The study of 60 countries identified a clear correlation between assessments of national mental ability and real gross domestic product, or GDP.

The authors of the work said that the findings showed that international aid agencies should do more to improve the nutrition of pregnant women and infants — the most important environmental determinant of intelligence — to help to lift developing nations out of poverty.

Richard Lynn, Professor Emeritus of Psychology at the University of Ulster, and Tatu Vanhanen, Professor Emeritus of Political Science at the University of Tampere in Finland, tested the non-verbal reasoning abilities of a representative sample of the different populations. They found that the countries of the Pacific Rim had the highest intelligence scores: Japan, South Korea, Taiwan, China, Hong Kong and Singapore averaged IQs of about 105.

The next brightest were the populations of Europe, the United States, Canada, Australia and New Zealand, averaging 100. In South Asia, North Africa and most Latin American countries, the score was an average of about 85, and in sub-Saharan Africa and the Caribbean closer to 70.

Set against international measures of economic performance, the academics concluded that about 58 per cent of the differences in national wealth could be explained by differences in intelligence. Each average IQ point above 70 was worth about £500 in GDP per head of population. The report says that people with high IQs can acquire complex skills to produce goods and services for which there is international demand.

It also says that they are more likely to develop efficient public services such as transport and telecommunications, which provide an efficient infrastructure, and are more likely to have intelligent political leaders who manage their economies effectively.

Variations from the trend could be explained by political and economic factors: countries such as China and Russia and in Eastern Europe with high average IQs (about 100) but low per capita incomes often had a history of socialist systems. These inhibited the natural relationship between skills and national wealth, the authors said.

“The per capita income in China is low — about £2,400 a year — because of the inefficiency of the communist system,” Professor Flynn said. “Now the Chinese have introduced a market economy the growth rate is rapid, about 10 per cent a year compared with about 2 per cent in Europe.

“China can be predicted to reach parity with Europe and the US in about 50 years time, and become the new economic and military superpower.”

Other variations could be explained by natural resources: the presence of oil in the Gulf states, diamonds in Botswana and the tourist-friendly climate in Bermuda, for example, all raised GDP beyond that in countries with comparable IQ ratings.

Although a large proportion of intelligence is thought to be inherited — about 50 per cent globally, according to the most recent estimates — environmental factors are also significant. Average IQs have been rising sharply in developed countries, in some by up to 25 points in a single generation.

“There is no doubt that poor nutrition has an effect on IQ levels,” Professor Flynn said. “Even in economically developed countries there are pockets of poor nutrition which affect intelligence. In Britain it is estimated that about 10 per cent of children have sub-optimum nutrition. If they are given supplements in adolecence, their IQs rise by about five points. In developing countries, where malnourishment is more serious, they would rise by between ten and fifteen points. Poor standards of health are a factor as conditions such as chronic diarrhoea affect nutrition. And it also has a detrimental effect if education standards are poor or nonexistent. It has also been suggested that the spread of ‘cognitively stimulating technology’ such as computer games — another corollary of economic development — has contributed to the rise.

“Our critics would suggest that we are confusing cause and effect, and that IQs are higher in rich countries because of better health, education and so on. But we don’t think that is likely: intelligence is the largest single factor behind national wealth. It then becomes a virtuous circle, with the benefits of the resulting affluence adding extra IQ points.”

The psychologist Oliver James said that too much reliance had been put on IQ measures as objective assessments of brainpower. “The IQ test is heavily culturally conditioned,” he said.

“In this country it tests your middle-classness and how well you know how to please the testers. The IQ of a working-class child adopted by a middle-class family will rise by about 12 points. (The authors) are confusing IQ with education. If a country has a good education system, their economy will benefit. It is rich countries that are likely to have those systems.”

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