Tactical Deception and theGreat Apes: Insight Into theQuestion of Theory of Mind

IntroductionIntelligence is divided up into

many specialized mental abilities, not theleast of which is an individual's ability toattribute independent thought, emotionand knowledge to another individual(Knecht 2007). In other words anindividual is able to attribute mental s~atesto others, recognizing others as individuals~ith ,their own thoughts, knowledge,mtentlOns and desires different from theirown (Byrne 1995: 144). This ability isdescribed as having a "theory of mind"(Premack & Woodruff 1978: 1),henceforth referred to as ToM. Mostanimals have never shown evidence ofhaving a ToM and it was once believed tobe an exclusively human trait; a separatorbetween animal and human cognititiveabilities. However, an increasing amountof evidence is breaking down this barrierbetween humans and animals bysuggesting that some other animals might

have a ToM; non-human primates inparticular show evidence of tacticaldeception in which they intentionallydeceive other individuals. Thisindicates that they have knowledge ofanother individual's point of view(Premack & Woodruff 1978: 1). Someanthropologists believe that tacticaldeception may be an answer towhether or not great apes can attributemental states to others, or similarly,have a ToM (Premack & Woodruff1978: 1). Instances of tacticaldeception are difficult to prove asevidence for a ToM. This is due to thefact that some actions and reactionsmay be explained through sociallearning in cause and effect situations(Byrne & Whiten 1991: 130). Thispaper will address the question ofwhether or not great apes possess aToM. I will give evidence that greatapes do intentionally deceive others,and that they therefore have someabilities of mental-state attribution.

Tactical Deception: IntentionalTrickery or a Learned RewardSystem?

Due to the abstract nature ofthe subject, it is impossible toeffectively communicate ToM to agreat ape. As a result, anthropologistsand primatologists must rely onobservations of ape behaviour in orderto determine their ability to attributemental states to others. However,most ape interactions offer littleinsight into the thoughts of the ape andcan often be interpreted in severalways (Tomasello & Call 1997: 329,340; Byrne & Whiten 1992: 611).Consequently, some anthropologistsnow focus on rare instances of tacticaldeception in an attempt to provemental attribution by great apes.

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Tactical deception is defined as "acts fromthe normal repertoire of [an] agent,deployed such that another individual islikely to misinterpret what acts signify, tothe advantage of the agent" (Byrne &Whiten 1991: 127) When consideringtactical deception as potential evidence fora ToM there are four behaviouralcategories that may help to demonstratethe ape's thought process: initial deceit,counterdeception, deception in play, andrighteous indignation.

Initial DeceitInitial deceit is one of the most

difficult forms of deception to prove asdemonstrative of a ToM since it can oftenbe explained through cause and effect, andtrial and error learning (Byrne 1995: 133;Tomasello & Call 1997: 311, 320, 322;Whiten 1997: 147). This form of deceit isusually seen in the form of concealment orhiding of oneself, an action, an object oran emotion or through distraction (Whiten1997: 162; Whiten & Byrne 1988: 212).A well-known example involves achimpanzee that was approached frombehind by an audibly aggressive rival(deWaal 1986: 233; Byrne & Whiten1991: 134). Here, the chimpanzeemanipulated his lips several times beforeridding itself of its fear grin and only afterhe had done so, he turned around to bravethe challenger, concealing his fearfulexpression. Other observations ofdeception recorded by deWaal (1986)involved several instances in which asubordinate male courted a female bydisplaying his penile erection. Whenevera dominant male unexpectedly appeared,the aroused subordinate would hide hiserection from the view of the approachingchimpanzee (deWaal 1986: 233; Whiten1993: 377; Whiten & Byrne 1988: 215-216). The chimpanzee dropped his arm,always leaving his hand to dangle between

the dominant male and his erection.This was done in order to avoid aviolent confrontation, which wouldhave been inevitable had the dominantbeen aware of the subordinate'sactions. There are also records of apesdiverting another individual's attentiqnfrom themselves or from food (Menzel1974: 134-135; Byrne & Whiten 1991:130-131; Byrne 1995: 132). In order toachieve this goal of distraction, thegreat apes usually use tactics thatinvolve feigning interest in otherthings, both real and imaginary. Thereare also instances in which apes havebeen known to inhibit their excitementor behaviour upon the discovery offood in order to keep the findings frombeing taken by other apes (Byrne1995: 134; Whiten & Byrne 1988:220).

CounterdeceptionAnother potential method for

proving a ToM through tacticaldeception is through the recognition ofdeception by apes and actions taken toreduce the losses suffered from beingdeceived (Byrne & Whiten 1991: 129).This struggle between deception andcounterdeception was seen in anexperiment on spatial knowledgeconducted by the Americanpsychologist, Menzel, in 1974. In theexperiment, food was hidden and onlyone individual, named Belle, in agroup of chimpanzees was informed ofthe location (Menzel 1974: 134-135;Byrne & Whiten 1991:130-131; Byrne1995: 132). Belle was eager to leadthe group to the food but when onechimpanzee, named Rock, began torefuse to share the food, Belle changedher behaviour (Menzel 1974: 134-135;Byrne & Whiten 1991: 130-131;Byrne 1995: 132). She began to sit on

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the food until Rock was far away, then shewould uncover it quickly and eat it(Menzel 1974: 134-135; Byrne & Whiten1991: 130-131; Byrne 1995: 132). Rockfigured this out though and began to pushher out of the way and take the food fromunder her (Menzel 1974: 134-135; Byrne& Whiten 1991: 130-131; Byrne 1995:132). Belle then sat farther and fartheraway waiting for Rock to look awaybefore she moved towards the food(Menzel 1974: 134-135; Byrne & Whiten1991: 130-131; Byrne 1995: 132). In anattempt to speed the process up, Rocklooked away until Belle began to run forthe food. On several occasions he wouldeven walk away, acting disinterested, andthen suddenly spin around and run towardsBelle just as she uncovered the food(Menzel 1974: 134-135; Byrne & Whiten1991: 130-131; Byrne 1995: 132).

A similar strategy was seen in anexperiment involving two chimpanzees.In this experiment, one chimpanzeeinhibited its excitement about theunlocking of a food box in an attempt tofool the other chimpanzee into thinkingthat nothing had happened (Byrne 1995:134; Whiten & Byrne 1988: 220). Thedeceptive chimpanzee continued this actuntil the second chimpanzee was out ofsight (Byrne 1995: 134). However, thesecond chimpanzee had heard the sound ofthe box unlocking and it hid behind a tree,where it watched the first chimpanzee(Byrne 1995: 134). When the deceptivechimpanzee went to retrieve the food theother chimpanzee ran out from his hidingplace and stole it (Byrne 1995: 134).Deception in Play

Deception in play requires theplayer to "[hold] simultaneousrepresentations of two conflicting sets ofknowledge or belief' (Byrne 1995: 138).There are many recorded examples ofgreat apes pretending both with and

without props. A wild mountaingorilla, named Maggie, was seenpulling up a bundle of soft moss,building a nest and sitting to nurse it asif it were an infant (Byrne 1995: 139).A chimpanzee named Viki wasobserved while pretending to drag animaginary pull-toy and pretending tostruggle to free it when she got itcaught on a real object (Byrne 1995:138-139; Parker & McKinney 1999:129). Viki tried many strategies tofree the pull-toy and showedfrustration throughout her efforts(Byrne 1995: 138-139). Kanzi, abonobo trained to communicate withkeyboard symbols, played with a toydog and toy gorilla (Savage-Rumbaugh et al. 1998: 60). He oftenpretended that the toys were biting himand he pulled back and shook hisfinger in reaction to the imaginary bite(Savage- Rumbaugh et al. 1998: 60).Kanzi also masqueraded in a monstermask and tried to frighten people. Onoccasion, he even asked the trainer towear the mask and pretend to scarehim back (Savage-Rumbaugh et al.1998: 60). In reaction to the trainerchasing him with the mask on, Kanziscreamed as though he was afraid ofhim. However, when the trainerstopped to see if he was really afraidKanzi "[seemed] puzzled as to why[the trainer] has stopped and [gave] noevidence of real fear at all" (Savage-Rumbaugh et al. 1998: 60).

Righteous IndignationIf great apes do have a ToM it

seems logical that they would show a"reaction specific to understanding that[they have] been deceived", otherwiseknown as showing righteousindignation (Byrne 1995: 131). On

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one occasion, a Dutch developmentalpsychologist, named Plooij, used a tacticthat he had seen chimpanzees use. Helooked into the distance to divert a youngchimpanzee's attention and she followedthe gaze, wandering off in that direction(Byrne & Whiten 1991: 129; Whiten1993: 375; Byrne 1995: 131). Uponrealising that there was nothing ofimportance to look at, the chimpanzeereturned, hit Plooij on the head andappeared to ignore him for the rest of theday (Byrne & Whiten 1991: 129; Whiten1993: 375; Byrne 1995: 131). While thisinstance certainly gives a clear example ofrighteous indignation, it is not the onlypossible explanation for this behaviour. Itmust be considered that the two eventsmay have been entirely unrelated (Byrne& Whiten 1991: 129).

In order to test for righteousindignation, an experiment was conductedinvolving the serving of a juice treat to achimpanzee (Whiten 1993: 376;Tomasello & Call 1997: 320). One personoffering the juice dropped the cup'accidentally', then a second personoffering the juice 'deliberately' poured thecontents of the cup onto the floor, therebymaking the offering of the juice adeception (Whiten 1993: 376; Tomasello& Call 1997: 320). The chimpanzee wasthen allowed to choose the person to servethe next cup of juice and the chimpanzeeconsistently chose the person who hadspilled the juice 'accidentally' (Whiten1993: 376; Tomasello & Call 1997: 320).This experiment indicates that thechimpanzee is able to differentiatebetween intentional and unintentionalactions (Whiten 1993: 376; Tomasello &Call 1997: 320). It also shows that thechimpanzee attributes these actions to thepersonality of the people involved andprefers the person that did not deceivehim.

DiscussionWhiten and Byrne (1988)

interpreted the concealment of the feargrin as the chimpanzee'sunderstanding that the rival wouldreact violently upon seeing the feargrin. Byrne and Whiten (1991) laterexpressed doubts about the validity ofthis observation as evidence of a ToMdue to the fact that the deceit may nothave been proof of mental attribution.Instead, they concluded that the apemight have learned the behaviouralpatterns of the rival ape in relation toits own actions (Byrne & Whiten1991: 134; Cheney & Seyfarth 1990:217; Seyfarth & Cheney 1996: 341;Tomesello & Call 1997: 269). In otherwords, the chimpanzee may not havenecessarily considered the rival'smental state, but instead intended todirectly alter its behaviour.

The case of the concealedpenile erection may also be argued tobe learned behaviour: However, itseems unlikely that the subordinatewould notice a connection between theposition of his hand and the dominantape's behaviour. It is more likely thatthe chimpanzee understood that theerection must be seen in order for thecompetitor to react (Whiten 1993:378). It is also possible that thechimpanzee made judgements aboutwhat the competitor might or mightnot notice (Whiten 1993: 378). Thismay also be interpreted as ademonstration of the chimpanzee'sability to make the connection betweenvision and knowledge (Whiten 1993:378). Since the chimpanzee couldaccurately compute the dominantchimpanzee's line of sight it is possiblethat he knows that sight is a precursorto knowledge, emotion and reaction

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(Whiten 1993: 378). If an ape believesand understands that other individualshave different lines of sight, it is possiblethat by extension, apes understand thatother individuals also have differentknowledge and independent thoughtprocesses (Whiten 1993: 378). In both thecases of the concealment of the fear grinand the penile erection, the evidencesuggests that apes might understand thatthe individual being deceived is ignorantto the knowledge that is available to thedeceiver (Whiten 1997: 160). In thissense, the apes can separate their ownthoughts from those of their target ofdeception.

The counterdeceptive tacticsdiscussed earlier are important because oftheir use of novel behaviour (Byrne 1995:133). Both spinning around in mid-stepand hiding behind trees are unusualbehaviours for great apes and so theycannot be accounted for by social learningin cause and effect situations (Byrne &Whiten 1991: 131; Byrne 1995: 133).Although spinning around in midstep isnovel behaviour, it is still unknown ifRock was able to predict Belle's thoughtprocess and anticipate her behaviour(Byrne & Whiten 1991: 131; Byrne 1995:133) or if he had simply learned herbehaviour through repetition (Tomasello& Call 1997: 272). In the case of the apethat hid behind the tree, there was norepetition from which the suspiciouschimpanzee could learn the deceptivechimpanzee's behaviour (Whiten & Byrne1988: 220; Byrne & Whiten 1991:131,1992: 624; Byrne 1995: 133). It ismore likely that the hiding ape hadunderstood the other ape's intent todeceive and taken actions to maximize itsown reward.

The use of deception in play isprobably the most complex category oftactical deception. Leslie (1987) argued

that human children first exhibit thedevelopment of a ToM when they arealso able to react accordingly topretend happenings. He proposed thatthere is an underlying foundationshared between pretence and mindattribution (Leslie 1987: 423). This isbecause, while pretending, the child isattributing a mental state to whomeveror whatever it might be playing with(Parker & McKinney 1999: 141).Playing apes, therefore, know thereality of the situation but also eitherbelieve that the individual present inthe game believes their pretence, orthat the individual understands boththe reality and the pretence, but playsalong anyway (Parker & McKinney1999: 141). In both cases, the apebelieves that an individual thinkssomething external to his/her own setof knowledge.

Byrne and Whiten (1991)suggested that the use of props inpretence may be even more complexthan pretence without a prop becauseof interference from perception of thereal nature of the prop. According toLeslie (1987), acts of play using propsshow that the pretend representation isderived from a primary one andtherefore the ape can suspend primaryrepresentations and attribute apersonality to an inanimate object.This may also apply to the use of theself as a prop as demonstrated in thecase of Kanzi scaring people with amask. In this example, Kanzi actuallysuspends his own personality and takeson an alternate persona. This showsthat Kanzi is aware that individuals arenot all alike; they do not act alike andperhaps they also do not think alike.This conclusion may also be reachedwhen addressing theintentional/unintentional spill test for

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righteous indignation. In this test thechimpanzee was able to differentiatebetween a person that spilled the juicedeliberately and a person that had spilled itaccidentally. Based on this alone, thechimpanzee attributed intention anddemeanor to the juice spillers andconsistently chose the one that spilled thejuice accidentally to serve the next cup.Since the chimpanzee was able todifferentiate between intentional andunintentional actions, the chimpanzeemust know that it is necessary for theperson to plan, or to think about,intentional actions or at least have theirown motivations and desires. Thechimpanzee must therefore be aware thatothers think and have different intentions,knowledge and emotions not shared withthem.

Summary and ConclusionsTactical deception in great apes is

difficult to interpret due to the problem ofintentionality (Tomasello & Call 1997:340-341). However, there is a growingnumber of cases, like those presented inthis paper, that are not easily explainedwithout a ToM, including great apes usinguncharacteristic or novel behaviour tocounterdeceive (Byrne 1995: 133), apesreleasing primary representations ofthemselves, others or objects during play(Leslie 1987: 417), and righteousindignation after being targeted bydeception (Whiten 1993: 375; Byrne 1995:131). These are all strong arguments for aToM in great apes with few alternativeexplanations. It follows that, by using themost parsimonious explanation, we maychoose to accept the hypothesis of a theoryof mind in great apes until it is found to beincorrect.

Unfortunately, there is not and maynever be, solid indisputable evidence for aToM in great apes. Great ape social

interactions are very complex and it isnear impossible to understand an ape'sthoughts by mere behaviouralobservations (Whiten 1997: 157, 159).In spite of this difficulty, there areother areas of investigation that mighthelp solve the question of ToM ingreat apes such as gaze following, selfrecognition, group relationshipdynamics, linguistics and recognitionof others. Further study andexperimentation in these topics shouldbe pursued to gain more insight intotheory of mind in great apes.

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Whiten, A. and Richard Byrne. 1988.The Manipulation of Attentionin Primate Tactical Deception.In Machiavellian Intelligence:Social Expertise and theEvolution of Intellect inMonkeys, Apes and Humans.Byrne and Whiten, (eds.).Oxford: Clarendon Press.

Whiten, Andrew. 1993. "Evolving aTheory of Mind: the Nature ofN on- Verbal Mentalism inOther Primates". InUnderstanding Other Minds:perspectives from Autism.Baron-Cohen, Tager-Flusbergand Cohen, (eds.). pp. 367-396.New York: Oxford UniversityPress.

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