Deafness, Deprivation, and IQ (Perspectives on Individual Differences)

In addition to the usual problems of `minorities', the deaf in the West carry special handicaps. Many of them suffered maternal rubella (12%), pregnancy complications or premature births (7%), and childhood meningitis (7%). Their physical (15%) and `cognitive-behavioural' (21%) problems reflect a high rate of medical trauma. In childhood, many had awesome family problems of incomprehension and impatience with their deafness. Unlike other minorities, most deaf people did not even have parents, siblings or playmates who shared their fate; and their only serious means of communication (signing) reinforced their social isolation. Facing the political tasks of adulthood, the deaf even lack a dominant, affluent group that they can unitedly blame for their historical position and milk for compensatory funding and `positive' discrimination.On conventional Verbal IQ (VIQ) tests, the deaf score at around 86; and levels of educational attainment are still lower . However, scores are higher with testing procedures that use both signing and speech; Performance IQ (PIQ) tests give a mean IQ of 97 - rising to 100 on motor-intensive tests that require the least verbal mediation; and the tiny proportion of deaf people who have two deaf parents (and markedly fewer medical problems - presumably being merely `genetically deaf') are 8 IQ points higher still. This grossly handicapped minority thus has essentially normal general intelligence and a Verbal-Performance discrepancy that is a mirror-image of Afro-American results. Moreover, whereas what especially defies environmentalist interpretation is the big Black deficit on Performance scales, there is no such problem with the big deaf deficit on Verbal scales: while degree of hearing impairment provides no prediction of PIQ deficit (r = -.05), its strong negative link with VIQ (r = -.50 ) is just the kind of thing that common-sense environmentalism can explain. Could it even be that PIQ is artificially boosted in the deaf - in some kind of compensation for their handicap? As amongst Black children, degree of provision for spatial and constructive play bears little relation to PIQ; and parents notoriously stop deaf children playing in order to make them concentrate on language. Anyhow, the notion of intelligence developing in compensation for a handicap has no conspicuous applicability to other minorities. Braden's thorough consideration of such explanatory options is impressive and persuasive. According to the Israeli educationalist, Reuven Feuerstein, Black children lack `mediated learning experience' (MLE) since their parents are inhibited from passing on Black culture; yet deaf children suffer no corresponding PIQ handicap despite their own parents being largely unable as well as quite often unwilling to serve as the `cultural mediators' that Feuerstein's theory requires. As Braden says (p. 191), MLE theorists have "emphasized the primary impact of MLE on intellectual development"; by contrast, across the wide range of past studies of the deaf, "heritability approaches could account for all of the major findings if minor allowances were tolerated".

As a bonus, Braden's investigations are also relevant to the newly re-opened question of how intelligence, personality and achievement may `differentiate' into more distinct dimensions at higher levels of general intelligence ('g'), Mental Age or IQ - as originally observed by the British psychologists Charles Spearman and Sir Cyril Burt and the American psychologist Henry Garrett. Time and again, the psychometric properties of IQ-type tests turn out to be normal in deaf samples - apart from the lower Verbal mean. By no conspicuous criterion are mental tests inappropriate for the deaf - any more than for Black people. The deaf are not qualitatively different from the hearing in how different types of mental tests correlate, so there is no support for H. R. Myklebust's `organismic shift hypothesis' of special deaf development. However, the lowered correlations among mental tests as higher 'g' levels are reached (through childhood) do seem to appear at a later chronological age in the deaf: recent evidence of Braden's own is that "deaf children lag behind normal-hearing peers in the differentiation of intellective abilities over the age span" (p.91). If it is accepted that the deaf have normal intelligence, this lag implies that differentiation requires development, time and effective application of intelligence as well as just relatively high 'g' itself . It is as if the branching of differentiated, less correlated abilities requires its own history of investment and even `interest accumulation', and not just the immediate availability of good central resources.

Braden's thorough consideration of deprivation makes the issues and relevant methods very clear even at the cost of some repetition of major themes. Here for once is an author who is too modest by half when he says that "the best conclusion from the study....is that it raises many intriguing questions for future research". Braden thoroughly deserves his warm Afterword from California's Emeritus Professor Arthur Jensen. Without this work no library of differential psychology will be complete - especially if a second edition gives it a decent index.