(intro music)
My name is Laurie Santos.
I teach psychology at Yale University, and today
I want to talk to you about peak-end effects.
This lecture is part of a series on cognitive biases.
I want you to think back to the last
time you went to a restaurant and had an expensive meal.
Now remember all the different parts of that event.
Done?
Well, then I want you to answer a very simple question: how was it?
No matter whether you said it was just
so-so or the best meal ever, I bet you experienced the act of answering
this question as relatively simple.
Deciding whether some event was good
or bad is something we find pretty easy.
We can quickly say whether we
liked a particular movie, or how much fun we had on vacation,
or even how our last job interview went.
But making this kind of judgment should involve some pretty
complicated computations.
To judge how your last restaurant meal was, you might
have to computationally combine how you rated a whole bunch of different
points in the experience, and you have to judge how each of them fits together, and
come up with an overall rating.
You also have to decide how many time points you're
going to sample to figure out your rating.
When you thought about the restaurant,
did your mind give you a rating to the experience across every
single minute, or every second, or even every millisecond?
It turns out that our minds figure out
this complicated problem by using a surprisingly streamline strategy.
In fact, when we remember an event,
we tend to ignore lots and lots of the parts of that event.
In fact, we seem to make an evaluation based on only two parts of our experience:
the peak (that is, the part of the experience that's most extreme,
either good or bad) and the end (that is, how it ended).
All of our memories, both good ones and bad ones,
are often remembered as such because of the action of these two points.
To study this effect, the psychologist Danny Kahneman and his colleagues
presented participants with a painful event.
They had to stick their hand in really, really cold, fourteen
degree water for sixty seconds.
After that, the subjects were given a second event.
It started out exactly the same as the first.
Their hands were placed in really, really cold, fourteen
degree water for sixty seconds.
But then the second painful event continued.
Participants kept their hand in the water
for thirty more seconds, as the temperature was increased
to a still painful, but not as painful, fifteen degrees.
Kahneman and colleagues then asked participants which event
they liked better, or which they would prefer to experience again.
Surprisingly, participants overwhelmingly preferred the second event.
Even though they were in pain for longer, the second event ended a bit better.
And when you average the peak and end point of each event,
the second one is better, even though it involves overall more pain.
Kahneman and colleagues wondered whether the same peak-end effect would work for
people's memories in situations that we experience in the real world.
They teamed up with doctors who were
giving patients a painful medical procedure.
Usually, the procedure went like this.
It started out as not so painful, and gradually got more and more
painful, ending in a moment of maximum pain.
Kahneman and his colleagues thought that this procedure would be
remembered as particularly awful, not because it was a painful procedure, but
because the peak and end point of this procedure were particularly bad.
To test this assumption, Kahneman and his colleagues ran a clinical trial.
They extended the length of the painful procedure so it worked like this.
Patients had to be in pain for overall longer,
but the procedure ended on a slightly less painful note.
Kahneman and colleagues found that people
reported liking the second procedure much better.
They reported not feeling as much pain, and were even willing to come
back for more repeated procedures.
Kahneman and colleagues' clinical trial highlights one of the most
surprising things about our peak-end heuristic, namely, the information that
it doesn't take into account,
and that's how long the event happens to be.
Patient would rather be in pain for twice
as long, so long as the average of the peak and end is more pleasant.
Since our minds only take into account the peak and the end when
remembering an event, there's no way to tell how long a particular event was.
We just kind of ignore that part of the event in our evaluations.
This phenomena is known as "duration neglect."
Our duration neglect means that wonderful experiences can stay just as wonderful
even when you keep them really short.
It also means that you can make somewhat
annoying experiences longer, and you won't even remember them that way.
The peak-end effect also gives us some
hints about how to make an event especially awesome.
Since each event's goodness involves only its peak and its end point, we can make
events particularly fun by making them end their best point possible.
In fact, lots of the events that we enjoy most involve ends that are also peaks.
>From the final winning goal to firework finales, saving the best for last
seems to make it an event better.
So next time you're having a really nice meal,
be sure to save some room for dessert
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