Don't worry be happy.

This programme is presented by Michael Mosley. Starting with charming home movie footage of Michael as a child, the programme explores how our personalities may be determined. Mosley visits Oxford, Ohio, where an ongoing social experiment has been running for the last 40 years looking into aging. Analysing the cohort using the participants' questionnaires, it was found that the people who were more positive in outlook added 7 years to their lifespan. Mosley goes to the University of Essex and meets Professor Elaine Fox who is one of the leading researchers into optimism. It has been discovered that more activity comparitively on the right hand side of the brain (cerebral assymetry) may indicate pessimism; the neurological test Mosley then goes on to perform measures this bias. Next, he goes to a karoake bar to prove how stress can influence your ability to perform under stress (he shouts the first few verses then his voice dries up). In Boston, Massachuscetts, Dr Rosalind Picard from MIT has Mosley wear wristbands which measure emotional states by monitoring minute changes in conductivity and temperature of the skin. The data reveals the subject's arousal level. Mosley suffers from insomnia; he is hoping to change this. Returning to the University of Essex, Professor Fox believes she has an exercise which can trigger a more positive cognitive bias. Mosley has to do the test three times a week (seeking happy faces on a computer programme). In his odyssey, Mosley goes to visit a former monk, Andy Puddicombe, who runs meditation workshops. Evidence suggests that regular meditation could trigger positive changes in the physiology of the brain (a session is shown in progress headed by Andy); Mosley reacts positively. Mosley watches home movies when he was a small child; his mother remembers him as an 'uncomplicated' child. A study at St Thomas' in London led by Professor Tim Spector has been following groups of twins to try and establish the interplay between nature and nurture; 40-50% of personality is heredity - the rest is due to other factors. Debbie and Trudi, twins, are interviewed as adults (there is also home movie footage of them as babies). As adults, however, Debbie has been diagnosed with clinical depression - they turn out to be 'discordant twins'. Spector has studied the differences in DNA which can occur during life (epigenetics). Michael's wife, Claire, gives a positive endorsement to the cognitive therapy and meditation he has been practising. Mosley returns to Dr Fox for a follow-up test and it looks as though his efforts have been rewarded.