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2005

THE DEGREE OF CIllMPANZEE THEORY OF MIND AND THE EVOLUTION OF MODULARITY

Benjamin Grant Purzycki University of Nebraska-Lincoln

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Purzycki, Benjamin Grant, "THE DEGREE OF CIllMPANZEE THEORY OF MIND AND THE EVOLUTION OF MODULARITY" (2005). Transactions of the Nebraska Academy of Sciences and Affiliated Societies. 46. https://digitalcommons.unl.edu/tnas/46

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THE DEGREE OF CIllMPANZEE THEORY OF MIND

AND THE EVOLUTION OF MODULARITY

Benjamin Grant Purzycki

Department of Anthropology and Geography University of Nebraska-Lincoln Lincoln, Nebraska 68588

ABSTRACT The difficulty of finding definitive evidence is quite a Whether or not chimpanzees have the ability to mentally task to overcome, as we tend to anthropomorphize our represent others' mental states or theory of mind (ToM) has subjects in order to explain their behavior. yet to be definitively established. This results from three problems. First, modular theory of mind accounts lead re­ searchers to adopt an either/or approach to psychological MENTAL ORGANS faculties which obfuscates both within- and across-species AND HUMAN DEVELOPMENT variability. Second, present research continues to rely on the continued trend to polarize nature and nurture. Third, the According to the most conservative 'definitions of bulk of the work compares humans with chimpanzees rather modularity, there are four key components to a modu­ than looking at the entire range of primate species. I propose lar faculty of mind: encapsulation, domain specificity, "degree approach" by way of the Integrated Causal Model inaccessibility, and innateness (Fodor 1983, 1998, which particularizes the key components to ToM while main­ Sperber 2002). Encapsulation, or "informational en­ taining the tenets of modularity theory. According to this account, while chimpanzees may not have a ToM that is equal capsulation" is the idea that within them, modules to our own, they nevertheless exhibit behaviors that are have hardwired information which informs perception. indeed indicative of having one as illustrated by comparison Domain-specificity is a given module's body of relevant to other extant primate research. . knowledge; it is specifically designed for a particular body of information (Hirschfeld and Gelman 1994), e.g. t t t language, a template-system of intuitive ontology, na­ ive physics, etc. (Boyer 2001, Chomsky 2000, Vosniadou Given our close genetic relationship to chim­ 1994). "Inaccessibility" refers to the idea that while panzees (Pan paniscus), much can be learned about our incoming stimuli can alter neither the encapsulated own cognitive processes by way of comparison. How­ information nor the state of the information therein, ever, the reverse is also true; with what we know of our the target module cannot inform outside information own minds, what can we learn about other organisms' (Fodor 1998). Put in an evolutionary perspective, the mental activities, and what are the constraints that question becomes how such discrete cognitive functions limit our ability to acquire such knowledge? The best evolve, given they are genetically determined. prepared theory for making such an inquiry is that of the computational or modular mind (Fodor 1983). How­ Tooby and Cosmides (1992) aptly articulate the ever, when comparing psychological faculties of two main theoretical difference between behaviorist and closely related species, new questions emerge that re­ nativist approaches to the mind. They distinguish quire rethinking previously held conceptions of the lim­ between what they call the Standard Social Science its of particular faculties. Two primary problems arise Model (SSSM) and the Integrated Causal Model (ICM). upon examination of chimpanzee ToM within the modu­ The SSSM is maintains that "the central concept in lar framework: namely, the tendency to think of mod­ psychology [has been] learning," rather than innate­ ules in an either/or manner ("you have the faculty or ness (1992). In other words, most behavior is learned, not," see Povinelli and Vonk 2004, Tomasello et al. rather than an expression of genetically endowed facul­ 2003) and the tendency to polarize unnecessarily na­ ties and their relationship with learned information. tUre (what is innate) and nurture (what is learned). And such learning, according to the SSSM, must be 59 60 B. G. Purzycki "equipotential, content-free, content-independent, gen­ year-old mental states including "beliefs [and false­ eral-purpose, domain-general.. .these mechanisms [of beliefs], pretences, and images" are but a few of the learning] must be constructed in such a way that they psychological categories acquired by normally devel­ can absorb any kind of cultural message or environ­ oped children. mental input equally well" (Tooby and Cosmides 1992). The ICM, on the other hand, attempts to locate specific Baron-Cohen's (1997) groundbreaking essay on "mental organs" (Chomsky 1980) of the mind, their "mind-blindness" of autistic children who lack or have function(s), and under what conditions are they func­ an impaired ToM illustrates that understanding men­ tion optimally. In sum, this dichotomy of nature/nur­ tal states is quite a task-if possible-for individuals ture is problematically too simple when confronted with afflicted with such disorders. In this domain of cogni­ the growth of mental faculties, and the dichotomy­ tive processing, one would expect, then, that chimpan­ based approach provides the first frame of dilemmas zees would behave in a similar manner to autists who arising from previous investigations of chimpanzee and have impaired theory of mind mechanism or module human ToM. There are two main assumptions that (ToMM). This raises the first problem with an Either/ guide the following investigation: 1) some components Or approach to ToM and modularity in general: ifmod­ of the mind are at the very least modular by Fodor's ules can be impaired, certainly there are aspects of a account (for a debate within the realm of computational given faculty that are operational, therefore implying psychology, see Fodor 2005, Pinker 2005a, 2005b) and that modules have degrees of functionality. Take for 2) the ToMM (theory of mind mechanism or module) is instance, individuals who suffer from Asperger's Syn­ a module in this sense at least in humans. drome (AS). AS is placed on what is called the "Autism Spectrum," just short of high-functioning autism (Baron­ Baron-Cohen (1999) notes that there are eight be­ Cohen 2003). Arguably, AS is a step above Attention havioral requirements that must be met in order to Deficit Disorder (ADD) and Attention Deficit and Hy­ grant an organism a ToM, namely: 1) intentionally peractivity Disorder (ADHD) since the symptoms rel­ communicating with others; 2) repairing failed commu­ evant to ToM (e.g. difficulty with empathy, poor social nication with others; 3) teaching others; 4) intention­ interaction, etc.) clearly overlap with that of AS and ally persuading others; 5) intentionally deceiving oth­ high-functioning autism (Booth et al. 2003, Clark et al. ers; 6) building shared plans and goals; 7) intentionally 1999, Williams 2004). sharing a focus or topic of intention; and 8) pretending. Baron-Cohen unnecessarily separates "persuasion" and Individuals who are diagnosed with AS, ADD, and "deception" as deception is simply a specific form of ADHD exhibit a number of behaviors that are found persuasion; deception is successful persuasion of some­ among autists who have impairments of what consti­ thing false. However, all of the above requirements tutes a ToM, ranging from a less functioning sense of spring from the core qualities of a ToM: understanding empathy, difficulty in social settings, etc. Frith and beliefs, desires, and intentions in others. As discussed Happe (1999) note that evidence suggests children with below, chimpanzees fulfill most of these requirements AS are not as good as normally functioning children at primarily by way of Machiavellian intelligence (see attributing mental states, but certainly improve their below) which, not surprisingly, is the most difficult to ability to do so as they develop, unlike those with isolate in an experimental setting. autism. Such difficulties are the result of a less elabo­ rate ToM. This, in turn, implies that ToM ought to be Concerning the growth of innate faculties, our own measured by way of a spectrum or "host of symptoms" species illustrates an interesting trend during develop­ rather than as a present/absent module. ment. Gopnik and Wellman (1994) note that there are three main stages of a child's cognitive development Can such a spectrum, then, extend to chimpanzees? with regards to the ToM. At two years, a child is This question represents another problem with the equipped with two basic categories of mental activity, Either/Or approach to modularity: if there is indeed namely desires and perceptions. In other words, a variation within species in terms ofthe functioning of a landmark achievement in childhood development is an module, is there inter-species variability of the same understanding of others' mental states such as needs­ faculty? Ifwe are to conceptualize modules as "mental the understanding that "what is in the mind can change organs," should we not then acknowledge the possibil­ what is in the world"-and the understanding that ity for variability across species as we would under­ "what is in the mind depends on what is in the world" stand differences in the heart, brain, eyes and other (Gopnik and Wellman 1994). By three years of age, an organs? Evolutionarily, the human eye was not se­ elaboration of mental activities and states occurs. Such lected for per se, but rather the gradual developments concepts of "think, know, remember, make-believe, of the eye, however, were (Tooby and Cosmides 1992). dream" are understood as mental activities, while 5- We should think of modules in the same manner. Chimpanzee theory of mind and modularity 61 CHIMPANZEE THEORY OF MIND pose the question to Perner et al.: where did only­ children "learn" a theory of mind? Premack and Woodruff (1978) were the first to ask whether chimpanzees have a ToM, and by extension, a If the answer is from the parents, that would cer­ ToMM. They argue that an individual's ability to at­ tainly not disqualify a single child from ''learning'' a tribute mental states to another is not a recent develop­ theory of mind, but rather reducing the amount of ment but rather an old faculty. The question of whether stimulation that engages the ToMM. But "poverty of or not the chimpanzee (or human, for that matter) is the stimulus" arguments contend that the stimulus correct in his/her inference of attributing a mental state itself is impoverished (in this case, behavior)-a great to another is irrelevant (but interesting)-the question deal of our thinking is the result of inference-making is whether such inferences occur. Byrne and Whiten by way of innate cognitive structures rather than a (1992) elaborate: "If an individual is able to respond recording of all behaviors and outcomes (Boyer 2001). differentially, according to the beliefs and desires of What we see is extremely limited-what we intuit is another individual (rather than according to the other's just as, if not more, important than the behaviors that overt behaviour), then it possesses a theory of mind." stimulate mental activity (Fodor 1984). In sum, then, In sum, then, a behavior exhibiting a reaction based on the question of ToM should not spring from the all-too an understanding of another's beliefs and desires would simplistic dichotomy of nature/nurture but rather how be the shadow cast from the substance of the ToMM. these two interact (Richerson and Boyd 2005). The same may be said of chimpanzees raised in captivity While most argue that "reading minds" is an innate that "learn" behaviors indicative of a ToM as discussed faculty of our species and-by extension-chimpan­ below. zees, others argue that such a trait is wholly learned. For instance, Perner et al. (1994) argue that children Machiavellianism has been defined as "a strategy with more siblings learn to infer others' mental states of social conduct that involves manipulating others for quicker than those with fewer siblings; and, therefore, personal gain, often against the other's self-interest" a ToM is learned. The main problem with the thesis of (Wilson et al. 1996, quoted in Byrne and Whiten 1997). Perner et al. is the fact that they confuse mastery of If a chimpanzee fools another in order. to, acquire re­ mind reading with the ability to read minds. In other sources (sexual or nutritional) for example, the "fool­ words, if a child is not employing or "exercising" this ing" alone does not necessarily suggest a ToM immedi­ faculty, they will not be as adept at identifying false­ ately. On the other hand, such acts of deception which beliefs, intentions, etc. to a given agent. It should be rely on "whether an individual can discriminate argued, however, that having more siblings better pre­ another's false belief would be the most convincing way pares the ToMM, rather than actually "bestowing" it to demonstrate a true reading of 'mind"' (Whiten 1997). upon an individual. Perner et al. (1994) contend that Has this been demonstrated? their findings create a "serious problem for nativist proposals and various developmental explanations re­ Franz de Waal (2000) recounts how a chimpanzee lying on internal maturation." Unfortunately, these called Yeroen mildly hurt his hand in a fight with authors remain unclear regarding the distinction be­ another chimp named Nikkie. One observer noticed tween learned vs. developed (what is already there) that Yeroen only limped when Nikkie was around. when they claim that "the finding that siblings help Franz de Waal confirmed this when he noticed that develop a theory of mind is compatible with the once Yeroen was out ofNikkie's field of vision , he would sociocognitive tradition [which emphasizes] intellectual walk normally. Not only does this imply that chimpan­ progress as a function of social interaction among peers zees are aware that "seeing is knowing" (see below), but and view intellectual growth as a process of internaliz­ also that an individual chimp wanted another to believe ing the knowledge already incorporated in the social he was hurt. This behavior lasted a week, during which interaction" (1994). Yeroen monitored Nikkie to see ifhe was being watched (Ibid.). This example fulfills not only the "pretending" In sum, the data of Perner et al. do not create qualification of possessing a ToM but the "persuasion" problems for "nativist proposals" as they claim-if any­ and "deception" components as well. The next group­ thing they support them, as "poverty of the stimulus" ing of criteria falls under the general heading of "social" arguments contend (see below for "Plato's problem"). or "shared intentions." Put differently, Chomsky (1980) argues that "a central part of what we call 'learning' is actually better under­ Tomasello et al. (2004) argue that the primary dis­ stood as the growth of cognitive structures [which are tinction between our own psychological faculties and innately endowed] along an internally directed course that of other species is the ability to cooperate with under the triggering and partially shaping effect of the other individuals to accomplish the same goal, a trait environment." If this truly is the case, one may feasibly with which human individuals affected by autism and 62 B. G. Purzycki AS have troubles. What immediately comes to mind is alleviating the tension has yet to occur (de WaaI2000). the question of chimpanzee collaborative hunting, which Tomasello et al. (2004) consider. The authors deter­ Turning to a related question: is seeing believing or mine such cooperation has no difference from hunting indicative of understanding another's mental states? carried out by other social mammals (e.g. lions and More specifically, does joint attention imply shared in­ wolves), which operates on impulse and opportunistic tention? Flombaum and Santos (2005) recently pub­ frenzies. In addition, they find it "almost unimaginable lished findings that suggest rhesus monkeys (Macaca that two chimpanzees might spontaneously do some­ mulatta) are equipped with the understanding that a thing as simple as carry something together or help one researcher's inability to see a hidden grape provides an another make a tool." In the case discussed below, it is opportunity to steal it. This begs for more research clear that chimpanzees-if given the chance-will be­ conducted with the full range of primates available for have in a manner that benefits the agent solely rather study (see below for anecdotal evidence). Povinelli and than any cooperative behavior that would indicate a Eddy (1996a) conducted a study to determine whether shared intention. chimpanzees followed a human's gaze. In one case, the human looked at a specific location with only his eyes, However, Tomasello et al. overlook the fact that while in another case the human looked with both eyes chimpanzees will act cooperatively by forging coalitions and head. They found that "subjects looked where the to overthrow an alpha male, let alone work together to human was looking equally often whether or not the perpetuate the reign of an alpha (de Waal 2000, Goodall head was moved, demonstrating the efficacy of eye 1990). It should be noted that coalitions are created at direction alone" (Tomasello and Call 1997). fantastically frequent rates, (ca. 1,000-1,500 per year in captivity), but the overthrowing of an alpha does not In another experiment (Povinelli and Eddy 1996b), (de Waal 2000). If this irrefutable fact of coalition­ researchers stared directly at a Plexiglas wall that was building to overthrow an alpha were a result from between the chimpanzee and a distant wall. The as­ "observation" (that is, assuming chimpanzees are true sumption was that the chimps would bypass the wall, behaviorists), it would be quite a feat to explain coali­ rather than inspect it, if the line of gaze were of no tion forging and alpha-overthrowing in such terms. particular significance in the chimps' minds. However, Individuals participating would collectively have to un­ chimps consistently looked at both sides of the parti­ derstand that their goal is, indeed, to get rid of an tion-with particular emphasis on the side available to existing alpha. If chimpanzees were incapable of doing the researcher's view-rather than exhibiting a pri­ so, all those involved in the toppling of an alpha would mary concern with the wall at the end of the room. In have to have already observed not only the removal of sum, chimpanzees determined that the Plexiglas wall an alpha but also a collaborative effort to do so. More­ was of the researcher's interest, rather than blindly over, they would have to be able to understand the following his line of vision. outcome as a result from the collaborative effort ifthey are to repeat the process. Individuals who build coali­ Franz de Waal (2000) also reports an occasion when tions are obviously goal-oriented and require assis­ researchers hid a number of fruits in an enclosed area. tance from others to achieve this goal. This suggests, Chimpanzees in an area close saw the researchers en­ indeed, that chimpanzees have a basic ToM. ter the area-with a box full of fruit-then leave the area with an empty box. When the chimps were al­ Mundane, everyday behaviors, however, are far bet­ lowed into the area, they searched "madly" without ter indicators for shared intentionality. Franz De Waal finding any of the fruit. One chimp, Dandy, passed by (2000), for instance, observed that individual chimpan­ the hidden fruit without acknowledging them. Later, zees will hold enormous branches for others to climb when the other apes were sleeping, Dandy made a "bee­ into trees guarded by electrical fence. The branches line" to the fruits, dug them up and quietly ate them are placed in a manner that requires one individual to without the others' awareness (2000). Even ifthis were reinforce the instability of the branch while another not the first time Dandy behaved with such cunning, he climbs the branches in order to gather otherwise unob­ still would require an understanding that if he sup­ tainable leaves. Even an adult helping an infant out of pressed acknowledgment of the fruit, others would not a tree indicates that there is some degree of sharing enjoy the bounty. Not only was Dandy planning, but intentions by way of understanding another's predica­ also intentionally, and probably consciously, deceiving ment. Moreover, after engaging in conflict, chimpan­ others in order to better himself. zees will avoid each other until one of the combatants expresses a behavior indicative of a truce (e.g. extend­ Elsewhere, Byrne and Whiten (1992) review the ing a hand). Such a "collaborative" avoidance not only complexity of tactical deception. Obviously, "Acts of indicates mutual animosity, but also suggests that each deception involve other primates: as objects to be ma­ individual involved in a conflict "keep in mind" that nipulated, as social tools to manipulate others, or even Chimpanzee theory of mind and modularity 63 sometimes as the resource to be gained." On the other agency, and arguably with experience, this attribution hand, it also implies that the deceivers/deceived must is elaborated and specified: in the case of our own be able to both retaliate and remember. The authors species, the mental states "dreaming" and "making­ note that "the two Pan species and the Papio baboons believe" are not innate, but elaborations or outgrowths are significantly overrepresented in records of decep­ of an agency-detection system (i.e. the ToMM). In the tion. By contrast, no clear case of deception has yet been case of chimpanzees, ToM seems less specific or sophis­ reported for strepsirhine primates or tarsiers" (Byrne ticated-rather than completely absent (see below). The and Whiten 1992). The data collected by Byrne and question, then, turns itself inward: are we simply an­ Whiten were exclusively anecdotal, which opens the thropomorphizing chimpanzees because of our own in­ procedural doors to many problems. Povinelli and Vonk nate faculties? (2003) rightly suggest that anecdotal evidence often "presupposes a behavioral abstraction" because our own Anthropomorphism has been included in Brown's ToMs are at work as mentioned below in the squirrel human universals, a characteristic that is demonstrated example. However, note that even with Byrne and around the world by all peoples (Brown 1991). While Whiten's study, researchers potential ToM attribution Brown notes that this trait is generally found in reli­ stops with a large body of the Prosimii suborder indi­ gious contexts, anthropomorphizing occurs in other con­ cating that such "presuppositions" are selective. texts as well. One common view of anthropomorphism is the notion that our species animates certain entities In other words, anecdotal "evidence" for chimpan­ (e.g. gods, ghosts, chimpanzees, etc.) in order to under­ zees' mental representations inherently relies on the stand them better and to mitigate fears surrounding assumption that representations of behaviors already them. Boyer (2001) rightly observes that firstly, "gods occur-something which has yet to be proven, accord­ and spirits are not represented as having human fea­ ing to Povinelli and Vonk (2003). So, for instance, if one tures in general but as having minds, which is much were to observe a chimpanzee deceiving another into more specific" and secondly, "the concept of a mind is thinking he does not have food, the observer is already not exclusively human," meaning we attribute agency attributing an understanding of mental states to the to all entities rendered intentional. In other words, we chimpanzee without testing. The problems with experi­ intuitively (i.e. naturally) attribute a will and desires to mental procedures that attempt to reveal definitively animate entities-this is the crux of anthropomorphism. that chimps have an understanding of others' mental Are primate psychologists guilty of inappropriately at­ states, however, are equally problematic for a variety of tributing "a mind" to chimpanzees in this case? reasons. Povinelli and Vonk (2003) suggest that the chim­ DISCUSSION panzee mind seems so much like our own because "the human mind may have evolved a unique mental sys­ One must be wary when regarding certain behav­ tem that cannot help distorting the chimpanzee's mind, iors as indicators of a ToM. Take, for example, a obligatorily recreating it in its own image." Like reli­ squirrel that takes flight each time a human approaches. gious ideas, we may be projecting our own qualities on While it may be inferred that the squirrel has a ToM chimpanzees by granting them a ToM because of our because it has an understanding ofthe human's mental own ToM. However, if in fact chimpanzees do have state (e.g. "wanting to eat it"), such a conclusion ignores such an understanding of others' mental states, and we the possibility that the squirrel is reacting to the hu­ agree that they do, we would still be anthropomorphiz­ man and not its mental states. However, the reverse ing-we would simply be accurate in our inference­ tactic of "turning off our ToM" creates even more prob­ making. Moreover, "turning off' our own ToM in order lems. Gopnik creates a first-person narrative describ­ to understand another's mental states is not a logica\ ing the world according to an autist. People sitting possibility; we require our ability to represent mentally around the individual are described as "bags of skin other's mental states in order to determine whether or [that] are draped over chairs, and stuffed into pieces of not he/she/it is able to do likewise. In other words, cloth, they shift and protrude in unexpected ways" determining whether a chimpanzee has a ToM (a men­ (unpublished essay quoted in Baron-Cohen 1997). Are tal state) is possible only if we are allowed to infer we to believe, then, that chimpanzees truly look at the mental states. world-especially their fellow chimps-in this man­ ner? Unfortunately, we tend to grant agency without In what may be the most comprehensive account of necessarily being aware of it. In other words, much of the complexity of the present debate, Heyes (1998) the time we do not look at others and acknowledge the proposes an experimental study designed to test whether fact that we are seeing much more than "hats and coats or not chimpanzees could follow the sight-path of re­ which could conceal automatons" (Descartes 1998). The searchers wearing different goggles (opaque and trans­ information that is encapsulated is the attribution of lucent). The chimps would be primed to learn the 64 B. G. Purzycki difference between the goggles. The hypothesis was Gordon is taking a purely behaviorist approach to the that if chimps did indeed have a ToM, they would not ToM-mostly a mental activity. bother to follow the gaze of a researcher wearing the opaque goggles. Kamawar and Olson (1998) conducted In addition, what Gordon does not acknowledge, this study with children. While 85% successfully passed but alludes to (perhaps not consciously) is what Chomsky the ToM tasks, half of these passed Heyes' experiment. calls "Plato's problem": "How is it possible that we have In this case, researchers are demanding more from the knowledge that we do have? What is the knowledge chimpanzees than humans. Andrews (2005) rightly that we do have and on what basis could we possibly argues that even a modified version of Heyes' experi­ have acquired it?" (Chomsky 1980, 2004; Lightfoot 2005). ment proposed by Povinelli and Vonk (2004) also as­ The strict behaviorist assumes such knowledge is sumes that human children do not have a ToM because learned and behaviors are reacted to based on either of their reliance on the assumption that predicting previous experience or processing a number of subtle behavior rather than explaining behavior is the best gestures that "do not await causal analysis." If such a indicator of the presence of a ToM. Moreover, as ar­ suite of subtleties do not "await causal analysis," then gued below, all present experimental studies fail sim­ such subtleties are arguably purely instinctual, rather ply because they rely on behaviorist (i.e. a persistent than a choice on the part of an agent. This fits nicely failure of the SSSM) interpretations of mental activity with Fodor's definition of inaccessibility but denies the (i.e. solved by the ICM). ability of researchers to explain such behaviors. In sum, then, the existence of a ToM cannot be ultimately False-belieftasks are designed to determine whether "proven" behaviorally or "behavioralistically." or not an individual is capable of understanding that others may entertain an incorrect perception. While Many have called such abilities "metarep­ chimpanzees have shown great difficulty with attribut­ resentations" (Sperber 2000). Andrew Whiten (2000) ing a false-beliefto other individuals compared to nor­ differentiates two types of metare presentations. Sense mally functioning children, some tasks they eventually 1 is "A mental representation of a mental representa­ learn (Call and Tomasello 1999). Autistic children fail tion." An example of this is (in your, the reader's, mind) these tasks consistently whereas children with Down's "John believes in ghosts." You understand that John's syndrome are successful (which is also indicative of a belief in ghosts is a mental activity-so John's repre­ ToMM; Baron-Cohen 1997). However, there should be sentation is now yours, so to speak. Sense 2 is "A a clear distinction between the ability to understand mental representation of a mental representation as a that another may be entertaining a false-belief and the representation (Sperber 2000). So, your understanding prevention of a belief that one may not want another to that John's belief in ghosts is a representation is itselfa have. As with the above-mentioned case of Dandy's representation. Do chimps have this ability? concealment of fruit , he has also been observed conceal­ ing erections from a threatening alpha male. There are Povinelli and Vonk (2003) note that there are two other cases of another non-alpha keeping his backs things which supporters of chimp ToM must establish: toward an alpha male while attempting copulation, a) that chimpanzees are capable of abstracting behav­ constantly looking over his shoulder at the alpha (de iors and b) they can mentally represent mental states Waal2000). (Sense 1). They argue that for the entire body of data produced by chimpanzee observation to be of any ex­ Gordon (1998) casts doubt that even humans, on planatory value, only "behavioral abstractions will suf­ the other hand, have a ToM because interpreting our fice." Similar observations made by Scott (2001) divide own quotidian social behavior depends primarily on the approaches between those who attribute ToM to such rapid computations of behavioral subtleties (e.g. chimpanzees and those who simply learn "from past vocal inflections) that do "not await casual analysis." experiences," in other words a representational memory In other words, our minds react to these observed mi­ of behavior rather than a representational understand­ nutiae, rather than an active mechanism abstracting ing of others' representations. However, as the elabo­ such details into a mental category. There are a num­ rate experiments that Call et al. (2004) conducted indi­ ber of problems inherent in this position. First, if all of cate, chimpanzees not only have the ability-spontane­ these "subtleties" that Gordon (1998) refers to are actu­ ously-to interpret intentions (Sense 1), but also react ally the sum-total ofthe stimuli, and behaviors that are to them based on researchers' intentions as untrained a response to the processing ofthat sum-total, this still chimpanzees quickly learned to not bother waiting for does not deny the possibility of a ToMM because such a food that researchers refused to give. module requires stimulation for engagement. Secondly, such arguments foreclose on the possibility of a "cre­ Premack and Premack (1983, 2003) conducted a ative aspect" of chimpanzee behavior. The point is, study in which the chimpanzees were shown video- Chimpanzee theory of mind and modularity 65 taped images of actors attempting to solve a number of made possible only by another psychological mecha­ problems. In the first test, ~n actor attempt~d to re~ch nism. inaccessible bananas (hangIng overhead, lymg outsIde a cage, blocked by a large box). In another number of What a "degree" model would throw into question tests, actors were confronted with "malfunctioning is how developed our own ToM truly is in terms of equipment: a disconnected hose, a phonograph whose informational encapsulation and/or the limits of the cord was unplugged, a gas heater that was unlit," etc. representational outgrowth of this mechanism. For (Premack and Premack 2003). After viewing the vid­ instance, it is probably not so much the case that "dream­ eos, Sarah (the Premacks' test subject) was given an ing" is an innate concept, but such innate mental ab­ envelope with photos of the solution and solutions to stractions such as "knowing" or "believing" are evolu­ other problems. Initially, Sarah chose the correct solu­ tionarily sound mechanisms to have. It is also more tion to 18 out of 20 problems. The Premacks note that likely that such initial characteristics of human ToM her mistakes were likely due to "her ignorance of the are not much different from a chimp's-we simply ob­ difference between chimpanzee and human strength" tain more stimuli, both quantitatively and qualitatively, (she "assumed" that a human could push a brick-filled which would expand our categories of others' mental box aside, rather than empty it) and "an unclear photo." states. In sum, then, a ToM spectrum should stimulate Children, on the other hand who were presented with the question that there may be some variability in the this task, failed 50 percent of the time. Even after information encapsulated within our modules (as indi­ altering the study to accommodate children's "subur­ cated by those with AS and high-functioning autism), ban lifestyles" (e.g. cookies out of reach on top of a just as there is variability in our eyes, stomachs, etc. In refrigerator), they continued to fail at the same rate. addition, it opens yet another question: is there vari­ ability in translation from essential information to be­ The Premacks argue that the difference lies in the havior? Put differently, if our ToMM contains the same ability of chimps to identify, i.e. mentally represent, a essential elements that a chimp's does, why is there a "problem" rather than a simple sequence of events on a cognitive limitation on how it is used? video. The chimps had to attribute agoal on the part of the actors presented in the film, whereas three-and-a­ The debate need not be black or white in the case of half year old children failed at a larger rate due to their ToM. The question should not be whether or not chim­ failure to attribute a goal to the actors. It would be panzees have a ToM, but rather to what degree. Even highly informative to give the same tests to older chil­ from the skeptics' corner (Povinelli and Vonk 2004), we dren, as their ToM is mostly fully functional (see above). see evidence of "seeing as knowing" in chimpanzees, Can one still maintain the stance that Sarah may have but when compared to other primates, there is a clear "learned" this ability-especially after being confronted divide. Conducting the same experiments with other with a novel test? Sarah represented not only the primates, particularly the prosimians, will offer a truly problem identified by the actors and the problem itself robust body of comparative knowledge. From an evolu­ (Sense 1), but recognized it as a problem (Sense 2). tionary standpoint, the chimpanzees' understanding of others' mental states may simply be regarded as less CONCLUSIONS developed or more restricted than humans' yet more articulated than other primates as recent research sug­ Is it then safe to think of the ToM in an Either/Or gests. Moreover, determining whether any organism manner? If we discount the prescribed "collaborative has a ToM requires one but also requires not relying intentionality," chimpanzees, it would seem, have the solely on our own tendencies to infer mental states. capacity to read other's minds-but with a limited num­ Future experiments should be designed for chimpan­ ber of abstraction-level mental state categories. The zees to attempt to deceive others in order to solve a category which they fail to fulfill is likely concomitant particular task without reflexively inferring that this to more socially complex animals-i.e. humans. If ToM already occurs. Observational and anecdotal data are is modular, "collaborative intentionality" should not equally important in order to observe chimpanzees and necessarily be a condition-such an extra or more com­ other primates interacting naturally. plex system of social cognition is likely equipped with another cognitive mechanism at work-rather than ACKNOWLEDGMENTS more encapsulated information. In other words, chimp ToM is likely only equipped with the mental abstrac­ I thank Dr. Shimelis Beyene for his guidance dur­ tions of "seeing" and "desiring," with an emphasis on ing the process of writing this paper. I would also like how to exploit others properly in order to benefit oneself to thank the students in Dr. Beyene's Spring 2004 (egocentric) whereas human ToM can be employed to primatology course for their helpful comments and ques- accommodate collaborative intentionality-arguably 66 B. G. Purzycki tions. Rory Larson deserves thanks for challenging my Clark, T., C. 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