Cognition in Primates


Human beings are primates. Yet we differ substantially from our closest relatives, the apes. The main differences, as well as similarities, between Homo sapiens and other primates are explored in this paper. The phenomenon of conceptualization is distinguished from intelligence. All primates share degrees of the latter, but is conceptualization unique to our species? In order to fully grasp that which makes us distinctively human other than our physical appearance, various studies done with chimps are reviewed. In the end we can gain a better perspective on this at times contentious issue.

Cognition in Primates

Gaining a Perspective

To look at humans from the perspective of being a primate, a member of a certain class of higher mammals, may make one wonder what the differences are between us and the other primates. Comments abound about how humans can use tools, interact in sophisticated social ways, create a complex culture full of traditions, rituals, and moral and legal codes, participate in mutually constructive endeavors, produce technological marvels, and of course, use language.

But it is the use of language that appears to set us apart in a basic way from the rest of the animal world. Not only the use of language but the end result of using language—to expand knowledge and relate to self and others in meaningful ways. Without our ability to communicate in a conceptual fashion—as opposed to merely perceptually—we would be no better off than our primate friends, living in an austere environment sustaining ourselves by a combination of learned and innate repetitive operations.

On account of favorable mutations over the course of hundreds of thousands of years of evolution, humankind has acquired this most distinctive trait of conceptualization. But do not the other primates possess some part of this?

Certainly, it can be contended that other animals communicate with one another in order to function in their environment. Numerous instances are given about sea mammals such as whales and dolphins or very vocal creatures such as birds. Attempts have been made to understand exactly what is going on with these numerous types of communication.

Because researchers have sought to discover what sets apart humans from the rest of the world’s creatures, their pursuits have commonly led them to the study of animals who share close resemblances to humans in physical, behavioral, cognitive, and sometimes even emotional ways.

Primates, which include Homo Sapiens, encompass more than 250 species and subspecies. Basically, there are the prosimians—a varied lot of monkeys and lesser apes—and the troika of great apes—the chimpanzee, gorilla, and orangutan. Apes seem to be the more exploratory, creative, and curious than monkeys. Of course, they all differ greatly in their brain size and complexity, not to mention their physical structure, social relations, daily habits, and so on (Rumbaugh, 1900).

Humans, of course, have the largest brain of all primates with the most extensive development of their frontal lobes. It has been noted that these quantitative changes have led to qualitative shifts in cognitive capability; that is, the increases in brain size were not merely additive, but gave rise to entirely different qualities (Rensch, 1972).

It has also been confirmed that chimpanzees are genetically our closest relative. Chimps have roughly 99% of the same genetic makeup as humans. This is the same minute disparity that exists between horse and donkey, water buffalo and cape buffalo, house cat and lion (Tanner, 1981). Since this is the case, why is it that the two species are so remarkably different? What is it about humans that separates us from all other primates. Answers like “our different cultures,” “language use,” or “instinctive tool-making ability” fail to grasp the fundamentals of this topic.

Conceptualization Versus Intelligence

A differentiation must be made between intelligence and conceptualization. The fundamental dimension of intelligence, according to some, is the ability to transfer and generalize learning to new situations to one’s advantage (Rumbaugh, 1990). In short, the main components of intelligence are: to deal with aspects of one’s world in creative ways, to solve new problems, and to make advantageous decisions.

Conceptualization, though, concerns the ability to represent existents in an abstract way, and to formulate symbols (words or signs) for these abstracted classes of similar objects, actions, attributes, etc. In strict epistemological terms a concept is a mental integration of two or more units which are isolated according to their distinguishing characteristic(s) and united by a specific definition (Rand, 1990).

Concepts are a completely new level of awareness that allow an organism to function in creative ways and alter behavior consciously or volitionally. But in order to be utilized, concepts need to have labels attached to them to represent them in a concrete way, such as the words on this page. Be they actual words, lexigrams (i.e., mechanistically ordered symbols), or signs, all are combined into a repertoire known as language.

Therefore, being intelligent and being able to conceptualize or abstract are two entirely different characteristics. Intelligence is a contextually related phenomenon, which depends on a standard to judge the level of intelligence being evidenced. For example, a dog would be considered more intelligent than a cat, or a horse would be considered more intelligent than a cow—when the standard is the extent to which the animal responds keenly to training.

It has been noted frequently by scientists and laymen alike that both humans and other primates posses intelligent behavior—albeit in differing degrees. But only humans can abstract and therefore utilize language. (An interesting example of how intelligent behavior can rival humans is with rhesus monkeys. With practice they are able to challenge humans in video games involving a joystick (Rumbaugh, 1990). Certainly these monkeys are on a lower cognitive level than chimpanzees, but in this arena they nonetheless excel.)

In order to scrutinize these observations we have to consider the evolutionary steps that humans took to get where they are today. Of course, these steps were not consciously teleological, but rather genetic progressions that were beneficial to the organism (Binswanger, 1990).

Early Origins

As we go back in time to when Homo sapiens was not really Homo sapiens, a time when the closest genetic hominid was called Homo erectus, we can try to grasp when the conceptual transition occurred—the transition that enabled humans to pull themselves out of a concrete bound world and begin to see relationships, form generalizations, and formulate categories and classifications of things in the world. But in doing so and on account of our desire to find causes, we need to keep in mind that evolution is an extremely slow process. Natural selection is not a process that creates miracles overnight. In fact any dramatic alterations from the status quo most assuredly lead to maladaptive functions in relation to others of the same species.

Change must be gradual enough to be maintained with a certain degree of similarity throughout the species in order to be fully adaptive and to replicate itself (Dawkins, 1987). So, if humans did not get their gift overnight from the gods, how did it happen? Additionally, can the cognitive disparity between humans and other close primates also be exhibited in working with apes?

Australopithecus is the name of the species that preceded Homo erectus. This creature seems to be the furthest removed from what might be related directly in genetic lineage to humans. This species at least had the cognitive capacities of present chimpanzees or gorillas. It has been suggested that the evolution towards conceptualization and hence language must have started with primitive hand gesturing (Hewes, 1992).

On account of these insights, studies have been done to see exactly what other primates, namely chimps, can do with gesturing techniques. This is in response to the observations that chimpanzees rarely vocalize in the wild, and when they do it is for some reason other than intentional, voluntary communication. Hewes (1992) has noted, however, that chimps do exhibit gestural communication consisting of attention-orientation toward leading individuals, some arm and hand gestures, facial expressions, body postures, and incipient locomotion. Complementing this, chimps (similar to other higher level animals) can interpret or read various gestures and movements of others. These consist of assessing or predicting the intentions of others by watching head and neck positions, flicking of the ears or tail, general body stance, gait, and other characteristic poses or movements. Furthermore, modern apes similar to Australopithecus can also imitate these mannerisms, which shows a higher cognitive grasp of the behavior and more facility in interpreting the world than most other species.

Teaching Signs to Chimpanzees

Some have noted that chimpanzees are at the stage of development that immediately preceded the emergence of language in hominids (Hewes, 1992). However, one must always keep in mind that humans evolved and chimpanzees did not. For this reason the Australopithecines were on a different genetic/evolutionary track; they had the necessary makeup to eventually evolve into Homo sapiens. Chimpanzees, on the other hand, as well as the rest of the species of apes and monkeys for definite reasons got stuck and did not evolve. Apparently, their adaptations were suitable to their environments and no mutations were sufficiently adaptive enough to put them on the course of becoming conceptual beings.

Still, the question arises again: Are primates (such as chimps) qualitatively, not just quantitatively, different than humans? Do they posses no capacity to conceptualize? We now move on to the studies that have addressed these queries.

Although American Sign Language (ASL) was originally developed for humans who were deaf or hearing impaired, it has emerged as a language entirely self-contained. In fact it has a rich complexity of semantics that rivals any verbal language, although for efficiency reasons it lacks the incredibly large vocabulary of languages such as English. Nevertheless, a person who is proficient in ASL can articulate any sort of concept he or she desires. This system was most conducive to training chimps because it does not demand more from them than they are capable of, physiologically. From an evolutionary perspective it is the next logical step for creatures who have developed characteristics somewhat resembling humans but lack the capability to vocalize an assortment of phonemes that is a prerequisite for utilizing speech.

The first major study that attempted to teach chimpanzees ASL was done in the seventies at the University of Nevada at Reno (Gardner, Van Cantfort, & Gardner, 1992). The names of the research apes were Washoe, Moja, Tatu, and Dar. The researchers wanted to simulate as closely as possible the living conditions and parenting practices involving human children who were taught to sign by their parents. This technique is known as cross-fostering, that is, the young of one species are reared by foster parents of another species (Gardner, et al., 1992). It turns out that chimps are especially right for such a practice due to their equivalent maturation processes with human infants. With this process the researchers thought that both the cognitive similarities and differences would be evident after a period of time working with the animals.

The researchers found that Washoe learned signs from her human companions and used these in a rudimentary way that resembled the early acquisition of speech and sign by small children. Additionally, Washoe’s stage-by-stage acquisition could be compared with the stage-by-stage acquisition of speech and sign by children. Moreover, in 51 months, Washoe acquired at least 132 signs of ASL and used them for classes of referents rather than specific exemplars. For example, she could use a sign such as dog to refer to any type of dog—be it actual or even a picture of one. Since Washoe was obtained when she was already 10 months old, her learning ability was somewhat remarkable.

The other chimps were obtained at a much younger age and also benefited from vicarious learning from Washoe’s experiments. It was soon observed that the chimpanzees easily transferred the signs they had learned for a few balls, shoes, flowers, or cats to the full range of the concepts, wherever found and however represented, as if they divided the world into the same conceptual categories that human beings use. Also, they seemed to develop the tendency to form even broader categories such names, verbs, and traits. The chimps were able to answer what is known as Wh-questions (e.g., who, what, where) with a level of accuracy that rivaled that of 2-3 year old children. The researchers stated that if Washoe had been a preschool child, then by current standards her replies to Wh-questions would place her at a relatively advanced level of linguistic competence (Gardner, et al., 1992).

The important aspect of this study was the way in which the researchers interacted with the chimps. The encouraging environment allowed the chimps to elicit responses and exchanges that are difficult to produce in a setting consisting of formal questioning. The surprising finding was that the chimps were able to apply their signs to pictures of particular things they had never seen before; for example, they could apply the sign for flower to any new type or color of flower that might arise. They could also describe things in different ways and were apparently flexible in assessing different aspects of things.

Teaching Chimps Lexagrams and Spoken Words

Other studies have been done on chimpanzees using lexagrams and also vocal words, which did not involve teaching of sign language. In these programs chimps were able to respond to vocal requests and use strings of lexigrams to make their own requests (Rumbaugh, 1990). The chimps could state with an extremely high degree of accuracy on the lexigram device what types of food or drink they wanted or whether they were going to obtain it from another room. The researchers stated that the symbols functioned representatively for things and events not necessarily present in time and space. Additionally, one of the chimps in a study named Kanzi was particularly intelligent in that he required very little training to respond and deal with words and symbols. It was noted that he could comprehend human speech, both single words and novel requests, with a precision only fictitiously imagined years previous.

Although studies with chimps like Kanzi and another chimp, Mulika, did not involve the teaching of ASL, the researchers still were able to reach the conclusion that they had a pattern of language learning similar to that of children. It was spontaneously acquired—with little instruction—with comprehension of words preceding production. Also many of the chimps’ responses were not contingent on any more praise or positive response than one would give a child; and much was not even dependent on this. In short the researchers concluded that the chimps were able to acquire a primitive semantics; something inherent in their intellectual capacity allowed them to ascribe meaning to various objects and events even when not present (Rumbaugh, 1990).

Epistemological Criticisms

Yet experiments with chimps involving lexigrams and verbal training and even ASL have been heavily scrutinized. Obviously, three types of researchers could seek to do studies on the language ability of chimps: (1) Those who desire to confirm their hopes that chimpanzees are in the same conceptual category as humans; (2) those who are skeptical from the outset and seek to disprove the notion that chimps can do anything remotely resembling the faculty of reason; and (3) those who are simply on a quest for knowledge and are curious about what they will discover regardless of the consequences. Since chimpanzees can come to be seen as lovable and endearing pets, vulgar and obnoxious nuisances, or just as experimental creatures, these emotional connotations could have a noticeable influence in the debate and conclusions reached.

Controversy abounds as to whether the use of lexigrams and signs by chimps is equivalent in cognitive ability to that of 1-2 year old children. Many of these criticisms come from researchers who have also worked with chimps in similar experiments and had less surprising results. Seidenberg and Petitto (1987) had worked extensively with a chimp named Nim They stated that the work with the chimpanzee Kanzi mentioned earlier has provided more evidence that language is an expression of a capacity that is specific to humans; moreover, it suggests that part of this innate endowment includes the capacity to understand that things have names.

Seidenberg and Petitto specifically addressed the problem of the semantic issue of what exactly the chimps are doing when they use symbols and respond to words. They contended that symbols and signs serve merely as instrumental functions to obtain desired results, rather than as higher cognitive processes involving understanding of their actions. They remarked further that Kanzi’s problem did not seem to lie in identifying categories; rather, it appeared to lie in grasping the idea that a lexigram designates a class of objects, or kind.

Here again we can differentiate between intelligent behavior and the ability to conceptualize. Seidenberg and Petitto (1987) thought that the apparent dichotomy between the apes’ cognitive and linguistic abilities is more proof that language is not just another expression of the general capacities to think and learn but rather a distinctive trait of the species reflecting the ability to abstract. Human children seem to use language—signs or words—to understand and grasp their world, whereas chimps appear to be using it (in whatever rudimentary and limited form) as a mere tool to achieve certain ends.

But the researchers involved in training Kanzi and other chimpanzees have attempted to refute these claims of apes’ inherent conceptual inability. Essentially Savage-Rumbaugh (1987) contended that much of their chimps’ behavior was not motivated through simply instrumental means. Many of the incidences evidencing Kanzi’s and others’ level of comprehension led to no greater positive consequences than one would give a child. Also, much of the intelligent behavior was not related in any way to the prospect of obtaining food or drink. Additionally, the researchers held that since Kanzi was unable to communicate vocally, his language behavior was often curtailed because of the inefficient mechanism of lexigrams (i.e., having to go to the symbol machine and select the proper buttons every time he wants to convey an idea). With this awkward output modality Kanzi was necessarily restricted in what he could do. Yet the researchers in their rebuttal failed to address the epistemological issues that Seidenberg and Petitto raised; they instead focused on more detailed experimental matters.

Nevertheless, in another reply to Seidenberg and Petitto’s initial remarks, Nelson (1987) addressed the epistemological side of the issue. She succinctly stated the two schools of thought: (1) that conceptualization via language is a species specific trait only found in humans and beyond the grasp of all other earth’s creatures or (2) that other animals such as chimpanzees have the capacity to abstract but cannot overcome that barrier of syntax, so syntax is the distinguishing characteristic in humans. Evidence is then cited as to how Kanzi’s use of symbols and flexible use of categories are not fundamentally different than those of small children, at least before their language explosion happens around 18-24 months of age. Yet Nelson too fails to take on the idea that there is a difference between using names and understanding what names mean or represent.


This last issue is, of course, a philosophical/psychological one. In trying to discover the cognitive/linguistic capacities of apes, researchers may be guilty of anthropomorphism, seeing the chimpanzees in a way that makes them seem more human-like than they really are. Even though the experimental chimps displayed many similarities to children, they also show many dissimilarities. For example, children have a basic drive to be aware and explore their world in a manner that is more focused and thoughtful. Children are constantly trying to make sense of their environment in an abstract way by asking questions and discriminating among a continuous flow of particulars. And in order to do this, they must conceptualize; they must see reality in a way that perceptual-bound creatures simply cannot, regardless of how many symbols they are taught to use.

In reading about the chimpanzees’ mental feats, one gets the impression that they view the whole process as a game. Most of their behavior consisted of requests, not functionally different than a dog who barks to be let outside or playfully brings one a rope to play tug-of-war. Children, on the other hand are active processors of information in their environment in a way that eventually evolves into more and more complex abstractions.

The rejoinder can be made that even though the chimps may not truly understand what they are doing, neither do small children. Certainly, a child between the ages of one or two does not think much about thinking. They just think. No doubt the persons working with Washoe and Kanzi would contend that the chimps are thinking, albeit in a limited sense of the term just as the human child. Here, it is noteworthy to mention that one only sees grown humans attempting to teach chimpanzees language; one does not see grown chimpanzees earnestly attempting to teach their youngsters a language. On this, one must refer to a final comment by Seidenberg and Petitto (1987) about humans’ ability to understand that things have names, which chimps do not possess: “We see no other explanation for the fact that although we literally cannot stop children from using symbols to name objects, we cannot stop apes from using symbols differently, as tools” (p.284).

In any event we must look at the final product, comparing a mature human to a mature chimpanzee. The fact that even the most intelligent chimps only learn and use a small fraction of the number of ASL signs that 1-2 year old children use should tell a person something about the cognitive nature of each species. In the end humans must appreciate the faculty that distinguishes them from all other known creatures, understanding that having a language is a necessary extension of the ability to conceptualize.


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