Pia Nystrom and Pamela Ashmore are university professors, researchers, and best friends. They are also passionate animal lovers. Nystrom and Ashmore both received PhDs in Anthropology from Washington University in St. Louis where they met as graduate students. Nystrom now lectures across the Atlantic at the University of Sheffield in the UK, while Ashmore is an Anthropology department head at the University of Tennessee at Chattanooga. Though they have lived in different continents since 1994, these two friends managed to write a book for undergraduates on their favorite subject, primates.
The Life of Primates (2008) gives the reader an in-depth yet straightforward review of nonhuman primate biology. This includes the social behaviors, environments, and cognitive processes of primates as well as basic physiology. The chapter we’ll be discussing is “The Primate Brain and Complex Behavior.” In this section, Nystrom and Ashmore cover a broad range of topics from they “why”s to the “how”s of primate brains and cognition.
Why study nonhuman primate cognition?
Because we ourselves are primates, the brains and behaviors of other apes and monkeys interest us and allow for interesting views of our own neurological evolution and psychology. Nonhuman primate cognition research is highly controversial-- especially in its interpretation. Many don’t believe that humans can ever truly understand the minds of other animals because we cannot experience their perspectives for ourselves. However, we continue with this research in order to answer both philosophical and evolutionary questions.
The philosophical questions relate to our desire to know our position in nature - how unique our minds are compared to other creatures. Those who seek answers to the evolutionary questions examine our closest extant relatives (bonobos, chimps, etc) while trying to understand the evolution of the human brain.
Nonhuman primate research began in 1927 with Köhler’s chimp observations in the Canary Islands. He was the first to suggest that chimps were capable of insightful behaviors. Systematic research into primate cognition did not truly begin until the 1960’s, however, and even then most of that was done on captive primates. The biggest discoveries of this time period were from two field studies in Tanzania where the researchers showed the chimps frequently construct and use tools. Later research revealed that chimps have tool kits and that these kits are different regionally. This is more than Homo habilis can say with its identical tools across time and geography.
Though brain size usually correlates with complexity, the discovery of Homo floresiensis in Indonesia means this assumption must be reevaluated. H. floresiensis has a small brain case and stature (around the size of a modern chimp), yet it used tools which were much more advanced than those of chimps. This leads us to believe that the internal organization of the brain may be more important than its size. Still though, primates have larger brains than expected based on body size alone and are known to have more complex behaviors than other orders of animals.
Now the question is why did primates evolve such large brains? The brain is a metabolically expensive organ to run. There must have been a very strong selective pressure for large brains that outweighed the energetic cost.
There are several hypotheses for why primates have large brains. Primates with larger home ranges and which also eat fruit (a high energy food) have larger brains. They also seem to have the most efficient routes between food sources on their home ranges mapped out in their heads - this relates to the expensive tissue hypothesis. Sociality is another characteristic which correlates with brain size. Primates which live in large groups have complex interactions and can use “social tools” to achieve their own goals. For example, many primates use manipulation to gain access to food. This is the social intelligence hypothesis.
Researchers are also interested in whether nonhuman primates have theory of mind. However, it is very difficult to ascertain whether or not nonhuman primates understand another individual’s mental perspective. In order to learn more about nonhuman theory of mind, researchers have attempted to study an individuals awareness. If an organism has theory of mind, it is assumed to also have awareness. Though awareness is also a complex subject, it may studied a bit more easily than theory of mind. Awareness can be divided into two levels, self-recognition and self-attribution. Self-recognition is the ability to identify oneself apart from others. Self-attribution is when an individual aware of their own mental state and can use this to predict the actions of others.
The mirror test is the most often used test for self-recognition. Chimps, bonobos, and orangutans appear to recognize themselves in the mirror and use it to examine parts of their body they might not normally see. Gorillas do not react in this way and instead try to threaten the image. However, the famous captive gorilla Koko is said to routinely examine herself with a mirror. This may be because of her increased level of social stimulation. Gordon Gallup, the mirror test deviser, suggested that self-recognition could be an index for self-attribution.
Why do primates need to think?
The ability to understand others’ mental states can create more effective cooperation as well as social manipulation. Both of these lead to gains for the individual. Organisms which can differentiate between friendly and unfriendly interactions and intentions are better suited to realize when they are being manipulated or give them the means to manipulate. These abilities also potentially allow for the exchange of knowledge through observation or teaching.
As we learned in the Leary/Buttermore paper, tool use is a very large component of research on primate cognition. Primates are hand-feeders, meaning they use their hands for eating and essentially all grabbing activities. Hands are represented extensively in the sensory and motor areas of primate brains. While not all primates use tools, the grasping ability of the hand makes tools fairly useful in the primate world. Chimps and orangutans frequently use them, other species do not quite as much or at all.
Tools are not always used for food either - they can be used in displays and grooming as well. Chimps have been known to throw rocks at enemies and monkeys often dislodge branches to frighten away predators.
Not only are primates able to use tools, but they are also capable of making them. To do this requires forethought. They must have an idea of what the final product should look like and an understand of what materials to use to make that product. Chimps have also been known to make tools hours ahead of time - up to 14 hours of reaching the goal.
The “how”s of tool use in nonhuman primates are widely disputed. Capuchins seem to via trial and error, whereas with chimps it seems to be a mixture of emulation and perhaps intentional teaching.
While we may not ever truly understand the cognitive processes of nonhuman primates, we can learn a lot about our own evolutionary history from this research. There does not seem to be a distinct dividing line between our mental capacities and their own, especially when in a stimulating environment.