The Decisive Moment: How the Brain Makes Up Its Mind
by Jonah Lehrer
277pp, Canongate, £16.99

The Element: How Finding Your Passion Changes Everything
by Ken Robinson with Lou Aronica
266pp, Allen Lane, £16.99

A great self-help current of philosophy, from the Stoics to cognitive behavioural therapy, conveys one simple message: you cannot change the world, but if you understand the bad habits of your thinking you can change how you react to the world, and that way lies wisdom. Modern popular neuroscience often holds out the same promise: armed with the knowledge of what scientists have learned from magnetic imaging of the brain, the reader will end up master of his own mind. If you know how that muscle inside your head works, you can exploit it better.

That is the thesis of Jonah Lehrer's The Decisive Moment, which marries grandiose claims of revelation with a predictably formulaic structure: each chapter opens with a magazine-drama mini-story - a period in an American football game; a pilot dealing with a cockpit crisis; a military emergency, and so on. He begins confidently: "In this book, you will learn how those three pounds of flesh inside the skull determine all of your decisions, from the most mundane choices in the supermarket to the weightiest of moral dilemmas."

The crux is in that little word "how". An increasing amount is known about what sort of patterns of neuron firing generally precede and accompany various kinds of decision - but exactly how they translate into what we experience as decisions is a much trickier proposition. And this difficulty is embedded in Lehrer's language. He is driven to anthropomorphise neurons themselves.

Of a British naval commander who somehow knew to shoot down an enemy missile that had the same radar profile as a US jet, Lehrer hypothesises: "a dopamine neuron somewhere in Riley's midbrain was surprised". How can a neuron be surprised, any more than a neuron can be happy, or a neuron can prefer Chopin to Wagner? Only if the neuron itself has a mind, which implies a useless infinite regress. With no apparent irony, Lehrer even calls dopamine, in one sub-heading, "The Molecule of Intuition", which rather recalls George Lucas's attempt to explain the Force by appeal to Midi-Chlorians in the Jedi bloodstream.

One of the main messages of Lehrer's book is that making decisions is not a purely rational affair but depends also on the emotions (which are the result, as he claims, of lots of unconscious information-processing done by the dopamine neurons). As usual, Lehrer overstates the novelty of his lesson. "The history of western thought," he claims, "is so full of paeans to the virtues of rationality that people have neglected to fully consider its limitations." Except all those philosophers who did precisely that, of course; and elsewhere Lehrer does remember to credit some of those poor benighted pre-neuroscience thinkers, such as Hume.

Throughout his book, indeed, we find familiar wisdom dressed up in shiny new scientific vocabulary. One lesson of those useful dopamine neurons, for example, is that you can only learn by focusing on your mistakes. The new empirical justification for the old cliché "learn from your mistakes" does, though, allow for stronger arguments in the field of educational policy, as Lehrer usefully shows. Telling children that they are intelligent has much worse results than telling them that they worked hard.

A similar argument is made in Ken Robinson's sympathetic and interesting book, The Element, which is about helping people to find out what matters most to them, and then to do it - if not as their job, then at least in their "recreation" time. Naturally a lot depends on the educational system: "If you're not prepared to be wrong, you'll never come up with anything original." Robinson, too, emphasises that there is a lot more to be valued in the mind than higher reasoning: there are "multiple intelligences ... linguistic, musical, mathematical, spatial, kinesthetic, interpersonal ... and intra-personal". This kind of thing is always a useful corrective to the kind of smug liberal-arts columnist who mocks the alleged "stupidity" of footballers, though the danger is that if you protest too much in the other direction, as both Robinson and Lehrer sometimes do, it looks as though you are arguing that what is needed in the world is less reason, rather than more.

But Robinson goes even further in one sense, citing research on the enteric nervous system, "a 'second brain' inside the intestines" (so "gut feelings" are not wholly metaphorical). In comparison, Lehrer's book seems to suffer from a rather old-fashioned kind of cranial bias, according to which everything of subjective interest happens inside the skull and nowhere else.

Halfway through Lehrer's book, however, things are turned upside-down and the book begins to concentrate on situations in which we'd be foolish to rely on our emotions - for instance if we were flying a plane that had lost all hydraulic control, or trying to figure a way out of a forest fire. Sometimes, Lehrer reveals, we should take the time to consciously and rationally think through a decision, because (believe it or not!) our emotions can be misleading.

Well, any self-help manual worth its salt would not leave the reader hanging on the horns of this dilemma without some general rule of thumb - when should we trust our feelings, and when shouldn't we? Both Aristotle and William James already knew, after all, that the key was choosing the right deliberative system for the job at hand. And now, promises Lehrer, neuroscience can explain how. He builds up slowly to the big payoff (enjoy the casual Oedipal swipe at Malcolm Gladwell in his use of the word "blink"): "It is the easy problems - the mundane math problems of daily life - that are best suited to the conscious brain. These simple decisions won't overwhelm the prefrontal cortex. In fact, they are so simple that they tend to trip up the emotions, which don't know how to compare prices or compute the odds of a poker hand ... Complex problems, on the other hand, require the processing powers of the emotional brain, the supercomputer of the mind. This doesn't mean you can just blink and know what to do - even the unconscious takes a little time to process information - but it does suggest that there's a better way to make difficult decisions. When choosing a couch, or holding a mysterious set of cards, always listen to your feelings. They know more than you do."

You might be surprised to be told that the most important choices we make are those involving a couch or other consumer "items". Still, Lehrer's system would no doubt help Robinson, who grumbles about the "excessive decision-making" involved in choosing a hire car. But it is Robinson who describes more explicitly the therapeutic ambition of both authors: "Many people have not found their Element because they don't understand their own powers." Falling back, in the face of an intractable world, on trying to understand one's own powers, is surely a major theme of our age.

A citation from William James in The Element could serve as an epigraph for both these books: "The greatest discovery of my generation is that human beings can alter their lives by altering their attitude of mind ... If you change your mind, you can change your life." Whether you become a dancer or drummer (as Robinson hopes), or just hunker down and make better shopping decisions (according to Lehrer's depressing assumption of his readers' interests), it seems happiness really is within your grasp.

• Steven Poole's Unspeak is published by Abacus. To order The Decisive Moment for £15.99 or The Element for £15.99, both with free UK p&p, call Guardian book service on 0330 333 6846 or go to theguardian.com/bookshop