Maturity, the thinking goes, comes with age. However, this journey from childhood to adulthood is uneven, with some mental attributes surfacing faster than others, some more pronounced in girls than boys and poverty and trauma, having an outsized influence on cognitive development, says one of the largest studies of its kind, spanning nearly 9,000 children and young adults from India.
The study is part of a long-term project called the ‘Consortium on Vulnerability to Externalizing Disorders and Addictions’ (C-Veda). It aims to follow up those tested over decades, evaluate the effect of biological and environmental risk on cognitive development, and also compare these effects across people in industrialising (India) and industrialised (U.K.) societies.
Brain development progresses from childhood to early adulthood with increasing and wide-ranging connections among neurons located in multiple parts of the brain. This connectivity significantly influences abilities such as holding chunks of information temporarily, called ‘working memory’ (memorising a phone number before writing it down, for instance) and ‘set shifting’ (iterating multiple ways to solve a puzzle). These skills are classified as executive functions. Another category of functions, called social cognition (learning social rules, empathising), help mediate relationships.
A consortium of psychiatrists, neurologists, psychologists from India and the U.K., investigating the role of environment and genetics on brain development, analysed four kinds of executive functions: verbal working memory, visuo-spatial working memory, response inhibition (the ability to stop one task and begin another), set-shifting and two kinds of social cognition: faux pas recognition (inferring social cues) and emotion recognition (inferring another’s state of mind).
Psychologists and those who study brain development rely on specialised, standardised tests – they could be questionnaires, but are mostly computer-aided ‘tasks’ or games – to assess each of these skills to investigate brain development, learning difficulties, mental disorders.
They report, in the April 2023 edition of the peer-reviewed Asian Journal of Psychiatry, that ‘working memory’ develops first, followed by inhibitory control and finally cognitive flexibility. However certain abilities like visual and verbal reasoning stabilised by late adolescence and didn’t rise as people aged, whereas cognitive ability and emotional cognition continued to develop even after adolescence.
“We didn’t find a stabilisation age for this even after 23 years. This is in line with literature that says the brain continues to develop even after the 20s,” Eesha Sharma, the lead author of the study, told The Hindu.
The studies, spanning a range of socio-economic groups, ages, urbanisation and gender, also found that children who manifested certain traits to a high degree outperformed their peers in that skill even as they aged, while other traits didn’t constitute a permanent advantage.
“Response inhibition has a ceiling. If you are low performing early on, you will catch up as you grow older. It was the other way, however, in verbal working memory. Those who did well in early childhood continued to significantly outperform their peers,” added Dr. Sharma, an assistant professor at the National Institute of Mental Health and Neurosciences, Bengaluru. “However, what all this means in the real world is a question that we are still analysing.”
The more ‘complex abilities’ – response inhibition, cognitive flexibility, and emotion recognition – are “maximally impacted” by environments such as poverty or childhood adversity. “No matter which ability you are looking at, children in wealthier households do better,” she said. ‘Wealth’ here was defined as being high on the ‘wealth index,’ a scale constructed by evaluating children’s access to assets that increase comfort and facilitate exposure to knowledge (a house, mobile phone, internet, etc.).
There were also variations by sex, the study noted. “Sex had a significant effect on cognitive ability for response inhibition and emotion recognition (greater in females), and set-shifting (greater in males). This effect was seen after controlling for age, childhood adversity and wealth index,” the authors noted in their paper.
The C-Veda project expects to map the brains of those participating in the study and thereby evaluate and compare neurological development. “If we can generate brain-development charts across ages, just like how there are charts for physical growth, it could be a valuable tool in schools and mental health assessments,” Dr. Sharma said.