It took 110,000 volunteers and a $5M brain scanner to do it, but finally, the notion that intelligence or 'IQ" is a single, measurable human trait that can literally 'divide nations', has been laid to rest.
That is the main finding to emerge from the world’s biggest intelligence test, which I launched in October 2010, along with my colleague at the University of Western Ontario, Adam Hampshire, and Roger Highfield, now of the Science Museum Group in London.
We expected a few hundred people to invest the half hour that it took to complete 12 tests of reasoning, planning, memory and attention, and provide some personal details. However, because the test was launched online on Discovery, New Scientist and The Daily Telegraph it went viral and, in the end, around 110,000 participants had a go.
After removing those who had not finished the test, along with the very young and the very old, we were still left with complete data on 44,600 people, making it the biggest exercise of its kind. The results have just been published in the journal Neuron.
Overall, we found that when we probe a wide range of cognitive abilities the observed variations in performance can only be explained with at least three factors: short-term memory, reasoning, and a verbal component. Being good at one of these factors doesn't mean you are going to be equally good at the other two.
We backed this with complementary brain scanning studies that showed that the three factors activate different brain circuits.
The bottom line is: cognitively, what makes one person different from another - what we often call intelligence - is too complex to boil down to a single factor or ‘IQ’.
The tests also give the most detailed and remarkable insights into the influence of various factors on our cognitive abilities:
AGE: Increasing age had a detrimental effect on two forms of intelligence – short-term memory and logical reasoning. These results are bad news for the elderly, with performance peaking in the late teens and declining rapidly thereafter. In fact, 60-year-olds performed about 1.2 standard deviations lower than 17-year-olds (technically speaking, using the same method to convert the range of performance into a scale as used for IQ, one standard deviation is equivalent to 15 points, thus, this decline is equivalent to a whopping 18 points). On the other hand, verbal intelligence was quite robust against age, with peak performance in the 30s-40s and little decline evident in the 60s.
BRAIN TRAINING: Recent studies have cast doubt on the efficacy of computer brain training and one of our most striking results was that individuals who played standard computer games often had significantly higher scores for short-term memory and logical reasoning scores. These results suggest that the general zeitgeist, that brain-training games are good whereas standard computer games are bad, is the wrong way around.
ANXIETY: We all know nerves affect our ability to concentrate. None the less, we found a surprisingly specific relationship between short-term memory performance and the tendency for individuals to feel anxious with little relationship with the reasoning and verbal factors at all.
The results of this test have been so illuminating that we are launching a new version to probe new questions. Do have a go on http://www.cambridgebrainsciences.com/theIQchallenge.
Professor Adrian M. Owen works at the Brain and Mind Institute, University of Western Ontario, London, Ontario.