Chimpanzees behave like teenagers during puberty
Young people are considered to be particularly willing to take risks. Scientists have now found that the same applies to growing chimpanzees. In one thing, however, they differ – and the monkeys even seem to be a little more mature.
IDuring puberty, adolescents usually behave differently than adults: they take more risks, often act thoughtlessly and react more impulsively. This doesn’t just apply to humans: adolescents chimpanzees In some situations, they behave in a risk-taking manner similar to that of human teenagers. In contrast to pubescent humans, however, adolescent chimpanzees are less impulsive, writes the group led by Alexandra Rosati from the University of Michigan in the journal “Journal of Experimental Psychology“.
Puberty is characterized by a rapid development of both physical and emotional maturity. In adolescents, cognitive and hormonal processes associated with risk-taking and impulsive behavior are well understood. However, the evolutionary origin of puberty is unclear. Do only people come into this phase of life? Or do other species also show pubertal behaviors as they grow up?
Chimpanzees are man’s closest living relatives. They can live up to 50 years and are not fully grown until they are 15 in the wild. Studies show that there are also significant hormonal changes in juvenile chimpanzees. And their behavior also changes: they behave more aggressively and compete for their position in the group.
But do chimpanzees also show cognitive changes comparable to puberty in humans? Rosati’s team tested this in behavioral tests with a total of 40 wild-born chimpanzees aged 6 to 25 years living in a sanctuary in the Republic of Congo. In addition, saliva samples from individual animals were examined for hormone levels.
In the first test, the chimpanzees were asked to choose between two shells, under which different rewards were hidden – similar to one gambling. Peanuts were always placed under one bowl – an acceptable food option for chimpanzees. The researchers ensured that the monkeys who could perceive peanuts and thus anticipate this reward.
Under the other bowl, on the other hand, they hid either a very tasty piece of banana or a slice of cucumber – definitely not a treat for the animals. So they could play it safe and choose the peanuts. Or they jumped at the coveted banana, risking ending up with the unsavory cucumber.
The team observed that younger chimpanzees chose the risky option more often than adults. After each experiment, the scientists also noted how the animals reacted to their reward: All animals – regardless of age – showed similar negative reactions to the cucumber. Sometimes they even tried to swap the cucumber piece for the better option afterwards.
Chimpanzees tend to be patient
In a second test, the chimpanzees were asked to decide whether they received a piece of banana immediately or whether they would rather wait a minute and finally get hold of three pieces of banana. While human juveniles tend to act more impulsively than adults and tend toward immediate rewards, the majority of both juvenile and adult chimpanzees choose to wait for the greater reward.
“Previous studies have shown that chimpanzees are quite patient compared to other animals,” Rosati said in a statement. “Here we also show that, unlike humans, they have the cognitive ability to prefer a delayed but larger reward at a fairly early age.”
However, the researchers have already noticed a difference between adolescent and adult chimpanzees: The longer wait for the additional banana slices triggered more frequent tantrums in the younger generation.
Increased risk-taking appears to be biologically ingrained in both adolescent chimpanzees and human teenagers, the team concludes. Yet increased impulsive behavior during puberty may be unique to humans.
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