by Richard Lynn, University of Ulster, Coleraine, Northern Ireland

The world literature on racial differences in intelligence is reviewed from three points of view. Firstly, studies using intelligence tests indicate that Caucasoids in North America, Europe and Australasia generally obtain mean IQs of around 100. Mongoloids typically obtain slightly higher means in the range of 100-106. African Negroids obtain mean IQs of around 70, while Negroid-Caucasoids in the United States and Britain obtain means of about 85. Amerindians and the South East Asian races typically obtain means in the range of 85-95.

A second source of evidence comes from studies of reaction times which provide measures of the neurological efficiency of the brain. These studies show that Mongoloids have the fastest reaction times, followed by Caucasoids and then by Negroids. Thirdly, the races can be assessed for their contributions to civilization. Here the Caucasoids and the Mongoloids have made the most significant advances both in the foundation of the early civilizations and in more recent developments.

The existence of racial differences in intelligence has been known since the time of the First World war when tests given to large numbers of military conscripts in the United States revealed that blacks had an average intelligence level about 15 IQ points below that of whites. In the following decades there has been debate over the question of whether these differences have a genetic basis. This debate has largely taken place in the context of the differences in intelligence found in different racial populations in the United States. Genetic theorists have pointed to the high heritability of intelligence and the difficulties of formulating credible environmentalist explanations to explain the difference (Jensen 1972, 1973, 1980; Eysenck, 1971). Environmentalists have pointed to a variety of factor-s which they consider capable of explaining the low Negroid IQ, of which the most important are bias in the tests, the adverse social and economic living conditions experienced by blacks, discrimination and prejudice from white majorities and the historical legacy of slavery which has demoralized blacks and destroyed their family structure (Flynn, 1980; Jaynes and Williams, 1989; Mackintosh and Mascie-Taylor, 1985). Neither side has yet succeeded in convincing the other and the issue remains unresolved, although a recent poll has shown that the majority of experts now believe there is some genetic basis to the low black IQ (Snyderman and Rothman, 1988).

The Purpose of the present paper is to consider the problem of racial differences in intelligence in a global perspective.

Part one
of the paper contains a review of the many studies which have been made of the intelligence of different races throughout the world. The principal question here is whether the world wide evidence supports the genetic or the environmental position.

In general terms the genetic theory requires that there should be a reasonably high degree of consistency of the intelligence levels shown by populations of different races in a variety of geographical locations. Thus, Negroids should universally have lower intelligence levels than Caucasoids and this difference should be found in Africa and the West Indies as well as in the United States and Britain. The reason for this is that the genes or alleles (alternative forms of genes) for low intelligence, if these exist, should be present in all Negroid populations and not merely in those whose ancestors were transported as slaves to the New World. Furthermore, Negroids in the United States and Britain are nearly all Negroid Caucasoid hybrids (Reed, 1969). Their Caucasoid genes should, on the genetic hypothesis, raise their intelligence level as compared with the pure Negroids of Africa. Hence the genetic theory demands that African Negroids should have lower intelligence levels than the Negroid-Caucasoid hybrids of the United States and Britain. Whether or not this is the case can be regarded as a test of the genetic theory and any studies showing that pure African Negroids have higher IQs than American or British Negroid hybrids would falsify the genetic hypothesis.

A similar degree of consistency of intelligence levels should be found for all races if the intelligence is largely genetically determined. The intelligence of Caucasoids should be approximately the same, whether they live in the United States, Britain, Europe, Australia or New Zealand. The same consistency should be present in the third major race of mankind, the Orientals or Mongoloids, who are present not only in their native habitat of north east Asia but also in the United States and Europe. Hence a world wide examination of the consistency of racial differences in intelligence would provide a perspective on the genetic and environmental theories which is lacking in the studies carried out in the local contexts of the United States and, more recently, in Britain.

Part two of the paper deals with the question of whether the racial differences in intelligence as measured by intelligence tests are also present in reaction times, i.e. the speed of response to simple stimuli. The interest of this question is that recent work has shown that reaction times are a measure of intelligence and appear to represent differences in the neurological efficiency of brain processes (Jensen, 1982; Eysenck, 1982). A positive finding of racial differences in reaction times would rule out many of the explanations for the intelligence differences advanced by environmentalists such as bias in the tests, the legacy of slavery and so forth, and would point to a genetically determined neurological basis for the differences. Whether or not there are racial differences in reaction times which run parallel with those in intelligence therefore provides a further test of the genetic and environmental theories.

Part three of the paper considers the racial differences in the foundation and advancement of civilization. The establishment of civilization required numerous discoveries such as the invention of writing and arithmetic and these must have been due to the work of highly intelligent individuals. This part of the paper considers whether the racial differences in the establishment of civilizations are the same as those found in the performance of intelligence tests. ...


The studies of racial differences in intelligence test results, reaction times and scientific and technological discoveries show a high degree of consistency. All three sources of evidence indicate that the two races with the highest intelligence levels are the Mongoloids and the Caucasoids. These are followed by the Amerindians, while the south east Asian races and the Negroids are ranked lowest. The intelligence test results and the reaction times tend to indicate that average Mongoloid intelligence levels are a little higher than those of Caucasoids, but the difference is relatively small as compared with other racial differences.

'The general consistency of the results from the three sources of evidence, and the consistency of the different intellectual achievements of the races over a long historical period, points to a substantial genetic determination for these differences. If genetic factors were not involved, there would have been much greater variation over time and place and the observed consistencies would not be present. Whatever criteria are adopted, the Caucasoids and the Mongoloids are the two most intelligent races and the historical record shows that this has been the case for approximately the last 5,000 years.

The environmentalist may argue that the Negroid peoples in Africa, the Caribbean, the United States and Britain, and the Amerindians, Maoris and Australian aborigines, all live in socially and economically impoverished conditions, as compared with Caucasoids and Mongoloids, and that these conditions are responsible for some or perhaps all of their low intelligence. This argument call be met by the concept of genotype-environment correlation, originally proposed by Ploinin, De Fries and Loehlin (1977) and developed by Scarr and McCartney (1983).

'There are two processes of genotype-environment correlation which are relevant to the present problem. The first is "passive" and has the effect that children tend to be reared in environments which are correlated with their own genetic potentialities. The principle applies for any trait which has a heritability, and this is undoubtably true of intelligence, and in the case of intelligence means that intelligent parents transmit the characteristic genetically through their genes and environmentally through the advantageous environment which they provide for their children. The two modes of transmission have the effect that intelligent children tend to be reared in intelligence-enhancing environments. This brings the genotypes and the advantageous environments into positive correlation and implies that those reared in advantageous environments tend to have superior genotypes. This applies, for instance, to middle class children as compared with working class children, and can also, arguably, be applied to Caucasoid and Mongoloid children as contrasted with those of other races.

There is a second "active" type of genotype-environment correlation which states that people play an active role in creating their own environments. Genotypically intelligent peoples are able to create a socially and economically affluent environment to an extent which cannot be done by less intelligent peoples. Scarr and McCartney call this "niche building", and the two peoples who have been successful in building socially and economically developed niches in which to live and rear their children have been the Caucasoids and the Mongoloids.

The argument frequently advanced that poor social and economic conditions are responsible for the lower intelligence of the Negroids, Aborigines and Amerindians places the cart before the horse. It assumes that the impoverished environments of these peoples are simply the result of external circumstances over which these peoples themselves have no control. Such a claim does not stand up to examination. There are so many cases which it cannot explain, such as the achievements of Chinese, Japanese, Korean and Vietnamese immigrants in the United States and of Indians in Britain and Africa. The only plausible explanation for why these peoples have succeeded where others, initially more advantageously placed, have failed is that they have the right genotypes for building socially and economically prosperous environments for themselves and their families.

Source: The Mankind Quarterly, V31:3, Spring 1991, 255-296.