Think you're clever, do you? Put your intelligence to the test right here.
Why are some people more intelligent than others? We all know a few clever-clogs types who play Scrabble backwards and seem to know all the answers when watching University Challenge, after all.
The difficulty is that "intelligence" is not a very smart word. Unlike weight, there is no absolute measure of intelligence, just as there is no true gauge of honesty. When you combine such a slippery word with an equally slippery one - namely "race" - you end up with the notorious claim that intelligence tests prove that some racial groups are genetically inferior.
This wrong-headed idea dates back years. Francis Galton (1822-1911), a pioneer of intelligence testing, also founded the Eugenics Society, which set out to "improve" the genetic composition of the population - a philosophy that helped to inspire the Nazis' extermination of "undesirable" groups.
Sadly, the notion survived its most brutal exponents. In the Seventies, the psychologists Arthur Jensen and Hans Eysenck asserted that blacks have IQs lower than whites. In the Nineties, the American Right-winger Charles Murray suggested that the lowest levels of society would always be "the underclass", held back by innate differences in mental capability.
This is, unsurprisingly, absolute poppycock. From a scientific point of view, the notion of race is meaningless. Genetic differences do not map neatly on to traditional measurements of skin colour, hair type, body proportions and skull measurements. In fact, a person who is considered black in one society may be non-black in another.
However, just as it is apparent that some people look darker than others, it is equally apparent that some people are indeed smarter than others. And just as there are tests that capture our differences in physical fitness, we are able to devise those that capture differences between our cognitive abilities, most of which demand the performing of various mental tasks.
The best-known of the bunch is for intelligence quotient, now most commonly measured using the Wechsler Adult Intelligence Scale. The first version of this was published in 1955 by the American psychologist David Wechsler: in it, the results from a 90-minute examination of comprehension, vocabulary and arithmetic are combined to derive a final IQ score.
The results seem to correlate with performance at school and work, so to that extent at least, our IQ scores can be said to reflect how smart we are. But we can do more to find a sophisticated measure of relative performance. That's why, for the past four years, Adrian Owen and I have been discussing a new way to gauge intelligence.
Dr Owen is part of the Medical Research Council's Cognition and Brain Sciences Unit in Cambridge. With his colleague, Adam Hampshire, he has devised the ultimate intelligence test. Drawing on data from brain scans, his test - featuring a dozen tasks - triggers as much of the brain's anatomy as possible, combining the fewest tasks to cover the broadest range of cognitive skills.
For example, spot-the-difference puzzles boost activity in a range of areas at the back and bottom of the brain. Similarly, when you navigate your way around an unfamiliar supermarket, you rely on visuospatial working memory, which is linked to activity in the ventrolateral frontal cortex behind the eyes and the parietal lobe at the back and on top of the brain. However, as the questions become more complex, demanding more use of strategies and stored memories, broader regions of the frontal and parietal lobes become active - in particular, the large area behind the temples known as the dorsolateral frontal cortex.
Adrian and Adam regard this as the ultimate intelligence test - so all that is left is to find out whether it works. To that end, New Scientist has put it online, in a joint project with the Discovery Channel. If you have a half-hour to spare, and want to put your brain through its paces while advancing the cause of neuroscience, have a go here.
Roger Highfield is the editor of New Scientist