by Oliver Sacks
113. Lenneberg, commenting on the critical age period for language acquisition (which he sees as related to the establishment of hemisphere dominance), speaks of normal lateralization being established in the congenitally deaf provided they acquire language by the age of seven. Sometimes, however, cerebral lateralization is not well established: perhaps, writes Lenneberg, ‘a relatively large percentage of the congenitally [and linguistically incompetent] deaf falls into this category.’
Early language acquisition, whether speech or Sign, seems to kindle the linguistic powers of the left hemisphere; and deprivation of language, partial or absolute, seems to retard development and growth in the left hemisphere.
With such an approach—so different from the classical doctrines of fixed hemispheral specificities—one can understand the role of the individual’s experience and his development, as he moves from his first gropings (in linguistic or other cognitive tasks) toward expertise and perfection. 114
114. Cudworth writes, in the seventeenth century, of how a skilful and expert limner will observe many elegancies and curiosities of art, and be highly pleased with several strokes and shadows in a picture, where a common eye can discern nothing at all; and a musical artist hearing a consort of exact musicians playing some excellent composure of many parts, will be exceedingly ravished with many harmonical airs and touches, that a vulgar ear will be utterly insensible of (R. Cudworth, ‘Treatise Containing Eternal and Immutable Morality,’ cited in Chomsky, 1966).
The capacity to move from a ‘common eye’ or ‘vulgar ear’ into artistic skill and expertise goes with the move from right to left hemisphere predominance. There is good evidence (both from studying the effects of cerebral lesions, as A.R. Luria has done, as well as experimentally, with dichotic listening) that while musical perception is chiefly a right hemisphere function in predominantly ‘naive’ listeners, it becomes a left hemisphere function in professional musicians and ‘expert’ listeners (who grasp its ‘grammar’ and rules, and for whom it has become an intricate formal structure). A special sort of ‘expert listening’ is required for those who use Cantonese or Thai, the morphology of which relies on tonal discrimination in a way European languages do not. There is evidence that this (normally a right hemisphere function) becomes a left hemisphere function in fluent Thai speakers: it is much improved in right ear (and thus left hemisphere) listening with them, and is grossly impaired with left hemisphere strokes.
A similar shift occurs with those who become mathematical or arithmetical ‘experts,’ who become able to see mathematical concepts, or numbers, as part of a vast, well-organized intellectual universe or scheme. This may be equally true of painters and interior designers, who see space, and visual relationships, as no ‘common eye’ can do. And it is true of those who acquire skill at whist, or Morse code, or chess. All the higher reaches of scientific or artistic intelligence, as well as banal game-playing skills, require representational systems that are functionally similar to language and develop like it; all of them seem to move into becoming left hemisphere skills.
(Neither hemisphere is ‘more advanced’ or ‘better’ than the other; they are merely suited for different dimensions and stages of processing. Both are complementary, interacting; and between them they allow the mastery of new tasks.) Such a view makes clear, without paradox, how Sign (though visuo-spatial) can become a left hemisphere function, and how many other sorts of visual ability—from perception of movement to perception of patterns, perception of spatial relation to perception of facial expressions—by having become part of signing, will be swept along with it, as it develops, into becoming left hemisphere functions too. We can understand why the signer becomes a sort of visual ‘expert’ in many ways, in certain nonlinguistic as well as linguistic tasks—how there may develop not just visual language but a special visual sensibility and intelligence as well.
We need more hard evidence about the development of a ‘higher’ visuality, a visual style, comparable to the evidence Bellugi and Neville have provided about the enhancement of ‘lower’ visual-cognitive functions in the deaf. 115
115. There is a considerable and somewhat controversial literature on the character of cognitive function in the deaf—whether there is, in fact, a ‘deaf mind.’ There is some evidence that their strong visuality disposes deaf people to specifically ‘visual’ (or logico-spatial) forms of memory and thinking; that, given complex problems with many stages, the deaf tend to arrange these, and their hypotheses, in logical space, whereas the hearing arrange them in a temporal (or ‘auditory’) order (see, for example, Belmont, Karchmer, and Bourg, 1983).
Clearly, in a cultural sense, we may speak of the deaf mind, as we may speak of the Jewish or Japanese mind, a mentality distinguished by particular cultural sensibilities, images, perspectives, beliefs. But there is no neurological sense in which we can usefully speak of a Jewish or Japanese mind whereas there may be, in relation to the deaf mind. There is an unusual number of deaf engineers, deaf architects, and deaf mathematicians, who have, among other things, great facility in picturing and thinking in three-dimensional space, picturing spatial transforms, and conceiving complex topological and abstract spaces. Probably this is partly based on a neurological disposition, on the neuropsychological or cognitive structure of the deaf mind.
Hearing children of deaf parents, who acquire Sign as a first language, and show striking visual enhancements even though they are hearing, may be not only bilingual, but ‘bimental,’ in the sense of having access to, or use of, two quite distinct modes of mental functioning. Certainly some of them will speak of ‘switching’ not only language, but mode of thought, depending on whether they find themselves, or wish to be, in a visual (Sign) or speaking mode. And some, like Deborah H., will switch from one to the other in response to their own thinking needs (n. 45, p. 34). It would be of great interest to investigate this further, to find, for example, whether such ‘switching’ corresponds to clear-cut neuro-physiological transitions in the brain, from a predominantly auditory to a visual mode, and vice versa.
As yet we have mostly anecdotes and accounts; but the accounts are extraordinary and demand close attention. Even Bellugi and her colleagues, who rarely depart from rigorously scientific description, are moved to include the following brief account, in passing, in their book, What the Hands Reveal about the Brain: 116
116. Poimer, Klima, and Bellugi, 1987, p. 206.
We first saw this mapping aspect of signing in its full form when a visiting deaf friend was telling us about his recent move to new quarters. For five minutes or so, he described the garden cottage in which he now lived—rooms, layout, furniture, windows, landscaping and so forth. He described it in exquisite detail, and with such explicit signing that we felt he had sculpted the entire cottage, garden, hills, trees and all in front of us.
What is related here is difficult (for the rest of us) to imagine—it has to be seen. It is very similar to what Charlotte’s parents say of her—her ability to create a real (or fictional) landscape with such precision, such fullness, such aliveness, as to transport the beholder. The use of such picturing, pictorial power, goes with the use of Sign—even though Sign is not in the least a ‘picture-language’ itself.
The other side of this linguistic expertise, and visual expertise generally, is the tragically poor linguistic and intellectual function that may afflict a large number of deaf children. It is clear that the high linguistic and visual competences of the well-functioning deaf lead to the establishment of strong cerebral lateralization, with a shift of language functions (and also visual-cognitive functions generally) to a well-developed left hemisphere. But what, we have to wonder, is the situation, neurologically, with the poorly functioning deaf?
Rapin was struck by ‘a remarkable linguistic deficiency’ in many of the deaf children she works with—specifically, an inability to understand question forms, to understand the structure of sentences—an inability to manipulate the language code. Schlesinger shows u
s other dimensions of this deficiency, dimensions that expand it from the linguistic to the intellectual: the low-functioning deaf, in her description, not only have difficulty in the understanding of questions, but refer only to objects in the immediate environment, do not conceive remoteness or contingencies, do not formulate hypotheses, do not rise to super ordinate categories, and are in general confined to a pre-conceptual, perceptual world. She feels that their utterances are somewhat deficient syntactically and semantically, but clearly are also deficient in a much deeper sense.
How then should we characterize their deficiency? We need another kind of characterization, one that transcends the usual linguistic categories of syntax, semantics, phonetics. Such a characterization has again been provided by Goldberg in his reflections on ‘isolated right hemisphere speech.’ 117
117. See Goldberg and Costa, 1981; and also Zaidel, 1981.
Right hemisphere language allows ad hoc referential relations (pointing to, labeling, this-here-now)—the establishing of a referential basis of a linguistic code—but cannot go beyond this to allow manipulations of the code, or internal derivations within it. In more general terms, right hemisphere functioning is restricted to perceptual organization and cannot shift to categorical, definition-based lexical organization; it is (in Zaidel’s term) ‘experiential’ only and cannot embrace the ‘paradigmatic.’ 118
118. This dichotomy is reminiscent of Bruner’s division into ‘narrative’ and ‘paradigmatic,’ which he sees as the two natural, elemental modes of thought (see Bruner, 1986). One is tempted to see the narrative mode as a right hemisphere function, the paradigmatic as a left hemisphere one. In the retarded, certainly, the narrative mode of thought and language may be remarkably developed, with the paradigmatic remaining grossly defective. (See Sacks, 1985).
This referential processing, with complete absence of rule manipulation, is precisely what we see in deaf people who are linguistically defective. Their language, their lexical organization, is like that of people with right hemisphere speech. Such a condition is usually associated with left hemisphere damage, acquired in later life, but it could also arise as a mishap in development—as a failure to shift from an initial, right hemisphere, quasi-perceptual functioning to a mature, left hemisphere, fully linguistic functioning.
Is there any evidence that this does indeed occur in linguistically defective, low-functioning deaf people? Lenneberg questioned whether a large number of the congenitally deaf might have poorly established cerebral lateralization, though at the time (1967) there had not yet been any precise delineation of the differential lexical capacities and characters of the hemispheres in isolation. The matter has been approached, neuro-physiologically, by Neville, who writes, ‘If language experience does impact cerebral development, then aspects of cerebral specialization ought to be different in deaf and hearing subjects when they read English.’ And indeed she finds that the majority of deaf people she tested do not show the pattern of left hemisphere specialization observed in the hearing. This, she hypothesizes, is because they lack full grammatical competence in English. And indeed, four congenitally deaf subjects of Neville’s who had perfect English grammar showed ‘normal’ left hemisphere specialization. Thus, in Neville’s words, ‘grammatical competence is necessary and sufficient for left hemisphere specialization—if it occurs early.’
It is clear from the phenomenological descriptions of Rapin and Schlesinger, and from the behavioral and neuro-physiological evidence amassed by Neville, that language experience can grossly alter cerebral development—and that if it is severely deficient, or otherwise aberrant, it may delay the maturation of the brain, preventing proper left hemisphere development, in effect confining the person to a right hemisphere sort of language. 119
119. This seemed to be the case with Genie’s language, which was poor in syntax but relatively rich in vocabulary (see p. 54):
Genie’s language [writes Curtiss] resembles right-hemisphere language. The dichotic listening tests indicate that her language is right-hemisphere language. Thus, Genie’s case may indicate that after the ‘critical period,’ the left hemisphere can no longer assume control in language acquisition, and the right hemisphere will function and predominate in the acquisition and representation of language (Curtiss, 1977, p. 216).
It is not clear how long-lasting such delays may be; Schlesinger’s observations suggest that, if not prevented, they may be lifelong. But they can be mitigated, and even reversed, by the right sort of intervention later, in adolescence. 120
120. See Schlesinger, 1987.
Thus Braefield, a primary school, presents a horrifying picture but a few years later, as adolescents, the same students—or many of them—may be doing better, for example, at Lexington, a secondary school. (And, in quite a different mode from ‘intervention,’ there may be a belated discovery of the deaf world, and this can provide a linguistic intimacy and a culture and community, an at-long-last ‘coming home’ that may compensate somewhat for earlier isolation.)
These, then, in very general terms, are the neurological hazards of congenital deafness. Neither language nor the higher forms of cerebral development occur ‘spontaneously’; they depend on exposure to language, communication, and proper language use. If deaf children are not exposed, early, to good language or communication, there may be a delay (even an arrest) of cerebral maturation, with a continuing predominance of right hemisphere processes and a lag in hemispheric ‘shift.’ But if language, a linguistic code, can be introduced by puberty, the form of the code (speech or Sign) does not seem to matter; it matters only that it be good enough to allow internal manipulation—then the normal shift to left hemisphere predominance can occur. And if the primary language is Sign, there will be, additionally, an enhancement of many sorts of visual-cognitive ability, all going along with a shift from right hemisphere to left hemisphere dominance. 121
121. There has recently been an educational experiment in Prince George’s County, Maryland, with the introduction of Sign into first grade and preschool education among normal, hearing children. The children acquire it readily and enjoy it, and as they do they show significant improvement of reading and other skills. It may be that this facilitation of reading, of the ability to recognize the forms of words and letters, goes with the enhancement of spatial-analytic ability that occurs with the learning of Sign.
Even when (hearing) adults learn Sign, they too may become conscious of changes in themselves—a disposition to more vivid visual description, enhancements of visual imagery and memory, and often a freer and more direct expressive use of the body. It would be interesting to find out if there occurs to some degree, in such adults, an enhancement of visual evoked potentials such as Neville finds in hearing native signers.
Interestingly, there is not a good correlation between ability to learn spoken languages and ability to learn Sign. Some polyglots are taken aback at finding how ‘hard’ it is; and other people, who have never been able to learn another spoken language, may be startled to find how ‘easy’ Sign is. These differences may reflect differing visual powers of individuals, and have little to do with intellectual powers, or linguistic powers, in general. In adult life, basic visual powers may be capable of only limited enhancement, whereas early training, seemingly, can enhance visual powers in us all.
Very recently, there have been some fascinating observations with regard to the brain’s disposition to sign language when it is exposed to it—in particular, its tendency toward ASL—like, or (in more general terms) Sign-like, forms whatever form of sign language it is exposed to. Thus James Paul Gee and Wendy Goodhart have shown dramatically that when deaf children are exposed to signed forms of English (manually encoded English), but not ASL, they ‘tend to innovate ASL-like forms with little or no input in that language.’ 122
122. Gee and Goodhart, 1988.
This is an astonishing finding: that a child who has never seen ASL nonetheless evolves ASL-like forms.
Elissa Newport an
d Ted Supalla have shown that children construct grammatically perfect ASL even when they are exposed (as they so often are) to somewhat less-than-perfect ASL—a clear illustration of an innate grammatical competence in the brain. 123
123. Newport and Supalla’s research is discussed in Rymer, 1988.
Gee and Goodhart’s findings go further, by showing that the brain moves inevitably toward Sign-like forms, and will even ‘convert’ non-Sign-like forms to Signlike-forms. ‘Sign is closer to the language of the mind,’ as Edward Klima says, and thus more ‘natural’ than anything else when the developing child is called upon to construct a language in the manual mode.
Sam Supalla has provided independent confirmation of these studies. 124
124. Supalla, in press.
Focusing in particular on the sort of devices used to mark grammatical relations (these are all spatial in ASL, but in signed English, as in spoken English, entirely sequential), he has found that deaf children exposed only to signed English replace its grammatical devices by purely spatial ones ‘similar to those found in ASL or other natural signed languages.’ Supalla speaks of these as being ‘spontaneously created,’ or evolved.
It has been known for many years that signed English is cumbersome and imposes a strain on those who use it: ‘Deaf people,’ writes Bellugi, ‘have reported to us that while they can process each item as it appears, they find it difficult to process the message content as a whole when all the information is expressed in the sign stream as sequential elements.’ 125