Thinking and Deciding

NORMATIVE AND PRESCRIPTIVE THEORY OF SOCIAL DILEMMAS 447
Figure 18.2: Total utility for cooperators (those who do not walk on the grass) and
defectors as a function of the percentage of cooperators. Utility comes from both the
appearance of the grass and taking the shortcut.
already walked on the grass, though, one more will not make any difference, because
it will be too late to save the lawn.
We can diagram the situation as in Figure 18.2. The upper curve is for defectors,
because there is always some personal benefit to taking the shortcut. Notice that
the slope — the benefit to others from cooperation — changes as a function of the
number of cooperators. In the middle region, around 50%, the slope is highest,
because at that point an additional defector ruins a little more grass, and so the benefit
to all decreases.
The cooperative theory states that one should choose whatever would be best
for everyone if everyone made the same choice. In all of the examples given so far,
it would be better if everyone cooperated, so everyone should cooperate. Indeed,
Dawes (1980) defines “social dilemmas” as situations in which defection increases
personal benefit (holding constant the actions of others) but the benefit of each is
maximized if all choose cooperation. In the grass-walking example, nobody should
take the shortcut, no matter how many others did likewise. The cooperative theory
is a natural extension of the contractual view of morality discussed in Chapter 16. It
holds that the right question to ask is “If we were all going to agree to do one thing
or the other, what would we agree to do?” Of course, given the choice between all
cooperating and all defecting, we are all better off if we cooperate, so that is what we
would agree to do. Then, by imagining that a hypothetical contract has already been
made, it holds that cooperation is what each of us should do. If we do not cooperate,
we violate the contract.
The problem with the cooperative theory is that following it often leads to harm
and no good (Regan, 1980). If everyone has already trampled the grass to death,