Of Apes and Men

A mere 1% difference in DNA separates humans from our closest living relatives - the chimpanzees. The “Great Ape Project” argues that because the differences between humans and other great apes (chimpanzees, bonobos, gorillas and orangutans) are so slight the Great Apes should share basic human rights. The Project aims to have the UN adopt a declaration on the rights of nonhuman apes that would make research on them impossible. Supporters of the Great Ape Project point to the psychological similarity between nonhuman apes and ourselves: nonhuman apes, they argue, are self-aware. As a consequence of self-awareness great apes must suffer in captivity in ways similar to what we would experience. This is no abstract debate. There are about 1,600 chimpanzees held for biomedical research in the US alone and are central to the study of several maladies. Perhaps the most important example is liver disease. Research on chimpanzees led to the vaccine against hepatitis B. Nearly half the global population is at high risk of contracting this virus. Chimpanzees have also been crucial for the study of hepatitis C. But hepatitis only heads the list. AIDS is another example, because chimpanzees are the only nonhuman species that can be infected with HIV. Chimpanzees are also helping scientists battle other health problems, including spongiform encephalitis (“mad-cow disease”), malaria, cystic fibrosis and emphysema. Because they are close to us, nonhuman great apes are suitable for research on several diseases that cause human suffering. Yet, does this similarity make biomedical experimentation difficult to justify ethically? One reason to think so is the idea that the minds of nonhuman great apes are similar to ours because some of animals have been taught sign language. But thirty years of research on the abilities of chimpanzees and bonobos to communicate using signs has demonstrated few compelling examples of anything close to human language. In all these studies, the animal’s vocabulary developed slowly, and never exceeded a couple of hundred signs (about two weeks’ work for a healthy two-year-old child). Chimpanzee utterances rarely extend beyond one or two signs – making discussion of grammar or syntax forced. More recent reports suggesting ape grammar are those of a bonobo named Kanzi, whose linguistic abilities are alleged to exceed those seen in earlier sign-language studies with chimpanzees. A critical test for Kanzi’s comprehension of sentence structure involved asking him to respond to an instruction such as “would you please carry the straw?” Sure enough, Kanzi picks up the straw. But although grammar may have conveyed the correct meaning of the test sentence, the circumstances could also have made the requested action obvious (given that Kanzi knows what the words carry and straw refer to). After all, a chimp may carry a straw; a straw cannot carry a chimp. The second tier of evidence for self-awareness in nonhuman apes comes from so-called mirror tests. While the subject is anesthetized, the experimenter places a mark on the forehead or ear with an odorless, tasteless dye. Upon waking, the animal is shown a mirror. Will the creature recognize that the splash of dye is on his own face? The answer is taken to be yes if the animal touches the marked area of skin more often with a mirror in front of him than without. It is now accepted that chimpanzees, bonobos and orangutans can recognize themselves in mirrors. Most other species examined (including fish, dogs, cats, elephants and parrots) react to themselves in a mirror either not at all or as if the reflection is another animal. The problem with the mirror test of self-recognition lies not in the results - clearly some nonhuman apes recognize themselves in mirrors - but in interpretation. Why equate self-recognition with self-awareness? Some people cannot recognize themselves in mirrors (blind people, say), but nobody suggests they lack self-awareness. In autistic children self-awareness is impaired. Yet autistics develop the ability to recognize themselves in mirrors at the same rate as normal children. So tests of self-recognition in mirrors may say something about how animals view their bodies, but says nothing about their self-awareness. The final set of evidence for self-awareness in nonhuman apes comes from something called “cognitive perspective taking.” A chimpanzee watches a trainer put food into one of four cups. The chimpanzee knows that the cups are there but cannot see where the food is being put. A second trainer who has watched where the food was put (the knower ) then points to the baited cup. A third trainer who has not seen where the food went (the guesser ) points to a different cup. A chimp - or child - who has an awareness that others have minds, can readily appreciate that one trainer knows where the food is hidden, and the other doesn’t. Therefore this individual should select the cup pointed to by the knower in order to receive the food. The chimpanzees ultimately succeeded in picking the cup with food, but required hundreds of training experiences before they could make the right choice consistently. This pattern of slow learning is more like the way any animal might learn where food can be found and does not suggest that the animal is treating the trainers as people with minds. In recent experiments, a chimpanzee was offered a choice between begging from a person who could see various pieces of food, and begging from someone blindfolded. To the experimenters’ surprise, chimps were initially as likely to approach the trainer who could not possibly see the food. With enough experience, the chimps learned to ask only the person with unrestricted vision. They showed no spontaneous understanding that being unable to see disqualified a person from providing snacks. There is little that indicates that apes have any awareness of the minds of others, much less that they are aware of their thoughts. Non-human great apes may be only 1% of DNA away from us, but their psychology is different. They do not share our self-awareness, nor should they share our human rights.