Biggest Intelligence Test Exposes The Limits Of IQ

By Adam Hampshire, Brain and Mind Institute, University of Western Ontario

To what extent are some people smarter than others? For a century, psychologists have believed that we can boil differences in cognitive skill down to a single number known as an Intelligence Quotient (IQ). But does one number really represent an individual’s ability to remember, to reason and to think? The answer is an emphatic no, according to the results of a landmark experiment conducted on many tens of thousands of people with the help of Roger Highfield of the Science Museum Group.

With Roger and my colleague Adrian Owen, who works with me at the University of Western Ontario, I describe our findings today in the journal Neuron.

Our  attempt to answer this simple question dates back more than five years, when Roger encountered work that I had conducted with Adrian at the Medical Research Council in Cambridge on a reliable way to carry out cognitive tests online so we could monitor rehabilitation after brain injury, the effect of smart drug trials and so on.

Roger wondered if we could use this test to carry out a mass intelligence test. Drawing on earlier data from brain scans,  Adrian and I came up with a series of tests which we knew would trigger activity in as much of the brain’s anatomy as possible, combining the fewest tasks to cover the broadest range of cognitive skills.

In half an hour, respondents had to complete 12 cognitive tests which look at memory, reasoning, attention and planning abilities, as well as a fill in a survey about their background and lifestyle habits (Roger and Adrian describe the tests here).

We expected a few hundred responses. But thanks to articles in Discovery and New Scientist, 110,000 people took part from every corner of the world. Once I had used statistical methods to analyse more than a million data points on a representative group of around 45,000, I found that when a wide range of cognitive abilities are probed, the variations in performance can only be explained with at least three distinct components: short-term memory; reasoning; and finally, a verbal component.

No one component, or ‘IQ’, explained all the variations revealed by the tests.

To bolster our results, Adrian and I used a $5 million brain scanner, which relies on a technique known as functional magnetic resonance imaging (fMRI), to study 16 participants as they carried out all 12 tests.  We found that each of the three different factors identified by the analysis did indeed correspond to a different brain network: these differences in cognitive ability map onto three distinct circuits in the brain.

The results disprove once and for all the idea that a single measure of intelligence, such as ‘IQ’, is enough to capture all of the differences in cognitive ability that we see between people. Instead, several different brain circuits contribute to intelligence, each with its own unique capacity. A person may well be good in one of these areas, but they are just as likely to be bad in the other two.

Because so many people took part, the results also provided a wealth of information about how factors such as age, gender and the tendency to play computer games influence our brain function.

For example, people who regularly played computer games did perform significantly better in terms of both reasoning and short-term memory. Smokers performed poorly on the short-term memory and the verbal factors, while people who frequently suffer from anxiety performed badly on the short-term memory factor in particular.

We are now launching a new version of the tests, to ensure we do not bias the results of the new tests, we can’t say much about the agenda other than that there are many more fascinating questions about the true nature of intelligence that we want to answer.

Adam Hampshire works at the Brain and Mind Institute, University of Western Ontario, London, Ontario.