Sonny starts to...

Our Sonny, aged one month, has done it at last. After weeks of yowling and grimacing, he's moved up the ladder. He's smiling.

He's not aware of doing so, of course, and heaven only knows what prompts these little turnings-up of his mouth. We've only glimpsed them when he's asleep, or almost, and for now they linger for mere seconds, like fleeting miniature rainbows.

Never mind. These are his first samplings of what are among the most profound aspects of being alive - and being human.

A smile, to start with, is our core expression of contentment. Shelter and a full stomach are fundamental to survival, and a smile tells us that such needs (and many a want besides) have been satisfied. Yet it can sum up something else, on another plane altogether: That we have found something to be just doggone funny. And where, at play or at work, would we be without a sense of humour, without jokes coarse or subtle? These move us to titter, or chuckle or downright guffaw - all three just advances on the demure smile, that basic unit of funniness.

And it will play a yet broader role. It is the conversation-starter, the friendship-proferrer, the wordless icebreaker. With it, Sonny can start plugging into the wider world. And there, from very early on, he must learn that there will be times when he will have to suppress his smile, to look sombre where serious things are afoot. More than that, he will have to learn to fake a smile, and become familiar with the different sorts of smiles he can deploy. The great social game must be played, often in deadly earnest, yet it must always be played with a light heart - or at least the appearance of it.

A smile, then, may be far more than a smile - unless spied on the lips of infants.