The Animal Personality Test
Ask pretty much any pet owner and they'll tell you without hesitation that individual animals have personalities. That said, science is still grappling with how to measure and label human personalities, and it's not like you can give a poodle the Myers-Briggs. (If you're looking for a reputable, reliable way to get into the nuances of personality, you shouldn't necessarily give a person the Myers-Briggs either, but that's another topic.)
Now, an international team of behavioral biologists from Austria, Brazil and the Netherlands has designed a set of tasks to measure some key personality traits of both wild and captive marmoset monkeys.
Marmosets, if you're not up on your New World monkey species, are a small tree-dwelling primate known to be highly social. They live in stable family units, with parents acting as breeders and siblings helping to raise the young. Father marmosets are unusually devoted as the animal kingdom goes, and have been spotted helping their female partners give birth, even biting the umbilical cord in two. The researchers looked at two different populations of marmosets: captive marmosets in Austria, and their wild counterparts in the forests of Northeastern Brazil.
The personality test consisted of allowing the monkeys to interact with a familiar environment, to investigate new foods or objects, and/or to engage with a fake predatory situation (such as a plastic toy snake). The researchers then carefully recorded the monkeys' reactions, looking specifically at the traits of Boldness and Exploration.
If marmosets didn't have distinct personalities, then their responses should've been largely the same as each other. Instead, some marmosets continually showed caution when approaching unknown objects, while others consistently sought out the new and unusual. Researchers studied the Austria-based population for four years and found that these behaviors remained relatively stable across the years; a cautious young monkey grew into a cautious older monkey. There was, however, an exception: if a monkey became a breeder for the group, and thus experienced an upward bump in status, they tended to become a little less careful.
“In humans and other non-human animals we see a similar pattern," says Vedrana Šlipogor of the University of Vienna. "People effective in leading positions often show higher levels of extraversion, as well as some other traits (e.g., high agreeableness and conscientiousness and low neuroticism)."
This study also represents the first look into the personality of wild marmosets, which showed extremely similar patterns to the personality of captive marmosets.
“We adapted our test battery from the well-controlled captive setting to the unpredictable conditions in the wild," notes Thomas Bugnyar, senior author of the study. "In the wild, monkeys have plenty of things to do in their day-to-day lives, however, and in exchange for some bananas, they decided to participate in these tasks. We were pleased to discover that wild monkeys show a very similar personality structure as those in captivity."
It may be a while before personality tests are developed for your golden retriever or tabby. In the meantime, we can appreciate that the wild marmoset results suggest we have a way to reliably measure personality variation of monkeys in both captive and wild settings. In other words, we aren't just monkeying around.