Similarly, a strategy for player 2 dictates whether he will continue or exit as a function
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Similarly, a strategy for player 2 dictates whether he will continue or exit as a function
of everything player 1 has done in the past. One relatively simple strategy for player 2
is to continue so long as player 1 has cooperated. If both players play according to this
pair of strategies, each time the temptation is low, player 1 cooperates and gets a, player
2 gets b, and the game continues with probability w until the first time the temptation
is high. Then, player 1 defects and gets c, and player 2 gets d. Some straightforward
calculations yield the players’ expected payoffs: player 1’s is [ap + c,(1 — p)] / [1 — pw]
and player 2’s is [bp + d(1 — p)| / [1 — pw]. Because a strategy specifies players’ moves in
every period and the game’s length is undetermined, infinitely many possible strategies
exist. We are primarily interested in the seven strategies represented in Figure 2, which
shows the expected payoff for each player for each strategy pair of interest.
Of particular interest is the strategy pair designated in the top left corner of figure 2),
in which player 2 discriminates between cooperators who look and those who do not
look, and player 1 cooperates without looking (CWOL). The following simple argument
demonstrates that this strategy pair is a Nash Equilibrium (which means no player has
an incentive to unilaterally deviate) whenever ~*~ > qp+cp(1—p). This condition has a
natural interpretation: player 1’s expected temptation from defection is less than the gains
from an ongoing cooperative interaction. Thus, player 1 would lose from deviating, for
example by looking, because this would end the lucrative ongoing relationship, reducing
a
Le
player 1’s payoff from an expected to 0. Player 2 would also lose from deviating, by
choosing to exit, because when player 1 is always cooperating, she expects oo from the
relationship, and exiting yields 0.
One potential concern with this equilibrium is that, since player 2 is not worse off by
not attending to looking, he might not do so. This turns out to not be the case. The
intuition is that if there is even a small probability player 1 looks, player 2 is better off
HOUSE_OVERSIGHT_026525
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