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For as long as human animals have pondered how we might differ from nonhuman animals (hereafter animals for convenience) many ideas have come and gone. For example, it's been postulated that humans are created in the image of God and are the only rational beings. People vary in their opinions on whether we are the only animals who are created in the image of God and of course it's not a claim that can be proven or disproven. However, ample research has shown that animals are rational beings and that they also share with us many other traits that were once thought to be uniquely human, including manufacturing and using tools, having culture, having a sense of self, using complex systems of communication, producing art, and having rich and deep emotional lives and knowing right from wrong. Two traits that seem to separate us from other animals are we're the only animals who cook food and no other animals are as destructive and evil.
Now, it's been suggested that perhaps mental time travel and having a theory of mind are two uniquely human ways of thinking that separate us from other animals. This idea is put forth in a book called The Recursive Mind by Michael Corballis. Corballis argues that recursion is a uniquely human trait. In an excellent review of Corballis's book, anthropologist Barbara J. King makes many of his arguments palatable to a lay audience. So for example, she writes, "it's a unique human trick to communicate by embedding structures within other structures, as when one noun phrase in a sentence is made to contain another. An example of such linguistic recursion is furnished by Corballis. The non-recursive sentences 'Jane loves John'' and 'Jane flies aeroplanes' may be combined to produce the recursive sentence 'Jane, who flies aeroplanes, loves John'. Less interested in language than the mind itself, Corballis states flatly that recursion is 'the primary characteristic that distinguishes the human mind from that of other animals'".
Mental time travel and theory of mind are recursive ways of thinking. King goes on to write, "During mental time travel, an experience that we've had in the past or that we imagine for ourselves in the future is 'inserted into [our] present consciousness'. Similarly, in theory of mind, we insert what we believe to be someone else's state of mind into our own."
So, how do Corballis's ideas hold up given what we know about the behavior and cognitive capacities of animals? Not that well according to King. I agree. King notes that other animals plan for the future and and have a theory of mind (see also and). As an example she writes about the hunting behavior of wild chimpanzees described by prominent primatologists Christophe and Hedwige Boesch-Ackerman. In their book The Chimpanzees of the Tai Forest these researchers wrote "A hunting chimpanzee 'not only has to anticipate the direction in which the prey will flee (recorded as a half anticipation), but also the speed of the prey so as to synchronize his movements to reach the correct height in the tree before the prey enters it (recorded as a full anticipation) . . . . We also recorded a double anticipation when a hunter not only anticipates the actions of the prey, but also the effect the action of other chimpanzees will have on the future movements of the colobus, that is he does not anticipate what he sees (the escaping colobus), but how a future chimpanzee tactic will further influence the escaping monkeys."
King concludes, "Humanity's recursive ways of thinking are more elaborate than those of other animals, but some other animals do think recursively as well. Can the degree of difference explain the origins of human thought, language and civilization?" We really don't know. But as more studies are conducted I'm sure we'll discover other examples showing that recursive ways of thinking are not reliable markers of human exceptionalism and that other animals show highly sophisticated recursive ways of thinking.
What's at issue here is whether or not humans are separate from, and above or better than, other animals. This sort of speciesist thinking doesn't have much support. Charles Darwin's ideas about evolutionary continuity that stress that differences among species are differences in degree rather than kind - shades of gray rather than stark black and white differences - argue that we need to keep an open mind about the cognitive capacties of other animals. Some of the research mentioned above supports this claim as do other research projects. Different doesn't mean smarter or better.
As I concluded in elsewhere, "The time has come to debunk the myth of human exceptionalism once and for all. It's a hollow, shallow, and self-serving perspective on who we are. Of course we are exceptional in various arenas as are other animals. Perhaps we should replace the notion of human exceptionalism with species exceptionalism, a move that will force us to appreciate other animals for who they are, not who or what we want them to be." And, what's really the most important question is what makes individuals unique as there are wide-ranging individual differences within all species, including Home sapiens.
I'm excited to see what future research shows us about the cognitive capacities of other animals. I'm sure they're much more than some give them credit for. Indeed, what we already know shows this to be the case.
