Animal Defenders International


Animal Defenders International

The Primate Nations: Primate intelligence, communication and emotions

Posted: 1 September 2006

Most nonhuman primate species (hereafter referred to as ‘primates’) share more than 90% of their DNA with humans (Homo sapiens)(1). The chimpanzee (Pan troglodytes) DNA sequence differs from ours by 1-1.5%(2),(3), whilst the baboon (Papio hamadryas) is 89% similar(4), with most monkey species somewhere in between. Studies have revealed that 99.4% of the bases are identical within the same genes in humans and chimpanzees. It has therefore been suggested that chimpanzees should take their place alongside humans within the genus Homo(5).

Whilst we do not believe that admitting other species to the community of those deserving human compassion should necessarily be based upon either intelligence, or appearance, or genetics, there is no doubt that the close relationship between Homo sapiens and the other primates is demonstrated in their sociality, their ability to feel and express their emotions, their communication, cultural practices and intelligence. We believe that the non-human primates are not lower than us, just different, and the differences between our species are as vital and exciting as the similarities. It is our knowledge of these similarities and the effect of our attitudes and behaviour on our next of kin which makes their suffering at our hands inexcusable.

It is broadly acknowledged that all primate species are intelligent and dextrous, that they can solve problems and set up extensive social structures, and that they require a stimulating environment(6). Chimpanzees in particular have been shown to be highly intelligent and co-operative, nurturing family bonds, adopting orphans, mourning, engaging in power struggles, etc. They also exhibit emotions commonly thought to be the preserve of humans – jealousy, envy, compassion, greed(7),(8).

Wild chimpanzees have been observed breaking twigs from trees and stripping away leaves to create tools to feed on termites(9). Bonobos and orang utans have been found to plan ahead, by collecting and storing tools for future use(10). Apes learn by observing each other’s behaviour, including tool use, which varies according to geography. Cotton-top tamarins can solve tasks that require the use of one object to attain another, for example the use of a tool to obtain food. Without training, they discriminate between tools of different colour, texture, shape and material, in terms of their ability to retrieve food(11). Comparisons can be made with children of between one and three years old(12).

Rhesus macaques can perform rudimentary arithmetic and think using symbols(13). Considered paramount among human cognitive abilities is the capacity to reason about what others think, referred to as ‘theory of mind’. Rhesus macaques have been shown to possess an essential component of this – the ability to deduce what others perceive on the basis of where they are looking(14). Capuchin monkeys, for their part, have shown similar psychological processes to humans(15).

Both chimpanzees and orang utans show ‘self’ directed behaviour when presented with mirrors – they make faces and use them to groom parts of their bodies normally out of sight(16). Children show some inkling of self recognition in a mirror from as young as nine months; this ability increases at around 18 to 24 months(17). The capacity for self recognition in a mirror is thought to emerge at the same time as the capacity for reflective thought(18).

Chimpanzees have communicated in American Sign Language (ASL) and other artificial communication systems(19) and passed this knowledge on to the next generation. They use their signs to converse spontaneously with each other when no humans are present; they sign to themselves and use their signs during imaginary play. Ape language therefore appears to possess a number of linguistic traits that are shared with human language(19).

An experiment undertaken with four chimps that had been reared by humans revealed that chimpanzees are capable of freely conversing in ASL. Their reactions to, and interactions with, a conversational partner resembled patterns of conversation found in studies of human children(20). Primatologist Dr. Roger Fouts taught ASL to a chimpanzee called Booee in 1978. In 1995, when Dr. Fouts returned to the laboratory Booee recognised him immediately and began signing both his own and Fouts’ name. They had not seen each other in seventeen years. Fouts was unable to stay long with Booee, and after he left, Booee retreated to a corner of his cage, visibly depressed(21). At the age of three, Booee had developed his very own personality, much like a human child(21).

Chimpanzees show ‘cross modal transfer of information’ in that they can, for instance, recognise by touch alone objects that they have previously only seen, and can understand and use abstract symbols in their communication(22).

Koko, a female Lowland gorilla born in 1971, can use ASL and understand spoken English. Koko first began learning sign language at the age of one(23) and her intellectual, physical and linguistic development has been studied since then.
She has a working vocabulary of over 1,000 signs and understands approximately 2,000 words of spoken English. Koko has an IQ of between 70 and 95 on a human scale (100 is considered normal for a human)(24).

Vervet monkeys can communicate symbolically, and have predator specific alarm calls which indicate whether to flee along the ground or up a tree; these sounds differ in turn from their social communications(25). Moreover, monkeys have been shown to form sentences whose specific meaning is different from the individual calls used to form the sentence(26).

Gestures and Emotions:
Chimpanzees display a range of postures and gestures similar to humans. They greet with kisses and embraces, play and reassure each other, and express emotions like anger and sadness. They hold hands, pat each other on the back, swagger, shake their fists, tickle and laugh (even in the same context as humans)(22). The discovery of gestural dialects amongst wild chimpanzees demonstrates that gestural communication and acquisition of gestures are natural for wild or captive chimpanzees. Although many human facial expressions are inherited, our gestures are largely acquired and have dialectical variation, much like the chimpanzees(27).

Gestures similar to those of humans can be seen in primates other than chimpanzees, too. When courting each other Capuchin monkeys behave in a way strikingly similar to humans, gazing into each other’s eyes, tilting their heads, raising their foreheads and blinking their eyes(28). Chimps who have lost a close companion will often grieve, become depressed and withdrawn, and refuse to eat(29). Vervet monkey populations display a range of personalities and temperaments from calm to anxious(30). An emotional trait that people deem most uniquely “human” is empathy. Yet chimps show sympathy and empathy for each other, and react emotionally to humans in pain(31).

The macaque social system is based on specific rules for relationships and social behaviour and rhesus macaques develop long-lasting social bonds that may last a lifetime(32). Capuchin monkeys work together to gather food and then share the fruits of their labour, the kind of cooperation essential to human society(33). We nurture and teach our children over a long period. Peer play is important in the development of young rhesus macaque monkeys because it promotes social development. During play, chimpanzees learn about nonverbal and other forms of communication(34). Juvenile
vervet monkeys display exploratory behaviour (such as playing with a new toy) which is common to both vervets and humans(35).

All these attributes are significant because they explain why primates can be harmed not just physically but through mental and emotional distress. This might be caused by transport, or isolated enclosure in barren environments.

Faced with such strong claims about how primates suffer in laboratories, in 2002 the EC commissioned its own analysis of primate use throughout the European Union. It went on to acknowledge, in considerable detail, both the cognitive complexity of the animals and their capacity to suffer in laboratories(7).

Next: Laboratory use of primates, page 1


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