Exploring great apes’ social attention with Harvard PhD student Laura Lewis


Laura Lewis, PhD (Photo courtesy of Laura Lewis)

The Hominidae family, whose members are known as the great apes, are a taxonomic family of primates that includes the bonobo, chimpanzee, gorilla, orangutan and humans. The great apes are our closest living relatives and are well-known for their advanced cognitive abilities and complex social behaviour. As a result of this, for the past 60 years chimpanzees and bonobos have been studied to further understand the evolution of human behaviour and cognition.

Bonobos and chimpanzees demonstrate remarkable similarities and differences in their socio-ecology. For example, chimpanzees are characterized as male-dominant, hierarchical, and aggressive in intergroup interactions. On the other hand, bonobos, the traditionally lesser studied species, often display female dominance over males, more social egalitarianism, and a general lack of aggression between social groups.

Laura Lewis is a third-year PhD student from the Human Evolutionary Biology Department at Harvard University, as well as a visiting scholar at the University of St. Andrews in Scotland.

Lewis does comparative research with chimpanzees living at the Edinburgh Zoo and bonobos living at the Planckendael Zoo in Belgium. She looks particularly at social cognition using eye-tracking methods to explore the ape’s social attentional biases. This means she studies who the apes pay more attention to, and she forms evolutionary hypotheses about why they may be paying more attention to certain individuals over others.


Laura Lewis using eye-tracking technology (Photo by Kate Grounds)

Lewis is currently running 4 different studies with the apes.

“At the Edinburgh Zoo there are 15 chimpanzees and about 11 of them like to come in and participate in my studies. At the Planckendael Zoo there are about 6 bonobos that like to participate. This research is completely non-invasive and voluntary, and the apes also live in their normal social groups in the zoo while we’re doing this research. Edinburgh Zoo visitors can watch us through the research room window as we’re conducting research.”


Rubani, a 2.5 year old bonobo participating in eye-tracking research (Photo courtesy of Laura Lewis)

“Eye-tracking is a really cool technology that uses an infrared camera in order to track the eye position and eye movement of an individual. So, we’ll show the animals pictures on a screen and the infrared camera, placed directly below the screen, can determine where the animal is looking on the screen at any given time. The camera works best when the apes keep their heads still, so to encourage them to stay still we give them a little bit of diluted juice through a tube, which they love!”

Eye-tracking software was originally developed to use with humans. However, about 10 years ago, researchers discovered that eye-tracking was also an effective method for studying non-human great ape cognition. For her research, Lewis shows the apes two different images on either side of the screen and uses the eye-tracker to determine whether the apes are looking towards one image or the other, and for how long.

The question arises then, how does showing apes images on a screen provide insights into their social cognition?

“The first of the four studies I’m doing is a simple in-group out-group study. We show them two images on the screen: one is an image of a groupmate and the other is of a complete stranger. What we’re measuring is how long they’re looking at their groupmate as opposed to looking toward the stranger. I do this same study with chimpanzees and bonobos in order to compare their attentional biases. These two species are very closely related and only diverged about 1-2 million years ago. They have really interesting similarities and differences in their socio-ecology, and these similarities and differences are what we use to form hypotheses about how their social attention has evolved.”

For there to be continual advancement in science, it is crucial to maintain transparency in the work. This is of the utmost importance to Lewis, who stated that she loves to engage the zoo attendees in the work she’s doing. They have lots of signage right outside the study area so that the public can both read about and see what’s going on. The research is also a form of cognitive enrichment for the animals, since they have the opportunity to look at images and play games while getting treats. This transparency is important to Lewis because there’s a lot of mistrust in the scientific community, “specifically with scientists who work with animals,” said Lewis. As a result of this, she’s been putting more effort into learning more about science communication and how to effectively explain her work to the public, not just to other scientists.

“In my study, our preliminary results suggest that the chimpanzees are more interested in looking at their male groupmates, while the bonobos are more interested in looking at their female groupmates. They both pay attention to their in-group members of the dominant sex, even though their sex-based dominance patterns are different.

When scientists originally started eye-tracking studies with apes, they found that chimpanzees and bonobos view images of faces differently. Chimpanzees focused heavily on the mouth region of the face while bonobos focused more on the eyes, which is similar to how humans view faces. Both humans and bonobos are much more focused on the eye region, which tells us something important about how they communicate. Chimpanzees likely communicate more with their mouths, using facial expressions made with the mouth. Whereas bonobos, like humans, likely glean a lot of social information by focusing more on the eyes. This tells us something about how we as humans have evolved to communicate, especially nonverbally.”

Lewis’ keen interest in wildlife began with a pet goat named “The Kid” when she was just 4 years old.  Her parents, at the time raising two young children, didn’t have the time to fully maintain their backyard while raising young scientist Lewis and her younger sister. The Lewis family decided to adopt a pet goat for a year in order to eat all the overgrowth in her family’s yard in California. Lewis fondly talked about how she remembered constantly playing with this baby goat, watching him and trying to figure out what he was thinking. It was her first time closely interacting with an animal that wasn’t a dog or a cat and it really sparked a fascination with trying to understand the minds of animals, which has now blossomed into her life’s work.


Four year old Laura Lewis with pet goat, “The Kid” (Photo courtesy of Laura Lewis)

In high school, Lewis was one of the only black people in her AP science and math courses, despite attending a very diverse public school. As Lewis moved up the ranks in her scientific career, she noticed that that pattern continued and intensified.

“I’m the only black person in my department at Harvard and not only that, I’m only the second black person to ever pursue a PhD through my department. What’s even more important is that along with seeing less and less people of colour around me as I progress in my academic career, I’ve started to experience more discrimination.”


Laura Lewis (Photo courtesy of Laura Lewis)

There is often not enough importance given to representation in STEM fields or even in the media. For underrepresented groups, seeing professors, scientists, musicians, or actors who look like them can have an uplifting effect. It can open up new vistas of possibilities with the resulting opportunities to express the breadth of their life’s experience and the importance of their social existence. Underrepresentation can shape a child’s view of themselves, and promote the idea that it isn’t “normal” for a person of colour to occupy certain spaces, thus limiting their imagination and eliminating important areas of endeavour.

Lewis described to me what she calls the moment that first shaped her experience as a graduate student. She went to open up a new bank account at Bank of America on her second day living in Boston as she started along her new path as a PhD student at Harvard. She proudly handed the banker her very first stipend cheque from Harvard. As she excitedly explained her situation, the banker interrupted her with a confused look on his face and said, “I’m sorry, you just don’t look like a PhD student, you look more like you have street smarts.”

This experience blew Lewis away.

“Society doesn’t see black women as PhD students. Again there’s this representation issue. Had he approached that topic differently, we could have had a really important dialogue, because people aren’t going to expect that I’m a PhD student purely based on my identity factors. This has shaped my entire career as a PhD student, because I am constantly walking around with the knowledge that others don’t expect me to be a PhD student. In a lot of ways, I’m actually really grateful for that experience because it so overtly communicated people’s expectations of me based on what I look like. It’s very eye-opening and I feel puts me at an advantage for tackling similar situations in the future.”

From that day on, Lewis used this experience as fuel to set even higher expectations of herself and to constantly surpass the expectations that society has set for her.

— MK

Do you have any questions or comments for Lewis? Share them below in the comments section!