Ahead of the Machynlleth Comedy Festival 2018, Adam Walton takes a closer look at the science and psychology of humour.

Laughter has been around for a very long time - and while we regard it as a human thing, primates have been having a laugh for millions of years. Dr Gil Greencross, an evolutionary psychologist and humour researcher at Aberystwyth University, says apes smile for different reasons to humans. He has studied the way humour is used by humans to attract mates. It seems that women believe funny men are more intelligent - while men are attracted to women who laugh at their jokes!

Laughter usually occurs when you're feeling happy. Neuroscientist and comedian Dean Burnett has written The Happy Brain - The Science of Where Happiness Comes From and Why. He explains that happiness is an extremely complex emotion and there's no neat hypotheses or 'checklist' to feeling good.

Comedians make you laugh, of course. And scientists can make good comedians. Ten years ago, Dr Steve Cross founded The Bright Club, helping scientists turn their research into a stand-up routine. And comedian Carys Eleri tells Adam why science is such a rich seam of comedy for her.