From the Buddha to modern gurus of self-help, there have been more than 100 exercises proposed which are alleged to increase lasting happiness, says Professor Martin Seligman a contributor to BBC Two’s The Happiness Formula.

In strange contrast, scientific investigation until recently thought none of these exercises would, as there was an unchangeable and biological “set point” for happiness.

This suggested that our levels of happiness were largely pre-determined by our genes and our upbringing, varying slightly but always returning to our set point of happiness.

It also explained the annoying fact that lottery winners eventually revert to their customarily curmudgeonliness and the rosier finding that paraplegics eventually return to almost the same happiness level they enjoyed before their accident.

I have spent more than 20 years testing the effects of various psychotherapies and drugs on depression.

So when I became a positive psychologist, I first explored many of these exercises and then decided to test rigorously whether any of them really increased happiness…

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