The rise of national intelligence: Evidence from Britain, Japan and the U.S.A

Myopia, intelligence, and the expanding human neocortex: behavioral influences and evolutionary implications

The first two parts of this monograph document that areas of the human neocortex heavily used to cope with a complex, language-driven society have been expanding rapidly and suggest strongly that this is linked with the huge upsurge that's occurred in myopia, and with the large gradual 20th-century increase in measured intelligence. Part III proposes mechanisms capable of supporting such rapid changes, without violating the basic precepts of Darwin's thinking. Part IV discusses the social and evolutionary ramifications of our apparent proclivity for rapid, progressive, adaptive neocortical change, and suggests areas for productive research.

A family study of autism: cognitive patterns and levels in parents and siblings

First-degree relatives of 99 autism probands and of 36 Down's syndrome controls were assessed with standardised tests of intellectual functioning, reading, and spelling. Higher mean verbal IQ scores, and discrepancies in favour of verbal scores, were characteristic of autism relatives. No consistent differences were found on performance scales, reading, and spelling tests. Among autism relatives, siblings affected with the broad phenotype of autism had significantly lower IQ scores and poorer reading and spelling performances than unaffected siblings. However, the small size of the cognitive difference and the lack of a distinctive cognitive profile indicates that standardised cognitive measures used in this study are unlikely to improve the operationalised definition of the broad phenotype of autism. The slightly superior verbal performance of relatives in the autism group might represent some form of heterozygote advantage.

Fluctuating asymmetry and psychometric intelligence

Little is known about the genetic nature of human psychometric intelligence (IQ), but it is widely assumed that IQ's heritability is at loci for intelligence per se. We present evidence consistent with a hypothesis that interindividual IQ differences are partly due to heritable vulnerabilities to environmental sources of developmental stress, an indirect genetic mechanism for the heritability of IQ. Using fluctuating asymmetry (FA) of the body (the asymmetry resulting from errors in the development of normally symmetrical bilateral traits under stressful conditions), we estimated the relative developmental instability of 112 undergraduates and administered to them Cattell's culture fair intelligence test (CFIT). A subsequent replication on 128 students was performed. In both samples, FA correlated negatively and significantly with CFIT scores. We propose two non-mutually exclusive physiological explanations for this correlation. First, external body FA may correlate negatively with the developmental integrity of the brain. Second, individual energy budget allocations and/or low metabolic efficiency in high-FA individuals may lower IQ scores. We review the data on IQ in light of our findings and conclude that improving developmental quality may increase average IQ in future generations.

Thirty-year secular trends in the cognitive abilities of Danish male school-leavers at a high educational level

A nationally representative sample of Danish males finishing school in 1989, or shortly before, with a studentereksamen (the highest qualification in the Danish school system) was found to score generally lower on a battery of four cognitive tests than a comparable sample of Danish males who had taken the same tests shortly after finishing school in the late 1950s or early 1960s. This decline appears attributable to the increasing proportions of students who obtain the studentereksamen and is quite compatible with an overall increase in test scores, also found in our data, for the general population over the same time period. For those who obtain the studentereksamen, the decline has been most marked in a test of verbal analogies. It has been smaller for tests of logical and spatial reasoning, and scores on a test of numerical ability have actually improved over the 30 years. This differential pattern may be the result of both student changes and curricular changes within Danish schools.

Auditory-visual spatial interaction and modularity

The results of dealing with the conditions for pairing visual and auditory data coming from spatially separate locations argue for cognitive impenetrability and computational autonomy, the pairing rules being the Gestalt principles of common fate and proximity. Other data provide evidence for pairing with several properties of modular functioning. Arguments for domain specificity are inferred from comparison with audio-visual speech. Suggestion of innate specification can be found in developmental data indicating that the grouping of visual and auditory signals is supported very early in life by the same principles that operate in adults. Support for a specific neural architecture comes from neurophysiological studies of the bimodal (auditory-visual) neurons of the cat superior colliculus. Auditory-visual pairing thus seems to present the four main properties of the Fodorian module.

The intelligence of American children is still rising

Children's intelligence increased in the United States by approximately 3 IQ points per decade over the period 1932-78. New evidence shows that these increases have been sustained during the last 20 years. Two recent studies indicate that the rates of increase for 1972-89 and 1978-89 were 3.3 and 3.5 IQ points per decade, respectively.

Reaction times and intelligence: a comparison of Japanese and British children

Japanese and British 9-year-old children were compared on the standard progressive matrices and twelve reaction time parameters providing measures of simple and complex decision times, movement times and variabilities. The mean of the Japanese children on the progressive matrices exceeded that of the British children by 0.65 SD units and on the decision times component of reaction times by 0.50 SD units, suggesting that the high Japanese mean on psychometric intelligence is largely explicable in terms of the more efficient processing of information at the neurological level. Japanese children also showed faster movement times but, contrary to expectation, had greater variabilities than British children.

INTELLIGENCE IN CHINA

Studies of the intelligence of' Oriental peoples in Japan, Hong Kong, Taiwan, Singapore and the United States have typically reported slightly higher mean IQs than those of British and American Caucasoids. Recently results have become available for a standardization of Raven's Standard Progressive Matrices in the People's Republic of China. The results show that Chinese 6–15 year-olds obtain a mean IQ of 102.1 in relation to an American Caucasoid standard of 100.

BLACK-WHITE DIFFERENCES IN REACTION TIMES AND INTELLIGENCE

350 black South African 9-year-old children were compared with 239 white British children on the Standard Progressive Matrices and 12 reaction time tests giving measures of decision times, movement times and variabilities in tasks of varying complexity. The black children obtained a mean IQ of approximately 65. They also had slower decision times and greater variabilities than the white children, but they had faster movement times. The magnitude of the white advantage on decision times was 0.68 of a standard deviation, about one-third of the white advantage on the Progressive Matrices. The result suggests that around one-third of the white advantage on intelligence tests may lie in faster information processing capacity.

The intelligence of six-year-olds in Hong Kong

Evidence has accumulated to suggest that the mean IQs of Orientals in the United States and in the countries of the Pacific Basin are higher than those of Whites (Caucasoids) in the United States and Britain. This paper presents evidence from IQ tests on 4858 6-year-old Chinese children in Hong Kong. On the Coloured Progressive Matrices these children obtained a mean IQ of 116. Samples from Australia, Czechoslovakia, Germany, Romania, the UK and the US obtain IQs in the range 95-102. It is suggested that these results pose difficulties for the environmentalist explanations commonly advanced to explain the low mean IQs obtained by some ethnic minorities in the United States.