Ramsay, Allan: Mrs Mary Adam (1754)

Researching his book, The Expression of the Emotions in Man and Animals, Charles Darwin turned to art. He was disappointed. "I had hoped to derive much aid from the great masters in painting and sculpture, who are such close observers. Accordingly I have looked at photographs and engravings of many well known works' but, with a few exceptions, have not thus profited. The reason no doubt is, that in works of art, beauty is the chief object' and strongly contracted facial muscles destroy beauty."

Darwin does not say which beautiful blank faces he had been looking at so unprofitably. But he does give a Favourable mention to Charles Lebrun, the 17th-century painter and theorist, who made a systematic study of human facial expression. Lebrun's results are mask-like diagrams that offer explicit and rigid templates for anger, grief, rapture etc. These "emoticons" exercised a strong grip on much subsequent art. They may look very rhetorical, but their motive is quasi-scientific. They want to get down to basics.

Darwin did not use any of Lebrun's images to illustrate his great work. But the pictures he did use are not much more subtle. You see a gallery of facial expressions that are mostly fixed and theatrical. There are good reasons for this. To establish the general principles of expression, he needed clear examples. He was also determined, where possible, to use photographic evidence. The Expression (1872) was one of the first scientific books to feature photographs. But the short-exposure snap had yet to be developed. Facial expressions had to be held for the camera.

Quite a few of Darwin's visual examples are provided by Victorian actors striking and holding a pose. He also included the rather frightening experiments made and photographed by a French doctor, in which an old man, with no facial sensation, has his facial muscles subjected to an electric charge, violently twitched one by one, demonstrating the action of each in isolation.

But The Expression itself is not a tick-box affair. Unlike the pictures, Darwin's descriptions are often nuanced and responsive. And he is conscious of the limits of scientific observation. He records coming across a toddler who had stolen some sugar, noting how it acted all innocent "by an unnatural brightness in the eyes, and by an odd, affected manner, impossible to describe". That "impossible to describe" is a fine touch in a work where description is everything.

There is no reason to think that Darwin would have had any trouble with the kind of insight contained in one of Wittgenstein's remarks. It's a brief imaginary dialogue: "I say of a smile: It wasn't quite genuine - Oh bosh, the lips were parted only 1/1,000th of an inch too much. Does it matter? - Yes."

That is something of which a painter, too, might be aware. When painting a face, a 1/1,000th of an inch can make all the difference. A tiny alteration in how the brush shapes a lip, how it shades a cheek, may change the expression decisively. And there are paintings that revel in such minutiae. They know that the human face is the most meaningful and meaning- sensitive object in the world. We don't need Lebrun's glaring templates. It takes only the smallest hints to get us reading.

Allan Ramsay's Mary Adam has a face like that. His portrait of this widow is one of the most real presences in British art. Painted over a century before the invention of photography, both its expression and its timing are deeply elusive - as the old lady puts down her book and her reading glasses, keeping her place, and turns towards us.

In away, that's a traditional trick. It's a version of the "interrupted" portrait, a pose designed to make the encounter between subject and viewer feel like an event, not a fixture. Just a while ago, the woman was doing something else, something to which she will return. The portrait is but an interval.

But Ramsay finesses it. In the pose, there are no overt signs of movement, or of temporariness. It is hard say how new or provisional or settled this woman's attention is. She turns towards us? She is turning, has turned, is turned? You can't tell the tense of this sitting. Her hands lie on her lap, peacefully. But her face...?

Her face is the heart of the mystery. You scan the eyelids, the brows, the eyeballs, the curve of cheeks, the lips, and you see them full of tiny clues. You find steadiness of gaze, and warm acknowledgement, and slight disengagement, and slight strain. In other words, the facial clues, just because they are small, can also be contradictory.

It was generous of Darwin to call artists "such close observers", but observation is seldomthe whole story. Ramsay's portrait is certainly very well observed. Or, rather, there's a lot of observation in it. But it would be of no use to a scientific study of human expression. The problem is not that it's beautifully blank. It's vividly expressive. The reason it's so vivid, though, is that it's a fiction, a composite. Mary Adam's face is so real because it is a kind of collage, a mixture of different hints that a single observed face would be unlikely to show. Yet they're not so strong or so divergent as to defy synthesis. The result is a complex, unstable, subliminal expression, impossible to describe: mild, compassionate, welcoming, wise, but not without wariness, not quite all ours.

The mystery isn't so mysterious. This face divides. Look at the right side. Here, things are friendlier, the mouth curves up a little, the eye and cheek muscles contract, smilingly. Now look at the left. Things are colder, the mouth shorter and straighter, cheek flatter, eye clearer. Even the wart has its part, providing a bit of interference, informational "noise" that further scrambles our reading of the face. And all over, those 1/1,000ths of an inch are at work.

THE ARTIST

Allan Ramsay (1713-84) was the greatest Scottish artist and British portraitist of his time. Son of the poet of the same name, he studied in Edinburgh and London, then trained in Italy for two years. He established a studio in London, and in 1767 was appointed portrait painter to George III. His work is entirely portraiture. He painted the Jacobite Flora MacDonald, the philosophers David Hume and Jean- Jacques Rousseau, and many ladies and gentlemen and members of the British royal family. Ramsay followed the French fashion for the informal, intimate and spontaneous likeness, doing it at times with melting sensibility, and sometimes with a laconic bluntness. At the age of 60, he fell off a ladder, smashed his right arm, and devoted the rest of his life to writing.