Human teenagers aren’t exactly known for their restraint. An incompletely developed region of the brain called the ventromedial prefrontal cortex (vmPFC), which acts a bit like a parking brake, can make teens more likely to engage in risky behaviors such as reckless driving, substance abuse and risky sexual behavior. As it turns out, the same can be said for adolescent chimpanzees, except that reckless behaviors to them can seem more like increased aggression.
A study published on January 23 by the Journal of Experimental Psychology: General of the American Psychological Association finds that while chimpanzees and adolescents share these risky behaviors, chimpanzees may be less impulsive.
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“Adolescent chimpanzees face, in a sense, the same psychological storm as human adolescents,” co-author Alexandra Rosati, an associate professor of psychology and anthropology at the University of Michigan, said in a statement. “Our findings show that several key features of human adolescent psychology are also seen in our closest primate relatives.”
Chimpanzees can live to be 50 years old, and their adolescence occurs between the ages of eight and 15. Chimpanzees show rapid changes in hormone levels during adolescence, form new bonds with peers, demonstrate some increases in aggression, and compete for social status just like their human counterparts.
In the study, the team of researchers conducted two tests using food rewards on 40 wild-born chimpanzees at the Tchimpounga Chimpanzee Sanctuary in the Republic of Congo in central Africa. It included 21 men and 19 women from six to 25 years of age and a mean age of 15 years.
During test one, adult and adolescent chimpanzees performed a game task and were given a choice between two containers. One of the bins always had peanuts, which chimpanzees like quite a bit. The other had a snack he didn’t like (a cucumber slice) or his favorite, a banana slice. They had the choice to play it safe and get some delicious peanuts, or risk the coveted banana at the risk of getting a disgusting cucumber.
The team recorded the chimpanzees’ emotional vocalizations and reactions, including moaning, screaming, moaning, table banging or scratching. To track hormone levels, they also collected saliva samples.
The adolescent chimpanzees took the risky option more often than the adults, but both expressed negative reactions if they got the cucumber.
Proof number two was inspired by the famous Stanford marshmallow experiment conducted on human children to examine delayed gratification. The chimpanzees could get a banana slice immediately or wait 60 seconds to receive three tasty banana slices.
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Both adult and adolescent chimpanzees chose to delay gratification at a similar rate. In this situation, human adolescents tend to be more impulsive than adults and are more likely to choose instant gratification.
“Previous research indicates that chimpanzees are quite patient compared to other animals, and our study shows that their ability to delay gratification is already mature at a fairly young age, unlike humans,” Rosati said.
What separated the adolescent chimpanzees from the adults is that they threw more tantrums during the delay than the adults.
According to Rosati, risky behavior in both adolescent humans and chimpanzees appears to be biologically ingrained, but also certain increases in impulsive behavior may be more of a human thing. Additionally, future studies could look at differences in impulsive behaviors in male and female chimpanzees.
“We are currently looking at the development of several other cognitive abilities in chimpanzees, including self-regulation abilities and the emergence of social skills that help chimpanzees form and maintain relationships,” Rosati said. pop science in an email.