After nearly 40 years, the theory of business strategy is well developed and widely disseminated. Pioneering work by academics such as Michael E. Porter and Henry Mintzberg has established a rich literature on good strategy. Most senior executives have been trained in its principles, and large corporations have their own skilled strategy departments.

Yet the business world remains littered with examples of bad strategies. Why? What makes chief executives back them when so much know-how is available? Flawed analysis, excessive ambition, greed, and other corporate vices are possible causes, but this article doesn’t attempt to explore all of them. Rather, it looks at one contributing factor that affects every strategist: the human brain.

The brain is a wondrous organ. As scientists uncover more of its inner workings through brain-mapping techniques, our understanding of its astonishing abilities increases. But the brain isn’t the rational calculating machine we sometimes imagine. Over the millennia of its evolution, it has developed shortcuts, simplifications, biases, and basic bad habits. Some of them may have helped early humans survive on the savannas of Africa ("if it looks like a wildebeest and everyone else is chasing it, it must be lunch"), but they create problems for us today. Equally, some of the brain’s flaws may result from education and socialization rather than nature. But whatever the root cause, the brain can be a deceptive guide for rational decision making.

These implications of the brain’s inadequacies have been rigorously studied by social scientists and particularly by behavioral economists, who have found that the underlying assumption behind modern economics—human beings as purely rational economic decision makers—doesn’t stack up against the evidence. As most of the theory underpinning business strategy is derived from the rational world of microeconomics, all strategists should be interested in behavioral economics.

Insights from behavioral economics have been used to explain bad decision making in the business world, and bad investment decision making in particular. Some private equity firms have successfully remodeled their investment processes to counteract the biases predicted by behavioral economics. Likewise, behavioral economics has been applied to personal finance, thereby providing an easier route to making money than any hot stock tip. However, the field hasn’t permeated the day-to-day world of strategy formulation.

An awareness of the brain’s flaws can help strategists steer around them. All strategists should understand the insights of behavioral economics just as much as they understand those of other fields of the "dismal science." Such an understanding won’t put an end to bad strategy; greed, arrogance, and sloppy analysis will continue to provide plenty of textbook cases of it. Understanding some of the flaws built into our thinking processes, however, may help reduce the chances of good executives backing bad strategies.