noises produced by the natural world (i.e. water, wind, fire).

In this sense, it does not seem that modern human infants possess any extraordinary adaptive advantage over any other vocal species. However, there seems to be a consensus amongst researchers that human language is intrinsically different from other forms of nonhuman animal communication. For example, the de Boysson-Bardies (1999:40) states:

Acquiring a language requires associating sounds and meanings according to the phonological and syntactic rules of a particular (human) language... Human infants must accomplish the following: select the proper sounds which constitute the repertoire of sounds used in the language of their environment, and acquaint themselves with the combinations of these sounds... They must assimilate the prosodic cues (accent, rhyme and intonation) which link linguistic units into organized forms.

Due to the influence of Chomsky's Universal Grammar theory, the study of early language acquisition in children tends to be focused upon the identification of adult-like categories of language (i.e. vowels, syntax). When studying language development, in the context of experimentation, extraneous variables tend to be removed from consideration of the desired observation. In the case of infant language acquisition, factors such as touch, eye contact, positive reinforcement, and constant repetition (training) are largely ignored. Since it is known that infants are capable of learning any of the world languages, elements of adult language have been correlated with specific infant behaviours (prosody preferences, babbling and first words). To this end, researchers have attempted to isolate elements of adult grammar that infants seem capable of identifying.

While it is difficult to perform experimental tests with infants younger than 6 months of age, it appears these infants are able to form associations between repeated prosodic phrases, such as their names and identities of their parents (Trainor et. al. 2000:188; Fernald 1991:44). These prosodic cues, cross-culturally, consist of changes in vocal pitch and tone, which are characteristic of (adult) human languages (Aslin et. al. 1998). In general, even adults without children of their own, and children, all adopt the higher pitched prosody when dealing with young infants (ibid.). It is uncertain whether this behaviour is similar that provoked by the physical features of babies (large head, big eyes, small body and limbs) which humans transfer to other young animals (and inanimate objects such as dolls), or strictly cultural in nature. Additionally, infants appear to be aware of foreign phoneme differences, and show a preference for prosodic cues which resemble the (adult) language of their home environment (Werker and Desjardins 1995:77).

The ability to pick out, arbitrary, visual and auditory patterns seems to be a highly developed trait of modern humans. One such auditory pattern is prosodic pauses, which adults identify as indications of separate vowel and consonant sounds (Blake 2000; Nazzi et. al. 2000; de Boysson-Bardies 1999; Aslin et. al 1998). Since human speech is, generally, produced during exhalations and not inhalations of air, minute pauses for inhalation provide cues to word breaks (Aslin et. al. 1998). From the adult perspective, these vocalizations are content (and contextually) rich (Morton and Trehub 2001).

In the development of language, vocal volubility in infancy is correlated with talking in childhood (Locke 1998:193). While it appears that vocalizing leads to talking, it also appears that talking leads to grammar (ibid.). A working knowledge of a language entails the simultaneous functioning of memory and emotive cues, working in conjunction with the physiological apparatus for speech production. However, one can listen to a conversation or song in a foreign language, and pick out both words and word stops without having any clear concept of the meaning of the spoken words. Infants seem to exhibit this type of behaviour. It seems questionable, in this instance, that anything other than the ability to identify a particular auditory pattern is occurring. There is obviously much more going on during early language development than has been revealed by the current directions in research. Cognitive development and visual cues must play some factor (Trainor et. al. 2000:194). For example, in the case of deaf infants raised in a signing household, babbling alters from being a vocal exercise to manual babbling (de Boysson-Bardies 1999:68).