Arguments rage whether this implies an innate moral sense in humans or whether it simply shows we are social animals who value co-operation. But it is plain enough infants know a good guy when they see one.

If babies of 6-10 months are that savvy, it follows that when they get to nursery and then primary school they are even more capable of distinguishing between helpful, triangular supporters and nasty, square people who push you down. Which should be obvious, but isn’t always.

An awful lot of early educational practice these days (and a lot of the tense critical atmosphere surrounding the training and programming of teachers) encourages staff to be terribly square: to criticise, judge, reprove, adjust and control. It is harder to be a merry triangle who comes and gives a useful shove to someone who is tottering, especially if they are struggling up a hill they chose and wasn’t on the curriculum.

Perhaps the next experiment at Yale should show the goggle-eyed ball rolling along tracks, nipping off them to explore a flowery field in company with the friendly triangle, and then being shoved back on the rails again by an angry square which is getting anxious about the next exam.

You could speculate that even if the children themselves are not affected - after all, the ball is only a figure in a video - they are attracted to people who, by nature and determination, are helpful and co-operative triangles and that they are repelled by those who are chronically unhelpful squares, always on the lookout for someone to score points off or shove downhill.

There is no point pretending that all those who work with children are nice natured, even if they are correctly behaved towards their charges. Some are arrogant, some depressed and pessimistic, some disillusioned, some solipsistic. The tone of most teachers is benign enough, but some are quite the opposite. And the quivering, hypersensitive antennae of even the youngest children rapidly pick up any sign of an unco-operative, socially hostile individual. The child registers “Square! Danger!” and backs away. There may be a Silas Marner moment later, of course, when the child realises that the curmudgeon means well. Or there may not. But the process of backing away is likely to involve blocking all receptivity to learning, co-operation and fellowship, and is best avoided.

The moral, I suppose, is that a good teacher is a triangle: a loving, affable, kindly disposed person, even when not on duty.

An old lady I know once looked at a visiting churchman and observed, antennae twitching, “Bishop he may be, but you don’t get a nasty face like that by thinking good thoughts and loving your friends.”

Libby Purves, Author and broadcaster and presenter of ‘The Learning Curve’ on Radio 4.