Why the Brain Talks to Itself: Sources of Error in
Emotional Prediction
Citation
Gilbert, D. T., and T. D. Wilson. 2009. Why the brain talks to itself: Sources of error in emotional
prediction. Philosophical Transactions of the Royal Society B-Biological Sciences 364, no. 1521:
1335-1341.

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http://dx.doi.org/10.1098/rstb.2008.0305

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Why the brain talks to itself: sources of error in emotional
prediction
Daniel T. Gilbert and Timothy D. Wilson
Phil. Trans. R. Soc. B 2009 364, 1335-1341
doi: 10.1098/rstb.2008.0305

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Phil. Trans. R. Soc. B (2009) 364, 1335–1341
doi:10.1098/rstb.2008.0305

Why the brain talks to itself: sources oferror in emotional prediction
Daniel T. Gilbert1,* and Timothy D. Wilson2
1

2

Department of Psychology, Harvard University, Cambridge, MA 02138, USA
Department of Psychology, University of Virginia, Charlottesville, VA 22904, USA

People typically choose pleasure over pain. But how do they know which of these their choices willentail? The brain generates mental simulations ( previews) of future events, which produce affective
reactions ( premotions), which are then used as a basis for forecasts ( predictions) about the future
event’s emotional consequences. Research shows that this process leads to systematic errors of
prediction. We review evidence indicating that these errors can be traced to five sources.
Keywords: emotional prediction; affective forecasting; prediction

Mark Twain worked hard to be funny. One of his
editors reported that before every speech, Twain‘mused his words to an imagined audience . He
studied every tone and every gesture and he forecast theresult with the real audience from its result with thatimagined audience’ ( Twain 1910, p. 11). Twain tested
new material on an imaginary focus group and assumed
that if the people in his head laughed at a punch line
then people in the theatre would do the same. This
technique may seem unremarkable, but in fact, there issomething decidedly odd about it. After all, MarkTwain was testing jokes on the people in his head, but
the people in his head were all . well, Mark Twain.
That is, the person who was telling the joke and thepeople who were reacting to the joke were all inventionsof the same brain—so why did that brain need to go
through an elaborate ritual of telling and listening justto find out whether its own jokes were funny?
If the brain were a single unified system, then thisritual would be puzzling. But the brain is not a single
unified system. Rather, it is a collection of independent
systems that specialize in receiving, processing, producing and transmitting different kinds of information.
The parts of Mark Twain’s brain that produced jokes
were not same parts that produced laughter, so to
determine whether a joke was funny, the jokeproduction system had to tell the joke to the laughterproduction system and then take note of its reaction. As
it turns out, this ritual is the one that most of us
perform every day—not just to find out whether ourjokes are funny, but to make the predictions by which
we guide our lives.

1. FROM PREVIEW TO PREMOTION TO
PREDICTION
Organisms remember the past so that they can predict
the future. If a bird can remember the appearance of acat followed by the tinkling of a bell, the bird can* Author for correspondence (gilbert@wjh.harvard.edu).
One contribution of 18 to a Theme Issue ‘Predictions in the brain:using our past to prepare for the future’.

thereafter use the sound of the bell to predict the cat’s
arrival. This is a valuable skill because a bird that can
predict the future can take action to preclude those
futures in which it plays the role of the entree. The
memory of the co-occurrence of the cat and the bellallows the bird to transcend the normal restrictions oflinear time, reacting to a future cat before it becomes apresent cat. The brain specializes in memory because
memory enables prediction, and prediction gives
organisms a head start. Alas, memory-based prediction
requires past experience: a bird can predict theappearance of a cat from the sound of a bell only if
those two stimuli have co-occurred in the past, whichmeans that a bird can act pre-emptively only after
having had at least one close encounter of the feline
kind. Because such encounters are a potentiallyexpensive way to gain the power of prognostication,
human beings have developed a different and moresophisticated technique that allows them to makepredictions about future events they have neverexperienced before.
For example, when asked how much they would
enjoy learning that they had pancreatic cancer, mostpeople can reliably produce the correct answer, which
is some version of ‘not so much’. They do not produce
this answer by remembering how it felt to receive suchnews in the past, but by closing their eyes for a moment,
simulating the event and then noting their emotional
reaction to that simulation. Just as Mark Twain
assumed that feeling amused by an imaginary joke
meant that he would be amused by the real thing, mostof us assume that if we feel anxious when we imagine
bad news then we would feel even more anxious
receiving it. In essence, we generate mental simulations
or previews of future events, which cause us to haveaffective reactions or premotions, which we then use as abasis for our forecasts or predictions about the event’s
likely emotional consequences (Damasio 1994; Schwarz &Strack 1999; Breiter et al. 2001; Berns et al. 2006;
Gilbert 2006; Gilbert & Wilson 2007). We know which
future events will feel good and which will feel bad because
we feel good or bad when we simulate them.

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D. T. Gilbert & T. D. Wilson

Emotional prediction

2. ERRORS IN EMOTIONAL PREDICTION
Previews and premotions are the building blocks ofprediction, and neuroscientists have recently begun toinvestigate them. For example, research suggests that
previews of future events are produced in large part by
the frontal regions of the brain (Ingvar 1985; Wheeler
et al. 1997; Fellows & Farah 2005), which are especially
activated when people are asked to simulate the future(Addis et al. 2007; Buckner & Carroll 2007; Schacter
et al. 2007; Szpunar et al. 2007). Patients with damage
to these regions are often unable to simulate future
events (Tulving 1985; Tulving et al. 1988; Klein et al.
2002) and are typically described as being ‘bound topresent stimuli’ (Melges 1990) and ‘locked into
immediate space and time’ ( Faglioni 1999). The
premotions that these previews produce appear todepend specifically on the ventromedial prefrontal
cortex, as people with damage to this area find it
difficult to predict their emotional reactions to theevents they are previewing (Bechara & Damasio 2005;
Shiv et al. 2005).
While neuroscientists have been investigating theneural substrates of previews and premotions, psychologists have been investigating how and how well they
allow people to predict their emotional reactions tofuture events (for recent reviews see Loewenstein &Angner 2003, Wilson & Gilbert 2003). This research
has uncovered two general sources of error. When we
generate a preview of a future event, our premotions are
influenced by the content of that preview (i.e. thosefeatures of the future event that appear in our mental
simulation) and by the context of that preview (i.e. thefeatures of the current situation in which we are
generating the mental simulation). When the event
actually happens, our emotions are influenced both by
the content and the context of our view. It follows,
then, that premotions will be good predictors ofemotions when the content and context of the event
we preview are similar to the content and context of theevent we view. For example, if one sunny day a man wason his way to his favourite cafe and imagined eating the
chocolate cake, he would probably experience a
positive premotion and expect to enjoy eating thecake when he arrived. If he arrived while the sun was
still shining and ate the chocolate cake he had
imagined, there is every reason to believe that hewould enjoy the experience just as he predicted(figure 1). On the other hand, if he arrived at the cafe
only to find that (a) the chocolate cake was gone andmincemeat pie was being served in its place (figure 2)or (b) the weather had turned cold and nasty (figure 3),then he might not enjoy his experience as much as heexpected to. The fact is that premotions accurately
predict emotions when the content and context of thepreview are similar to the content and context of the view,and the reason why errors in emotional prediction
occur is that these two criteria often go unmet. We shallnow explain why.
(a) The problem of dissimilar content
Events do not always unfold precisely as we imagine
them. One especially dull reason for this is that the
future is inherently uncertain: no matter how hard wetry, we can never know everything there is to know
Phil. Trans. R. Soc. B (2009)previewview

context

context

premotion

emotionFigure 1. Accurate prediction.

preview
context

view
context

premotion

emotionFigure 2. Unreliable previews lead to inaccurate predictions.

preview

context

view

context

premotion

emotionFigure 3. Unstable contexts lead to inaccurate predictions.

about the cakes and cafes that populate our tomorrows,
and even our best guesses are nothing more than that.
The inherent uncertainty of the future means that
previews and views often have dissimilar content.
Research shows that several other decidedly less dullfactors exacerbate these differences.
(i) Previews are unrepresentative
People who have difficulty remembering the past often
have difficulty predicting the future (Tulving 1985;

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Emotional prediction D. T. Gilbert & T. D. Wilson
Klein et al. 2002; Hassabis et al. 2007). When we
generate previews of a future event, we draw on a vast
network of information about similar events that have
happened in the past (Hawkins & Blakeslee 2004;
Dudai & Carruthers 2005; Addis et al. 2007; Buckner &Carroll 2007), and thus our previews are only as goodas the memories on which they are based. Ideally, apreview of a future event should be based on memories ofvery similar past events—but given that we cannot
know precisely how a future event will unfold, how
can we know which past events are the most similar to it?
The statistically sensible solution to this problem is tobase our previews on those past events that are mostrepresentative or typical of their class. For instance, we
may not know precisely what our next dental appointment will be like, but we do know that most past dental
appointments have involved cleaning and not extraction,and thus our preview of the next visit has a better chanceof being accurate if it is based on memories of flossing andbuffing rather than on memories of injecting and drilling.
But research shows that we tend to base ourpreviews on those memories that are most available
rather than the most typical and that, ironicallyenough, our most available memories are often of theleast typical events. For example, in one study,commuters who were waiting on a platform wereasked to imagine how they would feel if they missed
their train that day (Morewedge et al. 2005). Before
making this prediction, some of the commuters(the any-memory group) were asked to remember anddescribe ‘a time you missed your train’. Other
commuters (the worst-memory group) were asked toremember and describe ‘the worst time you missed yourtrain’. The results showed that commuters in the anymemory group remembered a past episode that was
every bit as bad as the episode remembered bycommuters in the worst-memory group. Apparently,
disastrous but atypical instances of train missing came
more readily to mind than did less disastrous but more
typical instances. As such, when commuters in the anymemory group were asked to predict how they would
feel if they missed their train that day, they expected tofeel terrible—and that prediction turned out to be
wrong. Commuters based their predictions on the
premotions that their previews produced, but because
these previews were based on atypical memories, they
provided a poor basis for prediction.
Like atypical experiences, recent experiences areespecially available and are thus likely to become thebuilding blocks of our previews. Participants in one
study (Kahneman et al. 1993) were asked to submerge
their hands in ice water while using an electronic rating
scale to report their moment-to-moment discomfort.
All participants performed a short trial and a long trial.
On the short trial, participants submerged their handsfor 60 s in a water bath that was 578F. On the long trial,
participants submerged their hands for 90 s in a water
bath that was 578F for the first 60 s and thensurreptitiously warmed to 598F over the course of theremaining 30 s. The short trial thus consisted of
60 cold seconds, and the long trial consisted the same
60 cold seconds with an additional 30 less-coldseconds. Although the participants’ moment-to-moment
reports revealed that they experienced equal discomfort
Phil. Trans. R. Soc. B (2009)

1337

for the first 60 s on both trials but much more discomfort
in the next 30 s on the long trials, they remembered thelong trial as less painful than the short trials because it
had a less painful ending. When participants were thenasked which of the two trials they would prefer torepeat (a question that required them to preview those
future events and predict how painful they would be),69 per cent chose to repeat the long trial.
The first reason why previews provide a poor basis
for prediction, then, is that they tend to be based on
memories that are not representative of the future
events that those previews were meant to simulate.
(ii) Previews are essentialized
If previews contained every detail of the views they weremeant to simulate, then imagining a dental appointment would take precisely as long as the appointment
itself. But it does not, and that is because previews
generally contain only the essential features that define
an event and omit the features that are merely
incidental to it. When we preview a dental appointment, we imagine sitting in the dentist’s chair or having
our teeth inspected but not parking the car or leafing
through magazines in the waiting room. The benefit ofomitting these incidental features from our previews isthat we can preview a 30 min appointment in 15 s. The
cost of omitting these incidental features is that
although they do not define the event, they can havea significant influence on our emotional reactions to it.
Most events have a small set of extremely positive or
extremely negative features that define them and amuch larger set of mildly positive and mildly negative
features that are incidental to them. Having someone
work on our teeth is the defining feature of a dental
appointment, and for most of us this feature is quite
negative. On the other hand, parking the car andreading magazines are incidental features of the eventand these features may be mildly positive (free parking)or mildly negative (old magazines). Our emotional
reaction to the actual dental appointment will be aweighted sum of its defining and incidental features.
The defining features are likely to be more powerfulthan the incidental features, of course, but the fact that
there are so many incidental features means that they
too may have a considerable combined impact.
Because some of these incidental features are likely tohave a valence opposite to that of the defining features,
these incidental features are likely to dilute the power ofthe defining features. In other words, we imagine theunpleasant features of going to the dentist because
these features are what going to the dentist is all about,and we fail to imagine the pleasant features of going to
the dentist because they are incidental to the purpose of
our visit. Anyone who has ever expected to enjoy agourmet meal at a famous restaurant and instead spent
the evening being irritated by the interminable wait andthe imperious waiter has experienced this phenomenon. Blanquette de veau may define a gastronomic
experience and waits and waiters may be incidental toit, but the latter features are likely to have some impact
on one’s experience of the event.
Studies confirm that our failure to preview theincidental features of future events can lead us
to mispredict our emotional reactions to them.

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Emotional prediction

For example, participants in one study ( Wilson et al.
2000) were asked to predict how they would feel the
day after their favourite football team won or lost agame against its arch rival. Before making thesepredictions, some participants were asked to describe
the day’s activities in great detail, i.e. to preview theincidental features of the event. Other participants were
not asked to preview the incidental features. The results
showed that the participants who were not asked topreview the incidental features of the event expected tobe very happy if their team won and very unhappy if
their team lost, but that those who were instructed topreview the incidental features of the event made much
more moderate emotional predictions—and these more
moderate predictions turned out to be more accurate.
Similar studies have shown that people overestimate
how happy they would be if they moved to California(Schkade & Kahneman 1998) or became wealthy(Kahneman et al. 2006) because their previews ofthese events include defining features such as sunshine
and money, but fail to include incidental features suchas traffic and taxes.
Our tendency to omit incidental features from ourpreviews of future events is especially pronounced
when the events are temporally distant (Vallacher &Wegner 1985; Trope & Liberman 2003). Participantsin one study (Liberman & Trope 1998) were told thatin a year there would be a lecture on an interesting topic
at an inconvenient location and a lecture on a boring
topic at a convenient location. Participants were asked
to predict which lecture they would attend. Because
their previews contained the defining feature of theevent (e.g. the topic) but lacked the incidental feature(e.g. the location), participants predicted that theywould attend the more interesting lecture, presumably
because they expected to enjoy that experience morethan its alternative. But participants who were told thatthe same lecture was taking place tomorrow instead ofnext year were more likely to include the incidental
feature of the event in their previews, and were thus
more likely to predict that they would attend the lecturethat was boring but convenient.
The second reason why previews and views differ,then, is that previews tend to omit features that are
incidental to the event but that nonetheless may have asignificant impact on our emotional reactions to it.
(iii) Previews are truncatedJust as previews tend to emphasize the defining rather
than the incidental features of future events, so do theytend to emphasize the event’s early occurring rather
than late-occurring moments. For example, in one
study (E. W. Dunn & C. E. Ashton-James 2008,
unpublished data), people were asked to predict how
much they would enjoy an experience that involved
putting their hand in an ice water bath for a few
minutes (which is painful) and receiving a massage(which is pleasant). Participants in the good beginning
condition were asked to predict how much they would
like the experience if the massage preceded the icewater bath, and participants in the bad beginning
condition were asked to predict how much theywould like the experience if the ice water bath preceded
the massage. Results showed that participants in thePhil. Trans. R. Soc. B (2009)

good beginning condition expected to like the experience more than did participants in the bad beginning
condition when, in fact, the order of the twocomponents had no influence on how much participants actually liked the experience. Just as people
represent past events by their endings, they appear torepresent future events by their beginnings.
One important consequence of emphasizing earlyoccurring moments is that previews take little accountof adaptation. For many reasons, emotions tend to
dissipate over time, which means that previews tend toemphasize precisely those moments that evoke themost intense emotion. This leads to one of the mostpervasive errors of emotional prediction—the impactbias—which is the tendency for predicted emotions to
be more extreme than actual emotions ( Wilson &Gilbert 2003). For example, when people are asked toimagine how they would feel some time after a negative
event (such as failing to get tenure or breaking up with aromantic partner) or a positive event (such as getting
tenure or beginning a new romantic relationship) they
typically overestimate how bad or good they will feelbecause they fail to simulate their adaptation to theevent (Gilbert et al. 1998). Similarly, research showsthat healthy people consistently overestimate howunhappy they would be in various states of ill-health(Menzel et al. 2002; Ubel et al. 2003; Riis et al. 2005)
because their previews of illness emphasize the early
moments in which they are making the difficulttransition from being healthy to being ill, but not themore numerous moments that follow, in which they
have adapted to their new state. People imagine
becoming disabled rather than being disabled (Kahneman
et al. 2006), and becoming is much worse than being
because over time most people adapt at least partially todisability (Lucas 2007; Oswald & Powdthavee 2008).
Because previews tend to ignore adaptation, theytend to be insensitive to those features of an eventthat might promote or inhibit it (Gilbert et al. 1998,
2004a,b; Gilbert & Ebert 2002). For example,
research has established that people adapt to events
more quickly when they understand why those events
happened than when they do not ( Wilson & Gilbert2008). When participants in one study ( Wilson et al.
2005) were approached at a library and given $1,
those who received an explanation for the gift wereless happy a few minutes later than were those who
received no explanation. But when asked to preview
these two incidents, a similar group of participantspredicted that they would be happier if they received
the gift with an explanation rather than without one.
Because their previews did not include the event’s lateoccurring moments, people who were asked to preview
receiving a gift with an explanation were unable toforesee their own adaptation. Similarly, research has
established that people adapt to events more quickly
when they cannot undo them than when they can.
Participants in one study (Gilbert & Ebert 2002) weremore satisfied with a gift when they did not have theopportunity to exchange it than when they did; andyet, a similar group of participants who were asked topreview these two incidents were insensitive to theopportunity for exchange and expected to be just as
happy in both instances. Because their previews did

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Emotional prediction D. T. Gilbert & T. D. Wilson
not include the event’s late-occurring moments,
participants who were asked to preview receiving a
gift that they could not exchange were unable toforesee their own adaptation.
The third reason why previews and views differ,then, is that they tend to emphasize the early occurring
moments of the event in which emotions are likely to be
the most intense.
(iv) Previews are comparative
How would it feel to buy a lottery ticket that paid $50 if
one’s friend bought a ticket that paid $80? Many of us
have the compelling intuition that we would be slightly
unhappy, and that we might actually be happier if we
had won only $40 and our friend had won only $10(Tversky & Griffin 1991; Solnick & Hemenway 1998).
The reason we make this prediction is that we imagine
comparing our $60 to our friend’s $80, which makes
our winnings seem paltry by contrast. But researchsuggests that in a wide range of circumstances, people
are less likely to make such comparisons than they
imagine ( Novemsky & Ratner 2003; Hsee & Zhang
2004). For example, in one study (Morewedge et al.
2007), participants were either asked to eat or to
imagine eating a potato chip in the presence of asuperior food (chocolate) or an inferior food (sardines).
Participants who imagined eating the chip predictedthat they would enjoy it more when it was eaten in thepresence of sardines than in the presence of chocolate.
In other words, these participants mentally compared
the food they would be eating with the food they would
not be eating. But participants who actually ate the chipenjoyed it just as much when it was eaten in presence of
chocolate as when it was eaten in the presence ofsardines. Similarly, students in another study (Golub
et al. in press) who imagined receiving a poor grade on
their midterm exam predicted that they would feelworse if they had been expecting a good grade than ifthey had been expecting a bad grade. In other words,
they believed that they would compare the grade theyreceived to the grade they had expected to receive. In
actuality, however, students who received a poor grade
felt equally bad regardless of their prior expectations. In
both of these studies, people’s previews included
comparisons that their views did not.
Just as our previews omit incidental features that
ultimately impact our emotional reactions, they tend toinclude comparative features that ultimately do not
impact our emotional reactions. Although we think wewill compare what we got with what others got, withwhat we thought we would get, with what we could
have got, or with what we have got in the past, the fact isthat real outcomes command our attention and thus
attenuate such comparisons. When we imagine eating
chips in the presence of chocolate, we naturallycompare the two; but when we actually have a mouthfulof crunchy, salty, greasy, fried potatoes, the experience
we are having is much more salient than the one we are
not having, which makes comparison less likely.
Imaginary chips are readily compared to imaginary
sardines, but real chips are not. The fourth reason why
previews and views differ, then, is that previews include
comparisons that views do not.
Phil. Trans. R. Soc. B (2009)1339(b) The problem of dissimilar context
Accurate predictions require that the content of ourpreviews be similar to the content of our views, and as
the studies reviewed above suggest, this is not always
the case. But accurate predictions also require that thecontext in which previewing occurs be similar to thecontext in which viewing occurs, and as it turns out,
this is not always the case either. Why do contexts
matter? Premotions are not just reactions to previews;
they are reactions to previews and to the context inwhich those previews are generated. That is why we feelhappier when we preview chocolate cake while we arelying on a comfortable couch than on a bed of nails, orwhen we are hungry rather than sated. When viewing
immediately follows previewing—for example, when
we see a doughnut, buy it and pop it into our mouths—
the contexts in which these two operations were carriedout are likely to be similar. But when previewing
precedes viewing by a substantial interval—for example,
when we see a doughnut, buy it, take it home and eat
it for breakfast the next morning—the two contexts
are likely to differ. When this happens, the premotions
we experienced at the bakery may be unreliableindicators of the emotions we will experience when
we eat the doughnut at home the next day.
All of this seems elementary, but research shows thatpeople often fail to realize just how easily differences in
the contexts of previewing and viewing can derail
emotional prediction (Loewenstein et al. 2003). For
example, in one study (Gilbert et al. 2002) hungry andsated people were asked to predict how much theywould enjoy eating a bite of spaghetti with meat sauce
for dinner the next day or for breakfast the next day.
The results showed that the people’s current level ofhunger strongly influenced their predictions and thatthe time of day at which they would be eating the
spaghetti did not. In other words, hungry people
mistakenly expected to like eating spaghetti for breakfast the next day and sated people mistakenly expected
to dislike eating spaghetti for dinner the next day. In a
related study ( Van Boven & Loewenstein 2003), people
who were working out at a gym were asked to predict
how much they would want food and water if they werelost in the woods. Those who had just finishedexercising predicted that they would want water morethan food, but those who were just about to exercise
predicted that they would want food more than water.
In both of these studies, people failed to realize that thecontext in which they were generating their previews
was having a strong influence on their premotions, andthat because the previewing context was different fromthe viewing context, their premotions would not match
their emotions.

3. CODA
Emotional prediction is the process by which we
discover what we already know. We evolved to haveemotional reactions to events in the present, and thus,
to find out how we will react to events in the future,
we simply pretend those events are happening now. But
the system that does the reacting (often called system 1)
and the system that does the pretending (often calledsystem 2) are not the same systems (Stanovich 1999).

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D. T. Gilbert & T. D. Wilson

Emotional prediction

System 2 generates simulations of dentists and doughnuts and system 1 generates emotional reactions tothose simulations. Because system 2 does not havedirect access to the information that system 1 uses
to generate these emotional reactions, it tells system
1 a fairy tale—sometimes enthralling, sometimes
frightening—and then listens closely to its response.
System 2 uses system 1 as a test audience and assumes
that if system 1 reacts with pleasure to a simulated
event, then it will react with pleasure to the event itself.
In essence, system 2 determines how system 1 will react
in the future by tricking it into reacting in the present.
This ritual of pretending and reacting, telling andlistening is an inventive way to make emotional
predictions, but it suffers from two shortcomings.
First, the simulations that system 2 generates are notfaithful facsimiles of the events they are meant tomodel. Compared to real events, simulated events are
unrepresentative (i.e. they are based on past events thatare not typical of their class), essentialized (i.e. theyomit features that are incidental to the event but that
influence emotional reactions to it), truncated (i.e. theyemphasize early occurring moments in which emotions
are most intense, and ignore late-occurring moments inwhich adaptation occurs) and comparative (i.e. they
include comparisons that are not unlikely to be madeduring viewing). Second, both the premotional andemotional reactions that system 1 generates are
influenced by the contexts in which they occur, andthese contexts are not necessarily the same. For both ofthese reasons, our premotional reactions to simulated
events often differ from our emotional reactions to theevents themselves, rendering our predictions inaccurate. When the human brain talks to itself, it does
not always tell the truth.
We gratefully acknowledge the support of research grant no.
BCS-0722132 from the National Science Foundation to
D.T.G. and T.D.W. We thank Lisa Feldman-Barrett forcomments on an earlier version of this paper.

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