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Abstract
So your friend talks to his car like it is a sentient being? Don't be alarmed. According to Daniel J. Povinelli at the University of Louisiana's New Iberia Research Center, you are just witnessing a uniquely human result of evolution. After spending the last decade studying chimpanzee cognition, Povinelli is convinced that humans and their closest living relatives have very different minds. "Humans constantly invoke unobservable phenomena and variables to explain why certain things are happening," says Povinelli. "Chimps operate in the world of concrete, tangible things that can be seen. The content of their minds is about the observable world."
| We behave alike, but do we think alike? |
The desire to understand animal cognition, particularly that of animals resembling ourselves, has a long tradition behind it. Charles Darwin concluded that if an animal's behavior is nearly identical to ours, then the mental activity supporting that behavior will also be very similar.
But just because an animal behaves like us, does that really mean that similar mental activity drives their behavior? Povinelli isn't so sure. But then he is something of an exception in a field that has long emphasized the similarities shared by chimps and humans, and has given little airtime to the differences.
Certainly there is no doubt that chimps are intelligent animals that interact flexibly with their environment. But how similar are the minds of chimps and humans?
| Are chimpanzees self-aware? |
To get at the answer, comparative psychologists and anthropologists design simple experiments, often set up like games, to test whether chimpanzees are aware of their own thoughts and those of others. After all, awareness of thought is a hallmark of human cognition.
In one such experiment, Povinelli's group tested whether or not the chimps understood the concept of seeing. Chimps regularly use information gathered through sight, but the question is, Do they think about seeing or know about others' experiences of seeing?
| Chimps begged from the blindfolded. |
The experiment is relatively simple and relies on chimpanzees' natural begging gesture. When a chimp wants something, it stretches out its hand, palm up, to the person or chimp with the desired object, be it a piece of food or a toy. In the experiment, the chimp enters a room and is confronted with two experimenters with food. One experimenter has a blindfold over his eyes and the other one doesn't; obviously, the experimenter with his eyes covered can't see the chimp enter the room or its request for the food. Povinelli reasoned that if the chimps understood the concept of seeing, then they would only ask for the food from the experimenter who could see them. But in numerous trials, and in variations on this theme, the chimpanzees did not discriminate between the two experimenters, begging equally often from the experimenter who could not see them.
Povinelli's interpretation of these data is that chimps don't think about seeing or about what others see. Other researchers aren't so sure. For example, Josep Call at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, thinks the data could be interpreted differently. "If you go to the street and you ask people, 'What is the part of your eye that allows you to see? Is it the retina? Is it the eyeball? Is it the iris?', some people," he points out, "will not know what part of the eye allows you to see. That does not mean that they do not know anything about seeing." Similarly, he thinks Povinelli's blindfold experiment tests more about whether a chimp knows which part of the anatomy is necessary for seeing than about whether the animal thinks about seeing.
| How can we know how a nonverbal animal thinks? |
This difference in interpretation highlights what is so intractable about the field of chimpanzee cognition: How do you ask how a nonverbal animal thinks when it can't tell you? Testing what it thinks about is relatively easy, but is it aware of its own mental states?
In all known cultures, Povinelli points out, humans constantly evaluate their interactions with others in terms of unobservable emotions, desires and beliefs, asking questions such as "What is she thinking? Why did he do that? Was he angry? Or did she believe such and such was true?" to explain the observable actions.
But Povinelli has yet to find evidence that chimps use this sort of abstract thinking about unobservable things, and he thinks that this sort of mental awareness is uniquely human.
"I think, based on a lot of empirical research that we have done," says Povinelli, "that humans and chimps share a common set of low-level psychological operations that drive most of our behavior. But during the course of human evolution, we wove in alongside those ancient neural and psychological systems - in parallel to them - an additional, more abstract and conscious way of representing those behaviors and thinking about those behaviors. That more abstract way of thinking about the world appeals to such unobservable things as beliefs and desires, intentions, goals, and internal unobservable emotions to explain why the social world is behaving the way it is, why people behave the way they do.
| Abstract reasoning is paired with language. |
"I think it is intimately tied up with the evolution of our language capacities," concludes Povinelli. "The representational capacities that underwrite language can support this kind of abstract reasoning capability."
If Povinelli is right that this sort of abstract thinking about the world around us is the instinctual result of evolution, then trying to discern how another type of mind, such as the chimp's, conceptualizes the world forces researchers to challenge their own evolution. In order to discover and describe how another type of mind works - one that doesn't use abstractions - the researcher has to check the involuntary attribution of emotions and logic to the chimp's actions.
"It is very difficult to shut down our human way of thinking about the world and step into the mind of another species," says Povinelli. Yet if researchers want to understand how another species thinks, then they must find another way to conceptualize thought.
| Is it similarity or anthropomorphism? |
The instinctual attribution of emotion to other animals, and even to inanimate objects like your friend's car, might also explain why cognition researchers have focused so much on the similarities between chimpanzees and humans. It is, after all, easier to assume that what is happening in our minds is what is happening in the mind of an animal that looks and behaves so much like us.
But Povinelli emphasizes that, in the end, all of the reproducible data about chimp cognition needs to be accounted for within a single theoretical framework. And although he stands out in his view that humans are uniquely cognizant of their emotions and thoughts, he is convinced that this is the only theory that will accommodate all of the data. After all, he concludes, "In every critical juncture, after the chimp has learned something and we gave him the option to tell us, 'are you really reasoning about seeing or are you using some surface behavior cue?', at every case, they have consistently said, 'What are you talking about? We are using what is there. We're using what is in the world.'"
Rabiya S. Tuma is a freelance science writer based in Oregon and New York.
Frederick H. Carlson is a professional artist and illustrator whose clients include The Saturday Evening Post, Baltimore Sun and Pittsburgh Magazine.
Animal Self-Awareness: A Debate - between Daniel Povinelli and Gordon Gallup, Jr., who discuss whether or not animals can empathize. From Scientific American Presents: Exploring Intelligence.
Cognitive Ethology and the Explanation of Nonhuman Animal Behavior - a research article by Marc Bekoff that discusses the evolutionary and comparative study of animal cognition.
Primate Info Net - a centralized resource for primatology jobs, journals, and general information. From the Wisconsin Regional Primate Research Center Library at the University of Wisconsin at Madison.
Chimpanzees in Research: Strategies for Their Ethical Care, Management, and Use - the National Academies' 1997 report.
Do the Eyes Have It? Cues to the Direction of Social Attention - a review of the role that gaze plays in social cues in humans and nonhuman primates. From Trends in Cognitive Sciences, 2000, 4:2:50-59. Full text available from BioMedNet.
Homologies for Numerical Memory Span? and A Conventional Approach to Chimpanzee Cognition - a comment and response concerning a recent finding that chimpanzees have a numerical memory span similar to humans. From Trends in Cognitive Sciences, 2000, 4:4:127-129. Full text available from BioMedNet.
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