Chimpanzees that are raised as performers or pets are more likely to suffer from long-term behavioral effects, a new study indicates. The study shows that chimpanzees that are taken from their mothers early in life are more likely to have behavioral and social deficiencies as adults.

The year-long study, conducted by scientists from Lincoln Park Zoo, observed 60 chimpanzees. The study offers new insight into the long-term impacts of such early life experience.

The multi-institutional research project was published in the September 23, 2014 open-access journal PeerJ and was led by Steve Ross, PhD, director of the Fisher Center for the Study and Conservation of Apes at Lincoln Park Zoo. During the course of 14 months the researchers studied chimpanzees with various personal histories and that were living in an array of zoos accredited by the Association of Zoos and Aquariums (AZA) and sanctuaries participating in the North American Primate Sanctuary Alliance (NAPSA). In the study group, 35 chimpanzees were former pets or performers.

The results indicate that chimpanzees raised mostly around humans and with less experience around other chimpanzees within the first four years of life typically have lower social competency as adults than chimpanzees with more natural early lives. Chimpanzees with a lot of human exposure in life generally engaged in less social grooming with their groupmates, an important social bonding behavior in chimpanzees. Such effects were still seen years, and in some cases decades, after the chimpanzees lived as pets or performers.

Ross said in a statement, “Unusually for a study on this topic, we looked at the degree of human and chimpanzee exposure on individual chimpanzees along a continuum.” He continued, “This showed that those chimpanzees with more atypical beginnings to their lives, spending much more time with humans than with their own species, tended to behave differently than those that stayed with their family through infanthood.”

According to the University of Wisconsin-Madison, chimpanzees have a lifespan of 40 to 45 years in the wild and up to 60 in captivity.