Baboons like to hang out with other baboons who are similar

The saying "birds of a feather flock together" might apply to non-human primates, as well. A new study shows chacma baboons within a troop spend more of their time with baboons that they resemble, choosing to associate with those of a similar age, status, and even personality. This is known as homophily, or "love of the same."

The researchers, led by the University of Cambridge and the Zoological Society of London, discuss these findings in light of the evolution of culture in primate societies. The research was published in May in the journal Royal Society Open Science.

Alecia Carter and her colleagues tracked two baboon troops in Namibia's Tsaobis Nature Park over six years. All the individuals in these groups had been given personality tests to determine their boldness and propensity to either generate or exploit information. Carter and her colleagues analysed how these personality traits, along with age, dominance rank, and sex, affected how baboons associate with one another. To define an association, the researchers measured time spent in proximity and time spent grooming.

Individual animals can acquire information first-hand, by directly interacting with their environment, or socially, by paying attention to the behavior of others. An individual's personality can affect its propensity to both generate social information (i.e. bolder baboons are more likely to act as a demonstrator) and exploit it from information generators (i.e. bolder types also tend to learn more than their shyer peers through observation).

Boldness also influences a baboon's response to an unfamiliar food item, like a hard-boiled egg or bread roll dyed green. More confident individuals spend more time inspecting and ultimately eating a novel food while shy types stick to the food they know. And in a previous experiment, Carter and her colleagues discovered that juveniles and their bolder elders were more likely than shyer animals to learn about a novel foraging task by watching another baboon demonstrate, and to later serve as demonstrators themselves.

Given these differences in personality and propensity to either generate or use social information, the researchers next focused on which baboons hung out with one another. They found that, like humans, baboons prefer others who are similar to themselves.

Carter and her colleagues show that, especially when it comes to grooming networks, baboons show homophily for boldness, age, rank, and propensity to both generate and exploit information, but not for sex.

The problem with these patterns of assortment is that they may impede the transfer of information between individuals. Social learning allows the rapid spread of novel information among group members. It has been implicated in the formation of traditions and cultures within species. But if information-generators – those baboons more likely to solve novel foraging tasks on their own, such as younger and bolder baboons – spend their time in the company of other information-generators, their knowledge might not spread throughout the troop. In this case, homophily could preclude some individuals from learning from others.

Carter and her colleagues hope that understanding baboons' personalities and social preferences will shed light on the conditions that may facilitate or retard the formation of culture in primate societies. It seems likely that both personalities and social networks play a role.

In baboon societies, it appears that the information producers, those individuals that find out new information, tend not to associate with individuals who need to access new social information. This would stop the formation of a tradition, as information cannot pass from informed individuals to uninformed ones. This tendency to associate with similar baboons could explain why these animals are not known for their cultural traditions in the same way that humans and great apes are. In this case, "birds of a feather flocking together" leads to cultural stagnation and a lower likelihood of new knowledge spreading throughout the group.

Although humans are known for their rich culture, Carter says that homophily could also slow down the transmission of ideas in human social groups. Conversely, diversity can help idea exchange, as shown in some tentative research on Twitter.

Post written by Mary Bates (@mebwriter) for the BPS Research Digest. Mary Bates is a freelance science writer specializing in the brains and behavior of humans and other animals. She has been published in National Geographic News, National Geographic's Weird & Wild blog, New Scientist, the Society for Neuroscience's BrainFacts website, Psychology Today, the Scientific American Mind Matters blog, on the Howard Hughes Medical Institute's News website, as well as in other online and print publications. Her Wired Science blog, Zoologic, was published from 2013-2015. She earned her PhD from Brown University, where she researched bat echolocation and bullfrog chorusing. You can follow her on Twitter and Facebook and see all of her work at her website.

Further reading

Carter, A., Lee, A., Marshall, H., Tico, M., & Cowlishaw, G. (2015). Phenotypic assortment in wild primate networks: implications for the dissemination of information Royal Society Open Science, 2 (5), 140444-140444 DOI: 10.1098/rsos.140444