For men, a loss of intelligence during holidays may well be exacerbated by the vision of the opposite sex in bikinis. For men, a loss of intelligence during holidays may well be exacerbated by the vision of the opposite sex in bikinis. Photo: Getty Images
Research suggests that taking a holiday can cut your brain power, says Michael Hewitt.
If your neurosurgeon announces that he has just returned from two weeks in Cancun, you may want to postpone that craniotomy. Holidays, it seems - particularly to sweltering destinations - can impair mental functioning. Perhaps not so much that, post-Ayia Napa, Stephen Hawking would want to switch to editing a lads' mag, but sufficient, nonetheless, to prove a hindrance to researching the Big Bang.
The problems begin when you book your holiday online, particularly if this entails a lengthy email exchange. According to a 2005 study by psychologist Glenn Wilson, visiting professor at Gresham College, London, email "bombardment" can reduce IQ by up to 10 points - more than double the effect of smoking a lot of cannabis.

Prof Wilson has labelled the condition "infomania". Concentration is impaired as sufferers' minds remain fixed in an almost permanent state of readiness to react to incoming messages, as opposed to focusing on tasks in hand. Even on a good day, the human brain finds it hard to cope with juggling multiple tasks simultaneously, so the email overload further reduces its effectiveness.
Then you actually have to get to your holiday resort. The stress of modern travel - worries over airport strikes, volcanic ash or whether you're in the right queue for priority boarding - can increase levels of cortisol, the stress hormone. This risks damaging cells in part of the brain called the hippocampus, which in turn adversely affects short-term memory and concentration.
Add a restorative drink while airborne and, depending on the beverage, you could drop another 10 to 20 IQ points, according to Alcohol Concern.
And you haven't even checked into your hotel yet. It is at this point that phrenic Armageddon really kicks in. Research by Prof Siegfried Lehrl of the University of Erlangen in Germany, a specialist in mental performance, suggests that sunbathing and relaxation cause one's frontal lobes to literally shrivel. Barbados or Benidorm, it doesn't matter.
Prof Lehrl says that inactivity reduces oxygen to the brain, which causes the dendrites and axons (parts of the nerve cells involved in sending electrical impulses) to degrade. Add dehydration caused by excess heat, alcohol, or both, and brain cell volume may decrease by up to 15 per cent.
"Fourteen days of complete rest can be enough to bring your IQ down by 20 points - more than the difference between a bright and an average student," says Prof Lehrl. "Vocabulary shrinks, and we even detect personality changes."
For men, this loss of intelligence may well be exacerbated by the vision of the opposite sex in bikinis. A 2008 study for The Journal of Con-sumer Research concluded that merely looking at women in beach garb "instigates generalised impatience in intertemporal choice". In layman's terms, men's judgment and self-critical faculties are compromised, and, in worst-case scenarios, they will propose to (or proposition) the first girl who winks at them.
At this point, you might be tempted to down a cold beer at the poolside bar. Don't! Researchers at Bristol University discovered that drinking anything overly cold reduces brain power by as much as 10 IQ points, as energy and blood are diverted from the brain to the stomach, to balance the drop in temperature.
So how can you negate the nightmare effects of your dream vacation? According to Prof Lehrl, you should exercise your brain on holiday for at least 10 minutes a day by playing an intellectually stimulating game (chess or Scrabble, for instance), mitigate inactivity with regular long walks, rehydrate constantly - and chew lots of gum. Gum? "The part of the brainstem that keeps us alert is constantly stimulated by chewing, as a result of which the attention level rises, as does flow of blood to the brain."
If you lack the willpower to follow the professor's advice, the good news is that, unless you did propose to the first girl who winked at you (and she accepted), the consequences of a vacation are temporary. Four days later, your IQ usually returns to normal.
So next time you see raucous holidaymakers necking beers and mooning passers-by, try not to be too judgmental: they are probably email-overloaded nuclear safety engineers who have neglected to chew gum. Hopefully, they will leave a sensible interval between returning to work and installing their reactor's control rods.
- The Telegraph, London