The wild chimpanzees at Tanzania’s Gombe Stream National Park are at the heart of Jane Goodall’s groundbreaking research. Now, for the first time in decades, behavioral scientists have revisited some of Goodall's original observations of the animals' personalities.
The new study provides fresh insight, suggesting that, like humans, chimpanzee personalities are stable over time—a discovery that could help scientists test ideas for how our own temperament evolved.
“It’s the most famous groups of chimpanzees in the world, and I thought this was a terrific opportunity,” says study leader Alexander Weiss, a psychologist at the University of Edinburgh.
“Studying personalities in zoos has its advantages, but if you want to ask questions about something like [whether] personality is related to reproductive success… you can’t address these questions in captive samples. You have to go out to the wild.” (See the groundbreaking documentary JANE, the untold story of Jane Goodall’s life and work.)
His personality ratings for 128 chimpanzees—many of whom Goodall herself studied in the 1960s and 1970s—were published October 24 in the journal Scientific Data.
Goodall’s field observations of Gombe’s chimpanzees, supported by the National Geographic Society, showed that chimpanzees not only eat meat but also use tools, make tools, and display unique personalities.
In 1973, researcher Peter Buirski visited Gombe with Goodall’s blessing to continue some of the personality research. Based on surveys of Gombe staff, the team profiled 24 Gombe chimpanzees’ personalities along 10 different behavioral traits, such as belligerence and playfulness.
The successful survey showed that male and female chimpanzees tend to have different personalities; for instance, females tended to be more trusting and timid than males.
The team chose not to include one outlier: a female named Passion, whom Gombe workers had cast as “a disturbed, isolated, aggressive individual,” Buirski and a colleague later wrote. In 1975, Passion went on a cannibalistic killing spree, kidnapping and eating at least three baby chimpanzees. (Read about the chimpanzee leader who was exiled, killed, and partially cannibalized.)
“The carcass was consumed in the way that normal prey is consumed, slowly and with relish, each mouthful of meat chewed up with a few green leaves," Goodall noted in her 1990 book Through a Window.
In Good Company
The 1973 survey was arguably ahead of its time; scientific interest in animal personality only really took hold in the late 1990s and early 2000s.
Amid the flurry of new research, scientists studying chimpanzees in captivity had devised a new kind of behavioral questionnaire that inspired Weiss and colleagues to re-survey Gombe’s field assistants.
In October 2010, Weiss first traveled to northwestern Tanzania and met with 18 Gombe field assistants, asking them to rate the personalities of 128 chimpanzees. After eight weeks, Weiss and his colleagues had collected more than 11,000 survey responses from the assistants, some of whom had observed the park’s chimpanzees for 35 years.
“It was pretty awe-inspiring—I knew about these field assistants, having read work by Jane Goodall before,” says Weiss. “It was an amazing privilege that they took the time to help out with this.” (What it's like to work with Jane Goodall in the field.)
When Weiss and his colleagues compared the new surveys with the 1973 results, they found consistencies in the chimpanzees' personalities.
For instance, many of the apes rated “gregarious” in the 1970s were considered “extroverted” in the new ratings. Few of the previously “depressed” chimpanzees were now regarded as “agreeable.”
Just the Beginning
Since the two Gombe datasets largely jibe, the team argues that chimpanzees’ personalities don't change much over time. (Read Jane Goodall's take on her own legacy.)
This stability, hinted at in other studies, could help scientists test how different personalities affect reproductive success and other life outcomes in people.
These questions are just a small example of what the dataset can help answer—which is why Weiss and team have released their work in full.
“I don’t have enough time in my life to do everything that can possibly be done with these data, so why not let other people explore them?” says Weiss.
“That’ll be really cool to see.”