Download Monkeys Show a Sense of Fairness

READINg
LESSoN B
SCIENCE In the News
A
B
Research suggests capuchin monkeys, such as this one in Costa Rica, care about fair treatment.
track 2-11
C
Monkeys Show a Sense of Fairness
A
Most humans expect to receive fair treatment. A recent study shows that brown capuchin
monkeys may feel the same way. This is the first time scientists have seen this kind of behavior in
a species other than humans.
B
D
Scientists chose brown capuchin monkeys for the research because capuchins are known to
have strong social bonds. In other words, they have close relationships with other capuchins.
They also cooperate; for example, they share responsibilities for food-gathering activities such as
finding fruit trees.
C
Sarah Brosnan, the leader of the study, put female monkeys in pairs. A different researcher
worked with each pair of capuchin partners. The researchers trained the monkeys to exchange
a small rock with them. “That may sound simple, but not very many species are willing to
[give things away],” says Brosnan. When a monkey exchanged a rock with the researcher within
60 seconds, she received a reward. Usually, the reward was a piece of cucumber.
E
D
17 2
|
The partner of each capuchin who made an exchange also received a reward. Sometimes the
partner got the same reward (a cucumber slice), but other times the partner received a better
reward (a grape). Brosnan said the response to the unequal treatment was astonishing.1 When a
capuchin saw its partner get better treatment, it was unhappy. Some capuchins did not want to
continue the test or eat the cucumbers they received. Some threw their food at the researchers.
UNit 9
42139_ch09_ptg01_hr_161-180.indd 172
7/19/12 9:08 PM
Brosnan’s research suggests there is a connection between animal cooperation and a dislike of unfair
treatment. However, as Brosnan explains, “We don’t know whether [monkeys] become cooperative and
then learn to not like being treated unfairly, or the other way around. But that opens up a whole new
research field.”
E
“Love Drug” Results in Kinder Monkeys
F
Scientists studying monkeys
recently found some surprising
results using a chemical called
oxytocin. Oxytocin is a hormone2
produced by humans and other
mammals. It is sometimes called
the “love hormone,” because it is
related to bonding and maternal3
behavior. Women produce large
amounts of oxytocin during and
after childbirth. Scientists believe
this makes mothers feel more
connected to their children.
G
The scientists at Duke University,
in North Carolina, USA, studied a
monkey species called macaques.
Aside from humans, macaques are the most widespread type of primate.
They live in places ranging from Japan (pictured) to North Africa.
They wanted to see how the
macaques responded
to larger-than-normal amounts of oxytocin. In the experiment, some of the monkeys inhaled4 the
hormone. Then they had to make a choice: drink a serving of fruit juice, give the fruit juice to another
monkey, or do neither.
H
The monkeys who inhaled the oxytocin were more likely to give the juice to other monkeys. The
researchers think that oxytocin made the monkeys pay more attention to other monkeys. “If that’s true,”
says researcher Michael Platt, “it’s really cool because it suggests that oxytocin breaks down normal social
barriers.”5
I
Scientists think the hormone might help people with conditions such as autism.6 People with autism
are often not interested in other people. Oxytocin might help because it seems to increase trust. It may
also improve social skills and make people more aware of others. However, scientists need to do further
research before oxytocin can be used as a medication.
Something that is astonishing is very surprising.
A hormone is a chemical that makes an organ in
the body perform a certain action.
3
Maternal relates to the feelings or actions of a
mother toward her child.
When you inhale, you breathe in.
A barrier is something that makes it difficult or impossible to do something.
6
Autism is a mental condition that can make someone less able to respond
to other people.
1
4
2
5
B e h av I o r
42139_ch09_ptg01_hr_161-180.indd 173
|
17 3
7/19/12 9:09 PM