Interestingly, Piaget himself and other Piagetian researchers (eg. Inhelder and Karmiloff-Smith, 1978) believe that linguistic interaction with other children may help the child to advance intellectually, even though verbal training does not. They consider that children's attempts to convince their peers of their own points of view, and the ensuing disputes and conflicts generated by being made aware of contradictions, are all necessary steps in cognitive growth.
Although we have considered apparently different theories about the relationship between language and thought, there are points of overlap between them. If we superimpose them on top of each other we may have a more comprehensive and accurate picture of the nature of that relationship than any on its own can provide. My view is that a certain sophistication of cognition is required before the child can think abstractly. Language is a system of symbolic representation, perfected over many previous generations, that allows the child to "abstract" the world. It provides the symbols for the child's equations concerning the world, permitting the child a far greater freedom of thought and leading to further cognitive development.
III
"Language may have created man, rather than man language."
Jaques Monod, 1910-1977.
We shall now consider the evolutionary evidence - do animals with more complex language possess more sophisticated thought processes? Brown (1973) states that true language is productive since speakers can recombine forms to make new utterances, it has semanticity as it can represent ideas, events and objects symbolically, and it offers displacement, messages need not be tied to the immediate context. In contrast the communication systems of birds, bees and lower animals are all tied to the stimulus situation, limited to the here-and-now and to a restricted set of messages.
Our closest biological relative, the chimpanzee, has been shown to possess cognitive abilities far surpassing any other animal save man. Infant chimpanzees display visual pursuit, an understanding of object permanence, the use of means to achieve desired ends, the ability to construct object relations in space and the use of operational causality. Redshaw (1978) found that not only did the chimps develop these abilities in the same sequence as human babies do, but that they were in general a few weeks more advanced! It was thus hypothesized that training chimps in the use of language would allow them to keep pace with the human's cognitive abilities beyond infancy.
Early attempts to raise chimpanzees as children, in the hope that they would acquire language spontaneously (eg. Kellogg, 1933; Hayes, 1951) failed because researchers were unaware that chimpanzees do not have the specialised articulatory and physiological abilities that make spoken language possible. Subsequent research has utilised sign language (Gardener, 1969) or specialised typewriters (Rumbaugh, Gill and Glaserfeld, 1973). Using this system, some higher primates have been taught almost 400 signs. Regarding Brown's criteria of language, as far as semanticity is concerned, the non-human primates certainly seem to use symbols meaningfully, and there is evidence of displacement too; for example, when a chimp signs "You me go there in" she is referring to a place she is not in at the moment. There is also evidence of productivity eg. one gorilla called a cigarette lighter a "bottle match", a zebra a "white tiger", and a mask an "eye hat".
However, Terrace (1980) analyzed films of the ape language projects and concluded that very little of what the chimp signed actually originated with the chimp. The chimps signed what had just been signed to them, responding to subtle cues from their trainers.
In conclusion, of all the discontinuities between man and animals, including abstraction, morality, culture and technology, and the division of labour, the evergreen candidate for the fundamental discontinuity, which might qualify all others, is language. The most unrelenting efforts to induce our closest living relatives to reveal hidden linguistic potential have left the discontinuity of speech bloodied, but unbowed. It is therefore still reasonable to say that animals do not think as we do, when we think in words, but tacit mental organisation is evident not only in ourselves but in many other species. Our organ of thought may be superior, and we may play it better, but it is surely vain to believe that other possessors of similar instruments leave them quite untouched. Surely we shouldn't expect so much from the chimps second language - after all, how far have we progressed in learning theirs?
IV
"How can I grasp what I think, till I know what I say?"
Graham Wallas, 1858-1932.
We shall now turn to neuropsychology to examine what occurs when either language or thought is damaged. The question to be considered is whether an impairment of linguistic function decreases the sophistication of an individuals thought processes. Unfortunately the evidence is very mixed. A patient may show multiple and severe language problems whereas perception, orientation, thinking, reasoning, memory, and so on remain intact (though needing to be tapped non-verbally). But these claims are not best evaluated by comparing groups of aphasic patients with groups of normals. For example, many group studies have found that aphasics perform poorer on tests of non-verbal intelligence than normal patients (eg. Bay, 1962; Kertesz and McCabe, 1975) whereas other studies have found no difference and no correlation between the severity of language impairment and reduced non-verbal intellect (eg. Basso, DeRenzi, Faglioni, Scotti, & Spinnler, 1973; Corkin, 1979). Still other studies have found aphasics to have very high non-verbal intelligence (eg. Van Harskamp, 1974; Welman and Lanser, 1974; Zangwill, 1964).
The problem is that language is not a single, unified human faculty; rather speech production, speech comprehension, writing and reading are capabilities which arise out of the coordinated activity of many language-sustaining cognitive processes or "modules". If each module is capable of being impaired independently of the others, then it becomes clear that the number of different language disorders could be very large. On top of this, symptoms could arise due to disconnection of modules, modules could be impaired in more than one way, and certain symptoms may be due to a particular combination of modules being damaged. Thus the grouping of aphasics together for assessment is probably not very useful and has thus contributed to the mixture of results above.
As discussed earlier there are many types of non-linguistic thought, and not surprisingly these can be lost without affecting language. Morrow, Ratcliff and Johnston (1985) described patients with impaired spatial thought, Henschen (1926) described patients with amusia, and manias and depressions characterise disturbed emotions, yet in none of these cases is language disrupted.
From neuropsychology it is probably safe to conclude that up to a point language and thought can be impaired separately. However, at the point where words and representations interface, ie. at the level of semantics and beyond, damage to one will affect the other.
V
"Only idealists can speak of thinking without language."
Josef Vissarionovich Stalin, 1879-1953
To summarise I think that language and thought are mutually dependent on one another. From an ontogenetical viewpoint a certain sophistication of thought is necessary before language can be acquired, but once it is obtained it leads to a far greater complexity of thinking. The phylogenetic evidence supports this view. I would postulate that chimps have advanced cognitively as far as is possible without a satisfactory system of symbolic representation. Teaching chimps our language has failed, not because of a lack of intelligence on their part, but a lack of understanding on ours. The gulf between English and French, immeasurable for many of us, is tiny compared to the gulf between chimp and human. Perhaps we would be better to try understanding chimp language, before teaching them ours. Finally the neuropsychological evidence gives us some idea of the language-thought relationship in adults. Some language is possible without thought (witness the schizophrenic) but thought is also possible with impaired overt language (the aphasic). Whether the latter also implies impaired covert speech is uncertain, but I would doubt this is the case. For adults it is many years since thought and language merged and I suspect one cannot be severely disrupted without affecting the other.
I will leave it to Piaget to conclude this essay, "language and thought are links in a genetic circle....in the last analysis both depend on intelligence itself, which antedates language and is independent of it."
Jonathan Wallis
Psychology and Neuroscience
BIBLIOGRAPHY
Bruner, J.S. (1975) From communication to language - a psychological perspective. Cognition, 3, pps. 225-287.
Linden, E. (1976) Apes, Men and Language. Second Edition. Harmondsworth: Penguin.
Piaget, J. (1959) The Language and Thought of the Child. London: Routledge and Kegan Paul.
Rochester, S. and Martin, J.R. (1979) Crazy Talk: a Study of the Discourse of Schizophrenic Speakers. New York: Plenum.
Vygotsky, L.S. (1962) Thought and Language. Cambridge, Mass.: MIT Press.
Zangwill, O. (1964) Intelligence in aphasia. In A.V.S. de Reuck and N. O'Connor, eds., Disorders of Language. London: Chruchill.
