In another respect, too, inequality has been retreating. Thespread o f IQ scores has been shrinking steadily - because thelow scores have been catching up with the high ones. Thisexplains the steady, progressive and ubiquitous improvementin the average IQ scores people achieve at a given age - at a rateo f 3 per cent per decade. In two Spanish studies, IQ proved to be9.7 points higher after thirty years, m ost o f it am ong the leastintelligent half o f the group. Known as the Flynn effect, afterJam es Flynn who first drew attention to it

Continual engagement with the mental rigors of modern life coincided in many parts of the world with improving nutrition, rising living conditions and reduced exposure to pathogens. These factors produced a century-long climb in average I.Q. scores — a phenomenon known as the Flynn effect, after James Flynn, the political philosopher who identified it.