Because we imagine, we can have invention and technology. It's actually play, not necessity, that is the mother of invention.

Knowing what to expect from a teacher is a really good thing, of course: It lets you get the right answers more quickly than you would otherwise.

If you wanted to design a robot that could learn as well as it possibly could, you might end up with something that looked a lot like a 3-year-old.

The science can tell you that the thousands of pseudo-scientific parenting books out there - not to mention the 'Baby Einstein' DVDs and the flash cards and the brain-boosting toys - won't do a thing to make your baby smarter. That's largely because babies are already as smart as they can be; smarter than we are in some ways.

I'm afraid the parenting advice to come out of developmental psychology is very boring: pay attention to your kids and love them.

Because we imagine, we can have invention and technology. It's actually play, not necessity, that is the mother of invention.