If cameras were allowed in the locker room of Japan’s national football team, viewers would see an odd sight: the minute the players are off the pitch, their noses are reportedly buried in “IQ supplement” puzzle books. This keenness for number, word and visual puzzles is part of a much wider trend sweeping Japan. Prompted in large part by the Su Doku boom in the UK, people have rediscovered the varied world of Japanese puzzles — a tradition that dates back centuries and has long been associated with self-improvement.

And thanks to research by neurologists such as Professor Ryuta Kawashima, Japan has decided that sweating over Su Doku and wrestling with word play can improve one’s IQ. Many parents foist them on their children to expand their minds.

Because of its Japanese roots, says a spokesman for Fusosha, a publisher of puzzle books, “Su Doku led the way in Japan’s rediscovery of the brainteaser. It has spread from there to many other forms of Japanese puzzle that have been dormant for many years.”

IQ supplement books have indeed resurrected puzzles: the last Japanese Su Doku boom was in the late 1980s, but matchstick puzzles, word enigmas and variants of logic puzzles have been gathering dust for far longer. Sales of Rubik’s Cubes have surged over the past 18 months, as have sales of metal puzzles and traditional Japanese brainteasers involving twisted ropes and wooden beads.

IQ supplement books have sold more than a million copies: a primetime on the subject on the Fuji TV network is beamed into tens of millions of Japanese homes every Saturday night, and Nintendo has scored a global hit with an IQ-related game for its hand-held DS console.