We compare the psychology of hominoids (human and non-human apes). Specifically, we seek to identify which features our problem-solving abilities have evolved since humans, bonobos, and chimpanzees shared a common ancestor (i.e., the 3 chimps). Our research reveals the biological basis of many of our species most sophisticated abilities as well as how they are constrained.
Our group also compares the psychology of apes and non-primates to identify cases of psychological convergence (i.e., distantly related species have similar cognitive skills). Such cases of convergence can provide a unique opportunity to infer how human-like social skills evolved.
We conduct the majority of our research in the African sanctuaries Lola ya Bonobo and Tchimpounga Chimpanzee Sanctuary. Therefore, we are actively involved in research promoting the conservation and welfare of nonhuman apes in the Congo Basin.
How can the knowledge we create be used in service for society?
- Mapping normal cognitive development in humans and identifying causes of developmental disorders such as autism.
- Understanding the biological basis of human trust, tolerance and aggression to aid in development of strategies to promote cooperation while preventing xenophobia, female coercion and even war.
- Describing the biological basis of human economic preferences that influence both rational and irrational decisions.
- Revealing how the portrayal of endangered animals such as chimpanzees on television can affect public attitudes toward their welfare and conservation.
- Evaluating the release of orphaned apes back into the wild as an education and conservation strategy.
The Hare Group also runs the Duke Canine Cognition Center.
Our First Goal
Is to determine which features of human social problem-solving and decision-making are unique amongst the hominoids – bonobos, chimpanzees, humans, gorillas and orangutans. (See "interactive ape family tree" in right column.) Identifying those psychological systems which are responsible for the unique features of human behavior is the first step to solving Darwin's greatest difficulty.
Knowing our evolutionary relationship to the other apes (our phylogeny) and the principle of parsimony allow us to take this first step.
Phylogeny: Our species shared an ancestor with bonobos and chimpanzees ~6 million years ago which means by comparing humans with bonobos and chimpanzees we can determine how our species' psychology changed since all three species shared a common ancestor. (NOTE: humans evolved from a common ancestor with chimpanzees and bonobos not directly from them. Bonobos and chimpanzees have also changed since they split from our common ancestor since they are now separate species!)
Parsimony: If bonobos and chimpanzees lack psychological systems that humans possess, we know these systems evolved since humans diverged from our last common ancestor. When bonobos, chimpanzees and humans are similar psychologically it is most parsimonious to assume all three species inherited this psychology from their common ancestor (it did not evolve three times independently).
Our Second Goal
Is to identify the evolutionary process by which cognition evolves between different species – including the process that led to the evolution of the unique features of human psychology. Understanding the selective pressures that can drive the evolution of such psychological systems is the second step in solving Darwin's greatest difficulty.
Comparing the psychology of primates and non-primates to identify cases of psychological convergence (where distantly related species share similar psychological traits) allows us to take this second step.
Convergence: If the psychology of two distantly related species converge, it is possible these shared traits arose independently due to similar selective pressures (i.e., high levels of tolerance in domesticated animals, bonobos and humans may be the result of similar selection pressures). Therefore, cases of convergence may provide a unique opportunity to infer how human-like problem-solving skills evolve.
We conduct our non-invasive behavioral research with chimpanzees and bonobos at:
Both are African sanctuaries belonging to the Pan African Sanctuary Alliance and are on the front lines in the fight against the illegal, international bushmeat trade threatening wild apes with extinction. By studying apes in African sanctuaries we hope to obtain the most accurate picture of what apes are capable of while supporting welfare and conservation efforts in African sanctuaries. Therefore, we are also actively involved in conservation and welfare research.
We also conduct research locally with great apes, lemurs and dogs at:
The Hare Group also runs the Duke Canine Cognition Center.
Ape Cooperation & Prosocial Preferences
Economists, biologists and psychologist have been fascinated by the seemingly altruistic behavior that humans demonstrate during cooperative economic games and in naturally occurring behavior. Theory and experimental evidence suggests that humans may show a level of altruistic behavior not observed in other species. This implies that during human evolution humans evolved a tendency to help others at a cost to themselves that is not observed in our two closest living relatives the bonobo and chimpanzee. However, while we know much about the naturally occurring cooperative behavior of bonobos and chimpanzees few experiments have been conducted to test for these species prosocial preferences. This is particularly the case for the more tolerant bonobo.
We are studying prosocial preferences in bonobos, chimpanzees and humans to test (1) whether bonobos and chimpanzees will share food or other resources with others in ways observed in young human children and (2) we are studying whether human cooperation is better promoted through mechanisms of punishment or communication in ecologically relevant social contexts. In doing so we will understand the evolution of social preferences thought to be responsible for the ultra-social species that we are. Understanding the evolution of our prosocial tendencies will shed light on how we might encourage cooperative behavior in our own species.
Ape Economic Decision Making
Economists, biologists and psychologist have long studied decision making preferences in humans and how these preferences interact with cognitive skill such as memory. Theory and experiments suggest that humans may show levels of patience and preferences for risk not observed in other species. Our species ability to save for the future, avoid investing in a losing cause, or engaging in conflict are all heavily influenced by such preferences. Taken, together with our species unusual memory abilities we have developed global economies, international treaties and more. However, we know almost little about the biological basis of the preferences that drive the economic and political decisions our species makes.
We are comparing the decision making preferences of bonobos, chimpanzees and humans to test (1) If human decision making preferences are shared with our closest living relatives and (2) to understand the biological basis of these preferences and how they interact with mechanisms for how we form memories. Understanding the evolution of our decision-making preferences will help inform why humans make the economic and political decisions they do helping to improve our decision making.
Ape Theory of Mind
Theory of Mind
Humans are capable of thinking about the thoughts of others. As young children we develop the ability to not only model the perceptions, intentions and beliefs of others, but also to recognize others can have thoughts that differ from our own. Developmental psychologists have suggested that it is this ability to think about the thoughts of others or “Theory of Mind” that may be the foundation of our species ability to intentionally cooperate and communicate in ways that other species do not. Without our Theory of Mind we cannot learn language and participate in other forms of cultural learning, we cannot form institutions (i.e., governments, Facebook, etc.) and we cannot teach or care for one another as only our species does (i.e., schools, hospitals, etc.). If this developmental hypothesis is correct then there is something truly unique about the way that our species thinks about the thoughts of others that evolved during human evolution.
We are studying Theory of Mind in bonobos, chimpanzees, lemurs and dogs to test whether they (1) have Theory of Mind capabilities at all and (2) how similar or different their Theory of Mind capabilities are to that of human infants (In collaboration with developmental psychologists at the Max Planck Institute for Evolutionary Anthropology). In doing so we will understand the evolution of cognitive skills thought to be responsible for the ultra-social species that we are. Understanding the evolution of these cognitive abilities will shed light on the causes of developmental disorders in humans.
Development & Domestication of Ape Psychology
Domestication of Psychology
It is easy to hypothesize but difficult to test which selection pressure(s) cause a species' psychology to evolve. Domesticated animals offer an unmatched opportunity to understand the effect of emotional evolution on the problem solving skills of animals. Experiments have demonstrated that selection against aggression in mammals leads to the domestication syndrome and that this selection also effects social problem solving abilities (e.g. dogs but not wolves are skilled at spontaneously using human social cues). Moreover, selection on aggression effecting morphology, physiology, behavior and cognition is thought to target developmental pathways in producing the suite of observed changes. Thus, selection on systems mediating emotions responsible for aggression may be a major target of selection that then has effects on social cognitive abilities across species. Given that humans are thought to have become more cooperative and tolerant during our species evolution, there may have also been selection on our species aggressive tendencies as well that in part might explain our cognitive evolution. Studying the comparative development of emotions and cognition can help test this hypothesis.
We are studying how emotional reactivity and social problem solving are related by testing (1) how dogs form trusting relationships with humans and how individual variance in how dogs bond may correlate with other behavioral and physiological parameters, (2) we are comparing how the less aggressive bonobo and the more aggressive chimpanzee react behaviorally and physiologically to novel objects and social conflicts and (3) we are comparing the development of the behavior, physiology and psychology of bonobos, chimpanzees and humans. We have also been working with geneticists at the Max Planck Institute for Evolutionary Anthropology to link our behavioral work to the comparison of the bonobo and chimpanzee genome. Understanding how animals form trusting relationships, how they respond to conflict, and how human development differs from that of other apes will help us test the relationship between emotion and cognition while pointing to the selection pressure that may have shaped our species during human evolution.
Also visit the Duke Canine Cognition Center for our related work with dogs.
Phylogenetic Psychology & Lemur Cognition
Comparative psychologists have become increasingly skilled at comparing the psychology of multiple species while evolutionary biologists have developed phylogenetic techniques to test evolutionary hypotheses for traits within and between clades. Together with Evolutionary Biologist Charlie Nunn, we obtained funds from the National Evolutionary Synthesis Center (NESCent) to establish methods and a large international collaboration that would bring the methods of comparative psychology and evolutionary biology together in order to test hypotheses for how cognition evolves.
We are are testing the phylogenetics of psychology by (1) validating comparative tests of inhibitory control, social skills, and spatial memory at the Duke Lemur Center for use with species of lemurs, monkeys, apes, and a variety of non-primates, (2) developing an international team of collaborators from half a dozen countries with access to large samples of dozens of non-human species and (3) conducting proof of concept analyses to demonstrate that this new synthesis of methodologies can provide powerful tests of cognitive evolutionary hypotheses. In the age of comparative genomics, our data will provide the basis for revealing genetic systems underlying cognitive evolution. In understanding how animal cognition evolves, we will gain inferences into how human cognition evolves.
The Media, Conservation, and Welfare
All species of great apes, with the exception of humans, are highly endangered. While habitat loss and disease transmission via contact with human populations are two of the major threats to the future of wild apes, the bushmeat and pet trades are the threats with which the entire international community is most tightly linked. Increasingly, wild apes are being killed to be sold as meat in restaurants in Africa and European cities. Moreover, the infants of mothers killed for meat are then sold as pets to expatriates in Africa or shipped to be sold in Europe, Asia, or the U.S. on the black market. It has been suggested that marketing campaigns by companies and even documentary companies that use infant chimpanzees in ads and T.V. programs are facilitating this trade by encouraging the public perception that apes make great pets. Just as in the illegal drug trade the desire for pet apes is encouraging the poaching of wild apes for sale as pets.
We are conducting research on the effects of media use of great apes on people’s perceptions of great apes by (1) conducting experiments in which subjects are shown previously-aired commercials including “entertainment” chimpanzees dressed up and acting like humans and (2) testing their attitudes and behavior toward ape conservation and testing for these same effects in Congolese school children. Understanding the relationship between how we present animals on T.V. and the public’s attitude toward their conservation can help aid strategies to protect these animals.
For more on why such research is necessary:
- The Human Spark (PBS) – Hollywood Chimps: The Debate
- ChimpCARE – Chimpanzees in Entertainment
- Chris Palmer, American University – Shooting in the Wild (book and documentary)
Post-Release Monitory of Bonobos
In response to the illegal bushmeat and pet trade, orphanages have been established across Africa to confiscate infant apes that are for sale in African markets. Our research groups works with Friends of Bonobos to support their welfare and conservation efforts to protect bonobos in the Democratic Republic of Congo. The orphanage has conducted the world’s first bonobo release in which a group of orphan bonobos raised at the orphanage were released back into the wild. The question is now how well will these orphans adapt to life in the wild after a life in captivity.
We are advising Friends of Bonobos on observational methods to measure the activity budgets of the released bonobos so that they can be compared to that of wild bonobos. This research is being conducted to monitor the health of the bonobos and document the strengths and weaknesses of release as a strategy in the effort to conserve wild bonobos in the future.
Links and Recommended Reading
Related Ape Conservation and Welfare Organizations
Friends of Bonobos runs Lola ya Bonobo and Ekolo ya Bonobo, the world's only bonobo orphanage and release site.
Terese and John Hart are leaders in the effort to save wild bonobos and the Congo Basin.
The Jane Goodall Institute runs the Tchimpounga Chimpanzee Rehabilitation Center.
Pan African Sanctuary Alliance (PASA) is an alliance of African primate orphanages working to stop the illegal international trade in pet primates (especially apes) and bushmeat.
The Bushmeat Taskforce is an alliance of NGOs working to stop the illegal trade in the meat of endangered animals.
chimpCARE is a nonprofit organization working to improve captive care of chimpanzees in the United States (including ending the trade of pet chimpanzees in the United States).
The World Clock show real-time world population growth and resource use – crazy!
Other Related Research Groups & Collaborators Outside of Duke
Kibale Chimpanzee Project @ Harvard – Dr. Richard Wrangham
Laboratory for Developmental Studies @ Harvard – Dr. Felix Warneken
Baboon Research @ University of Pennsylvania – Dr. Dorothy Cheney & Dr. Robert Seyfarth
Comparative and Developmental Psychology @ Max Planck Institute for Evolutionary Anthropology – Dr. Mike Tomasello, Dr. Josep Call & Dr. Malinda Carpenter
Cognition Biology @ Vienna University – Dr. Thomas Bugnyar & Dr. Tecumseh Fitch
LIVING LINKS @ Emory University – Dr. Frans de Waal
Primate Research Center @ Kyoto University – Dr. Tetsuro Matsuzawa, Dr. Masaki Tomonaga & Dr. Misato Hayashi
Scottish Primate Research Group (SPRG) @ Edinburgh, St Andrews and Stirling Universities – Dr. Klaus Zuberbuhler, Dr. Andrew Whiten, Dr. Carlos Gomez & Dr. Richard Byrne
Comparative Cognition Lab @ Cambridge University – Dr. Nicola Clayton & Dr. Nathan Emery
Comparative Cognition Laboratory @ Yale University – Dr. Laurie Santos
Anthropological Institute & Museum @ University of Zurich – Dr. Carel van Schaik & Dr. Judith Burkart
Yerkes National Primate Research Center @ Emory University – Dr. Lisa Parr & Dr. Bill Hopkins
Behavioral Biology Laboratory @ Chicago University – Dr. Dario Maestripieri
Primate Research @ Carleton College – Dr. Julia Neiworth
Comparative Communication Laboratory @ Penn State University – Dr. Daniel Weiss
Cebus Lab @ Georgia State University – Dr. Sarah Brosnan
Language Research Center @ Georgia State University – Dr. Michael Beran, Dr. David Washburn & Dr. Charlie Menzel
Ethocebus @ University of Georgia – Dr. Dorothy Fragaszy
Social Cognition Lab @ University of George Washington – Dr. Francys Subiaul
Psychology @ University of Wisconsin – Dr. Charles Snowdon
Anthropology @ UCLA – Dr. Joan Silk
Evolutionary Genetics @ Max Planck Institute for Evolutionary Anthropology – Dr. Svante Pääbo
Related Academic Societies, Journals, and Resources
- International Primatology Society
- Animal Behavior Society
- Human Behaviour and Evolution Society
- American Association of Physical Anthropology
- Society for Research on Child Development
Top Scientific Journals in Our Field
- Animal Behaviour
- Animal Cognition
- Journal of Comparative Psychology
- Evolution and Human Behaviour
- Evolutionary Anhtropology
- Human Evolution
- International Journal of Primatology
- American Journal of Primatology
- Primate Info Net
- Duke Lemur Center
- North Carolina Zoo
- Durham Museum of Life & Sciences
- North Carolina Museum of Natural Sciences