INTELLIGENCE and how to measure it is one of life's great contentious questions. We can be coached to pass exams, but how much does that say about our innate ability? We might outCarol Carol on the Countdown numbers game, but does that really qualify us as "good at maths"? And if someone is a prize-winning scientist but can't empathise with those who are not, do they deserve the label "genius"?

These questions are continually reassessed in the light of cultural and social change. The notion of emotional intelligence, for instance, has gained profile as the importance of communications in our globalised economy has increased. Traditional intelligence testing, meanwhile, has been overhauled due to suspicions of a cultural bias: how can someone from overseas compete fairly in a test which assumes you've been educated in the UK, for instance?

IQ testing, however, is more popular than ever. Psychometric tests for job applicants are still used in the UK, which gives job seekers an incentive to check out how they might do. Most people, however, are just curious to know where they fall in the general spread of intellectual ability.

Nathan Haselbauer is at the very top of that range. He has just celebrated his 30th birthday, but three years ago he retired as a trader on Wall Street to pursue the hobby that was taking over his life. Now it is an enjoyable business, even when he is up until the early hours devising fiendish puzzles to meet the deadline for his next book.

The latest, published in the UK by Robinson, comes out in February. Haselbauer is the founder and president of the International High IQ Society, which has nearly 11,000 members and which came into being when Haselbauer became frustrated with "the number of hoops you have to jump through to join Mensa". He looked instead for an online equivalent, which would provide instant test results.

There wasn't one, so he created his own, attracting like-minded young people who were more interested in sharing experiences on the internet at convenient times than turning out to local meetings. The pass rate for joining was set at 126, a level which, he says, puts members in the top 5-per cent of the population.

The International High IQ Society has now celebrated its fifth birthday. According to its founder, it is not a group of social misfits, although 78-per cent are men, most of them under 35.

The 500 puzzles contained in Haselbauer's latest book include 30 from the annual High IQ Society Goat (greatest of all time) challenge, which start tough and get tougher. Each year the person who scores most points claims the title of smartest person in the world. So far, nobody has achieved a perfect score and, of the hardest puzzles, only a handful of the 500,000 people who have tried them have answered any. Haselbauer and his problem-setters estimate that only one in every 400,000 people is in that league.

We've selected 12 puzzles from Haselbauer's new book for you to test yourself, with individual difficulty ratings between one and four. Good luck - and if you don't get the score you hoped for, you can always blame the test.

The Mammoth Book of IQ Puzzles is published on February 24 (Robinson, pounds-7.99). Visit the International High IQ Society website: www. highiqsociety. org

VOLUNTEERS' RESULTS

Roisin Clarke, 21 English literature graduate Score: 19 "I consider myself intelligent but I was surprised at how difficult I found it. That was mainly because it was biased towards numerical processes, I think. These tests would not measure verbal reasoning, creative skills or emotional intelligence."

Gary McNair, 18 Drama student Score: 25 "I would regard myself as being of above-average intelligence, but I found it a little bit stressful. Some of the puzzles were not very clearly worded. I don't think being able to put dots in a line is a real evaluation of intelligence."

Neil Gillies, 21 History student Score: 23 "It was mainly basic mathematics, so I don't think it was a comprehensive test of intelligence."