I graduated in psychology and took my Ph.D. at the University of Cambridge and have worked as lecturer in psychology at the University of Exeter, professor of psychology at the Economic and Social Research Institute, Dublin, and at the University of Ulster.
Most of my work has been on intelligence. My major discoveries are that the Oriental peoples of East Asia have higher average intelligence by about 5 IQs points than Europeans and peoples of European origin in the United States and elsewhere; and that men have a higher average IQ than women by about 5 IQs points. I first published the high IQ of the Oriental peoples in 1977 in a paper on the intelligence of the Japanese. In subsequent years the high Oriental IQ has been confirmed in numerous studies of Oriental peoples in Hong Kong, Taiwan, South Korea, China, Singapore and the United States.
In 1983 I published a paper in Nature showing that the IQ in Japan had increased over the course of the previous half century, a phenomenon now known as the Flynn Effect following the demonstration by Jim Flynn of secular increases in intelligence in number of countries. In 1989 I proposed that the increases in intelligence have been caused by improvements in nutrition. I have also published several papers showing that intelligence is associated with brain size and reaction times.
My work on intelligence and brain size led me to consider the problem that women have smaller brains than men even when allowance is made for their smaller bodies. This implies that men should have higher average IQs than women, but it has been universally asserted that men and women have equal average IQs. In 1994 I proposed that the solution to this problem is that girls mature faster than boys and this compensates for their lower IQs, which only appear at the age of 16 onwards. Among adults men have higher average IQs than women by about 4 IQ points. This advantage consists largely of higher spatial abilities but is also present in non-verbal reasoning. In two meta-analyses of sex differences on the Progressive Matrices carried out with Paul Irwing (2004, 2005) we showed that in the general population men have a higher IQs than women by 5 IQ points, and in university students the advantage of men is 4.6 IQ points.
In 1991 I extended my work on race differences in intelligence to other races. I concluded that the average IQ of blacks in sub-Saharan Africa is approximately 70. It has long been known that the average IQ of blacks in the United States is approximately 85. The explanation for the higher IQ of American blacks is that they have about 25 per cent of Caucasian genes and a better environment.
The theory I have advanced to explain these race differences in IQ is that when early humans migrated from Africa into Eurasia they encountered the difficulty of survival during cold winters. This problem was especially severe during the ice ages. Plant foods were not available for much of the year and survival required the hunting and dismembering of large animals for food and the ability to make tools, weapons and clothing, to build shelters and make fires. These problems required higher intelligence and exerted selection pressure for enhanced intelligence, particularly on the Orientals.