Thinking and Deciding

LABORATORY VERSIONS 445
Table 18.3: Payoffs for cooperating (C) and defecting (D) as a function of the number
of others who cooperate
Number of others who cooperate
0 1 2 3
D $6 $10 $14 $18
C $4 $8 $12 $16
everyone one step to the right on their respective line. A decision to cooperate,
however, moves the person who makes it from one line to the other, as well as one
step to the right.
In general, these laboratory situations present people with a choice of two actions:
cooperate (C) and defect (D). Such games are analogous to many situations
in daily life in which the interests of individuals conflict with the interests of “society”
or, more generally, other individuals. In many of these real-world situations,
people do not have a chance to try to make others cooperate. They cannot develop
a “strategy,” and their behavior does not influence others. It is as though the game
was played only once. Both in real life and in the laboratory, social dilemmas do not
need to be simple as the examples just given. The benefits provided to others by an
additional cooperator may not be constant, for example. They may depend on the
number of other cooperators. In some cases, a minimal number may be required for
any benefits at all. The benefit to the defector from defecting may also depend on the
number of other cooperators.
Figure 18.1: Effects of the number of cooperators (those choosing C) on the payoffs
of cooperators and defectors (those choosing D), based on Table 18.3