Experiments by psychologists and economists (on happiness)

From The Economist: an article on happiness leads indirectly to a very important conclusion about experiments (see below):The U-bend of life: Why, beyond middle age, people get happier as they get older

"Happiness doesn’t just make people happy—it also makes them healthier. John Weinman, professor of psychiatry at King’s College London, monitored the stress levels of a group of volunteers and then inflicted small wounds on them. The wounds of the least stressed healed twice as fast as those of the most stressed. At Carnegie Mellon University in Pittsburgh, Sheldon Cohen infected people with cold and flu viruses. He found that happier types were less likely to catch the virus, and showed fewer symptoms of illness when they did. So although old people tend to be less healthy than younger ones, their cheerfulness may help counteract their crumbliness.

"Happier people are more productive, too. Mr Oswald and two colleagues, Eugenio Proto and Daniel Sgroi, cheered up a bunch of volunteers by showing them a funny film, then set them mental tests and compared their performance to groups that had seen a neutral film, or no film at all. The ones who had seen the funny film performed 12% better. This leads to two conclusions. First, if you are going to volunteer for a study, choose the economists’ experiment rather than the psychologists’ or psychiatrists’. Second, the cheerfulness of the old should help counteract their loss of productivity through declining cognitive skills—a point worth remembering as the world works out how to deal with an ageing workforce.