Imagine that you are standing in a room measuring 8 by 7 foot wide. There is a small straw mat on the floor beneath your feet – this is your bed, should you choose to sleep. You are imprisoned here but you haven’t really done anything wrong. Now, imagine that this is also your reality for the next 27 years. How would you behave if you were released after all this time?

This is the experience of Nelson Mandela, who was subject to years of psychological and physical mistreatment during his incarceration. However, once released he went on to campaign extensively for human rights and subsequently became the first black head of state in South Africa.

Scientists would term this strength ‘resilience’ – the idea that in spite of traumatic, stressful or adverse life events, a person can ‘bounce back’, and become psychologically stronger as a result.

So why do some people become resilient, and others don’t? In Mandela’s autobiography Long Walk to Freedom, we are given an intriguing insight into why: ‘I am fundamentally an optimist. Whether that comes from nature or nurture, I cannot say…’

Psychologists and neuroscientists, too, have tussled with the question of what can make someone resilient. Is it ‘nature or nurture?’. On the one hand, research has shown that resilience could originate from our biological make-up: our genes (genetics), the microscopic interactions in our brain and nervous system (neurobiology), or the way that we think (our cognition).

In 2007, academics from London and New York used fMRI (one of the most popular tools used to carry out brain imaging scans) to examine why it is that humans as a whole tend to expect positive events to take place in the future, even when no evidence suggests that this will happen – a term they coined ‘optimism bias’.

According to Tali Sharot’s findings, two areas of the brain were ‘more’ active in participants with a tendency for ‘optimism bias’ – the amygdala and the rostral anterior singulate cortex.

Could it be, then, that humans have the capacity to become ‘prisoners’ of a troubled childhood, facing an outcome determined by biology? Many scientists now argue that this is ‘not’ the case. Research has shown that resilience could just as foreseeably stem from other parts of our lives such as positive aspects of the environment we grew up in, the level of parental support we received, or a number of other ‘protective factors’.

When Emmy Werner and Ruth Smith began a landmark longitudinal study on all of the children born in the Hawaiian island of Kauai in 1955, they found that a large number of these children (30%) had been born or raised in poverty or had come from troubled family backgrounds. However, 1 in 3 of the children went on to experience a fulfilled life, largely because of stable personal relationships.

So, it appears that both biological and environmental factors are important when it comes to optimism and resilience. If we are not prisoners of our biology then, is it possible for people to learn optimism, and to subsequently become more resilient?

Good news. Yes, say researchers Jane Gillham and Karen Reivich – especially in young people. For example, the Penn Resiliency Program demonstrates how a school-based intervention can help to prevent symptoms of depression and anxiety.

It has also been shown to build resilience, well-being, and optimism. Research has also shown that some types of therapy, such as cognitive behavioural therapy (CBT) can promote more optimistic feelings in both children and adults. It appears then that you can be (as Mandela would say), the master of your fate.

Bessie O’Dell is currently a postgraduate fellow in the Anticevic Lab at Yale University’s School of Medicine/ Department of Psychiatry.