The hardback edition of The Decisive Moment is adorned with a shiny, red, embossed button that says in large capital letters ‘DON’T PRESS’. As my copy slid out of the envelope, I can report that without a great deal of conscious thought, the first thing I did was reach out and press that button, thus (I hope) nicely illustrating the central thesis of Johan Lehrer’s excellent book.

Lehrer is interested in the science of decision making. He is particularly interested in the distinction between the rational and the emotional brain, and illustrates persuasively what the differences are and what kinds of decisions each one is best able to make. The emotional brain, which is powered by the chemical dopamine, is capable of learning what works and what doesn’t in a given situation, and is what provides intuition and gut instinct. When this book slid out of the envelope, I imagine my emotional brain had a fairly solid idea that nothing bad ever happened to someone who pressed a button on the front of a book, hence the irresistible urge to press it right now. If my rational brain, the part that we use for making more complicated decisions, was brought to bear, it would have reached the same conclusion, but would have travelled by a different route entirely, and taken longer.

Through extensive use of case studies, Lehrer illustrates the strengths of the emotional brain as a system for decision-making: sportsmen (the American football examples didn’t mean a lot to me, but the points were well made anyway) and air defence officers who used the power of their emotional brains to make the right decision even they couldn’t explain . When we try to decipher why our emotional brains react in a certain way to something, we may not always be able to explain it (something I know only too well as a frequent book reviewer), and if we apply rationality and logic to a decision, the outcome may be different.

The rational brain has its own limitations, of course – its decisions may be affected by its own tendency to distort perception, or by the terms in which something is expressed (we are loss averse, for one thing, and unable to truly weight up the meaning of long-term consequences, hence credit card debt misery; we also allow perceptions of monetary value to distory our perceptions of merit – expensive things must be better, mustn’t they?).

The Decisive Moment is a very compelling piece of popular science, in the best tradition of writers like Oliver Sacks (whose complimentary quote adorns the front cover). I came away from it with a better understanding of my own decision making processes, and a resolution to recognise more in future when my emotional brain is giving me good advice and when it’s giving me a bum steer and I might be better of taking the time to think something through. Both halves of my brain, however, are in perfect agreement in thinking you will both enjoy and learn a lot from this book.

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