What is the strongest predictor that a child starting school will do well academically? Is it IQ? Good vocabulary? Strong maths or reading skills? Actually, it may be none of these. To find out more, we have to look at the findings of a longitudinal study known as the marshmallow experiment. It was conducted in the Seventies and Eighties by Walter Mischel, a psychologist at Stanford University.
The experiment begins with a four-year-old child sitting at a table, staring at two marshmallows on a plate, beside which sits a small bell. Mischel asks whether the child would like one marshmallow or two (not too hard for a four-year-old). He then mentions that he has to leave the room, but says that if they wait until he returns they can have both.
However, if at any point while he is away they decide they can't resist, no problem: they should ring the bell and they can have one of the sweets. The children sit on their hands, stare at the wall, even lick round the plates, but more often than not they last only a few minutes before giving in and ringing the bell.
Fifteen years later, Mischel follows up the progress of the children by sending questionnaires to their parents, asking about aspects of their teenager's personality and academic performance. Remarkably, Mischel discovers that the amount of time they waited before ringing the bell predicts not only what their parents said about them as a teenager, but also the likelihood of their performing well in college entrance exams.
The "grabbers" were reported to suffer lower self-esteem and the viewed as more stubborn and prone to frustration. The "waiters" were better copers, more assertive, trustworthy and academic.
What set the waiters apart - and what made them successful - is that they demonstrated better self-regulation, part of a set of cognitive abilities known in psychology and neuroscience as executive functions. This group of mental activities can be difficult to define, but I think most scientists would agree that they centre around our ability to control our thoughts and actions, so that we can respond to our changing environment.
The decision-making, planning, control of attention, inhibition of impulses, working memory and introspection that we use throughout our lives to work out what we want, plan how we might get it and then carry out that plan, are all captured under this umbrella term.
Neuroscientists are only just beginning to understand how the brain gives rise to executive functions, but it is increasingly clear that the front regions of the brain - the frontal lobes - play a crucial role. That doesn't paint the full picture, however, as the frontal lobes are strongly interconnected with other brain regions: no area is an independent mini-brain. Indeed, it is this vast connectivity that provides the frontal lobes with their key co-ordinating and controlling function.
From an evolutionary perspective, we can see how the relative expansion in the size of our frontal lobes has given us a selective advantage over other species by freeing us from responding only to our immediate situation.
As the nature of learning places children in unfamiliar situations, where they need to develop new modes of thinking and behaviour, they depend hugely on executive function abilities at school.
Take the example of a group of 15-year-olds on a hot Friday afternoon in a science class. As they struggle to concentrate on planning their class project, the teacher reads out more instructions. Some give up straight away and start chatting excitedly about their weekend plans. (They wouldn't have waited long before scoffing a marshmallow).
- Some sit up and listen and try to ignore the group chatting. But then, when they realise there's just five minutes of the lesson left, they decide - reasonably enough - to join in the chat and finish planning the project on Sunday.
Only one has enough concentration and control to carry on working till the end. That's the one who would have waited ages for two marshmallows - and who has made the best decision of all.
Unsurprisingly, this ability to control our thoughts and actions is central to success, from the personal to the creative and academic. Over the next seven weeks in Brain Behaviour, scientists will look at how this ability develops in children, from the early years through to adolescence, and how it affects performance in areas from mathematics to music.
As we share these insights with you, we will explain how you can help children take control of their developing brains
Baroness Susan Greenfield is Professor of Pharmacology at the University of Oxford and Director of the Royal Institution of Great Britain
Mischel, W., Shoda, Y., Rodriguez, M. L. (1989) Delay of gratification in children. Science, 244, 933-938
Blair, C. (2003) Behavioral Inhibition and Behavioral Activation in Young Children: Relations with self-regulation and adaptation to preschool in children attending Head Start. Dev Psychobiol. 42(3):301-11
Overview of the Science of Learning project at The Institute for the Future of the Mind: