Rose A. Sevcik

Language comprehension in ape and child.

Previous investigations of the linguistic capacities of apes have focused on the apes ability to produce words, and there has been little concern for comprehension. By contrast, it is increasingly recognized that comprehension precedes production in the language development of normal human children, and it may indeed guide production. It has been demonstrated that some species can process speech sounds categorically in a manner similar to that observed in humans. Consequently, it should be possible for such species to comprehend language if they have the cognitive capacity to understand word-referent relations and syntactic structure. Popular theories of human language acquisition suggest that the ability to process syntactic information is unique to humans and reflects a novel biological adaptation not seen in other animals. The current report addresses this issue through systematic experimental comparisons of the language comprehension skills of a 2-year-old child and an 8 year-old bonobo (Pan paniscus) who was raised in a language environment similar to that in which children are raised but specifically modified to be appropriate for an ape. Both subjects (child and bonobo) were exposed to spoken English and lexigrams from infancy, and neither was trained to comprehend speech. A common caretaker participated in the rearing of both subjects. All language acquisition was through observational learning. Without prior training, subjects were asked to respond to the same 660 novel sentences. All responses were videotaped and scored for accuracy of comprehension of the English language. The results indicated that both subjects comprehended novel requests and simple syntactic devices. The bonobo decoded the syntactic device of word recursion with higher accuracy than the child; however, the child tended to do better than the bonobo on the conjunctive, a structure that places a greater burden on short-term memory. Both subjects performed as well on sentences that required the ability to reverse work order as they did on sentences that did not require this capacity. These results are discussed in light of a model of the evolution of language that suggests that the potential for language comprehension preceded the appearance of speech by several million years at minimum. The onset of speech is linked to the appearance of fully adapted bipedalism, which necessitated reorientation of the laryngeal tract and made closure of the soft palate possible. For the first time, such closure permitted mammals to easily produce sounds that could be interpreted by the mammalian auditory system in a categorical manner. When these sounds were paired with the previously extant capacity to produce vowels, it became possible to form bounded vowels or sound units that could readily be discriminated as units by the auditory system. It is suggested that this physical adaptation allowed the extant cognitive capacity of the hominids to embark on a speech-like mode of communication.

Augmentative and Alternative Communication Systems: Considerations for Individuals with Severe Intellectual Disabilities.

Augmentative and alternative communication (AAC) research and intervention for individuals with severe intellectual disabilities has advanced significantly in the last 5 years. This paper provides an integrated review of the current literature in this area, suggests future research directions, and delineates clinical and educational implications. The integration of behavioral and technological advances in the AAC field provides an optimistic outlook for the future development of functional communication systems for persons with severe intellectual disabilities.

An analysis of visual-graphic symbol meanings for two nonspeaking adults with severe mental retardation

In the language acquisition literature, the childs use of a word for a referent (or referents) has provided information about the nonlinguistic meaning of that word for him or her. With the increased use of augmentative and alternative communication (AAC) systems for persons with mental retardation, examination of the meanings symbols have for an individual can provide insights into the ways in which symbols are learned. As well, such analyses can serve as an indicator of the underlying conceptual knowledge the individuals have for the symbol meanings they are being taught. This preliminary report describes a post hoc analysis of the ways in which 2 young adults with severe retardation extended the meanings of visual-graphic symbols in an instructional setting. Two types of extensions were observed and subsequently characterized. Clinical and research implications are provided.