A weekly column on how the mind works
It's a tall man's world. Psychologists long ago established that a man's height is a powerful indicator of success in almost every field. As well as earning more money than their vertically challenged brethren, tall men have been found to be significantly more attractive to women. And in the past 13 US presidential elections, the taller man has won 10 times. US presidents also tend to be well above average height. Traditional thinking says being tall triggers something at a deep biological level evolved from more violent and unstable times - perhaps tall people are worth getting close to because they could be useful in a fight.
Each extra inch in height is also associated with a rise in earning power of between 0.025 per cent and 5.5 per cent worldwide, while in Britain it's linked with 1.7 per cent increase in income. To put it another way, the shortest quarter of the population in the UK and the US earns roughly 10 per cent less than the tallest quarter.
Recent research suggests that the key is not your adult height, but how tall you were during your teenage years. Unlike gender or race, height varies - particularly during adolescence. Many who start out short shoot up suddenly; those who have an early growth spurt often plateau, allowing others to catch up and pass them. Could all these changes in adolescence permanently affect your psychology as an adult?
Nicola Persico, Andrew Postlewaite and Dan Silverman, economists from the University of Pennsylvania, drew data from Britain's national child development study and the US's national longitudinal survey of youth. When they studied correlations between a man's income and his height at the ages of seven, 11 and 16, as well as his adult height, they found that all of the effects of height on income were attributable to height at the age of 16. Variations after that age or earlier in childhood had no independent correlation with income.
The reasons remain unclear. Employers' prejudice seems implausible: an employer is unlikely to have any idea of an employee's height when young.
The key, argue the researchers, is the "social and cultural stigma" attached to being a short 16-year-old. Men who were relatively short youths were less likely to have taken part in social activities, such as athletics, that may boost self-esteem and inculcate valuable social skills.
It seems that a complex set of factors is at work. Being short may lower your self-confidence and, perhaps, immediate popularity, so hampering your social life or holding you back from extra-curricular activities that would help develop social and cognitive skills. It could trap you in a vicious psychological cycle of lowered self-esteem derived from poor levels of social participation.
The work has much broader consequences. The differences in school and family backgrounds between tall and short youths are tiny compared with those between white and black youngsters. The finding that a teenage sense of social exclusion influences future earnings may have great implications for young people from minority or unpopular groups, such as the overweight.
Above all, it suggests teachers should be aware of the importance of a teenager's self-esteem in predicting what happens to you as an adult. They must discourage teenagers with low self-esteem from opting out of what's going on and instead encourage social participation.
Dr Raj Persaud is a consultant psychiatrist at the Maudsley hospital and senior lecturer at the Institute of Psychiatry in London. He is a fellow of University College London, and author of From the Edge of the Couch published by Bantam Press, pound;12.99. Email: firstname.lastname@example.org