Here’s a simple arithmetic question:
A bat and ball cost a dollar and ten cents. The bat costs a dollar more than the ball. How much does the ball cost?
(the vast majority of people respond quickly and confidently, insisting the ball costs ten cents; this answer is both obvious and wrong — the correct answer is five cents for the ball and a dollar and five cents for the bat)
Here’s another one:
In a lake, there is a patch of lily pads. Every day, the patch doubles in size. If it takes 48 days for the patch to cover the entire lake, how long would it take for the patch to cover half of the lake?
(your first response is probably to take a shortcut and to divide the final answer by half, leading you to 24 days. But that’s wrong — the correct solution is 47 days)
While we like to think (hope) that human beings are rational agents, studies such as the bat and ball question from Daniel Kahneman (a Nobel Laureate and professor of psychology at Princeton) can indicate the opposite: when people face an uncertain situation, they don’t carefully evaluate the information or look up relevant statistics. Instead, their decisions depend on a long list of mental shortcuts, which often lead them to make foolish decisions. These shortcuts aren’t a faster way of doing the calculation; they’re a way of skipping it altogether. Asked about the bat and the ball, we bypass our arithmetic and default to the answer that requires the least mental effort. We assume that intelligence is a buffer against bias, but a 2012 study suggests that, in many instances, smarter people are more vulnerable to these thinking errors.
Find out more about bias blind spots, anchoring bias, framing effects and “cognitive sophistication” in this interesting New Yorker article: “Why Smart People Are Stupid“.