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Daniel Kahneman on What Colonoscopies Teach Us About Memory

By Morgan Housel – Jun 30, 2013 at 7:45AM

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Studies of patients undergoing an unpleasant medical procedure lead to some surprising conclusions about perception and memory.

Dr. Daniel Kahneman, winner of the 2002 Nobel Prize in economics, joins us to discuss his book Thinking, Fast and Slow. 

In this segment, Kahneman discusses how working with patients undergoing colonoscopies allowed him to compare people's documented experiences with their recollections after the fact. His findings led him to develop the concept of the Experiencing Self, versus the Remembering Self. The full version of the interview can be watched hereA transcript follows the video.

Morgan Housel: You write in the book about how not only are we not good at predicting the future, but we're not even good at remembering the past in certain situations. There was one example where you have two groups of people who are getting colonoscopies.

I'll butcher the example. I'll let you tell the story.

Daniel Kahneman: OK. Well, you know, in the first place, people here are too young to talk about colonoscopies, but in addition, colonoscopies have changed since we did that research. They used to be very painful procedures. Now they put you under and you just wake up.

At the time, it was a painful thing to go through, and colonoscopies used to last ... in a study that we did, the shortest one was four minutes, I think, and the longest one was an hour and a quarter, so there's a tremendous range in terms of how long they last. There is variability within a colonoscopy. Sometimes it really hurts, and other times it's just unpleasant.

In a couple of big experiments, we had somebody next to the patient, and every 60 seconds they would ask the patient, "How much does it hurt now?" on a scale from 0 to 10, I think. You get a profile of the patient's pain, and you know exactly what went on, so you know how long the colonoscopy was, and you know ... then later, and in many different ways, we asked them about the memory they had kept from the colonoscopy. What was left with them?

It turned out that what was left was determined completely differently from what we would have thought. It was simply an average of the worst moment in the colonoscopy, and how badly it hurt when the procedure ended.

Those two variables really gave you excellent prediction of, when you ask people, "Would you want to have another one of those, or would you rather have another painful procedure?" Or you ask them, "How much total pain was it? How bad was the whole experience?"

There was one variable that had essentially no effect on that, and that's how long the colonoscopy was. That astonished us, how clear it was.

That's led me into a lot of thinking about what I call the Remembering Self and the Experiencing Self. That is, you have the Experiencing Self, the one who lived through the colonoscopy, but the Remembering Self is the one that keeps a score -- assigns a score and keeps a score.

Another interesting thing is that if we make our decisions, it's the Remembering Self that makes the decisions, and it doesn't always do what's best for the Experiencing Self.

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