Barbara J. King

Friday Animal Blog

Chimpanzee Conformists

April 22, 2011

Earlier this week, my husband and I drove our daughter up past the wine country of Charlottesville, over fog-bound Afton Mountain and west on into Harrisonburg to attend the admitted students’ day at James Madison University. Our Sarah (and forgive me, but what use a blog if not to house the occasional maternal brag comment?) is one of 200 high school seniors (out of a planned freshmen class of 4000) invited into the JMU Honors Program. We were there to soak up some campus culture and learn about the dedicated honors seminars and study-abroad trips.

Suffice to say I have a teenager with some smarts. So it was interesting to watch her as we hunted for a seat in the huge Convocation Center at the start of the day’s programming. I gestured towards some open seats but Sarah balked: But no one’s sitting there, Mom! she said. When I plonked myself down in another open section, she was equally unhappy because we were colonizing a place to which no one had yet gone.

Now, my child is an independent thinker in many ways. So I couldn’t help but reflect that she toggles between asserting her own stance and acting like a well-evolved herd mammal. To some degree, I could say the same for my own behavior – and perhaps for that of almost all humans.

An article published online at the journal Animal Behaviour now proposes that chimpanzees too may choose to be conformists -- even when doing so compromises their efficiency in some way. Written by Lydia M. Hopper, Steven J. Schapiro, Susan P. Lambeth and Sarah F. Brosnan, the work is entitled Chimpanzees’ socially maintained food preferences indicate both conservatism and conformity.

The researchers wanted to know if chimpanzees would exhibit conformism in a social setting even when that meant giving up their individual food preferences. “Conformity is of particular interest,” they write, “because it may be a mechanism by which individuals identify the most successful strategies without having to spend time and energy on trial-and-error learning, and without inadvertently choosing strategies that may appear superficially beneficial but are not over the long term. Conformity exists even in species that presumably have the cognitive capacity to contrast alternative possibilities, such as humans.”

In prior work, chimpanzees were shown two methods of food procurement. The first was a simple method to acquire honey; the second was more complicated but result in a better reward, honey plus peanuts. The chimpanzees never switched and adopted the second method. However, as Hopper et al. point out, this apparent inability to transition “could either be explained by the second method being sufficiently difficult that learning it was not worth the better reward, or be due to an evolved conservatism in chimpanzees.”

Hopper et al. wanted to tackle this confound, and offer chimpanzees two methods of action to get food, with the single difference being in the quality of the food reward. “Would chimpanzees,” they asked, “continue using the first method they encountered if another method that resulted in a more preferable food reward was observed, even when both methods were identical?”

Their data say yes. Twelve adult captive chimpanzees were divided into the MR group (designating the medium food reward, carrots) and the HR group (named for the high reward, grapes). In each case, one model- an adult female chimpanzee- was chosen as demonstrator. Out of sight of their groups, these models were trained to exchange a token (called the CC for candy-cane token) for either carrots or grapes.

During the test phase, an experimenter placed 20 tokens of two types—the CC type and a variant called SS for short-squat tokens-- into the chimpanzees’ enclosure, and waited for the apes to bring her tokens to exchange for food rewards. Here’s the key fact to keep in mind: “Chimpanzees could exchange either token form at any time and were rewarded according to their group’s pattern.” Thus, HR chimpanzees were given one HR for each CC token offered, and one MR for each SS token, whereas MR chimpanzees were given one MR for each CC exchanged and one HR for each SS.

During this time, the chimpanzees observed each other exchange tokens—having first observed the model for their group offering the CC tokens up (the tokens on which they were trained).

In both groups, “chimpanzees showed conformity to a group-level behavioral strategy of exchanging CC, but not SS, tokens with the experimenter.” What this means is that chimpanzees followed the model even when their own taste buds suffered. Even after discovering that SS tokens led to the prized grapes (which happened because some chimpanzees did follow a minority pattern), the group persisted in not using those tokens as a significant behavioral choice. “The chimpanzees did not switch to the more profitable strategy but instead they continued with the introduced method of exchanging CC tokens for the less preferred carrots.”

Some token-stealing went on among the chimpanzees. Only CC and never SS tokens were stolen. The chimpanzees developed counter-strategies when their tokens were stolen, so clearly it’s a smart system in some ways—yet one rooted in not-always-so-smart conformity.

It’s not every day I see the chimpanzee in my child. As I parent, I wonder how the impending switch from the conformity-prone high school milieu to the independence-prone college environment will affect my daughter. As an anthropologist reflecting on chimpanzee research, I wonder this: When female chimpanzees carry out some innovative action in the wild (natural tool-using behavior for example), are they likely to be accepted as models by the community, given that wild male chimpanzees are so dominant to females?


  1. April 22, 2011 6:50 AM EDT
    I wonder if older primates in their natural settings are more likely to care less about conformity? It's certainly true among the older ones I associate with--both male and female---
    - Mary Pratt
  2. April 22, 2011 8:21 AM EDT
    Mary, I was thinking the same thing. In terms of feeling pressure to conform I'm in a totally different place in my 50s than in my teens or even 20s. I have no trouble speaking up, veering off in a direction I think is right, etc. Does something similar (species-appropriate of course) happen with apes? This could be tested.

    But full disclosure, if I'm really honest with myself, I know I still sometimes conform on (rare) occasions to 'groupthink,' the kind one reads about when people convince each other that one course of action (later seen to be dubious) is right. I had a strong gut feeling that my daughter shouldn't go out to a concert last weekend because of severe storm warnings, very unusual ones-not just the run of the mill, as tornadoes had been marching East all weekend and there was a certain barometric sort of feeling in the air I didn't like. Other parents were unconcerned and I didn't want to be "the bad cop" or overprotective so I relented and off 4 teenagers went. That is the same evening an F4 tornado struck 5 miles from our house, causing death, injuries, and incredible destruction. My daughter had gone in the other direction, and was fine, but I have been seriously annoyed with myself. That kind of conformism especially where safety is concerned goes against my usual strong confidence in asserting myself, but still it happened.
    - Barbara J. King
  3. April 23, 2011 7:01 AM EDT
    Barbara--a good example, and I agree that I still find myself conforming now and again, though it is much easier to go my own way than it was when I was younger. I wonder, too, thinking more about this, about that possible gender difference in the need to conform, and if more dominant primates are not under as much pressure to conform as animals (including humans) lower on the hierarchy. SO much to learn about ourselves!

    I'm thankful that you and your family escaped the tornadoes.
    - Mary Pratt

Selected Works

Why are animals so irresistible to us? Why do we live with and care so deeply about them? From the famous "art caves" of ice-age Europe, to the ancient villages where animals were first domesticated, to stories of apes, whales, dogs, and cats doing fascinating things today, King weaves together a scenario about the animal-human bond that encompasses our past, present and future.
Can scientists discover a prehistory of religion just as they have traced the evolution of technology, language, and art? What does compassion in chimpanzees, or burial patterns in our human ancestors and Neanderthals, tell us about the origins of religion? In Evolving God, named a Top Ten Religion Book for 2007 by the American Library Association, Barbara King explores these questions.
How do chimpanzees, bonobos, and gorillas-- the African apes -- communicate using body postures and gestures? Using her many years of experience studying these apes, Barbara King answers this question in a book that offers a new perspective on the evolution of language.