Last Christmas I took my young son to the theatre. The show, called Antarctica, was for 4-7 year olds and, from an adult perspective, it was all a bit surreal. The actors flung around snow made of pieces of white paper and let it flutter to the ground. Later, they would dress up as seals and roll around in the paper-snow, honking at each other whilst wearing fake moustaches.

But if I thought that was strange it was nothing compared to what happened after the show. When the actors had left the stage and the parents were busy gathering up coats and bags, a woman carrying a small box walked, virtually unnoticed, to the back of the stage. Without saying a word or looking at anyone in particular she put the box on the floor and quietly stepped back.

A split-second later every child in the room rushed forward, grabbing handfuls of paper snow and putting them in the box. No-one told them to. There was no discussion between them and no arguments about who grabbed what. They just did it. Parents started exchanging glances, totally confused. It was spooky, as if they'd been hypnotised.

So what was going on? Did the woman with the box use some kind of mind trick on the children? Did one child start it off and make it look like such fun that the rest of them joined in? Or could it be that young children simply like to be helpful?