Art review: The BP Portrait Award 2013 reveals our endless fascination with self-scrutiny and the human face

There is no end to our fascination with self-scrutiny, the human quizzing the human: the full-length figure; the head and shoulders; the face alone. The posings, the slight awkwardnesses, the vainly glamorous flourishes. How the body defines the space that it occupies, with that almost inevitable drift of attention towards the face. Yes, our attention always tends to pivot about the face, and within the face, the eyes...

This passionate attachment to the idea of self-scrutiny explains in part the continuing appeal of the annual BP Portrait Award, now in its thirty-fourth year, with fifty-five paintings selected from almost two thousand entries, spanning seventy-seven countries.

This year's winner, by Susanne du Toit from South Africa, is a portrait of a son by his mother. It is a clothed body on a chair, set precariously against a scrubbily indeterminate ground, a little angular in its construction. The figure, informally, naturally rendered, feels marooned, rendered all the more vulnerable, by the scrutinising eye. The large, fiercely knitted hands are a dominating feature, how they clutch the raised crossed leg, giving the entire composition a precarious solidity, a locked in, locked down feeling, even as the body is displaced slightly to the left of the canvas.

In all, the exhibition is painting in pursuit of a definition of character, a searching which sees through the outward likeness to the defining characteristic. Some of these painters have tackled the same subject again and again, forever pursuing its essence. Painting, by this definition, is a matter of digging and digging behind the surface for a truth which will unite what you see with what you feel. This is the case with Julie Held's portrait of her elderly father, who feels timelessly rooted in his character, or of Saied Dai's affectionate rendering of his friend the pianist Alan Rowlands, whose painful thinness of face, in profile against a slightly darkened ground, seems to be an echo of his life strivings. The elderly writer Ved Mehta is visually impaired, and we see that by both the slight misting of the surface of this wonderfully assured portrait by Paul Oxborough, and the way he seems to be looking askance, as if seeing sightlessly.

What deserves to be said about this fine show above all is that a number of these paintings seem to have reached much further into the ever elusive truth of the mystery of the self than most photographic portraiture ever does.

BP Portrait Award 2013 until 15 September, National Portrait Gallery, London