In an experiment, two strangers are given the
opportunity to share $100, subject to the following
constraints: One person—the “proposer”—is to
suggest how to divide the money and can make only
(5) one such proposal. The other person—the
“responder”— must either accept or reject the offer
without qualification. Both parties know that if the
offer is accepted, the money will be split as agreed,
but if the offer is rejected, neither will receive
(10) anything.
This scenario is called the Ultimatum Game.
Researchers have conducted it numerous times with a
wide variety of volunteers. Many participants in the
role of the proposer seem instinctively to feel that
(15) they should offer 50 percent to the responder,
because such a division is “fair” and therefore likely to be
accepted. Two-thirds of proposers offer responders
between 40 and 50 percent. Only 4 in 100 offer less
than 20 percent. Offering such a small amount is
(20) quite risky; most responders reject such offers. This is
a puzzle: Why would anyone reject an offer as too
small? Responders who reject an offer receive
nothing, so if one assumes—as theoretical economics
traditionally has—that people make economic
(25) decisions primarily out of rational self-interest, one
would expect that an individual would accept any
offer.
Some theorists explain the insistence on fair
divisions in the Ultimatum Game by citing our
(30) prehistoric ancestors’ need for the support of a strong
group. Small groups of hunter-gatherers depended for
survival on their members’ strengths. It is
counterproductive to outcompete rivals within one’s
group to the point where one can no longer depend
(35) on them in contests with other groups. But this
hypothesis at best explains why proposers offer large
amounts, not why responders reject low offers.
A more compelling explanation is that our
emotional apparatus has been shaped by millions of
(40) years of living in small groups, where it is hard to
keep secrets. Our emotions are therefore not finely
tuned to one-time, strictly anonymous interactions. In
real life we expect our friends and neighbors to
notice our decisions. If people know that someone is
(45) content with a small share, they are likely to make
that person low offers. But if someone is known to
angrily reject low offers, others have an incentive to
make that person high offers. Consequently, evolution
should have favored angry responses to low offers; if
(50) one regularly receives fair offers when food is
divided, one is more likely to survive. Because oneshot
interactions were rare during human evolution,
our emotions do not discriminate between one-shot
and repeated interactions. Therefore, we respond
(55) emotionally to low offers in the Ultimatum Game
because we instinctively feel the need to reject dismal
offers in order to keep our self-esteem. This
self-esteem helps us to acquire a reputation that is
beneficial in future encounters.