Consider the following recent headlines:
"Don't touch baby wild animals, no matter how cute they might be" (Alaska Dispatch News)
"Animals are smarter than humans give them credit for" (New York Magazine)
"DNA from humans, rats and other animals found in some veggie burgers" (FOX7 Austin)
"Researchers show humans and other animals can understand quantities, even without language" (Phys.org)
In each case, we have no trouble understanding what is meant by "animals." Yet looking at all four headlines together, it's clear that they don't all mean the same thing. For the first two headlines, "animals" doesn't include humans. For the second two headlines, it clearly does.
This inconsistent usage points to a fundamental tension in the way we view ourselves as humans: as part of the biological world, on one hand, yet special and set apart, on the other. Where do these perspectives come from? And are they universal to all humans, or a quirk of our own culture?
One approach to answering these questions comes from research in psychology and anthropology. Researchers have studied how people think about humans in relation to the natural world, and how the way we reason about humans and other animals changes over the course of development and as a function of education and culture.
The findings from this body of work suggest that by age 5, Western children growing up in urban environments are anomalous in the extent to which they regard humans as central to the biological world. Much of the rest of the world — including 3-year-olds, 5-year-olds in rural environments and adults from indigenous populations in South America — is more inclined to think about humans as one animal species among others, at least when it comes to reasoning about the properties that human and nonhuman animals are likely to possess.
To illustrate, consider a study by Patricia Herrmann, Sandra Waxman and Douglas Medin published in the Proceedings of the National Academy of Sciences in 2010. In one experiment, 64 urban children, age 3 or 5, were asked a series of questions that assessed their willingness to generalize an unknown property from one object to another. For instance, they might be told that people "have andro inside" and would then have to guess whether it's right or wrong to say that dogs "have andro inside."
The findings with 5-year-olds replicated classic work in developmental psychology and suggested a strong "anthropocentric" bias: The children were more likely to generalize from humans to nonhumans than the other way around, consistent with a privileged place for humans in the biological world. The 3-year-olds, by contrast, showed no signs of this bias: They generalized from humans to nonhumans and from nonhumans to humans in just the same way. These findings suggest that an anthropocentric perspective isn't a necessary starting point for human reasoning about the biological world, but rather a perspective we acquire through experience.
So what happens between the ages of 3 and 5 to induce an anthropocentric bias?
Perhaps surprisingly, one influence seems to be anthropomorphism in storybooks. A 2014 paper by Waxman, Herrman, Jennie Woodring and Medin found that urban 5-year-olds were more likely to show an anthropocentric pattern of reasoning after reading a Berenstain Bears story, which features a humanlike bear family, than after reading a book that included more encyclopedia-like facts about bears. These findings suggest that children are sensitive to all sorts of information from their environments, and they also point to a great deal of conceptual flexibility. Just as adults have no trouble understanding the headlines that began this post — some of which cast humans as animals and some of which do not — young children, too, can shift between multiple perspectives.
But the shift to an anthropocentric perspective isn't a universal cultural endpoint. A paper by Andrea Taverna, Medin and Waxman, published earlier this year, underscores the important role of culture in how we come to view our place in the natural world. Using a guessing game similar to that used in the previous studies, the researchers tested a total of 44 children and adults from an indigenous population living in the Chaco forest in the lowlands of Argentina. They found evidence that neither children nor adults in this community showed an anthropocentric tendency to generalize more from humans to nonhumans than the reverse.
The indigenous participants' patterns of reasoning did reveal that they differentiated humans from nonhumans, but their responses also suggested an especially important role for the category of "animals (including humans)" when it came to generalizing biological properties across biological kinds. So the anthropocentric tendencies that might seem "natural" to urban, Western-educated 5-year-olds — and perhaps also to their parents — could reflect more about human culture than about the structure of the broader biological world.
Of course, generalizing unknown properties (like "andro") from one species to another is just one marker of people's reasoning about humans in relation to the natural world. Other perspectives may dominate in the context of religious beliefs, or when thinking about human minds rather than human bodies. But the ease with which we shed our identity as animals should perhaps give us pause. Whatever else we are, we're certainly biological creatures, and our fate is entwined with that of our fellow animals.
Tania Lombrozo is a psychology professor at the University of California, Berkeley. She writes about psychology, cognitive science and philosophy, with occasional forays into parenting and veganism. You can keep up with more of what she is thinking on Twitter: @TaniaLombrozo