Young people are considered to be particularly willing to take risks. A number of studies prove this. But is this behavior during puberty a purely human phenomenon or does it also occur in the animal kingdom? A current study with adolescent chimpanzees provides the answers.
During puberty, young people usually behave differently than adults: they take more risks, often act thoughtlessly and react more impulsively. This doesn’t just apply to humans: Adolescent chimpanzees behave in some situations in a risk-taking manner similar to that of human teenagers. In contrast to pubescent people, 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 only 15 years old 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 who lived 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 bowls, under which different rewards were hidden – similar to a game of chance. Peanuts were always placed under one bowl – an acceptable food option for chimpanzees. The researchers made sure that the monkeys could perceive the 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 researchers 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.
In a second test, the chimpanzees were asked to decide whether they received a banana piece immediately or whether they would rather wait a minute and finally get three banana pieces. While human juveniles tend to act more impulsively than adults and tend toward immediate rewards, the majority of both juvenile and adult chimpanzees chose to wait for the greater reward.
“Previous studies have shown that chimpanzees are quite patient compared to other animals,” Rosati is quoted as saying in a statement from the journal. “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.
