Psychology Friday: Piaget

Everyone who's ever trained as a teacher or studied child psychology will have heard of Jean Piaget. For years his work has formed the basis of many of our commonly-held opinions about child development and his theories of education have influenced governments and school boards across the globe.

He was actually a biologist (publishing over twenty papers on molluscs, of all things) but it's for his ground-breaking work in child psychology that he's best known. In fact he's often placed on something of a pedestal by many psychologists. Equally, there are others keen to topple him.

Out of sight is out of mind

One of the foundation stones of Piaget's developmental theories is the idea that young children - under the age of one year - lack what he called object permanence. In other words, when things are out of sight, they might just as well not even exist. Now, when we grown ups close the curtains we don't believe the outside world just disappears. If you doubt it's there when you're not looking you might well be on the verge of career as a philosopher; most of us, however, just take it for granted. Except young babies. Before the age of about eight months babies won't search for something even if they've seen you hiding it. It's said that Piaget own seven-month-old daughter Jacqueline inspired this discovery, when daddy Jean noticed she made no attempt to find a plastic duck even though she'd seen where it had gone.

'Do' try this at home

So, here's a psychology experiment you can try for yourself:

• Take one child (under the age of eight or nine months) and hide one of their toys. Let them see you do it; make sure they know where the toy is hidden. Now watch what happens.
• Next take a child over the age of one year and repeat the experiment. What difference (if any) do you see?

Piaget concluded from further experiments and observations that children don't start to think about things they can't see until a later stage in their development. It's a lovely game to play for anyone at home with tiny children. Don't believe me? Have a look at Lucille - first at six months, then at ten - and see the difference.

That Piaget was on to something!