Elkhonon Goldberg is a clinical and academic neurologist based in New York. He wrote The Wisdom Paradox in his late 50s - old enough to have begun worrying about the effect of ageing on his brain. Of course, the usual bad news is that our cognitive powers decline with age. This story is a familiar one of slower thought, poorer sensory awareness, weakening concentration, faltering memory, and decreased learning ability.

The Wisdom Paradox highlights a different aspect of the process.

Goldberg provides a detailed and upto- date account of the development, structure and functioning of the human brain, all clearly explained and accompanied by easily understood diagrams. The detail is fascinating in itself, and it supports an argument that our minds can become more powerful - at least in a particular way - as we advance in years. We can make up for what we lose by developing a masterful, high-level competence in solving intellectual and creative problems.

As Goldberg explains, new nerve cells form in our brains for as long as we live, contrary to what scientists believed until recently. Although there is an overall shrinkage of the brain, this occurs mainly on the right side. The left cerebral hemisphere is more resilient, and can develop an increasing inner connectivity that pays out in superior power to solve highly complex and apparently novel problems with little experience or effort. This sort of practical mastery - which may be evident in many fields, from statesmanship to high art - to practise in the learned professions, is what Goldberg means when he speaks of 'wisdom'.

Better still, we can actually exercise our brains to enhance their power and increase their longevity. Among other points, Goldberg emphasises art as an exercise for the mind, much as athletics exercises the body. This distinguishes him from theorists who discuss art's power to achieve insight, complement religious belief and ritual, convey emotion, or (more irreverently) attract sexual partners. Goldberg's own clinical practice includes what seems to be a successful program of cognitive exercises for participants in their 60s and 70s, and older, who want to defy time's erosion of their faculties.

Goldberg finds satisfaction in the balance of cognitive losses and gains that attend the ageing of a well-exercised brain. I'm not so sure.

If we are lucky, and if we treat our brains well, the kind of mastery that he describes may come to us. Yet we lose youth's vivid awareness and openness to genuine novelty. Taken together with the decline of physical abilities, this appears to be an unwanted diminution of our powers.

That said, The Wisdom Paradox is a welcome addition because it offers some good news, for a change, about how age can affect us.

What use is art? As Goldberg observes, art permeates the breadth and depth of our lives. Yet, attempts to define its function in human civilisation always meet with exceptions - or else are highly speculative. One evolutionary psychologist, Geoffrey Miller, speculates that the Darwinian function of art is to advertise mental fitness to prospective partners. Miller sees artistic creation or performance as a form of sexual exhibitionism similar to the display of a peacock's tail.