In many domains people are tempted to think, after the fact, that an
outcome was entirely predictable, and that the success of a musician, an ac-
tor, an author, or a politician was inevitable in light of his of her skills and
characteristics. Beware of that temptation. Small interventions and even
coincidences, at a key stage, can produce large variations in the outcome.
Today’s hot singer is probably indistinguishable from dozens and even
hundreds of equally talented performers whose names you’ve never heard.
We can go further. Most of today’s governors are hard to distinguish from
dozens or even hundreds of politicians whose candidacies badly ﬁzzled.
The effects of social inﬂuences may or may not be deliberately planned by
particular people. For a vivid and somewhat hilarious example of how social
inﬂuences can affect beliefs even if no one plans anything, consider the
Seattle Windshield Pitting Epidemic.
In late March 1954, a group of peo-
ple in Bellingham, Washington, noticed some tiny holes, or pits, on their
windshields. Local police speculated that the pits had resulted from the ac-
tions of vandals, using BBs or buckshot. Soon thereafter, a few people in
cities south of Bellingham reported similar damage to their windshields.
Within two weeks, the apparent work of vandals had gone even farther
south, to the point where two thousand cars were reported as damaged—
these evidently not the work of vandals. The threat approached Seattle. The
Seattle newspapers duly reported the risk in mid-April, and soon thereafter,
several reports of windshield pits came to the attention of local police.
Before long those reports reached epidemic proportions, leading to in-
tense speculation about what on earth, or elsewhere, could possibly be the
cause. Geiger counte
some odd atmospheric event must have been responsible; others invoked
sound waves and a possible shift in the earth’s magnetic ﬁeld; still others
pointed to cosmic rays from the sun. By April 16 no fewer than three thou-
sand windshields in the Seattle area were reported to have been “pitted,”
and Seattle’s mayor promptly wrote the governor and President Eisen-
hower: “What appeared to be a localized outbreak of vandalism in dam-
aged auto windshields and windows in the northern part of Washington
State has now spread throughout the Puget Sound area.... Urge appro-
priate federal (and state) agencies be instructed to cooperate with local au-
thorities on emergency basis.” In response, the governor created a com-
mittee of scientists to investigate this ominous and startling phenomenon.
FOLLOWING THE HERD
Their conclusion? The damage, such as it was, was probably “the result
of normal driving conditions in which small objects strike the windshields
of cars.” A later investigation, supporting the scientists’ conclusion, found
that brand new cars lacked pits. The eventual judgment was that the pits
“had been there all along, but no one had noticed them until now.” (You
might have a look at your car right now; if you’ve had it for a while, there’s
probably a pit, or two, or more.)
The Seattle Windshield Pitting Epidemic was an extreme example of un-
intentional social nudging, but every day we are inﬂuenced by people who
are not trying to inﬂuence us. Most of us are affected by the eating habits
of our eating companions, whatever their intentions. As we have said, obe-
sity is contagious; you’re more likely to be overweight if you have a lot of
overweight friends. An especially good way to gain weight is to have din-
ner with other people.
On average, those who eat with one other person
eat about 35 percent more than they do when they are alone; members of
a group of four eat about 75 percent more; those in groups of seven or
more eat 96 percent more.*
We are also greatly inﬂuenced by consumption norms within the rele-
vant group. A light eater eats much more in a group of heavy eaters. A
heavy eater will show more restraint in a light-eating group. The group av-
erage thus exerts a signiﬁcant inﬂuence. But there are gender differences as
well. Women often eat less on dates; men tend to eat a lot more, apparently
with the belief that women are impressed by a lot of manly eating. (Note
to men: they aren’t.) So if you want to lose some weight, look for a thin
colleague to go to lunch with (and don’t ﬁnish the food on her plate).
If you ﬁnd yourself nudged by your friends’ eating choices, it is unlikely
to be because one or another friend decided to nudge you. At the same
time, social inﬂuences are often used strategically. In particular, advertisers
are entirely aware of the power of social inﬂuences. Frequently they em-
phasize that “most people prefer” their own product, or that “growing
numbers of people” are switching from another brand, which was yester-
HUMANS AND ECONS
. A chicken
who has already eaten enough to feel sated will start eating again if a hungry chicken is
brought into the next cage.
epresents the future. They try to nudge
you by telling you what most people are now doing.
Candidates for public ofﬁce, or political parties, do the same thing; they
emphasize that “most people are turning to” their preferred candidates,
hoping that the very statement can make itself true. Nothing is worse than
a perception that voters are leaving a candidate in droves. Indeed, a per-
ception of that kind helped to account for the Democratic nomination of
John Kerry in 2004. When Democrats shifted from Howard Dean to John
Kerry, it was not because each Democratic voter made an independent
judgment on Kerry’s behalf. It was in large part because of a widespread
perception that other people were ﬂocking to Kerry. Duncan Watts’s amus-
ing account (2004) is worth quoting at length:
A few weeks before the Iowa caucuses, Kerry’s campaign seemed
dead, but then he unexpectedly won Iowa, then New Hampshire,
and then primary after primary.. When
everyoneis looking to someone else for an opinion—trying, for ex-
ample, to pick the Democratic candidate they think everyone else
will pick—it’s possible that whatever information other people
might have gets lost, and instead we get a cascade of imitation
that, like a stampeding herd, can start for no apparent reason and
subsequently go in any direction with equal likelihood.... We
internal abilities and desires and therefore solely responsible for
our own behavior, particularly when it comes to voting. No voter
ever admits—even to herself—that she chose Kerry because he
won New Hampshire.
Social Nudges as Choice Architecture
The general lesson is clear. If choice architects want to shift behav-
ior and to do so with a nudge, they might simply inform people about
what other people are doing. Sometimes the practices of others are sur-
prising, and hence people are much affected by learning what they are.
Consider four examples.
FOLLOWING THE HERD
Conformity and Tax Compliance
In the context of tax compliance, a real-world experiment con-
ducted by ofﬁcials in Minnesota produced big changes in behavior.
Groups of taxpayers were given four kinds of information. Some were told
that their taxes went to various good works, including education, police
protection, and ﬁre protection. Others were threatened with information
about the risks of punishment for noncompliance. Others were given in-
formation about how they might get help if they were confused or uncer-
tain about how to ﬁll out their tax forms. Still others were just told that
more than 90 percent of Minnesotans already complied, in full, with their
obligations under the tax law.
Only one of these interventions had a signiﬁcant effect on tax compli-
ance, and it was the last. Apparently some taxpayers are more likely to vio-
late the law because of a misperception—plausibly based on the availabil-
ity of media or other accounts of cheaters—that the level of compliance is
pretty low. When informed that the actual compliance level is high, they
become less likely to cheat. It follows that either desirable or undesirable
behavior can be increased, at least to some extent, by drawing public at-
tention to what others arties: If you would
like to increase turnout, please do notlament the large numbers of people
who fail to vote.)*
Preserving Petriﬁed Wood
In many contexts, of course, the incidence of undesirable behavior
is high. This unhappy fact seems to be a real obstacle to change: if people
follow one another, we might end up with a vicious cycle or even a spiral.
Is it nonetheless possible to nudge people in better directions?
An ingenious study suggests an afﬁrmative answer, and it reinforces the
view that the speciﬁc framing of the problem can have a powerful effect.
The study was conducted in the Petriﬁed Forest National Park in Arizona,
HUMANS AND ECONS
*In the same category is the finding that people are more likely to recycle if they
learn that lots of people are recycling. If a hotel wants people to reuse their towels, for
environmental or economic reasons, it would do well to emphasize that most other
guests are reusing their towels. The hotel would do even better to provide guests with
information about how responsible the previous guests in their room have been!
where some visitors like to take souvenir samples home with them, a prac-
tice that threatens the very existence of the park. Signs at the park implore
people not to take samples away. The question at issue is what the signs
should say. The investigators, led by Robert Cialdini, the great guru of so-
cial inﬂuence who is a professor down the road in Tempe, were pretty sure
that the signs currently being used in the park could be improved.
arranged an experiment.
In all the conditions of the experiment, pieces of petriﬁed wood were
two-hour intervals, the language on the signs along the trail was varied.
Some signs, similar to those currently used in the park, stressed how bad
the problem was: “Many past visitors have removed the petriﬁed wood
from the park, changing the natural state of the Petriﬁed Forest.” Other
signs emphasized an injunctive norm: “Please don’t remove the petriﬁed
wood from the park, in order to preserve the natural state of the Petriﬁed
Forest.” Cialdini’s theory predicted that the positive, injunctive norm
would be more effective than the negative, informational one. This pre-
diction was conﬁrmed.
A related example is the “social norms” approach, which tries to
reduce drinking and other undesirable activities.
Consider, for instance,
the problem of alcohol abuse by (mostly underage) college students. A
survey by the Harvarr-
cent of college students engaged in binge drinking in the two-week period
preceding the survey.
This is, of course, a problem, but a clue to how to
correct it lies in the fact that most students believe that alcohol abuse is far
more pervasive than it actually is.
Misperceptions of this kind result in part from the availability heuristic.
Incidents of alcohol abuse are easily recalled, and the consequence is to
what other college students do, and hence alcohol abuse will inevitably in-
crease if students have an exaggerated sense of how much other students
Alert to the possibility of changing behavior by emphasizing the statisti-
cal reality, many public ofﬁcials have tried to nudge people in better direc-
FOLLOWING THE HERD
tions. Montana, for example, has adopted a large-scale educational cam-
paign, one that has stressed the fact that strong majorities of citizens of
Montana do not drink.
One adverrect misper-
ceived norms on college campuses by asserting, “Most (81 percent) of
Montana college students have four or fewer alcoholic drinks each week.”
Montana applies the same approach to cigarette smoking with an adver-
tisement suggesting that “Most (70 percent) of Montana teens are to-
bacco free.” The strategy has produced big improvements in the accuracy
of social perceptions and also statistically signiﬁcant decreases in smok-
Smiles, Frowns, and Saving Energy
Social nudges can also be used to decrease energy use. To see how,
consider a study of the power of social norms, involving nearly three hun-
informed about how much energy they had used in previous weeks; they
were also given (accurate) information about the average consumption of
energy by households in their neighborhood. The effects on behavior were
both clear and striking. In the following weeks, the above-average energy
users signiﬁcantly decreased their energy use; the below-average energy
users signiﬁcantly increased their energy use. The latter ﬁnding is called a
boomerang effect, and it offers an important warning. If you want to
nudge people into socially desirable behavior, do not, by any means, let
them know that their current actions are better than the social norm.
But here is an even more interesting ﬁnding. About half of the house-
holds were given not merely descriptive information but also a small, non-
verbal signal that their energy consumption was socially approved or so-
cially disapproved. More speciﬁcally those households that consumed
more than the norm received an unhappy “emoticon,” like Figure 3.2a,
whereas those that consumed less than the norm received a happy emoti-
con, like Figure 3.2b.
Unsurprisingly, but signiﬁcantly, the big energy users showed an even
larger decrease when they received the unhappy emoticon. The more im-
portant ﬁnding was that when below-average energy users received the
happy emoticon, the boomerang effect completely disappeared! When
they were merely told that their energy use was below average, they felt
HUMANS AND ECONS
Documents you may be interested
Documents you may be interested