As a psychology graduate working in animal- behaviour labs, Seligman discovered "learned helplessness" and became a big name. Dogs who experience electric shocks that they cannot avoid by their actions simply give up trying. They will passively endure later shocks that they could easily escape. Seligman went on to apply this to humans, with "learned helplessness" as a model for depression. People who feel battered by unsolvable problems learn to be helpless; they become passive, slower to learn, anxious and sad. This idea revolutionised behavioural psychology and therapy by suggesting the need to challenge depressed people's beliefs and thought patterns, not just their behaviour.

Now Seligman is famous again, this time for creating the field of positive psychology. In 1997 the professor was seeking a theme for his presidency of the American Psychological Association. The idea came while gardening with his daughter Nikki. She was throwing weeds around and he was shouting. She reminded him that she used to be a whiner but had stopped on her fifth birthday. "And if I can stop whining, you can stop being a grouch."

Seligman describes this as an "epiphany". He vowed to change his own outlook, but more importantly recognised a strength — social intelligence — in his daughter that could be nurtured to help her withstand the vicissitudes of life. Looking back on "learned helplessness", he reflected that one in three subjects — rats, dogs or people — never became "helpless", no matter how many shocks or problems beset them.

"What is it about some people that imparts buffering strength, making them invulnerable to helplessness?" Seligman asked himself — and now he's made it his mission to find out.

Excellent article on controlling your own reality.