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Brain power: determined by nature or nurture?

Researchers are testing DNA samples from a group of people with well-above-average IQ to see which genes control intelligence. Image credit: Pixabay/ jarmoluk

Geneticists are studying the super-intelligent in search of genes that control cognitive ability while psychologists explore whether memory training can improve social skills and make us smarter.

Our ability to communicate, recall information and solve problems results from a combination of our genes and our experiences. But just how much of the brain’s fate is set before parents and teachers have had a chance to mould young minds?

Professor Robert Plomin, from King’s College London, UK, has spent decades decoding the genetics of the human mind. His studies of g – general cognitive ability – reveal the strong influence of DNA on how smart people are, how they learn and a host of long-term life outcomes.

The level of g can be measured by a battery of psychometric tests – similar but subtly different to intelligence quotient (IQ) – and predicts how far individuals will make it in the education system, as well as their earning capacity.

Prof. Plomin said: ‘g is at least 50 % heritable. However, only 2 % of the genes have been identified so we need to fill these gaps.’

Much of the work in this area has focused on studying the genes of large numbers of people with ‘normal’ levels of g in search of genes associated with intelligence. The sample sizes have grown significantly yet no genius genes have been found.

Prof. Plomin has taken an alternative approach. As part of the Genetics of High Cognitive Abilities (GHCA) project, funded by the EU's European Research Council (ERC), his team has been studying the genomes of some of the world’s smartest individuals to see what gives them the intellectual edge.

To do this, Prof. Plomin has obtained DNA samples from a unique group of more than 2 000 individuals with an average IQ of 170. This puts them in the top 0.0003 % of the population, well above the average for Nobel Laureates which is estimated to be a nonetheless impressive 145. (The average IQ is 100.)

‘What’s cool about our sample is that, because it is a concentration of individuals at the extreme end of the spectrum, we reckon it has statistical power comparable to a sample of many hundreds of thousands of people from the general population,’ said Prof. Plomin.

Where did he find this super-elite group? In 1972, scientists in the US launched Project Talent to track the country’s brightest students. They first asked schools to nominate their best-performing 13-year-olds and gave them a standardised college entrance test.

Kids who scored in the top 1 % that year – compared to college applicants who were usually five years their senior – were earmarked for further study. From there, the US researchers took the very top of that group and further whittled it down until they were left with the crème de la crème of adolescent intellects. This cohort has been followed ever since.

The question for Prof. Plomin was whether they had a common ‘genius gene’ or group of genes that set them apart from their peers. Perhaps they had benefited from a mutation that gave them superhuman memories, computational skills or an iron-clad logic.

However, rather than identifying a special gene mutation that all geniuses share, one of the key findings to date is a distinct absence of mutations in ‘functional variants’ – forms of genes that can affect human health and behaviour. What they have in common is a lack of notable mutations rather than the presence of an optimal set of genes that most people are born without.

‘Super-high intelligent individuals have fewer mutations in these functional variations,’ said Prof. Plomin. ‘The brain is a highly tuned organ – mutations are not good for the brain.’

Controversial

The search for genius genes continues but researchers say the weight of evidence supports the theory that at least half of our intelligence is determined by our genes. In the past, this broad area of genetic research has proven controversial, with some interpreting the strong influence of genes of learning ability as a sign that some are destined to succeed while others are doomed to struggle.

For his part, Prof. Plomin says that the ability to predict which children will have trouble learning opens the door to a more tailored approach to education. ‘A universal educational curriculum which assumes a one-size-fits-all approach isn’t working – teachers already know that,’ he said.

‘Research on the genetics of cognitive ability may help to focus more energy on those who need it. Medical researchers speak of precision medicine or personalised medicine based on genetics; education is also moving towards personalised learning.’

Brain training

While genes have a strong influence on cognitive ability, psychology researchers have found that crucial skills such as social community, good memory, flexibility and a capacity for planning are not set in stone. IQ is seen as being more or less constant, whereas memory can be improved through training and may have a positive knock-on effect on how people perform in other cognitive and social tasks.

‘We want to see whether social communication can be improved through training.’

Dr Heath Ferguson, University of Kent, UK

‘A lot is known about how children develop social skills, but it had been presumed that these skills are acquired around the age of four and are then fully formed by adulthood,’ said Dr Heather Ferguson of the University of Kent, UK. ‘More recently, research has shown that this development continues throughout life and adults can begin to lose some social skills as early as their mid-20s.’

Through the ERC-funded CogSoCoAGE project, Dr Ferguson is looking at the cognitive basis of social communication and how it changes across the lifespan. Her team is testing hundreds of people with ages ranging from nine to 90 years.

Participants are given a battery of tasks that assess 10 aspects of social communication – including the ability to read emotions in people’s faces, to understand a character’s intention or desires in a story, and to observe and imitate actions. This is done through a combination of questionnaires, computer-based tasks, eye-tracking tasks and electroencephalography to measure electrical activity in the brain during the tests. 

Physical activity is also being assessed, as some research has shown a link between physical fitness and cognitive ability. The testing has just begun and the group will be retested in two and a half years to see how their abilities have changed over time. Participants will be given training to see if their cognitive skills can be enhanced, and whether in turn this can improve their social abilities. This may reveal whether age affects the scope for improving these skills or for arresting cognitive decline.

‘We want to explore whether we can improve social communication by training underlying cognitive skills,’ explained Dr Ferguson. ‘If we find that, for example, working memory is the key to understanding someone’s intentions we can improve social skills by improving memory.’

The approach could help people showing early signs of dementia and may even hold promise for people who have conditions associated with poor social skills such as autistic spectrum disorders.

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