Wise groups follow the advice of confident
decision makers. So do foolish groups. But a group’s success or failure depends
on whether what’s commonly known corresponds to the truth in a given situation,
a new study finds.
Heeding
recommendations of the most confident member of a two- or three-person group
often works well, says psychologist Asher Koriat of the University of Haifa in
Israel. That’s because in many settings, high confidence is associated with
majority opinions, which are frequently correct about general types of
knowledge, Koriat reports in the April 20 Science.
Confidence-based
group decisions go awry when majority opinions don’t jibe with reality. Most
people assume, for example, that the larger of two countries in area also has a
larger population, but there are exceptions to this rule. In these instances,
the opinion of the least confident group member is most accurate, Koriat
observes.
This
finding raises the provocative possibility that, in uncertain environments
where common knowledge can’t be trusted or doesn’t exist, groups should rely on
the guidance of those who express the most doubt about a decision.
Opting
for hesitant over self-assured suggestions when the going gets tough doesn’t
come easy. “Can you think of a group that would be willing to follow the lead
of the least confident member?” Koriat asks. “I cannot.”
Koriat
assembled data from individuals who had completed experimental tasks into
simulated two- and three-person groups. Group decisions thus involved no
negotiations or haggling. Instead, accuracy rates were calculated for simply
going with the choices of more- or less-confident group members on each lab
problem.
Koriat’s
findings challenge studies suggesting that overconfidence typically leads
decision makers astray. That’s because experimenters often cherry-pick
questions so that what people assume to be true based on their experience
yields incorrect answers, remarks psychologist Ralph Hertwig of the University
of Basel in Switzerland.
One
such example: It’s relatively easy to infer that more people live in Paris than
in Toulouse. Paris is widely known as the capital of France, and in many
countries the capital is the largest city. Having confidence that capitals are
more populated than other cities makes sense. Yet that handy rule of thumb
sometimes doesn’t work. In Switzerland, for example, residents of Zurich
outnumber those of Bern, the nation’s capital.
Koriat
examined how well a confidence-based strategy works in groups. He administered
general knowledge questions, involving choices between two options, to
individual college students. In some trials, volunteers who expressed a lot of
confidence in their choices were usually right, suggesting they had tapped into
a store of common knowledge. In other trials, high-confidence choices were
frequently wrong.
Participants
rated their confidence in each of their answers. Koriat then created simulated
groups by analyzing responses of pairs of volunteers with different accuracy
rates and confidence levels. When most people knew the correct answers to
problems, two-person decisions based on the more confident member’s choice were
more accurate even than those of the best-performing individual. In another
test, Koriat showed that three-person decisions guided by the most confident
member slightly outperformed two-person decisions.
When
most people didn’t know the answers, confidence-based group decisions were
worse than those of even the worst-performing individual.
“One
ought to be conservative in deciding whether to trust group decisions, because
the price might be heavy if the issue is one for which people are predominantly
incorrect,” Koriat says.
Bruce
Bower
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