What makes you you? Psychologists say human personalities include what they call "the big five” traits: agreeableness, openness to experience, extroversion, neuroticism and conscientiousness. No doubt you've seen some measure of each trait within yourself. Well, now an international team of researchers have published a study suggesting that chimpanzees and orangutans really do share these traits with humans.

It's not the first study suggesting that these apes have personalities. But some of the previous research has come under criticism, with some scientists arguing that the idea of chimps and orangutans having human-like personalities could be the result of anthropomorphism--which occurs when a person projects human-like characteristics on something they're observing.

"Up until now we've had more debate than study into whether these personality domains were real or simply projections of human personalities on the animals by those who observe them," Dr. Alexander Weiss, lead author and senior lecturer at the University of Edinburgh in the U.K., told The Press Association.

So the research team asked zoo workers and volunteers who frequently interact with chimpanzees and orangutans in several countries to rate the apes’ personalities based on a questionnaire. The researchers then used that questionnaire to identify any biases.

"We used a statistical technique to remove these observer differences before extracting personality traits from the data," Mark Adams, a member of the research team, told BBC Nature. "What we found is that controlling for these differences among observers made no difference, which suggests that the observers are not projecting their own ideas about personality onto the animals."

The study cited previous ratings-based research that suggests chimpanzees exhibit all five of the personality traits seen in humans. Orangutans share three of the five traits: extraversion, neuroticism and agreeableness.

The researchers point to Jane Goodall as inspiration behind measuring human-like traits in these great apes. “Goodall’s impressions of the human-like personalities of the chimpanzees she studied reflected the chimpanzees’ individual behavioral differences,” the researchers wrote in their study.

The study was published online May 4, 2012 in the journal Animal Behaviour.

Also on HuffPost: