Edinburgh International Science Festival 2017 / A Very Short Introduction to… Intelligence

There are ten important things to know about intelligence, each discussed in Professor Ian Deary’s book A Very Short Introduction to Intelligence. In a fast-paced public discussion presented by Oxford University Press at Summerhall, Professor Deary outlined these ten factors in an hour’s talk, allowing the audience five minutes per point to ask questions. From a discussion so jam-packed with information the speaker had to use an egg timer to adhere to his time limit, here are some highlights.

The talk began with the point “Intelligence: It’s one thing, it’s a few things, it’s many things.” People who score well on one type of cognitive test tend to score well across the board. Using the Wechsler intelligence test – the ‘gold standard’ intelligence test – as an example, general cognitive ability can be divided into four broad areas – verbal comprehension, perceptual organisation, working memory, and processing speed. These can then be categorised into thirteen sub-tests. Generally, people who score well in one sub-test score equally as well in each of the twelve other sub-tests.

Secondly, “It matters for education.” People who score highly on cognitive ability tests stay in education for longer and have higher qualifications that those who score lower. Data from cognitive tests taken by children aged 11 was very closely correlated to their GCSE marks. This may seem obvious, but here’s the twist: males and females get the same average scores in cognitive ability tests, but females tend to get better GCSE marks. This may mean that females are better at applying their intelligence to this particular style of academic test.

Interestingly, the discussion touched upon the point “It matters for survival”. Linking this to a discovery made by his team in 2001, Professor Deary showed some graphs that illustrated that people with higher IQ at the age of 11 have improved survival rates in most causes of death, including cardiovascular disease, cancer, and stroke. This could be because people with higher IQ are more conscientious, so they avoid risks to their health, or perhaps because they have a ‘healthier’ brain and less mental illness. Maybe it even has to do with social class.

On that note, the discussion turned to how much of our intelligence is down to our environment and how much is down to our genes. Looking at the IQ score of twins, studies show that until adolescence, genetics contributes 30% towards someone’s intelligence, but in adulthood, genetic factors account for 70% of your intelligence and environmental effects matter much less. With recent developments in DNA sequencing technologies, the latest studies are now able to link intelligence directly to genetics, bypassing the need for twin studies.

Next, Professor Deary covered an area of his own particular interest, cognitive ageing. In ageing, most types of intelligence – such as inductive reasoning, spatial orientation, perceptual speed and verbal memory – decline gradually after the age of about 25. However, two areas of intelligence are maintained with age. These are numeric and verbal ability, which together are known as crystallised intelligence. Crystallised intelligence is the ability to use learned knowledge (in contrast to fluid intelligence, the ability to solve problems and use logic), and scores for these tests do not tend to decrease with age.

The final point was: “It has gone up with time; or has it?” This point makes reference to the Flynn effect, which describes the phenomenon that average test scores for cognitive ability tests have gradually increased over time since 1949. There are several potential explanations for this: for example, people may be becoming more intelligent due to environmental factors such as improved nutrition, or, conversely, people may be becoming more familiar with these types of tests.

The ten points were illustrated clearly with easy-to-follow graphs and charts and backed up by impressive data from huge datasets that have been collected from birth cohorts (of which some members were present in the audience). With the increasing availability of big data, there is so much that can be learned. Experts like Professor Deary and his team are in high demand to mine these kinds of data in order to improve our understanding of population health and, in this case, population intelligence.


This report was written by Bonnie Nicholson and edited by Teodora Aldea.

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