System One and System Two
Decision Hygiene: Two Modes Of Thought
I’m going to be leaning very heavily on the work of Daniel Kahneman throughout this series of posts. In Thinking, Fast and Slow, he describes two modes of thought, which he calls System One and System Two.
System One
System One is described as being fast, intuitive, confident, and effortless. How is the woman in the image above feeling? The answer comes to you immediately.
Here are some other examples:
2 + 2 = ?
Complete the phrase “tips and…”
Read a children’s book.
Drive on an empty road.
In each case, very little effort is required. This is the mode we all enjoy using. It feels good when the answer to a math question materializes immediately, or when an answer choice feels right at first glance.
System Two
Now try this problem: 343 x 57 = ?
Not quite as fun, is it? To get the right answer, you’ll likely have to grab a pencil. And you might need to check your calculations when you’re done. That’s System Two at work. It’s described as being slow, analytical, doubtful, and effortful.
Here are some other examples:
Count the number of Hs on a page.
Park in a narrow space.
Answer an ACT sentence placement question.
Paraphrase a paragraph written by Edmund Burke.
Many test prep strategies encourage students to use System Two. For example, students are instructed to show their work on math problems, go back to find information in the passage, and read to the end of the sentence when answering a grammar question. In each case, System One is the enemy. An intuitive answer appears to the student, but it could be incorrect. The strategy protects the student from mistakes of System One by engaging System Two.
But System One isn’t all bad. Experts are able to intuit correct answers right away. Those of you who teach SAT Math will know the answer to this question almost without thinking:
You’ve seen variations of this questions dozens of times, and hundreds of others that are conceptually similar (function shifts, the Pythagorean Theorem). In a test, you’d be rewarded for this mastery with extra time, which you could spend later on harder questions. In real life, lawyers, accountants, business analysts, and many other professionals are expected to render accurate judgments on common questions without much thought. (If your accountant couldn’t describe the difference between an LLC and S Corp, you’d be concerned.)
Intuition can also point us in the right direction. Mikhail Tal was famous for his brilliant chess sacrifices.
He could not see every move that would occur after the sacrifice, but his countless hours of experience made him feel that a seemingly-terrible move (like trading his queen for a knight) could ultimately result in a winning position. Similarly, a pediatrician might intuit that something is seriously wrong with her patient, even if she can’t immediately diagnose the problem. She might know that’s vital to run a certain series of tests, even if they are expensive and she doesn’t know what they will reveal.
System One Vs. System Two
So System One is excellent when we are experts at something. The problem is, we aren’t always experts . . . but we go on acting like we are anyway. We like the feeling of effortless excellence, and we don’t want to trade that feeling for uncertain drudgery. Consider this classic question from the research literature:
A bat and ball cost $1.10.
The bat costs one dollar more than the ball.
How much does the ball cost?
The immediate (and seemingly obvious) answer is 10 cents. That was the answer of more than half of the students at Harvard, M.I.T., and Princeton. But it’s wrong. To discover the correct answer (5 cents), you’ll likely need to grab a pencil and paper, or at least think it through very carefully.
We see this error over and over in test prep: a student gets comfortable answering questions with System One, but fails to engage System Two when necessary. As I’ll demonstrate in the next post, our students aren’t the only ones. Many cognitive errors are the result of our failure to use the right system, and we feel the consequences in every arena of life.