Learning starts here!

It is both thrilling and heart-rending to witness babies starting to encounter the world and trying to make sense of it. At nine weeks these twins can focus on near and not-so-near objects, follow movement, favour faces as the most interesting things to look at, and they can smile. When an object appears in front of them they clench their fists and flip their arms, unable yet to reach or grasp but rehearsing the muscles that will later seize on things in the world.

Here the twins have just seen their grandmother climb on a chair and point a camera at them, which is pretty interesting, but in a moment he will revert to gazing at a huge brightly painted parrot which beats its wings slowly above him, while she will turn to peer again into the mirror on the wall beside her where two more babies lie cycling their legs and waving their arms. She doesn't look at these movements though: she gazes at the face she can see, close to hers. "Knowing it's her face" is not a concept available to her; but it is a face and, like hers, it smiles. The smiles generate excited responses: faster breathing, even more frantic paddling of limbs, a succession of experimental mouth shapes.

But he lies back with his arms spread out, his face still and his mouth closed in a pensive line, staring at the bird that hovers above him. His expression is tranquil but his eyes are awestruck: it's tempting to imagine that he is composing a poem or trying to work out the bird's flight trajectory.

Thus identities develop. He becomes the big placid boy; she becomes the little excitable girl. It's impossible not to respond to these offers of distinctive traits and potential difference, and instinctively to reinforce them, to ascribe feelings and motives, to offer gender roles, and to imagine futures.

Later they have a restless night, driving their mother crazy with their random sleeping patterns and snuffly wakefulness. Do they dream about faces and birds?