At the outset of this fascinating and provocative book, the social psychologist Gerd Gigerenzer tells the story of a friend in love with two women. He invoked the advice of Benjamin Franklin. Make a scorecard of the pros and cons, then choose. He did, but “something unexpected happened”. He rejected the rational choice on realising that “his heart had already decided for him” – in favour of the woman with the lower total.

The power of intuition, and its occasional advantages over calculation, will surprise nobody who’s ever read a fairy tale. But are gut feelings always to be trusted? And are they susceptible to scientific scrutiny? The strength of Gigerenzer’s book – a work designed to appeal to readers of Malcolm Gladwell’s Blink and Nassim Taleb’s The Black Swan – lies in the impressive range of his underlying research, including computer science, social psychology and economics. He is at his best linking theory with statistical studies of human behaviour; in other words, in demonstrating how people actually choose an investment, a house, a wife, a job. He is not as good when striving for analogies to explain to the general reader the underlying multidisciplinary theories.

But his message is clear enough: when humans make decisions, they invariably prefer a rule of thumb to rigorous analytical calculation. And they are right to do so. We may think we always need maximum choice, maximum data, maximum information – but our behaviour tells another tale. Less really is more.

Gigerenzer cites a study set in an American supermarket, in which tasting tables had either 24 or six different jars of jam. Although more customers stopped at the table with the greater choice, only 3% of those who paused actually bought anything – as compared to 30% of those who stopped at the six-jam table. Shoppers are drawn by the idea of many alternatives but they shop more when the choice is limited.

Why should this be so? Gigerenzer explains with admirable clarity our need for simplification. If consciously performed, catching a ball would involve juggling with differential equations in our heads. We have acquired through evolution, he argues, a prodigious number of adaptive “short cut” capacities, accumulated over the ages by the brain and central nervous system. In the case of catching a ball, the evolutionary trick is what he calls the “gaze heuristic”, a “keep your eye on the ball” tactic. It is nature’s rule of thumb, employed by many animal species, as well as by pilots and sailors, to by-pass the otherwise unquantifiable computations necessary. There are similar rules of thumb, he maintains, operating unconsciously in a variety of activities and skills.

Gigerenzer’s most eye-catching example of these rules of thumb is the simplest: recognition. He tells us that he invested $50,000 in a portfolio created using company names supplied by a group of financial illiterates picked off the street. “After six months, the portfolio had gained 47% better than the market and mutual funds managed by financial experts fared.” This was good news twice over for Gigerenzer, whose fame in the world of behavioural psychology rests on proving what he calls “the recognition heuristic” – heuristic being a fancy word for rule of thumb. He has demonstrated in many studies that the less people know about the details of a company, a city, a product, the more they will ascribe size, complexity, success and value to it. So a bunch of students asked questions about the relative sizes of a pair of cities will tend to do better if they don’t know much than if they are really knowledgeable. The same holds true if one is asked to predict the outcome of a tennis match. In groups, humans instinctively assume that the fact of not recognising a name – whether of a stock, a city or a sportsman – is itself significant. And, more often than not, they are right. Groups of real experts, however, equipped with up-to-date data and analysis, seldom agree – and their choices are hampered by a surfeit of unquantifiable knowledge.

Some of Gigerenzer’s examples of “more meaning less” are highly familiar, not least the idea first propounded by the neuro-physiologist, Alexander Luria, that forgetting is as important as remembering to avoid intellectual overload. What is fresh to Gigerenzer’s argument is the clincher citation of the American cognitive scientist Jeffrey Ellman, who created a computer model for learning a language, only to find that it was crucial for the programme to forget words systematically, in order to make progress by building on essentials.

Read this book, and your next trip to the supermarket, or a restaurant, or the race track, is sure to be a queasily enhanced experience. Gigerenzer finds no scope, however, for what is surely the most intriguing and awesome of human skills: the exercise of conscious selection and unconscious inspiration that underpins imagination in art, literature and spirituality. But then, this book does not deal in the poetic or meditative, but in practical, mundane, everyday survival. In a world that seems increasingly hazardous, and beset by a baffling prodigality of choices, Gut Feeling may well be the recipe for a simpler, less stressful life.

On the ball

Nobody catches a ball by calculating its trajectory. Good catchers have an unconscious rule of thumb that boils down to: ‘Fix your gaze on the ball, start running, and adjust your running speed so that the angle of gaze remains constant.’ This ‘gaze heuristic’ helps explain why the hardest ball to catch is the one that heads straight towards you, making a constant angle of gaze impossible. Useful, no? You can now safely blame your next missed catch on self-consciousness.

GUT FEELINGS: The Intelligence of the Unconscious by Gerd Gigerenzer
Allen Lane £14.99 pp280
Buy the book here at the offer price of £13.49 (inc p&p)

Read on... books:
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