Prior to this study, the aquisition of language by animals had been studied in a range of ways.Chimpanzees had been shown to have some capacity to learn languages based on American Sign Language (ASL), symbols,or plastic tokens,using rewards. Furthermore, such chimps demonstrated communication skills including requesting, labelling and comprehending, and, without further training, their language extended from asociative references about the present to include:
- Referential symbol usage, and
- Communicating about what they intend to do (i.e. in the future)
In these respects, the aquisition of language by apes resembles that of young children. However, some aspects of the language aquisition of apes differ from that of children, parrticularly in the need for repeated exposure and reinforcement to learn associations between symbols and their meaning. Children make the transition between associative and referential use spontaneously and quickly. If a child asks for a teddy, and their mother holds up a duck and says "what's this?" the child can answer because they do not become confused between the symbol (the words 'teddy' and 'duck') and their respective referents. In contrast, Savage-Rumbaugh (1986) reports that two common chips- Sherman and Austin- could request things they were unable to name, and name things they were unable to request. They required reinforced training to make the cognitive step to distinguish between naming and requesting. Following their training in referential symbol use and retrieving unseen objects, Sherman and Austin began to show spontaneous representational symbol use. This then appeared to follow the same pattern as is observed in children:
- They began to initiate word games by selecting objects and offering the correct symbol without prompting.
- They generalised symbol usage beyond the origional context. For example, Austin referred to a chimp screaming outside with the symbol 'scare', which had been learned through a game involving pretend 'scaring', using a mask over the face.
- Like Kanzi, they aquired some symbols without explicit training.
- They assigned new symbols to food and tools they had not encountered before.
- They could make categorical judgements based on symbolic information only. For example, the 'apple' symbol would be placed in the 'fruit' category, even when no actual apples were present.
Difference in language learning between children and apes:
Apes lack the vocal apparatus to produce spoken language, and there is little evidence to suggest that apes can understand spoken language. One reason for this might be that the ability of a species to analyse sounds is realted to its capacity to produce these sounds. Because chimps cannot produce human speech, the limits to their understanding are unsurprising.
The key difference therefore is that children learn to extract words from the speech they hear in order to comprehend their meaning, and they learn to reproduce those words in context, without reinforcement. This has no been observed in apes. However, even though apes are unable to produce spoken language, evidence of spontaneous development of comprehension would indicate a level of cognitive equivalence with human language…