(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 Subtitles by the Amara.org community
