DECISION-MAKING THEORY AND RESEARCHflips, spins of a roulette wheel, etc.). Dependent
events are causally related; what happened in the
past has some bearing on what happens in the
present (e.g., the amount of practice has some
bearing on how well someone will perform in a
competition). The confusion arises when people’s
expectations for independent events are violated.
For example, if a roulette wheel comes up black
eighteen times in a row, some people might think
that red must be the result of the next spin.
However, the likelihood of red on the next spin is
the same as it is each and every spin, and the same
as it would be if red, instead of black, had resulted
on each of the previous eighteen spins. Each and
every roulette wheel spin is an independent event.
The conjunction fallacy (Tversky and Kahneman
1983) occurs when people judge the conjunction
of two events as more likely than (at least) one of
the two events. The ‘‘Linda scenario’’ has been
frequently studied: Linda is thirty-one years old,
single, outspoken, and very bright. She majored in
philosophy. As a student, she was deeply con-
cerned with issues of discrimination and social
justice, and also participated in anti-nuclear dem-
onstrations. Following that description, subjects
are asked to rank order in terms of probability
several statements including the following: Linda
is active in the feminist movement. [F] Linda is a
bank teller. [B] Linda is a bank teller and is active
in the feminist movement. [B&F]
The conjunction fallacy is committed if people
rank the B&F statement higher (so more likely)
than either the B or F statement alone, because
that is logically impossible. The likelihood of B&F
may be equal to B or F, but it cannot be greater
than either of them, because B&F is a subset of the
set of B events and the set of F events.
People find events with multiple parts (such as
B&F) more plausible than separate events (such as
B or F alone), but plausibility is not equal to
likelihood. Making an event more plausible might
make it a better story, which could be misleading
and result in erroneous inferences (Markovits and
Nantel 1989). Indeed, some have suggested that
people act as if they are constructing stories in
their minds and then make judgments based on
the stories they construct (Pennington and Hastie
1993). But of course good stories are not always
true, or even likely.
INDIVIDUAL DIFFERENCESAnother question about decision processing is
whether there are individual differences between
people in their susceptibility to erroneous deci-
sion making. For example, do some people tend to
inappropriately use the heuristics outlined above,
and if so, is there a factor that accounts for that
inappropriate use?
Stanovich and West (1998) had participants
do several judgment tasks and related the per-
formance on those tasks to assessments of cogni-
tive ability and thinking styles. They found that
cognitive capacity does account for some perform-
ance on some judgment tasks, which suggests that
computational limitations could be a partial expla-
nation of non-normative responding (i.e., judg-
ment errors). Also, independent of cognitive abili-
ty, thinking styles accounted for some of the
participants’ performance on some judgment tasks.A similar suggestion is that some erroneous
judgments are the result of participants’ conversa-
tional ability. For example, Slugoski and Wilson
(1998) show that six errors in social judgment are
related to people’s conversational skills. They sug-
gest that judgment errors may not be errors, be-
cause participants may be interpreting the infor-
mation presented to them differently than the
researcher intends (see also Hilton and Slugoski 1999).Finally, experience affects decision-making abili-
ty. Nisbett, Krantz, Jepson, and Kunda (1983)
found that participants with experience in the
domain in question preferred explanations that
reflected statistical inferences. Similarly, Fong,
Krantz, and Nisbett (1986) found that statistical
explanations were used more often by people with
more statistical training. These results suggest that
decision-making ability can improve through rele-
vant domain experience, as well as through statisti-
cal training that is not domain specific.GROUP DECISION MAKINGSocial Dilemmas. Social dilemmas occur when the
goals of individuals conflict with the goals of their
group; individuals face the dilemma of choosing
between doing what is best for them personally
and what is best for the group as a whole (Lopes
1994). Hardin (1965) was one of the first to write
about these dilemmas in describing the ‘‘tragedy