Consider this fact: “Highly intelligent men tend to marry women who are less intelligent than they are.” Now, you probably have your suspicions why this is the case. Perhaps it’s something to do with what men and women really want, or how society shapes us, or the stupidity of intelligence tests. If so, you have overlooked the most obvious explanation of all: this outcome is statistically inevitable. Indeed, it is as inevitable as the fact that highly intelligent women tend to marry less intelligent men.
Think about it: if the IQs of most people belong to the average, then people far above the average must pair up more often than not with people who are closer to the average. (In maths-speak, this is called “regression to the mean”.) As long as people don’t always marry their intellectual equals, as long as one gender is not smarter than the other, then the above statement simply has to be true. So why do we overlook this obvious explanation and reach for a more controversial one first?
Over the past five decades, psychologist Daniel Kahneman has developed the heuristics and biases approach to human judgment, exploring problems like these. He argues that most judgments are products of heuristics: mental rules of thumb that provide us with rough and ready answers to problems.
These serve us well for much of the time, but in certain situations they lead us systematically astray. Our bias for causal explanations, as we have already seen, can steer us off course, leading us to search for causes that may well be irrelevant.
Kahneman’s approach has proven extraordinarily successful. His early research papers, co-written with collaborator Amos Tversky, remain among the most frequently cited in the social sciences. The work earned him the Nobel Prize in Economics in 2002 (Tversky died in 1996) and laid the foundations for behavioural economics, the study of how people actually make decisions, rather than how they ought to as rational agents. This in turn has further inspired a spate of recent best-sellers – Freakonomics, Nudge, Black Swan and Predictably Irrational among them – which have extended Kahneman’s influence.
Kahneman, now aged 80, published a book of his own for general readers: Thinking, Fast and Slow. Here is Kahneman in his own words, personable and even-handed, prodigious if a little diffuse, exposing the breadth and abundance of human daftness. The book is indispensable, its greatest strength its impressive hoard of anecdotes, mostly lifted from his research and the work of his contemporaries, but also drawing on personal experience. The Financial Times called the book a “masterpiece”; the Economist called it “profound”.
The nub of Kahneman’s book is the distinction between two types of thinking, the intuitive and the deliberative, the “fast” and “slow” of the title. Following convention, he calls these System 1 and System 2.
System 1, the intuitive mind, is fast, automatic and effortless. Its judgments arise unbidden in our minds as feelings, seemings or fully fledged convictions.
System 2, on the other hand, is the system we inhabit as conscious creatures, the arena of reason and deliberation. It is slow and labour-intensive, it applies rules and evidence, and it demands and directs our attention.
To sense the distinction, consider the following puzzle:
A bat and ball cost $1.10. The bat costs $1 more than the ball. How much does the ball cost?
If you are like most people, your immediate answer will be 10c. But this is the wrong answer: a 10c ball and a $1.10 bat add up to a total cost of $1.20. To work out the correct answer, you need to slow down, to override the fast and frugal thinking of System 1 and employ the careful deliberation of System 2. (The answer is 5c.) We need to “pay attention”, as the idiom goes, and we pay with mental effort.
Yet because the brain is an organ, this extra effort costs energy. Indeed, if you (like I did) had to struggle to solve the bat and ball puzzle, you would have undergone some subtle physiological changes: your pupils would have dilated, your prefrontal cortex would have flushed with oxygen-rich blood, and your consumption of glucose would have heightened.
For this reason, System 2 is what Kahneman calls “a lazy controller”, abiding by “the law of least effort”. It has veto power, the power to reject an intuition and deduce a better answer, but it rarely ever does so, content to conserve energy instead by endorsing the guesstimates of System 1.
Most of the time, this works quite well. Indeed, waking life would be intolerable if we had to “make up our minds” about everything. But the speed and effortlessness of our snap judgments come at a cost to accuracy. Like some cunning riddle, the bat and ball puzzle exploits a particular weakness.
A version of this article was first published in January, 2012.
Read how Kahneman’s ideas apply to parenting in this week’s Listener cover story: The parent trapsSubscriber contentIcon definitionSubscriber content
See what’s inside the latest edition of the Listener.