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An association account of false belief understanding

L.C. De Bruin ⇑,1, A. Newen 1

Ruhr-University Bochum, Institute for Philosophy II GA3/153, Universitätsstr. 150, D-44801 Bochum, Germany

a r t i c l e i n f o

Article history:Received 24 February 2011Revised 27 December 2011Accepted 31 December 2011Available online 31 January 2012

Keywords:False belief understanding in infancyTheory of MindRegistering associations

a b s t r a c t

The elicited-response false belief task has traditionally been considered as reliably indicat-ing that children acquire an understanding of false belief around 4 years of age. However,recent investigations using spontaneous-response tasks suggest that false belief under-standing emerges much earlier. This leads to a developmental paradox: if young infantsalready understand false belief, then why do they fail the elicited-response false belieftask? We postulate two systems to account for the development of false belief understand-ing: an association module, which provides infants with the capacity to register congruentassociations between agents and objects, and an operating system, which allows them totransform these associations into incongruent associations through a process of inhibition,selection and representation. The interaction between the association module and theoperating system enables infants to register increasingly complex associations on the basisof another agent’s movements, visual perspective and propositional attitudes. This allowsus account for the full range of findings on false belief understanding.

� 2012 Elsevier B.V. All rights reserved.

1. New findings on false belief understanding

For several decades it has been close to common senseamongst developmental psychologists that the develop-ment of a Theory of Mind (ToM) is a prerequisite for suc-cessfully navigating the social world. To have a ToM is tobe able to attribute mental states such as beliefs and de-sires to others in order to predict or explain their behavior(e.g., Baron-Cohen, 2001; Garfield, Peterson, & Perry, 2001).This allows us to understand, for example, that John goesto the fridge because he wants a drink and believes thereis a carton of milk in the fridge. Most ToM-research has fo-cused on the development of false belief understanding. Theonset of this ability, possibly unique to humans (Call &Tomasello, 2008), has long been considered to be a reliableindicator that children have acquired a basic ToM (Well-man, 2002).

False belief understanding has traditionally beentested by means of the elicited-response false belief test

(FBT), in which children are asked to give a verbal predic-tion of another agent’s behavior based on her false belief.In the ‘unexpected location’ elicited-response FBT (e.g.,Baron-Cohen, Leslie, & Frith, 1985; Wimmer & Perner,1983), for example, children observe a protagonist whosees an object being placed in a certain location. The pro-tagonist leaves, and the object is moved. When the pro-tagonist returns, she mistakenly believes the object isstill in its initial location. At this point, the children areasked to verbally predict where the protagonist will lookfor the object.

Results show that 3-year-olds typically fail this test,while 4-year-olds give a correct prediction of the agent’sbehavior. Other elicited-response FBTs, such as the ‘unex-pected identity’ test, yield similar results (Moses & Flavell,1990; Perner et al., 1987; Wellman, 1990). These findingshave lead many researchers to conclude that false beliefunderstanding does not emerge until 4 years of age (Flav-ell, 2004; Sodian, 2005; see Wellman (2002) for a review,and Wellman, Cross, and Watson (2001) for a meta-analysis).

The elicited-response FBT places rather strong demandson children’s cognitive capacities (Bloom & German, 2000;

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⇑ Corresponding author.E-mail address: [email protected] (L.C. De Bruin).

1 Tel.: +49 234 32 22139; fax: +49 234 32 14963.

Cognition 123 (2012) 240–259

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Carlson & Moses, 2001). Recent studies on false beliefunderstanding have attempted to reduce these demandsin order to see whether children might be capable of falsebelief understanding at an earlier age. In order to achievethis, researchers have employed spontaneous-responseFBTs that no longer require an explicit answer to a ques-tion about the protagonist’s belief. Instead, children’sunderstanding of false belief is inferred from the behaviorthey spontaneously produce (Baillargeon, Scott, & Zijing,2010).

Clements and Perner (1994) have shown that thismakes an important difference in terms of FBT perfor-mance. They employed an ‘anticipatory looking’ spontane-ous-response FBT to test whether children are able tovisually anticipate where an agent with a false belief aboutthe location of an object will search for the object. In thetask, children observed how the protagonist, a mousecalled Sam, stored an object in a box in front of one oftwo mouse holes. While Sam was asleep, the object wasmoved to another box in front of the other mouse hole.The experimenters monitored where the children werelooking in anticipation of Sam’s reappearance, given hisfalse belief about the object’s location. They contrasted thisspontaneous behavior with the explicit answers childrengave to the question where Sam would look for the object.Interestingly, Clements and Perner found that 3-year-oldslooked to the initial (correct) location when anticipatingSam’s return, even when they explicitly made the wrongprediction that he would go to the second location. Thisearly manifestation of false belief understanding has beenlabeled ‘implicit’ because the participating children werenot explicitly aware of the knowledge conveyed in theireye gaze. Though apparently present in 3-year-olds, nosign of implicit false belief understanding was found in2-year-old children (Clements & Perner, 2001; Garnham& Perner, 2001; Perner & Clements, 2000; Ruffman, Garn-ham, Import, & Connolly, 2001).

Recent studies, however, have challenged these find-ings. Onishi and Baillargeon (2005) conducted a ‘viola-tion-of-expectation’ spontaneous-response FBT in orderto investigate whether children look reliably longer whenagents act in a manner that is inconsistent with their falsebeliefs. In the experiment, 15-month-old infants werefamiliarized with a protagonist hiding a toy in one of twolocations. The protagonist left, and the toy was movedwithout her knowledge. Then the infants were shownscenes of the protagonist searching for the hidden toy:either in the location she falsely believed it to be, or inthe location it was actually located. Onishi and Baillargeonfound that infants looked significantly longer at thosescenes in which the protagonist searched at the correctlocation despite her false belief about where the toy washidden.

These findings contradict the results of Clements andPerner (1994). Southgate, Senju, and Csibra (2007) have ar-gued that this is because the experiment by Clements &Perner’s (1994) experiment still included a verbal element:in order to maximize the frequency of anticipatory lookingat one of the mouse holes, the investigator said aloud, ‘Iwonder where Sam is going to look?’ before asking thequestion. According to Southgate et al. (2007), this primed

2-year-old infants to look at the incorrect location. In theirown study, they removed the verbal element from the de-sign and used an eye-tracker to measure anticipatory look-ing in 25-month-olds. The infants observed how aprotagonist witnessed a puppet bear that hid a ball inone of two boxes. Then the protagonist got distractedand turned away from the scene. Meanwhile, the bear re-moved the ball from its original hiding place. Southgateet al. (2007) found that most 25-month-olds correctlyanticipated the protagonist’s behavior (i.e., where shewould search for the ball on her return) and looked atthe location where she falsely believed the ball to be hid-den (for similar results with 18-month-olds, see Neumann,Thoermer, & Sodian, 2008).

Other spontaneous-response FBTs have reported falsebelief understanding in, among others, 14.5-month-olds(Song & Baillargeon, 2008), 13-month-olds (Surian, Caldi,& Sperber, 2007) and even 7-month-olds (Kovács, Teglas,& Endress, 2010). Importantly, several of these studiesindicate that infants do not only understand false beliefsabout locations, but also about number, identity, and otherproperties (see Baillargeon et al., 2010; Poulin-Dubois,Brooker, & Chow, 2009 for reviews). Contrary to what theelicited-response FBT findings seems to imply, then, thissuggests that false belief understanding may be presentmuch earlier in development.

2. The developmental paradox of false beliefunderstanding: problematic solutions

Whether or not spontaneous-response FBT findingsshould be interpreted as indicative of false belief under-standing has been a weighty topic of discussion (Csibra &Southgate, 2006; Herschbach, 2008; Perner & Ruffman,2005; Ruffman & Perner, 2005; Sirois & Jackson, 2007).The issue is important because a very early onset of falsebelief understanding (during the first or second year) sug-gests that ToM development is largely driven by biologicalinheritance, whereas a much later onset at 4 years makes itmore plausible that ToM development is influenced by cul-tural processes and closely tied to language acquisition.

Those who defend a late ToM onset at 4 years of agetypically deny that the spontaneous-response FBT findingsare indicative of false belief understanding. Perner andRuffman (2005), for example, have proposed two differentinterpretations of the reported results. First, the lookingtimes in the experiment by Onishi and Baillargeon (2005)could be explained in terms of behavioral rules, such as‘people tend to look for an object where they last saw itand not necessarily where the object actually is’ (see alsoPerner, 2009; Ruffman & Perner, 2005; Povinelli & Vonk,2003). Very young infants could have a grasp of this rulewithout any notion of false belief as something that causesbehavior (but see Baillargeon et al., 2010 for objections).Second, it could be that young infants create ‘actor-ob-ject-location’ associations in order to understand thebehavior they perceive (Perner, 2009; Perner & Ruffman,2005). If an association consisting of, for example, the ele-ments ‘actor-object-yellow box’ is still sustained in thefrontal cortex when infants are exposed to the test stimuli,

L.C. De Bruin, A. Newen / Cognition 123 (2012) 240–259 241


a consistent test combination will need less processingand, consequently, a shorter looking time than a new com-bination of elements (e.g., ‘actor-object-green box’).

By contrast, proponents of an early ToM onset arguethat spontaneous-response FBT findings consistently dem-onstrate that false belief understanding arrives much ear-lier. This usually goes hand in hand with a commitmentto the innateness of ToM and the meta-representationalconcept of belief (e.g., Fodor, 1995; Leslie, Friedman, & Ger-man, 2004; Southgate et al., 2007). However, if the sponta-neous-response FBT results are indeed to show that younginfants understand false belief, then an important questionis why 3-year-old children consistently fail the elicited-re-sponse FBT (Wellman et al., 2001), even when paradigmsare employed that reduce cognitive demands (e.g., Call &Tomasello, 1999 Sodian, Thoermer, & Dietrich, 2006). Thisis what we call the ‘developmental paradox’ of false beliefunderstanding.

Several researchers have argued that we need two dif-ferent systems to explain this developmental paradox(e.g., Apperly & Butterfill, 2009; Call & Tomasello, 2008;Doherty, 2006; Gomez, 2007; O’Neill, 1996; Penn, Holyoak,& Povinelli, 2008; Perner, 1991; Whiten, 1994, 1996).Apperly and Butterfill (2009), for example, propose thatthe spontaneous-response and elicited-response FBT find-ings are best explained by respectively a cognitively effi-cient but inflexible ‘minimal’ ToM, and a flexible butcognitively demanding full-blown ToM. Furthermore, theyoffer an interpretation of spontaneous-response FBT per-formance in terms of ‘belief-like’ states rather than full-blown beliefs. Understanding another agent’s behavior asgoal-directed does not require sensitivity to her mentalstates as propositional attitudes – which only comes witha full-blown ToM.

Apperly and Butterfill’s approach allows us to accountfor the different forms of false belief understanding astested by spontaneous-response and elicited-responseFBTs. However, it also raises an important question:how are the two ToM systems (functionally) related?Apperly and Butterfill propose that there is no directinteraction between them. They argue that this proposalis supported by the findings of Clements and Perner(1994) and Southgate et al. (2007), which show that in-fants correctly anticipate another agent’s behavior (interms of looking behavior), even when they fail to maketheir prediction verbally explicit. This, according toApperly and Butterfill, is consistent with the possibilitythat an early-developing ToM system for tracking be-lief-like states is guiding children’s eye movements,whereas a later-developing ToM system underlies theirexplicit judgments about false beliefs.

The claim that there is no interaction between the twosystems at all strikes us as implausible, however. For thiswould imply that the later-developing ToM system re-mains invisible during the first years of development andsuddenly becomes fully operational at age four. At leastwe would expect to see precursors to such a ToM systemthat contribute to the system’s functioning. For example,although Baron-Cohen’s (1995) Theory of Mind Mecha-nism can be understood as a separate, late-developingmechanism, it depends on and receives input from the

earlier developing Intentionality Detector, Eye-DirectionDetector, and Shared Attention Mechanism.

Furthermore, recent studies (e.g., Aschersleben, Hofer, &Jovanovic, 2008; Kristen, Sodian, Thoermer, & Perst, 2011)indicate that specific competencies required for the spon-taneous-response FBT (e.g., looking-time patterns, eye-direction detection, etc.) actually predict performance onthe elicited-response FBT. While this does not imply thatthere has to be interaction ‘all the way down’ or ‘all theway up’ between the two ToM systems, it seems that acomplete theoretical account has to explain not only thedissociations but also the continuations in the develop-ment of false belief understanding. Therefore, we assumethat the later-developing, cognitively more demandingToM system should depend at least to some extent onthe early minimal ToM system for its operation (Csibra &Gergely, 1998; Russell, 2007; Surian et al., 2007).

Baillargeon et al. (2010) have recently proposed a dif-ferent solution to the developmental paradox. Accordingto their proposal, infants come equipped with a psycholog-ical reasoning system that consists of two subsystems:sub-system 1 and sub-system 2 (see also Onishi & Baillar-geon, 2005; Song & Baillargeon, 2008; Song, Onishi, Baillar-geon, & Fisher, 2008). Sub-system 1 enables infants toattribute both motivational and reality-congruent infor-mational states to other agents, and is well in place bythe end of the first year. Motivational states are definedas states that specify the agent’s motivation in the sceneand include goals and dispositions. Reality-congruentinformational states, by contrast, specify what knowledgeor accurate information the agent possesses about thescene. Sub-system 2 deals with reality-incongruent infor-mational states, i.e., false beliefs, and becomes operationalin the second year of life.

Baillargeon et al. (2010) argue that the developmentalparadox of false belief understanding can be solved bymeans of a careful analysis of the task-requirements ofspontaneous-response and elicited-response FBTs. Theyclaim that, whereas the spontaneous-response FBT only in-volves (i) a process of false belief representation, the elic-ited-response FBT also requires (ii) a response selectionprocess (when asked the test question, children must ac-cess their representation of the agent’s false belief to selecta response) and (iii) a response-inhibition process (whenselecting a response, children must inhibit any prepotenttendency to answer the test question based on their ownknowledge (see also Scott & Baillargeon, 2009).

What is problematic about the solution offered by Bail-largeon et al. is this: if we accept that spontaneous-re-sponse FBT indeed involves representing false belief, thenit remains unclear why it does not also involve response-inhibition and selection processes. Baillargeon et al. followothers (e.g., Fodor, 1992; Nichols & Stich, 2003; Gergely &Csibra, 2003; Leslie et al., 2004; Leslie, German, & Polizzi,2005) in assuming that sub-system 2 innately predisposesinfants to attribute their own (true) beliefs to other agentsand respond to them on the basis of their own knowledge(Birch & Bloom, 2003, 2007; Goldman, 2006; Carlson &Moses, 2001; Russell, 1996). But it follows from thisassumption that, in order to perform successfully on thespontaneous-response FBT, infants already have to inhibit

242 L.C. De Bruin, A. Newen / Cognition 123 (2012) 240–259


any pre-potent tendency to act on the basis of their ownbelief and select a response based on their representationof the other’s false belief. As a result, it seems unlikely thatinfants fail the elicited-response FBT because they have tojointly activate false-belief-representation plus inhibitionand response-selection processes, since all these processesare already presupposed by successful spontaneous-re-sponse FBT performance.

Although Baillargeon et al. (2010) postulate two sys-tems for psychological reasoning in infancy, only one ofthem (sub-system 2) is used to explain false belief under-standing. However, as the above analysis shows, the differ-ences between spontaneous-response FBT and elicited-response FBT cannot be accounted for by a single system.This is because both spontaneous-response and elicited-re-sponse FBT performance seem to presuppose a three-stepinhibition–selection–representation mechanism. There-fore, we will follow Apperly and Butterfill (2009) in assum-ing that we need a dual-system approach to do justice tothe differences between spontaneous-response FBT andelicited-response FBT and solve the developmental para-dox. However, contrary to what Apperly and Butterfill(2009) claim, we think such an approach also has to shedlight on the interaction between these systems and theirontogenetic development.

Furthermore, we are not sure whether the traditionalconcept of belief (as a propositional attitude) is fine-grained enough to explain the findings of both the sponta-neous-response FBT and elicited-response FBT. We alreadymentioned Apperly and Butterfill’s (2009) Minimal ToM,which allows infants to track ‘belief-like’ states rather thanfull-fledged beliefs. In advancing this proposal Apperly andButterfill’s (2009) are following a recent trend that empha-sizes the need to get away from the standard folk psycho-logical concept of belief when thinking about thesensitivity that young infants display towards the internalstates of other agents. Even Baillargeon et al. (2010), whointerpret the infant’s performance on spontaneous-re-sponse FBTs in terms of false belief, merely characterizethis as the ability to attribute ‘reality in-congruent infor-mational states’ (instead of propositional attitudes) to oth-ers. This indicates that we probably need moresophisticated explanatory concepts to account for thespontaneous-response FBT and elicited-response FBT find-ings (De Bruin, Strijbos, & Slors, 2011).

Our diagnosis shows that current explanations of falsebelief understanding fail to recognize (a) the need forsystem interaction, (b) the importance of a dual-systemapproach and (c) the requirement of sufficiently fine-grained explanatory concepts. In the remainder of thisarticle, we will present a novel association account of falsebelief understanding that addresses these problems.

3. An association account of false belief understanding

Our account of false belief understanding resemblesother dual-system theories insofar it postulates two differ-ent systems to explain the spontaneous-response and elic-ited-response FBT findings discussed in the previoussections. However, it is fundamentally different in that it

involves an association approach to false belief understand-ing. Moreover, our account also goes beyond current dual-system theories of false belief understanding by proposingspecific interactions between the two systems, andby clarifying these interactions and showing how theyfacilitate new and more advanced modes of false beliefunderstanding.

We postulate the following two systems to account forthe development of false belief understanding: an associa-tion module, which provides infants with the capacity toregister congruent associations between agents and ob-jects, and an operating system, which allows them totransform these associations into incongruent associationsthrough a process of inhibition, selection and representa-tion.2 The interaction between the association module andthe operating system, which is present almost from thebeginning of life, enables infants to register increasinglycomplex associations on the basis of another agent’s move-ments, visual perspective and propositional attitudes (seeJung & Newen, 2010, 2011 for a similar distinction). In thisway, we are able to account for the full range of findingson false belief understanding.

3.1. The association mechanism

The association module provides infants with a basiccapacity to form associations between other agents andobjects in the outside world. In what follows, we willuse ‘registration’ to refer to the process of creating anagent–object association. The term ‘association’ is bor-rowed from Perner and Ruffman (2005), who used it toexplain the spontaneous-response FBT findings withouthaving to assume that infants understand false belief.Accordingly, performance on the spontaneous-responseFBT can be interpreted in terms of associations that en-code configurations of persons relating to objects, whichare then used to guide infants’ expectations about the ac-tions of other agents (see also Perner, 2009; Ruffman &Perner, 2005).

Some theorists are wary of the notion ‘association’ be-cause they think it commits them to the idea that spa-tial–temporal contiguity is everything, we can learnanything, and our mental lives are almost non-existent(see Smith, 2000 for why this idea is misguided). However,our use of the term ‘association’ implies none of this. Weconceive of associations as structured representations ofgoal-directed behavior, which come in different degreesof complexity. In this respect, our interpretation and useof the term ‘association’ differs from Perner and Ruffman(2005). As we will explain below, the interaction betweenthe association module and the operating system allowsinfants to register increasingly more complex associations,

2 Baillargeon et al. (2010) use the term ‘reality-congruent association’ torefer to those associations infants register on the basis of their owninformation about the scene, and ‘reality-incongruent association’ to referto associations that are incompatible with their own information about thescene. However, as an anonymous reviewer pointed out, the notion ‘reality’might be confusing in this context as it differs from its application in theclassic elicited-response FBT, where it is related to the normativity ofbeliefs. Therefore, we will use the terms ‘congruent’ and ‘incongruent’associations in what follows.



and use them to form increasingly more specific expecta-tions about another agent’s future behavior.

Since the association module is an ‘acquired module’(Garfield et al., 2001), which develops through interactionwith the operating system and the social environment,there are certain constraints on the information that isrelevant to the registration of agent–object associations.Most importantly, infants need to have an understandingof human beings as intentional and goal-directed agentswho stand in a specific relation to certain objects in theworld.

This understanding develops rapidly throughout thefirst year of life. Various studies show that very young in-fants selectively match the behavior of human agents ver-sus inanimate objects (Jones, 2007, 2009), and processspecific information about face expressions (Johnson, Dzi-urawiec, Ellis, & Morton, 1991; Slater & Kirby, 1998) andbodily movement (e.g., Bertenthal, Proffit, & Cutting,1984; Bertenthal, Proffitt, & Kramer, 1987; Bertenthal,1993; Fox & McDaniel, 1982). Although these findingsshow that infants are increasingly able to individuate hu-man agents on the basis of their (physical) surface features,this still falls short of perceiving human agents as goal-di-rected agents – a crucial requirement for the functioning ofthe association module. In order to register an agent–ob-ject association, infants need to be able to understandother agents as being directed towards objects (rather thanbeing accidentally in their vicinity).

The association module initially allows infants to reg-ister relatively basic associations based on the agent’smovement towards a given object. Visual habituationexperiments indicate that this capacity emerges from5 months onwards, when infants begin to respond selec-tively to the goals of other agents rather than the phys-ical details of their actions (Biro & Leslie, 2007; Gergely& Csibra, 2003; Woodward, 1998, 2005). Early studieshave shown that infants do not register goals for eventsinvolving inanimate objects, such as rods or claws(Woodward, 1998), or for events in which the agent’shand is disguised by a metallic glove (Guajardo & Wood-ward, 2004). Recent findings, however, suggest that in-fants do sometimes perceive inanimate entities asgoal-directed agents (Biro & Leslie, 2007; Csibra, 2008;Johnson, Booth, & O’Hearn, 2001; Kuhlmeier, Wynn, &Bloom, 2003; Luo & Baillargeon, 2005; Mahajan &Woodward, 2009; Shimizu & Johnson, 2004). This seemsto depend on the availability of additional cues (e.g., self-propelled motion) indicating the animacy of the agent.The current debate is mainly concerned with the rangeof cues that might contribute to the infants’ understand-ing of the goals of other agents (Biro & Leslie, 2007) andthe extent to which infants are able to distinguish be-tween another agent’s intentional versus accidental orambiguous actions on objects (Hamlin, Hallinan, &Woodward, 2008; Woodward, 2005).

At this first stage of development, the association mod-ule registers associations primarily by encoding the motorinformation that specifies the goal-directed behavior of theagent towards the object. By 9–12 months, however, it alsostarts taking into account the looking behavior thatinforms this behavior. That is, the association module

enables infants to register more ‘distal’ associations onthe basis of the agent’s visual perception of the object.

Despite the fact that gaze-following emerges early indevelopment, with responses to turned heads and ad-verted eyes arising between 3 and 6 months (D’Entremont,2000; D’Entremont et al., 1997), several researchers haveargued that this is not yet accompanied by an understand-ing of gaze as an association between a person and an ob-ject (Butterworth, 1998; Butterworth & Jarrett, 1991;Moore & Corkum, 1994; Povinelli & Eddy, 1996). In a studyby Woodward (2003) for example, 7- and 9-month-old in-fants followed the gaze of another agent. When the infantssaw the agent look at a toy and grasp it, they did not onlylook at that toy themselves, but also selectively registeredthe association between agent and object over other as-pects of the event. However, when the infants only sawthe agent looking at the object without touching it, theyfailed to register an association. By contrast, 12-month-old infants were capable of registering an agent–objectassociation solely on the basis of the agent’s gaze towardsthe object.

This suggests that the ability to register associationssolely on the basis of the agent’s visual perception ofthe object requires a further development of the associa-tion module. In Section 3.3, we explain how this develop-ment is scaffolded by the association module’s interactionwith the operating system. According to Woodward(2003), there are several reasons why registering an asso-ciation on the basis of perception is more difficult. Thereis not only lack of physical connection in the sense thatagent and object are separated in space, but also in thesense that gaze has no effect on the object, and the con-sequences of gaze for the agent are not as readily ob-served (whereas grasping often involves physicalconsequences for the object, which could help infants tounderstand the agent’s goals). This last considerationcould also explain why the ability to register associationsbetween gestures such as pointing and their specific tar-get objects only emerges towards the end of the first year(Phillips, Wellman, & Spelke, 2002; Sodian & Thoermer,2004; Woodward, 2003, 2005; Woodward & Guajardo,2002). Woodward (2003) advances yet another reasonwhy infants may find it harder to register association onthe basis of the agent’s perception of the object: infantscan observe their own grasp, but they cannot observetheir own gaze. To the extent that there is an analogy be-tween infants’ understanding of the actions of otheragents and their own actions, they may do this morereadily for grasping than for gaze.

3.2. Registering associations: self versus other

An important assumption of our association account isthat the infants’ capacity to register associations betweenagents and objects is grounded in their capacity for ‘self-registration’, i.e., the capacity to register associations be-tween objects and their own movements and lookingbehavior. In this respect, the association module can beseen as an implementation of what Meltzoff (2004) callsthe ‘like-me hypothesis’ (cf. Gallese, 2005 Tomasello,1999). This, however, should not be interpreted as a



constraint on the infants’ understanding of others. That is,we are not assuming that the association module allowsinfants to understand only those actions they are familiarwith themselves. Developmental studies clearly show thatthere is in fact a two-way interaction between the infant’sunderstanding of self and others, to the extent that: (i) theinfant’s own action towards an object influences her per-ception of another agent’s goal-directed behavior towardsthis object, and (ii) the infant’s perception of anotheragent’s goal-directed behavior towards an object influ-ences her own goal-directed action towards this object.

With respect to (i): a study by Sommerville, Woodward,and Needham (2005) demonstrated that even 3-month-olds focus on the relation between an actor and her goalif they reached for a toy (and not just watched) beforeobserving another agent grasping it. The more they them-selves were engaged in object-directed contact with thetoys, the more sensitive they were to the agent’s goal-direc-ted behavior. More recently, Sommerville, Hildebrand, andCrane (2008) also found that 10-month-old infants who re-ceived active training in pulling a cane to retrieve a toysubsequently registered another person’s cane-pulling ac-tions as goal-directed behavior, while infants who under-went observational training were unable to do this.

With respect to (ii): Hamlin et al. (2008) demonstratedthat, when 7-month-old infants see an adult reach for oneof two toys, they subsequently select that toy themselves.By 18 months, infants are capable of imitating other’sapparent goals, rather than the precise movement pat-terns, even when the goal is unfulfilled (Meltzoff, 1995).Moreover, the infants’ perception of another agent’s goal-directed behavior towards an object also influences howthey themselves perceive the object. For instance, it hasbeen shown that behavioral cues (Biro, Csibra, & Gergely,2007; Biro & Leslie, 2007), infant-directed talk and eye-contact induce gaze-following towards specific objects(Senju & Csibra, 2008), and the use of specific linguistic la-bels increases the salience of objects over others (Xu, 2002;Xu, Carey, & Quint, 2004). Other experiments suggest thatreaching behavior promotes the infant’s perception of the‘spatiotemporal’ properties of the object of interest,whereas pointing behavior promotes the ‘surface proper-ties’ of the object (e.g., Csibra & Gergely, 2007).3

These studies raise important questions about how theinfant’s own action informs her perception of goal-directedbehavior and vice versa. We assume not only that the in-fant’s understanding of herself as an intentional agentguides her understanding of the intentional behaviour ofothers (Meltzoff, 2006; Shipley & Zacks, 2008; von Hofsten,2004), but also that both capacities are enabled by theassociation module. This could explain why the ability toregister associations between agents and objects and theability to register associations between oneself and objectsdevelop in tandem. Research on self-registration (usuallydone under the header of ‘object processing’) shows that,

whereas infants are already capable of registering objectson the basis of spatiotemporal information from2.5 months onwards (e.g., Aguiar & Baillargeon, 1999;Spelke, Phillips, & Woodward, 1995; Wynn, 1992; Xu &Carey, 1996), the ability to register them in terms of theirvisual surface features only emerges towards the end ofthe first year – between 10 and 12 months of age (e.g.,see Xu, 2003; Xu & Carey, 1996; Xu, Carey, & Welch,1999 for a review). A number of studies (e.g., Wilcox &Baillargeon, 1998; Wilcox & Schweinle, 2002) have chal-lenged these findings by showing that much younger in-fants (4.5 months) under some circumstances are alsoable to use visual information about surface features toindividuate individual objects. However, as Xu and Baker(2005) argue, we can explain this discrepancy as follows:when spatiotemporal information is weak, surface featuresplays a role in object individuation. By contrast, when spa-tiotemporal information is strong, it overrides informationabout surface features (cf. Nakayama, He, & Shimojo,1995).

This suggests that infants primarily understand ob-jects in terms of the actions they afford, and only laterstart to appreciate visual information about their surfacefeatures (cf. Southgate, Johnson, & Csibra, 2008). Thereseems to be an important parallel here with our findingsin the previous section, namely, that the associationmodule initially registers associations on the basis ofthe agent’s movement towards the object, and only to-wards the end of the first year starts to take into accountthe agent’s visual perception of the object as well.Importantly, Woodward’s (2003) explanation of this phe-nomenon (see previous section) can also be used to ac-count for the fact that infants’ perception-basedunderstanding of objects is ontogenetically secondary totheir action-based understanding of objects. Again, thereis not only a lack of physical connection between infantand object, but the infant’s gaze also has no effect on theobject. Moreover, infants can observe their own grasp,but they cannot observe their own gaze.

Based on the above considerations, we assume that theassociation module provides infants with a bi-directionalcapacity for action–perception coupling. What are theunderlying mechanisms that facilitate this two-way inter-action between action perception and action production?Georgieff and Jeannerod (1998) have introduced the term‘shared representation’ in order to articulate the idea thataction perception and action production might essentiallyshare the same representational space (cf. Daprati et al.,1997). Drawing on this idea, we propose to understandassociations as a special kind of shared representationsthat specify the relation between goal-directed agents(including one-self) and certain objects in the world interms of action/perception-information. Because the asso-ciations registered for oneself have the same representa-tional format as those registered for others (Kovács et al.,2010), it is possible to explain how one’s understandingof the goal-directed actions of others inform one’s owngoal-directed action and vice versa.

This proposal is compatible with the findings of mirrorneurons – neurons that fire during both action productionand action perception (e.g., Rizzolati & Craighero, 2004;

3 In the object processing literature, the term ‘surface features’ is used torefer to the color, texture, and local configuration of features of a stimulus.This is contrasted with the term ‘spatiotemporal information’ that refers tothe spatial location, trajectory, and action-relevant shape of an object (e.g.,Mareschal & Johnson, 2003).



Rizzolatti, Fogassi, & Gallese, 2006; Gallese & Sinigaglia,2011). It has been argued that these mirror neurons showa ‘human bias’, in the sense that they resonate strongerwith perceived actions of human versus non-humanagents (Press et al., 2007; Tsai, Kuo, Hung, & Tzeng,2008). This link between perception and action has alsobeen found in early infancy (Kanakogi & Itakura, 2010),and research on newborn imitation has been cited asevidence for an inherited mirror neuron system thatunderlies imitative behavior in human infants (e.g.,Iacoboni et al., 1999; Decety, Chaminade, Grezes, &Meltzoff, 2002; Grezes et al., 2003; Iacoboni, 2005;Iacoboni & Dapretto, 2006).

We can explain how the association module enables in-fants to anticipate the goal-directed action of anotheragent by mapping the neural circuit of the mirror neuronsystem onto an inverse-forward model (Iacoboni, 2003,2005).4 Accordingly, the superior temporal sulcus (STS) isresponsible for the visual representation of an observed ac-tion. An inverse model then feeds this visual representationinto the fronto-parietal mirror neuron system and convertsit into a motor plan. In a next step, this motor plan is sentback from the fronto-parietal mirror neuron to the STS andconverted into a predicted visual representation (a sensoryoutcome of action) by means of a forward model (Iacoboniet al., 2001). This two-step process explains how infantsare able to track another agent’s goal-directed behavior to-wards objects with predictive eye-movements, the gazeshifts anticipating the other’s hand motion with the sameadvance as seen when tracking one’s own actions (Flanagan& Johansson, 2003).

Claims about the development of a mirror neuron sys-tem in early infancy seem to fit the experimental data dis-cussed in the previous sections. Falck-Yttr, Gredebäck, andvon Hofsten (2006), for example, showed that 12-month-old but not 6-month-old infants are capable of anticipatinga goal-directed action towards an object (picking up andplacing it in a container) by making eye movements aheadof the moving hand. They argued that these findings pro-vide direct support for the view that the infants’ under-standing of goal-directed behavior depends on a mirrorneuron system, which is activated by the registration ofan agent–object association.

At the same time, however, there are still many openquestions about the existence of a mirror neuron system(e.g., Turella, Pierno, Tubaldi, & Castiello, 2009, Dinstein,2008; Jacob, 2008, 2009) and the role it plays in infantdevelopment (Gerson & Woodward, 2010; Meltzoff,2006). Therefore, it should be emphasized that mirror neu-rons are just one way of getting at the more general ideathat action production and action perception can be under-stood in terms of shared representations, and that infantsregister associations by encoding action–perception infor-

mation. There are other grounds for supporting this ideaas well, e.g., proposals about action coding (Elsner &Hommel, 2001; Hommel & Elsner, 2009; Prinz, 2002),findings from developmental studies (Meltzoff, 2004,2006; Meltzoff & Moore, 1977, 1994; Meltzoff & Brooks,2001), or considerations about representational formats(Kovács et al., 2010). Moreover, the hypothesis that theinfant’s motor system is recruited during the observationof goal-directed action has been tested with other para-digms as well. For example, Southgate, Johnson, El Kar-oui, and Csibra (2010) showed that 9-month-old infantsare capable of anticipating goal-directed action by mea-suring the attenuation of the sensorimotor alpha signalduring action observation (cf. Southgate, Johnson, Os-borne, & Csibra, 2009).

What is attractive about the shared representationhypothesis is that it explains how associations enable amapping from self to other (and vice versa) that serves asa catalyst for the infants’ understanding of their own andother’s goal-directed behavior. However, the shared repre-sentation hypothesis also gives rise to an important ques-tion about the registration of agency (Schutz-Bosbach,Avenanti, Aglioti, & Haggard, 2009). If the association mod-ule enables the registration of associations as shared repre-sentations, then how it is able to differentiate conditions inwhich infants observe the goal-directed behavior of an-other agent from those in which they perform the same ac-tion themselves – as is shown, for example, in the studiesby Sommerville et al. (2005, 2008)? This is a serious prob-lem if we endorse a neurobiological implementation of theassociation module in terms of mirror neurons. Since bothconditions activate the same cortical mirror sectors, anadditional mechanism is needed to determine whetherthe infant performs or observes the action. More ingeneral, the question of agency registration is problematicfor proponents of Simulation Theory. The question is, asGordon (1986) puts it, how infants manage to make‘adjustments for the relevant differences’ while avoiding‘total projection’.

Although we think this is indeed an important problem,it should not be overstated. To start with, researchershave proposed various solutions to address this issue (DeVignemont, 2004; Georgieff & Jeannerod, 1998; Jeannerod& Pacherie, 2004; Gallese, 2005; Hurley, 2008). Moreimportantly, however, the question of self-other differenti-ation seems mainly problematic for those aiming to ex-plain action understanding solely in terms of mirrorneuron processes. But this is certainly not a position thatwe wish to defend. The shared representation hypothesisallows us to explain associations as ‘self-other’ representa-tions (Decety & Chaminade, 2003; Jeannerod, 2001; Jeann-erod & Pacherie, 2004). But it does not explain how infantsbecome capable of registering associations between agentsand objects that are radically different from their own, i.e.,incongruent agent–object associations (Decety & Grèzes,2006). This, however, is crucial if we want to give an ac-count of the development of false belief understanding.What additional mechanisms are needed to explain thiscapacity besides the association module? In the nextsection, we introduce the operating system to explainhow infants become capable of registering incongruent

4 Inverse models map the relationship between intended actions or goalsand the motor commands to reach those goals. Forward models map therelationship between motor commands and the resultant change in thestate of the motor system, which is monitored by re-afferent sensoryinflow. Hence a forward model estimates the next (sensory) state of themotor system based upon information about its current state, its dynamics,and the current motor commands being issued to it (e.g., Wolpert,Ghahramani, & Flanagan, 2001).



associations. The interaction between the operatingsystem and the association module also allows us to ac-count for the developmental data discussed in Section 3.1,which showed that infants learn to register associations onthe basis of another agent’s movement and later also onthe basis of another agent’s perception.

3.3. The operating system

3.3.1. Motor-based associationsThe shared representation hypothesis implies that the

associations we register for others have the same represen-tational format as those we register for ourselves, in thesense that both encode action–perception information(cf. Jeannerod, 2003). As we showed in the previous sec-tion, evidence from developmental studies suggests thatinfants acquire the capacity to register such associationstowards the end of the first year. We can use Elsner andHommel’s (2001) two-stage model of voluntary actioncontrol to explain how infants are able to select a goal-di-rected action on the basis of an association. The idea is thatthe motor and visual patterns of a particular associationare integrated in such a way that activating one patternon a later occasion also leads to the activation of the otherone. This allows infants to select the motor program for aparticular action simply by reactivating the perceptual pat-tern of the relevant association. However, in order to dothis, infants first have to be able to refrain from acting onthe basis of action perception (Baldissera, Cavallari, Craig-hero, & Fadiga, 2001). If perceiving an action automaticallytriggers the execution of a corresponding action, then itseems that voluntary action requires a special inhibitorymechanism that allows the infant to make discrete move-ments under visual control, thus avoiding endless repeti-tion (Schutz-Bosbach et al., 2009). Inhibition is not onlynecessary to prevent infants from imitating themselves,but also from imitating others (Baldissera et al., 2001;Brass, Bekkering, & Prinz, 2001; Fadiga, Fogassi, Pavesi, &Rizzolatti, 1995). This is where the operation system comesinto play.

First, the operating system allows infants to registermotor information by decoupling their associations fromaction-output. In order to explain how this works, considerthe A-not-B task. In this experiment, an experimenterhides an attractive toy under box A within the infant’sreach (Diamond, Cruttenden, & Neiderman, 1994). The in-fant searches for the toy, looks under box A, and finds itthere. This is repeated several times so that the infant isable to register a sufficiently strong enough association be-tween her perception of the toy and her subsequent actiontowards it. Then, the experimenter moves the toy underbox B, which is also within easy reach of the infant. Infantsof 10 months or younger typically make a ‘perseverance er-ror’, in the sense that they keep looking under box A – eventhough they saw the experimenter move the toy under boxB (Ahmed & Ruffman, 1998; Clearfield, Diedrich, Smith, &Thelen, 2006).

In order to overcome this perseverance error, theoperating system enables the infants to (i) inhibit theassociation they registered in the familiarization trials,(ii) select on the basis of their perceptual information

about the new location of the toy (box B) the motor infor-mation that specifies a movement trajectory towards boxB, and (iii) represent this information in an appropriateway. Step (i) leads to motor-based associations or ‘motor-simulations’ at the neuronal level (Decety & Grèzes, 1999,2006; Gallese, 2005; Hurley, 2008; Jeannerod & Pacherie,2004). Although motor-based associations are no longerautomatically translated into action, they are still basedon the infant’s potential movements towards the object.It has been hypothesized that this underlies infants’ abilityto anticipate the consequences of their behavior: the braingenerates motor-simulations of intended movements bysending efference copies through a forward control mech-anism in order to compare them with an ongoing move-ment to predict its success (e.g., Blakemore & Frith, 2003;Blakemore, Wolpert, & Frith, 2002; Frith, Blakemore, &Wolpert, 2000; see Synofzik, Vosgerau, & Newen, 2008for criticism). In principle, there are two ways in whichthe operating system can select the motor information re-quired for step (ii): either the relevant information is al-ready part of the infant’s own motor repertoire, or it isacquired by means of ‘shared resonance’ through the in-fant’s perception of the action of the experimenter. In step(iii), the operating system translates the information intoaction, thus enabling the infant to search under box B.

This explains how the operating system makes it possi-ble for infants to update their associations on the basis ofnew visual information and change their behavior towardsthe object accordingly. But the operating system also en-ables infants to anticipate the behavior of other agents onthe basis of associations. Many dual-system explanationsof false belief understanding postulate a basic sub-systemwhich provides infants with a non-mentalistic, teleologicalunderstanding of goal-directed behavior (e.g., Gergely &Csibra, 2003; Leslie, 1994a, 1994b; Tager-Flusberg, 2005).That is, they assume that infants are not yet able to distin-guish their own representation of reality from that of an-other agent. Baillargeon et al. (2010) argue that thisassumption is no longer plausible because several studieshave shown that young infants already take into accountthe ‘motivational’ and ‘reality-congruent’ informationalstates of other agents (e.g., Csibra, 2008; Hamlin, Wynn,& Bloom, 2007; Johnson et al., 2007; Luo & Baillargeon,2005; Premack & Premack, 1997; Gergely, Bekkering, &Király, 2002; Liszkowski et al., 2006; Luo & Baillargeon,2007; Luo & Johnson, 2009; Song & Baillargeon, 2007;Tomasello & Haberl, 2003). For example, Woodward(1998) demonstrated that 5-month-olds, after watchingan agent repeatedly reach for object A as opposed to objectB, register the disposition of the agent (a preference for ob-ject A over object B). When the objects’ positions are re-versed, infants expect the agent to reach for object A inits new position, and they look reliably longer if the agentreaches for object B instead.

Although these findings may indeed be problematic fortraditional dual-systems accounts, our association accountcan explain them by distinguishing between two ways inwhich the association module enables infants to registerassociations, namely: (a) on the basis of the agent’s move-ment towards the object, i.e., what the other does, and (b)on the basis of the agent’s visual perspective, i.e., what



the other sees (see Section 3.1). This distinction is oftenoverlooked in the current debate, but we think it is cru-cial to properly address the objection by Scott and Baillar-geon (2009) mentioned above, and account for thedifferent ways in which the operating system enablesthe registration of associations. This is because studieslike Woodward (1998) do not deal with incongruenciesbetween the visual perspective of the infant and that ofthe agent. In the experimental conditions both infantand agent perceive the same scenes, and the infant doesnot need to make adjustments for differences in visualinformation or take into account the visual perspectiveof the other agent in order to correctly anticipate herbehavior. What the infant does need to grasp is the moti-vational state of the agent, but in order to do so it onlyhas to deal with differences in motor information. Thatis, the infant has to be able to anticipate the agent’sbehavior on the basis of a motor-based association be-tween the agent and the object. Motor-based associationsencode motor information, and represent the proximalgoal-directed actions of agents towards objects.

Anticipating the behavior of others on the basis of mo-tor-based associations requires the same operating sys-tem processes as those involved in the AnotB task. Thistime, however, the operating system selects the motorinformation on the basis of the infant’s perception of an-other agent’s movement towards the object in step (ii).Accordingly, we can explain what happens in the experi-ment by Woodward (1998) as follows. During the famil-iarization trials of the experiment, the associationmodule registers a motor-based association between theagent and object A – one that is congruent with the in-fant’s own motor-based association (AM01, see Fig. 1). Itis likely that the strength of this association is determinedby various factors, such as repetition, communicativecues, presence of others, salience of the object, workingmemory etc. Then the positions of the objects are re-versed. The association module registers a new motor-based association that is incongruent with the one regis-tered in the familiarization trials (AM02, see Fig. 1). In thenext step, the operating system: (i) inhibits the motorinformation of the infant’s own association, and (ii) se-lects the motor information that specifies the agent’smovement towards object A (OS01/OS02, see Fig. 1). Inthe final step, the operating system (iii) represents theassociation as an expectation of the agent’s behavior to-

wards object A (OS03, see Fig. 1). If the agent reaches forobject A in its new position, the infant’s expectationmatches with the behavior of the agent and no extra pro-cessing is required. However, if the agent reaches for ob-ject B, the infant’s expectation is violated and theassociation module has to register a new agent–objectassociation. This arguably requires extra processing andhence a longer looking time. Notice that we can explainhow the infants select the motor information requiredfor step (ii) by appealing to the shared representationhypothesis: the infant’s perception of the agent’s actioninforms her own action.

3.3.2. Perception-based associationsHow does our association account explain experiments

in which there is a discrepancy between visual perspec-tives? These studies seem to be the main focus of Scottand Baillargeon’s (2009) criticism of traditional dual-sys-tem approaches, and they also take center stage in theirargument against association accounts of false beliefunderstanding (cf. Baillargeon et al., 2010).

In the previous section, we showed how the operatingsystem allows infants to decouple their associations fromaction output, and register motor-based association be-tween agents and objects through a process of inhibition,selection and representation. A second important functionof the operating system is to provide infants with the op-tion to decouple agent–object associations from perceptualinput. This results in perception-based associations, whichencode both motor and visual information and representmore distal goal-directed actions of agents towards objects(see Section 3.1).

Like motor-based associations, perception-based asso-ciations are by default registered on the basis of the in-fant’s own visual perception of the current situation (cf.Gergely & Csibra, 2003; Leslie, 1994a, 1994b; Tager-Flus-berg, 2005). In order to anticipate the behavior of anotheragent on the basis of his or her visual perspective (whatthey can or cannot see), the infant has to be able to reg-ister incongruent perception-based associations. This re-quires three operating system processes that are similarto those involved in the registration of incongruent mo-tor-based associations: (i) a response inhibition process,(ii) a response selection process, and (iii) a representationprocess.

B M

B

MA M A

M B M

MA M = motor-based association

A = agent- object association

B = infantobject association

= activated association

= inhibited association

1

2

3

Familiarization Trials Test Trials

AM01 OS01 / OS02 OS03AM02

Object Transfer Anticipation

Fig. 1. Anticipating another agent’s action on the basis of a motor-based association I.



The extent to which these processes are recruited de-pends in the first place on whether the infant actuallyneeds to anticipate the behavior of the agent on the basisof an incongruent perception-based association (and notsimply on the basis of an incongruent motor-based associ-ation). Consider, for example, the experiment by Onishiand Baillargeon (2005) discussed in Section 1. In thisexperiment, 15-month-old infants are first familiarizedwith an agent hiding the object in one of two locations,say location A. Consequently, the association module regis-ters a motor-based association between the agent and theobject that is congruent with the infant’s own motor-basedassociation (AM01, see Fig. 2). The agent leaves, and the ob-ject is moved to location B without her knowledge. Theassociation module registers a new motor-based associa-tion that is incongruent with the one registered in thefamiliarization trials (AM02, see Fig. 2). Then the agent re-turns, and the operating system decouples the motor-based association from perceptual input, which results ina perception-based association (OS, see Fig. 2). At the sametime, the reappearance of the agent also reactivates thepreviously registered motor-based association. Driven bythe infant’s interest in the agent’s grasping behavior, theoperating system (i) inhibits the infant’s own perception-based association, and (ii) selects the motor-based associa-tion that specifies the agent’s movement towards object A(OS01/OS02, see Fig. 2). In the final step, the operating sys-tem (iii) represents this association as an expectation ofthe agent’s behavior towards A (OS03, see Fig. 2). If theagent reaches for the object, the infant’s expectationmatches with the behavior of the agent and no extra pro-cessing is required. However, if the agent reaches for objectB, the infant’s expectation is violated and she has to regis-ter a new agent–object association. This arguably requiresextra processing and hence a longer looking time.

Although the study by Onishi and Baillargeon (2005) re-quires infants to decouple their motor-based associationfrom perceptual input, they do not yet have to deal withan incongruent perceptual perspective – only with anincongruent motor perspective. That is, infants have to in-hibit their own perception-based association, but they donot have to select or represent the visual information that

specifies the agent’s previous perception of the object(since there is no perception-based agent–object associa-tion available).

The operating system processes are also only partly re-cruited for processing perception-based associations wheninfants have to anticipate the behavior of an agent who isignorant about some aspect of the current situation, andthus has a (relatively) incomplete representation of thescene. Several experiments (e.g., Brooks & Meltzoff, 2005;Caron, Butler, & Brooks, 2002; Liszkowski, Carpenter, Stri-ano, & Tomasello, 2006; Luo & Baillargeon, 2007; Sodian,Thoermer, & Metz, 2007; Tomasello & Haberl, 2003) showthat towards the end of the first year infants become capa-ble of registering congruent agent–object associations onthe basis of the visual information that is available to theother agent. Luo and Baillargeon (2007), for example,showed that 12.5-month-olds who watch another agentrepeatedly reach for object A over object B do not attributeto this agent a preference for object A if object B is hiddenfrom her by a screen. However, they do attribute such apreference if the agent is aware of object B’s presence be-hind the screen because she saw it there earlier.

Baillargeon et al. (2010) have argued that we need topostulate a masking mechanism that blocks the visualinformation that is not available to the agent in order toexplain how the infant is able to anticipate the agent’s ac-tions in terms of the remaining shared information.According to our association approach, however, besidesthe operating system no additional mechanism is neededto account for the fact that infants can take into accountthe knowledge or ignorance of other agents. In order toregister a congruent agent–object association on the basisof the visual information that is available to the otheragent, infants only have to inhibit the information aboutthe scene that they do not share with the other agent, (pro-cess i), and represent this as an anticipation of the agent’sbehavior (process iii). This does not require operating sys-tem process (ii), since infants do not have to select the vi-sual information that specifies the agent’s perception ofthe object.

Operating system process (ii) becomes important forprocessing perception-based associations when the infant

MA

M A

M B

P B

M A

M B P B

1

2

3


AM01 OS OS01 / OS02 OS03AM02


M = motor-based association; P = perception-based association; A = agent-object association;

B = infant-object association

= activated association; = inhibited association

Fig. 2. Anticipating another agent’s action on the basis of a motor-based association II.



has to register an incongruent association based on anotheragent’s visual perspective that is incompatible with that ofher own. This is for example what happens in the anticipa-tory looking experiment by Southgate et al. (2007). In thisstudy, 25-month-old infants observe how an agent wit-nesses a puppet bear that hides an object in one of twolocations, say location A. As a result, the association mod-ule registers a perception-based association between theagent and the object that is congruent with the infant’sown perception-based association (AM01, see Fig. 3).5 Thenthe agent gets distracted and turns away from the scene.Meanwhile, the bear moves the object to location B withouther knowledge. The association module registers a new per-ception-based association that is incongruent with the oneregistered in the familiarization trials (AM02, see Fig. 3).6

In the next step, the operating system (i) inhibits the infant’sown perception-based association, and (ii) selects the per-ceptual information that specifies the agent’s previous per-ception of the object at location A (OS01/OS02, see Fig. 3).In the final step, the operating system (iii) represents theassociation as an expectation (anticipatory looking) of theagent’s behavior towards A (OS03, see Fig. 3).

Importantly, several studies have shown that operatingsystem process (iii) allows infants to use their incongruentagent-object associations not only to guide their lookingbehavior, but also their communicative actions and activehelping behavior. Knudsen and Liszkowski (2011), forexample, demonstrated that 18-month-olds actively cor-rect the actions of other agents after having registered anincongruent agent–object association; Buttelmann, Car-penter, and Tomasello (2009) showed that 18-month-oldsare also able to actively assist another agent on the basis ofan incongruent agent–object association.

3.3.3. Symbol-based associationsMost spontaneous-response FBTs involve violation of

expectation paradigms, and investigate the ability to antic-ipate the behavior of another agent on the basis of her per-ception of the location of the object (e.g., Kovács et al.,2010; Onishi & Baillargeon, 2005; Surian et al., 2007;

Träuble, Marinovic, & Pauen, 2010). However, a numberof violation of expectation experiments suggest that younginfants are also capable of registering associations on thebasis of the agent’s perception of the object’s identity. Thishas been reported in 18-month-olds (Scott & Baillargeon,2009) and 14.5-month-olds (Song & Baillargeon, 2008). Inthe study by Song and Baillargeon (2008), for example, in-fants witness an experimenter’s hand placing a doll withblue hair and a stuffed skunk with a pink bow on place-mats or in shallow containers during familiarization trials.An agent who observes this process then shows her prefer-ence for either of the two toys by reaching for it. In the nextstep, without the agent watching, the toys are put in twoboxes. One of the boxes has a tuft of blue hair on the lid,suggesting it contains the doll. The doll is placed in theplain box, and the skunk in the box with the tuft of bluehair on it. When the agent returns and reaches for thebox with the tuft of hair after having showed a preferencefor the skunk, the infants look considerably longer thanwhen she reached for the plain box - and conversely.

Baillargeon et al. (2010) argue that these findings onwhat they call ‘false perception’ are difficult to explain interms of associations. However, the association accountwe propose can account for them in at least two ways.According to the first explanation, the results show that in-fants are capable of registering an incongruent perception-based association that is not only incompatible but alsoincomplete relative to that of their own. As in the South-gate et al. (2007) experiment, the operating system facili-tates this by inhibiting the infants own association. Thistime, however, the operating system only selects the visualinformation about the scene that the infant shares with theother agent (the tuft of blue hair on the plain box that be-longs to the doll), and represents this information as ananticipation of the agent’s reaching behavior. This explana-tion is in line with Song and Baillargeon’s (2008) false per-ception hypothesis, except that it does not presume thatinfants expect the agent to ‘falsely conclude’ that the dollis hidden in the hair box.

However, there is another possible explanation of theresults in terms of symbol-based associations. Symbol-based associations represent the distal goal-directedbehavior of agents toward a symbol, which refers to an ob-ject that is not (visually) present in the current situation.Thus, a symbol functions as a ‘stand-in’ for the object inquestion. For the purpose of this paper, we distinguish

5 Since the experimenter is wearing a visor, the infants are not able tofollow her gaze. However, they are still capable of perceiving what entitiesare in the agent’s visual field (Sodian & Thoermer, 2004).

6 We assume that this incongruency triggers the operating system tobecome operative. However, this is not necessarily a conscious process.

P P A A

P B P B

P A

P B

M = motor-based association;

P = perception-based association;

A = agent-object association;




1

2

3




Fig. 3. Anticipating another agent’s action on the basis of an incongruent perception-based association.



between three kinds of symbols: natural, conventional andlinguistic symbols. One way in which natural symbols referto objects is by exemplifying a part-whole relationship (seeSection 4 for other ways in which symbols may refer to ob-jects). For instance, in the Song and Baillargeon (2008)study, the tuft of blue hair (part) could be taken to referto the doll with the blue pigtails (whole). According to sucha ‘natural symbol’ interpretation of this experiment, theagent reaches for the box with the tuft of blue hair on it be-cause the tuft of blue hair is a natural symbol for the factthat the box contains the doll with the blue pigtails. Howdoes the infant anticipate the behavior of the agent onthe basis of a symbol-based association? Assuming thatthe agent shows a preference for the doll with blue pigtailsduring the familiarization trials, the association moduleregisters a motor-based association between the agentand the doll that is congruent with the infant’s own mo-tor-based association (AM01, see Fig. 4). Next, in the ab-sence of the agent, the experimenter shows the infantstwo large boxes, one with a plain lid and one with a tuftof blue hair attached to it, and then hides the doll in theplain box and the skunk in the hair box. The associationmodule registers two new motor-based associations: onebetween the infant and the skunk (B1) in the hair box,and one between the infant and the doll (B2) in the plainbox (AM02, see Fig. 4).

In the next step, the reappearance of the agent reacti-vates the previously registered motor-based associationbetween the agent and the doll. At the same time, the in-fant’s background knowledge that the tuft of blue hair isa natural symbol for the doll with the blue pigtails triggersthe association module to update the motor-based associ-ation between the infant and hair box with the tuft of bluehair attached to it, despite the fact that it contains theskunk. This results in a symbol-based association (AM03,see Fig. 4). Subsequently, the operating system (i) inhibitsthe motor-based association between the infant and thedoll in the plain box, and (ii) selects the motor-based asso-ciation that specifies the agent’s movement towards the

skunk in the hair box (OS01/OS02, see Fig. 4). In the finalstep, the operating system (iii) represents this associationas an expectation (in terms of anticipatory looking) of theagent’s behavior towards A (OS03, see Fig. 4). If the agentreaches for the hair box, the infant’s expectation matcheswith the behavior of the agent and no extra processing isrequired. However, if the agent reaches for the plain box,the infant’s expectation is violated and she has to registera new agent–object association. This arguably requires ex-tra processing and hence a longer looking time. As we willshow in Section 4, future research could help to determinewhich of the above explanations of the Song and Baillar-geon (2008) is correct. Furthermore, notice that the updatefunction of the association module also allows us to ex-plain how the infants’ background knowledge (under-standing of causal connections and behavioral rules)informs their registration of agent–object associationsand expectations about the behavior of others. As Rakoczy,Tomasello, and Striano (2006) have shown, this becomesincreasingly important when infants begin to understandconventions and social rules.

So far, no experiment has investigated the infant’s abil-ity to register symbol-based associations on the basis ofanother agent’s actions on conventional symbols. Conven-tional symbols refer to objects in virtue of social rules, oras the result of training, explicit agreement etc. This couldbe an interesting direction for future research (seeSection 4).

Before infants acquire linguistic competence, theircapacity to register motor- and perception-based associa-tions already provides them with a proximal understand-ing of the goal-directed behaviors of other agents (e.g.,the agent reaches for the box in order to get the doll). Whatis important about the linguistic symbols provided by lan-guage is that they allow infants to (re)configure motorand perceptual informational in much more complex ‘in-order-to’ associations, thereby enabling an increasinglysophisticated and distal typing of the goal-directed actionsof other agents.

1

3

M A

M B

MA

S B

M B1

MB2

M B

S A

S A


AM01 AM03 OS01 / OS02 OS03AM02

Object Transfer Anticipation 2

M = motor-based association; S = symbol-based association; A = agent-object association


= activated association; = inhibited association

Fig. 4. Anticipating another agent’s action on the basis of a congruent symbol-based association.



Studies such as those by Clements and Perner (1994)and Southgate et al. (2007) seem to suggest that the inclu-sion of linguistic symbols is the most important contribu-tor to the difficulty of elicited-response FBTs vis-à-visspontaneous-response FBTs. Indeed, many experimentshave found strong correlations between linguistic compe-tence and elicited-response FBT performance (Dunn,Brown, Slomkowski, Tesla, & Younblade, 1991; Astington& Jenkins, 1999; Gale, deVilliers, deVilliers, & Pyers,1996; De Villiers & De Villiers, 2000; Watson, Painter, &Bornstein, 2002). There are several hypotheses about whychildren have more difficulty with FBTs that involving lin-guistic symbols. Some researchers propose that they re-quire infants to master the semantics of language(Moore, Pure, & Furrow, 1990), whereas others argue thatwhat is required is getting a handle on its syntactic struc-ture (e.g., Hale & Tager-Flusberg, 2003; Lohmann & Toma-sello, 2003).

However, recent studies show that this cannot be thewhole story. In a spontaneous-response FBT by Songet al. (2008), 18-month-olds observed while an agent hida ball in a box. Then the agent left, and in her absencethe experimenter moved the ball to a cup. When the agentreturned, the infants expected her to search in the cup ifthe experimenter told her ‘The ball is in the cup!’ (informa-tive condition), and they looked reliably longer when shesearched in the box instead. However, if the experimentertold her ‘I like the cup!’ (uninformative condition), the in-fants expected her to search in the box and looked reliablylonger when she searched in the cup instead. This showsthat 18-month-old infants are able to update their agent–object associations on the basis of Woodward (1998) lin-guistic symbols. Our association account explains this ina similar way as the study by Song and Baillargeon(2008). This time, however, the background informationis not provided by the infant who knows that the tuft ofblue hair is a natural symbol for the doll with the blue pig-tails, but instead by the experimenter who informs theagent about the location of the ball.

In another study by Scott et al. (2011), 2.5-year-oldswere tested with two verbal spontaneous-response FBTsthat imposed significant linguistic demands: a preferen-tial-looking spontaneous-response FBT in which childrenlistened to a false belief story while looking at a picturebook (with matching and non-matching pictures), and aviolation-of-expectation task in which children watchedan agent answer (correctly or incorrectly) a standard falsebelief question. Despite their linguistic demands, positiveresults were obtained with both tasks. This suggests that2.5-year-olds are able to process abstract experimentalscenarios that involve a complex network of linguisticsymbols, i.e., stories or pictures instead of the interactingreal-life agents and objects that feature in the non-verbalspontaneous-response FBT.

According to Scott et al. (2011), the difference betweenthese verbal spontaneous-response FBTs and the classicelicited-response FBTs is that they do not require infantsto answer a direct question about another agent’s false be-lief. Although this is certain true, it does not yet explainwhy the latter is more difficult. According to our associa-tion account, the two studies by Scott et al. (2011) are

different from the one by Song et al. (2008) not onlybecause they require infants to process more linguisticsymbols, but also because they require them to deal withincongruent symbol-based association. However, althoughboth studies involves (i) a response inhibition process, and(ii) a response selection process, they do not involve (iii) arepresentation of incongruent symbol-based associations.The difference with the classic elicited-response FBT is pre-cisely that not all the operating system processes are re-cruited in the verbal spontaneous-response FBTs testedby Scott et al. (2011): the infants do not have to representthe incongruent symbol-based association between agentand object.

Consider, for example, the following explanation of theclassic Sally-Anne elicited-response FBT (Baron-Cohenet al., 1985). Children read a cartoon scenario in which Sallyputs her ball in the basket. The association module registersa symbol-based association between Sally and the basket –one that is congruent with the infant’s own symbol-basedassociation (AM01, see Fig. 5). After Sally leaves, Anne placesthe ball in the box. The association module registers asymbol-based association that is incongruent with the oneregistered previously (AM02, see Fig. 5). When Sally returns,the operating system enables the infants to predict whereshe will look by: (i) inhibiting the infant’s own symbol-basedassociation, (ii) selecting the symbol-based association thatspecifies Sally’s belief about the location of the doll (OS01/OS02, see Fig. 5). In the final step, the operating system (iii)represents this information as a verbal prediction aboutSally’s behavior to search in the basket (OS03, see Fig. 5). Onour association view, this last step is not required in the verbalspontaneous-response FBTs by Scott et al. (2011).

Interestingly, our account offers a solution to the devel-opmental paradox which is the exact opposite of the oneoffered by Baillargeon et al. (2010). As we already men-tioned, Baillargeon et al. claim that the difference betweenthe spontaneous-response FBT and the elicited-responseFBT should be construed as follows: whereas spontane-ous-response FBTs only involve false belief representation,elicited-response FBTs also require the inhibition of one’sown (true) belief, and the selection of another agent’s falsebelief. Our association account, however, proposes that(verbal) spontaneous-response FTBs only require inhibi-tion and selection, whereas the elicited-response FBT alsorequires the representation of an incongruent symbol-based association. This basically means that what distin-guishes the elicited-response FBT from the spontaneous-response FBT is a capacity for meta-representation. That is,the infant not only needs to be able to represent what an-other agent represents (the ‘content’), but also how sherepresents it (the ‘propositional attitude’). This capacity isnot required for successful performance on the (verbal)spontaneous-response FBT. Thus, the association accountpresented in this section solves the developmental paradoxof false belief understanding insofar it claims that childrenfail the elicited-response FBT because they are not yetcapable of representing incongruent symbol-basedassociations.

If the elicited-response FBT requires children to repre-sent incongruent symbol-based associations, this arguablyplaces additional demands on the operating system.



Evidence suggests that the elicited-response FBT indeed in-volves more executive functioning. For example, severalstudies have found robust correlations between elicited-response FBT performance and response inhibition (e.g.,Carlson & Moses, 2001; Cole & Mitchell, 2000; Perner &Lang, 1999) and working memory (Carlson, Moses, & Bre-ton, 2002; Hala, Hug, & Henderson, 2003; Perner, Lang, &Kloo, 2002). However, the increased demand in executivefunctioning is probably not only related to the elicited-re-sponse FBT requirement to represent incongruent symbol-based associations, but also to the inhibition and selectionprocesses that are already involved in verbal spontaneous-response FBTs such as those tested by Scott et al. (2011).Further research should investigate the relation betweenthe development of executive functioning and spontane-ous-response and elicited-response FBT performance inmore detail.

4. Remaining questions and directions for futureresearch

In the previous section, we have put forward an associ-ation-based, dual-system account of false belief under-standing that includes two different components: anassociation module and an operating system. These sys-tems allowed us to explain a large range of findings onhow infants understand other agents: (a) the registrationof incongruent motor-based associations shows how theyunderstand the motivational states of other agents (Sec-tion 3.3.1), (b) the registration of incongruent perception-based associations explains their understanding of others’visual perspective and the spontaneous-response FBT find-ings (Section 3.3.3), and (c) the registration of incongruentsymbol-based associations shows how they understandothers’ false belief and explains the elicited-response FBTfindings (Section 3.3.3).

Of course there are several remaining issues that stillneed to be addressed. In Section 3.2, we discussed whichbrain areas could be part of the implementation of theassociation module. If we understand the capacity to regis-ter congruent associations between agent and objects interms of shared representations, then the association mod-ule could be implemented by a mirror neuron system con-sisting of the premotor area, inferior parietal lobule andSTS (Chaminade, Schwarzlose, Baker, & Kanwisher, 2005;

Decety et al., 2002; Iacoboni, 2005; Iacoboni et al., 2001;Koski et al., 2002, 2003). This proposal is very much in linewith the ‘associative hypothesis’ recently offered by Heyes(2010).

But what is the neural substrate that underlies the oper-ating system? Like Leslie et al.’s (2004) Selection Process-ing system, the operating system is a decouplingmechanism which central functions are inhibition andselection. However, the operating system is not domain-specific (cf. Friedman & Leslie, 2004); it depends on thechild’s general capacities for executive functioning. In theToM literature one can find different claims about theimportance of executive functioning for the developmentof false belief understanding. According to so-called ‘emer-gence’ accounts, executive function only scaffolds thedevelopment of false belief understanding by enabling dis-engagement from the immediate objects of attention. Thismakes it possible for children to learn abstract conceptssuch as that of belief (e.g., Carlson & Moses, 2001; Moses,2001; Russell, 1996). Other accounts argue that executivefunction is a lasting feature of false belief understanding.For instance, ‘competence’ accounts propose that explicitfalse belief reasoning requires the conceptual capacity (inworking memory or other aspects of executive function)to construct representations with a certain level of com-plexity (e.g., Andrews, Halford, Bunch, Bowden, & Jones,2003; Frye, Zelazo, & Palfai, 1995; Russell, 1996). By con-trast, ‘expression’ accounts claim that false belief reasoningcomes with specific performance demands, namely, theability to overcome default ascription of one’s own true be-lief (e.g., Leslie et al., 2004) or to resist any tendency to re-spond on the basis of one’s own knowledge (Birch & Bloom,2007; Carlson & Moses, 2001; Russell, 1996). Our associa-tion approach offers a synthesis between these differentaccounts: the operating system not only scaffolds thedevelopment of false belief understanding, but also facili-tates the construction of associations with different levelsof complexity and enables the inhibition of congruentassociations.

As Saxe, Schultz, and Jiang (2006) have shown, how-ever, there is more to false belief understanding than exec-utive functioning. They found that verbal and non-verbalfalse belief attribution not only recruited brain regionsassociated with executive functioning (such as the medialprefrontal cortex), but also brain regions of the ‘Theory ofMind’ network, which consists of the medical prefrontal

M = motor-based association

S = symbol-based association

A = agent-object association




S A

S A

S B

S B

S A

S B

1

2

3

First Event Test Event



Fig. 5. Anticipating another agent’s action on the basis of an incongruent symbol-based association.



cortex, the temporoparietal junction, the superior tempo-ral sulcus and the temporal poles (Amodio & Frith, 2006;Frith & Frith, 2003). This network is reliably activated dur-ing elicited-response FBT performance, and thus seems tofulfill the criteria for the neural circuit underlying the reg-istration of incongruent symbol-based associations (cf.Saxe, Xiao, Kovacs, Perrett, & Kanwisher, 2004). However,it is not yet clear whether and to which extent this net-work is also involved in the more basic operating systemfunctions of registering incongruent motor-based and per-ception-based associations.

An important question for further research concerns thespecific interactions between the mirror neuron system,the brain areas recruited for executive functioning andthe Theory of Mind network during various spontaneous-response and elicited-response FBT tasks. A number ofstudies have already begun to address this question. Forexample, De Lange, Spronk, Willems, Toni, and Bekkering(2008) have shown that the inferior frontal gyrus (part ofthe mirror neuron system) is involved when subjects regis-ter motor-based associations between agents and objects,whereas parts of the Theory of Mind network are recruitedwhen they register symbol-based associations and are lar-gely insensitive to the visual properties of the observed ac-tion. Paus (2001) has argued that in particular the anteriorcingulate cortex (ACC), which is also involved in executivefunctioning, could play a crucial role as interface betweenregistering motor-based and symbol-based associations.Future research has to show whether the association ac-count presented in this article could function as an over-arching, integrative framework for understanding theinteraction between mirror neuron system, Theory of Mindnetwork and executive functioning.

One of the strengths of our association approach is thatit provides us with a fine-grained analysis of what pre-cisely is involved in the different forms of false beliefunderstanding measured by spontaneous-response andelicited-response FBTs. We have shown that these tasks in-volve registering incongruent associations on the basis ofdifferent kinds of information, which are processed in adifferent way and depend on specific interactions betweenthe association module and the operating system. Thismakes it possible to design experiments specifically onthe basis of the kind(s) of information processing they re-quire (i.e., motor, perceptual or symbolic information),and the interactions between association module andoperating system they presuppose. We already showedhow this allows us to bring out some important differencesbetween the experiments by Onishi and Baillargeon (2005)and Southgate et al. (2007): whereas both involve inhibi-tion, only the latter also requires infants to select the per-ceptual information that specifies the agent’s perception ofthe object. In Section 3.3.3, we hypothesized that the spon-taneous-response FBT by Song and Baillargeon (2008)could be explained in terms of symbol-based instead ofperception-based associations. One way to disentanglethese possible explanations is to set up an experiment sim-ilar to the one by Song and Baillargeon (2008) but this timewith more abstract natural symbols, such as symbols thatare (to some extent) visually similar or exemplify one ormore properties of the object (e.g., the color blue as a sym-

bol for the doll with the blue pigtails). Future researchmight also focus on the infant’s ability to register sym-bol-based associations that involve conventional symbols.This could be done, for instance, by introducing an addi-tional object during the familiarization trials of the exper-iment that is systematically related to the protagonist’smain object of interest. If it turns out that infants are in-deed capable of processing these symbol-based associa-tions, the next step would be to investigate what thismeans for the interaction between the association moduleand the operating system, and measure how this influ-ences the infant’s performance when it comes to anticipat-ing another agent’s behavior. The fact that the associationmodule and the operating system are associated with dif-ferent brain regions also makes it possible to look at thespecific contributions of mirror neurons, executive func-tioning, and Theory of Mind.

It is in particular with respect to future studies on falsebelief understanding that our association account has anedge over existing models of psychological reasoning. Thenotion of false belief by itself simply seems to be toocoarse-grained to do justice to all the complexities in-volved in spontaneous-response and elicited-responseFBTs. This does not mean that we shouldn’t talk about falsebelief understanding; it rather implies that false beliefunderstanding should be taken as explanandum instead ofexplanans. That is, we should try to explain different formsof false belief understanding by appealing to an explana-tory terminology that does not include ‘false belief’ as anexplanatory concept. This is where our association accountcan do some important work.

Another direction for future research concerns thestudy of false belief understanding in monkeys. Recently,Ruiz, Marticorena, and Goddu (2010) conducted a sponta-neous-response FBT in order to investigate whether rhesusmacaques had an understanding of false belief. During thefamiliarization condition of the experiment, a macaquemonkey observed how a human protagonist witnesses alemon being placed in box A. Then the protagonist eitherhid behind a screen (false belief condition) or kept looking(true belief condition) while the lemon being was trans-ferred to box B. During the test trials, the human subjecteither reached for box A or B. The study by Onishi and Bail-largeon (2005) showed that infants looked reliably longerwhen the protagonist reached for box A versus B, suggest-ing that they were sensitive to the protagonist’s false be-lief. What about the macaque monkeys? Interestingly,the experimenters found that the monkeys showed thesame looking response in the true belief condition, indicat-ing that they were capable of registering motor-basedassociations for the purpose of anticipating the protago-nist’s behavior. In the false belief condition, however, theydid not look reliably longer and thus showed no sign ofsuch anticipation. According to our association approach,this shows that monkeys somehow fail to anticipatebehavior on the basis of incongruent motor-based associa-tions. Experimental findings indicate that mirror neuronsin macaque monkeys primarily code for the perceptualconsequences of certain actions (Fogassi et al., 2005; Naka-hara & Miyashita, 2005), whereas human mirror neuronsseem to have a division of labor: frontal mirror neurons code



for the perceptual consequence of an action, whereas parie-tal mirror neurons code for the specific movements requiredto achieve this (Iacoboni, 2005; Iacoboni et al., 2001). Maybethis allows humans to inhibit their own motor-based associ-ation, and select the motor information that specifies theagent’s movement towards the object – something that isnot within the reach of a macaque monkey. It would there-fore be interesting to investigate mirror neuron activity andinhibitory processing during this experiment and macaquespontaneous-response FBTs more in general.

Acknowledgments

We would like to thank Colin Allen, Ian Apperly, RenéeBaillargeon, Gergely Csibra, Anika Fiebich, György Gergely,Dan Hutto, Lena Kästner, Ágnes Kovács, Josef Perner, MarcSlors, Derek Strijbos and three anonymous reviewers fortheir helpful comments on/discussions of earlier drafts ofthis article and presentations on this topic.

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