Investing, Fast and Slow

Behavioral economics, the social science founded by psychologist Daniel Ksahneman and his partner Amos Tversky, has had many profound insights into the decisions made by not just investors but the sort of small-bore economic choice we make every day. Kahneman’s best-selling new book, Thinking Fast and Slow, moves away from behavioral economics to focus more on the way we think about everything in our lives, yet its principles apply to investing decisions as well.

The “fast” and “slow” in the title of Kahneman’s new book refer to our two methods of thought. System 1 is quick and intuitive, and can never be switched off; it’s the mode of thinking that’s in constant use for us. System 2 can be long and difficult, and requires a great deal of our attention, which means it tends to let System 1 take over most of the time. One way to illustrate how it feels to use System 2 is to solve a complicated multiplication problem, like 17 times 24, that demands all of your focus. “You could not compute the product of 17 x 24 while making a left turn into dense traffic,” Kahneman notes, “and you certainly should not try.” It’s easier, for most issues that confront us, to let that fast and easy System 1 do our thinking for us.

But obviously, System 1 thinking needs some help when we’re making serious, long-term decisions. Kahneman tells the story of a CIO at a financial firm who had just decided to make a multimillion-dollar investment in Ford stock. His rationale was that he had just attended a car show and was very impressed with Ford’s new line of automobiles. The investment officer was not ashamed to admit he had gone with a gut feeling.

“I found it remarkable that he had apparently not considered the one question that an economist would call relevant: Is Ford stock currently underpriced?” Kahneman writes. “Instead, he had listened to his intuition; he liked the cars, he like the company, and he liked the idea of owning its stock. From what we know about the accuracy of stock picking, it is reasonable to believe that he did not know what he was doing.”

Kahneman believes that the CIO was simply taking the easy way out. Thinking carefully about a long-term investment decision requires a lot of our time and mental energy, and it’s not exactly a fun process. “The question that the executive faced (should I invest in Ford stock?) was difficult,” Kahneman says, “but the answer to an easier and related question (do I like Ford cars?) came readily to his mind and determined his choice.” Kahneman makes that case that this is not unusual, that our System 1 thinking is far more influential than we give it credit for, even in huge decisions like a major investment. 

That might help explain why so many people, left to their own devices, often make such poor investment decisions, even poorer than can be explained by random chance. Kahneman discusses the research by Terry Odean, a finance professor at the University of California, Berkeley. Odean looked at the trading records for 10,000 individual investors and found that the shares these investors sold consistently did better than those they bought. The margin was substantial, 3.3 percentage points a year.