Aged six: Happiness The first episode of series six looked at the essential ingredients necessary to make children happy.

We used electroencephalography (EEG) techniques to explore the latest neuroscience research, which suggests happiness can be located in a particular part of the brain.

Scientists believe the prefrontal cortex may be partly responsible for why we feel happy or unhappy.

People who experience more negative moods tend to have a more active right prefrontal cortex, while people who're more positive tend to have a more active left prefrontal cortex.

Activities that challenge our potential to the full produce an emotional state called 'flow', which is essential in developing happiness. We asked our children to conduct a jazz trio to find out who experienced the most 'flow'.

We also explored the environmental factors responsible for a child's wellbeing - a secure attachment to their parents, a loving and stimulating home life and an active social life. How did these help our children cope with life's ups and downs?

The children

Jamie was diagnosed with diabetes at the age of four. This could have knocked him for six, but we found him to be one of the happiest and most optimistic of our children. What enabled him to stay so happy?

Ethan had serious problems concentrating at school, which worried his teacher and parents. Learning difficulties can cause many problems, including low self-esteem, depression and frustrated behaviour. How were these tackled so they didn't affect his long-term happiness?

Rubin was an outgoing and friendly child, but he also took things to heart. Was this linked to his traumatic birth? Or did he need more attention from his mum to develop his self-belief and independence?

Helena was born more than four months early and had to be protected from the outside world to survive. For her first four years, she was kept away from other children and her parents made up for this by giving her every toy they could.

Studies have shown those who value material possessions and fame over achievement and friendships are more likely to suffer depression. Was Helena's unusual childhood affecting her happiness for life?

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