Tolerance of eye contact across the primate order: Looking across phylogeny

A behind the scenes view of how a gap in the literature led to a multi-disciplinary journey, my first contribution to academia, and the acquisition of more monkey facts than I could have ever hoped to know.

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When humans enter a social interaction, it very often begins with eye contact (although, presently, it might be more accurate to say that it begins with an invite to a Zoom meeting). The locking of gaze with another person confers an amazing exchange of information, sometimes intimate information, about intentions and motives. However, across cultures and individuals, there is wide variability in the frequency and use of this seemingly simple social behavior. It should be noted that, the work you are about to read about did not initially spawn from this question. We had a few ideas about the basis of this variability in humans, and I’ll develop some of those ideas below. But before they could be fully fleshed out, we wanted to first ground them in the nonhuman primate world. We had a feeling that when developing an egalitarian society, tolerance of the frequent exchange of intentions and motives that occurs through eye contact is likely one of the first things to arise. With the topic of eye contact, and the differences in its use and interpretation being so widely researched within psychology, it seemed obvious to us that such questions were also being asked about our primate relatives. Yet, we found no such work. Although there was speculation in some corners of the literature that matched our hunch, no cross-taxa studies existed. So, we turned to our great primatology connections here at UW-Madison and asked our colleague, Dr. Christoper Coe, for a hand. 

“That research does not exist.” is certainly not the answer we expected to get. And so, we found ourselves in a unique situation. With a clear question in mind, to which there was no clear answer, we jumped upon the opportunity to make use of Dr. Coe's expertise in primatology, and Dr. Paula Niedenthal (my graduate advisor)’s expertise in culture, and answer the question ourselves.

Ethan Harrod, Christopher Coe, Paula Niedenthal

The first step to answering this question was figuring out how we (a lone group of three psychologists) could acquire ratings of eye contact tolerance and social structure for a representative group of primates. To this end, Dr. Karen Strier was invaluable. As president of the International Primatological Society (IPS), she was kind enough to afford us a platform from which we could survey a vast number of primatologists who have devoted their careers to studying a particular primate. Our survey circulated through Twitter, Facebook, and the IPS website, allowing us to poll over 60 researchers in the field of primatology. This crowd-sourcing method allowed us to effectively gather data on over 19 taxa (a task that would otherwise be impossible for a single team to accomplish). After just three months from our initial conversation with Dr. Coe, we had collected data from a representative sample of primates and were able to examine the suspected relationship between eye contact tolerance and social structure that had sent us down this unique path. A relationship, which to our delight, appeared to not only exist, but exist in the same direction as we had predicted. The more egalitarian a primate’s social structure, the more eye contact was tolerated.

Conflict between Japanese snow monkeys. Photo Credit: Christopher Coe

Eye contact between brown lemurs. Photo Credit: Christopher Coe

If you wish to explore our findings in greater detail (we certainly hope you do), please look over our newly published articleHowever, you may recall that I mentioned that we had initial ideas about the basis of the variability in eye contact across human cultures. Although our article does touch on these ideas lightly, we feel that this blog may be the perfect place to elaborate on what might have otherwise muddied a humble, exploratory article. So rather than go on at length about our findings (you’ll read all about them in the article), I’d like to focus on what these nonhuman findings might mean for humans.

Although the terms egalitarian and hierarchical are not often used in reference to human societies, we can draw connections between human and nonhuman societies by way of the social tasks that are common to daily life within said societies. For example, tasks common to hierarchical nonhuman social structures, such as navigating hierarchies and maintaining social status, are comparable to tasks commonly seen in human cultures with tighter social norms (such as Malaysia or India).  Conversely, tasks more common to egalitarian nonhuman social structures, such as conciliatory behaviors and establishing social bonds, can be compared to tasks more common among human cultures with looser social norms (such as Australia or Belgium). It is our suspicion that the frequency with which these different tasks occur in a society (both human and non), as well as how important certain tasks are to successfully living within said society, is directly linked to that society’s tolerance and use of social behaviors. More specifically, we believe that as the social tasks common to a culture become more reliant on affiliative behaviors and the open communication of emotions from one person to another, the more important the use and tolerance of eye contact becomes. Certainly, the use and tolerance of other behaviors, such as smiling, should become more common as well, but it is because eye contact serves as the first step in social interactions that it became the focus of our work. In this context, the present findings provide the foundational evidence needed to begin examining this proposed relationship between human cultures and the use/tolerance of social behaviors. This newly documented relationship across nonhuman primates is a promising start that will hopefully motivate deeper investigations that bolster our claims across primates, nonhuman and human alike.

As this post comes to an end, let me now say, that at the time of writing this, I am nearing the end of my second year as a graduate student at the University of Wisconsin-Madison. The paper I am discussing is my first true experience in the world of scientific publications. So, although I write this blog post with what may seem like confidence, or as if the path forward was always clear, that was not the case in the moment. The process of stepping from a social psychology program into the world of primatology was not something I had ever prepared myself for. Writing and revising my first academic paper with two renowned psychologists with expertise on either side of this paper (and at times maddeningly different approaches to writing), was not something I expected to do. I found myself wrapped up in a novel, multidisciplinary study, between two wizened experts, utilizing a crowd-sourcing method that drew a fair amount of skepticism. But it was fun. I enjoyed learning far more about primates than I could have ever hoped. I enjoyed the difficulties of tying together two different fields of study. I enjoyed encountering a hole in the literature and realizing that I had the tools to fill that hole. As a graduate student working during a time that, in all honesty, presents publishing as a painful necessity, I am extremely grateful that I found this experience to be just the opposite. If you are reading this post as a graduate student feeling the same tension, or as a researcher attempting to publish across disciplines, or as someone attempting to fill in a gap with exploratory work, I hope you can look to an experience like this and find the enjoyment that assuredly lives within yours.

Japanese snow monkey. Photo Credit: Christopher Coe

Ethan Glenn Harrod

PhD student, UW-Madison

Ethan is a graduate student at the University of Wisconsin-Madison, in the Department of Psychology. He obtained his M.A. in psychology from the University of Chicago, with a concentration in psychophysiology. His interests include how autonomic nervous system (ANS) activity relates social interactions, anxiety and rejection, and emotional contagion. His current research explores the potential relationship between Vagal Tone and one's ability to tolerate social interactions. Most recently, his interests in these topics has led him to begin exploring the field of Primatology.

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