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  Imitation, Mind Reading, and Social Learning

  Philip S. Gerrans

  Received: 18 February 2013 / Accepted: 20 February 2013 ! Konrad Lorenz Institute for Evolution and Cognition Research 2013

  Abstract Imitation has been understood in different ways: as a cognitive adaptation subtended by genetically specified cognitive mechanisms; as an aspect of domain general human cognition. The second option has been advanced by Cecilia Heyes who treats imitation as an instance of associative learning. Her argument is part of a deflationary treatment of the ‘‘mirror neuron’’ phenome- non. I agree with Heyes about mirror neurons but argue that Kim Sterelny has provided the tools to provide a better account of the nature and role of human imitation. What we call imitative learning is an instance of social learning. It has little to do with empathy, emotional contagion, or mind reading.

  Keywords

  

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  Mill was wrong to contrast these executive capacities with a less cognitively demanding capacity for imitation. Imitation is itself a cognitively demanding capacity, one of those which in fact distinguishes Homo sapiens from the great apes, and which most likely played a role in the development of the modern Homo phenotype.

  The uniqueness of human imitation has been explained in different ways. For some theorists it is an innately specified cognitive module. In the rest of this article I offer an alternative account building on the account of inheri- tance of cognitive traits provided by Kim Sterelny in The

  Biol Theory DOI 10.1007/s13752-013-0112-4

Emulation ! Imitation ! Mind reading ! Mirror neurons ! Modularity ! Social learning ! Tool use

   The presence in the human phenotype of sophisticated

  but domain-specific cognitive capacities such as language leads to hypotheses about innateness and modularity. The main argument for innate modularity in the case of lan- guage is that the primary linguistic data (PLD) underde- termines hypotheses about syntactic structure (Garfield

  A domain-general learning process

  such as inductive inference could not solve the frame

  Colloquium on Kim Sterelny’s The Evolved Apprentice: How Evolution Made Humans Unique. P. S. Gerrans (&) Philosophy Department, University of Adelaide, Adelaide, SA, Australia e-mail: philip.gerrans@adelaide.edu.au ¹ This article is one of four in Biological Theory’s Colloquium on Kim Sterelny’s The Evolved Apprentice: How Evolution Made Humans Unique ( this issue).

  Evolved Apprentice ( ; hereafter, EA). Ultimately I will problem without prior restriction of the domain of possible solutions. Yet children automatically and effortlessly acquire the correct syntactic structure of their native lan- guage without explicit instruction and without being able to explicitly represent that structure. This is the poverty of stimulus (POS) argument. It is used to argue that language acquisition depends on a genetically specified, specialized computational system whose canalized maturation explains the development of linguistic competence (Segal

  Famously, John Stuart Mill did not think imitation a sophisticated cognitive capacity. He gives a brief account of what he takes to be characteristically human cognitive fac- ulties only to contrast them with the ‘‘ape-like one of imi- tation (Mill p. 65).’’ His list of human capacities is one that any cognitive scientist might endorse: ‘‘use observation to see, reasoning and judgment to foresee, activity to gather materials for decision, discrimination to decide, and when he has decided, firmness and self-control to hold to his deliberate decision.’’ We might characterize this suite as attentive observation, planning, inference, and executive function involving the ability to represent, more or less abstractly, a distant goal and use that representation to reg- ulate goal-directed behavior (Zelazo and Mu¨ller ).

  argue that imitation, of the type that matters for the transmission of cultural knowledge, is a sophisticated cognitive ability that involves the suite of domain-general abilities described by Mill.

  Even though some non-modularists resist the idea that language is modular, the structure of the POS argument for innate modularity is not generally contested; so despite controversies over the nature and extent of modularity the way to contest modularity hypotheses is relatively clear. One can provide a ‘‘wealth of stimulus’’ (WOS) argument and show that the information necessary to determine cognitive architecture is present in the child’s environment, either implicitly in the social interchanges in which it is embedded or explicitly through direct instruction or dem- onstration (Pullum and Scholz ). A corollary of the WOS is that domain-general cognitive systems (operating on input provided by specialized per- ceptual and quasi-perceptual systems) must be able to construct the necessary cognitive architecture scaffolded by the wealthy environment. The result is the emergence of domain specificity in the cognitive phenotype without innate modularity (Karmiloff-Smith The interaction of general-purpose learning mechanisms and specialized input systems kept on track by supervision and teaching is sufficient to account for the acquisition of a specific domain of information.

  Sterelny has given a version of the WOS argument in arguing that there is no unique cognitive adaptation that explains human cognitive modernity. Important adapta- tions for humanity are quite basic ones such as tolerance for juveniles, (relative) lack of aggression, and prosociality, which jointly enable intensive social learning. Together with the suite of (relatively) domain-general capacities provided by the large prefrontal cortex in humans, these adaptations make us learning machines. Crucial to the argument is the idea that the necessary WOS is provided by cognitive niche construction. The interaction between individual human minds and the social milieu of peers and caregivers provides a wealth of information and intensive teaching. As a consequence there is no need to postulate the presence of innate modularity to explain the develop- ment of sophisticated, domain-specific cognitive traits.

  An example of this approach is the explanation of mind reading, understood as the ability to meta-represent the mental states of others (Currie and Sterelny ). The theory of mind (TOM) explanation of mind reading argues that such meta-representational abilities are necessary for mind reading. The innatist version of TOM argues that unless the architecture necessary for TOM is genetically specified, the reliable intergenerational transmission of mind reading cannot be accounted for. Sterelny and others have pointed out that an analogy between language and mind reading is imperfect: the child develops in an inten- sively engineered cognitive niche in which not only the behavior of others but the decoupled mental states under- lying that behavior are the most emotionally and conver- sationally salient items. There is, in fact, a wealth of information, both tacitly and explicitly conveyed, about others’ mental states in the child’s environment (Gerrans

   ).

  Sterelny additionally points out that the early emergence of TOM is not really consistent with the Machiavellian intelligence hypothesis of TOM often used to support the innatist hypothesis. Preschoolers do not use their meta- representational capacities for competitive ends or for collaborative enterprises that depend on the detection of defectors. ‘‘But they do face a pressing problem: social learning’’ (EA, p. 146). Thus the rapidly developing executive capacities, interacting with quasi perceptual precursors (like joint attention and social referencing) in a cognitive niche designed to enable transmission of social knowledge explain the ubiquitous appearance of mind reading. It is an adaption for social learning, not co-oper- ation or competition. But its reliable transmission is pro- duced, not by maturation of an innate module for TOM but by learning within a niche constructed by humans for the transmission of social knowledge.

  In the rest of this article I will argue that the human capacity for imagination should be explained the same way.

  Imitation is one of the cognitive traits, such as language and mind reading, displayed by humans to a unique extent. And, like language and mind reading, it has been proposed as a cognitive adaptation that drove the transition to human modernity. Almost uniquely, humans can transmit complex cultural artifacts, both concrete and abstract, with a very high degree of fidelity across generations. Such transmis- sion reproduces the human cognitive niche and enables cultural inheritance. Imitation might well be a key to such social learning: after all, a reliable way to learn how to use tools, make fishing nets, hunt, play music, pronounce words, or reproduce stories is to imitate an expert. Given that humans teach and demonstrate to a unique extent in order to transmit expertise, imitation becomes a crucial part of the cognitive repertoire.

  It also seems to constitute a specific domain of human cognition, to develop early and reliably, buffered against interference. Thus it is a candidate for innate modularity hypotheses. Indeed, since Meltzoff and Moore published a

  P. S. Gerrans

Author's personal copy paper two decades ago claiming that neonates imitate

  automatically , the innatist hypothesis of human imitation

  has been a default hypothesis for some developmental cognitive scientists (Gopnik and Meltzoff ; Meltzoff and Moore The (comparative) inability of great apes and monkeys to imitate also lends weight to the idea that imitation is uniquely human (Tomasello Whiten, Horner et al.

  

  Of course uniqueness does not show that the trait in question is a cognitive adaptation with a genetically specified neurocomputational architecture. However, Meltzoff and Decety ), for example, have made that claim. They argue that (1) imitation is innate in humans; (2) imitation precedes mentalizing and TOM (in develop- ment and evolution); and (3) behavioral imitation and its neural substrate provide the mechanism by which TOM and empathy develop in humans.

  They go on ‘‘to suggest that infant imitation provides an innate foundation for social cognition’’ (p. 497). This set of claims is anchored within an approach to social cognition, the simulation theory, opposed to the TOM hypothesis. They do not directly address conceptual arguments for innateness, resting their claim largely on the interpretation of evidence from developmental and cognitive neurosci- ence about the neural mechanisms underpinning imitation.

  However, these conceptual issues are relevant. For example, one could argue against their hypothesis on the grounds that that the abilities involved are not really imi- tative, or can be explained as learnt behaviors not depen- dent on a genetically-specified neural system specialized for imitation. While the first approach is a possibility for some aspects of human learning (perhaps what we interpret as imitation is actually emulation; see below for the dif- ference between imitation and emulation) it does not generalize. There are many clear cases of imitation central to social learning. So the second strategy is a better option, viz., to show that the imitative behavior can be explained, not as the product of a modularized capacity, but as the outcome of the deployment of one or more of the domain- general capacities available to humans as they develop.

  While Sterelny does not discuss the nature of imitation, he has provided a crucial resource for this second strategy in his general account of cognitive apprenticeship. Formal results in learning theory and empirical studies of concept and skill acquisition show that the domain of possible solutions to a problem must be appropriately restricted if domain-general learning strategies are to succeed. If, however, infants are apprentices whose development is scaffolded by intensive teaching, this constraint is met. We would not need to evolve a modular capacity for imitation in order to reproduce observed actions if the process of motor learning is supervised and corrected.

  Cecilia Heyes gives an instructive domain-general account of imitation congenial to Sterelny’s approach (Brass and Heyes ). She identifies two explananda for any theory of imitation that might lead to the modularity hypotheses, before rejecting it. The first is what she calls the ‘‘correspondence problem.’’ The observer needs to map a representation of the observed movement onto a corre- sponding motor plan. This is a complex unconstrained computational problem. It is difficult to see how it could be solved as instantaneously as humans do unless the domain of possible motor encodings was restricted.

  The second is the need to avoid ‘‘abstraction,’’ a term I will use for the process of categorizing a movement or movement sequence in terms of a potential hierarchy of goals. For example, pushing a piece of food towards a conspecific might be coded as a motor sequence. More abstractly, the same movement is a push, feeding, or a strategic move in alliance building. Abstraction is often of vital importance. Does the trajectory of the arm of some- one gesturing back to the shore from the ocean represent a cry for help, an invitation to come for a swim or simple joie

  de vivre ? Only in the last case is imitation the right

  response. These are cases where an identical (or very similar) movement sequence can realize multiple goals.

  Emulation is the converse case in which the same goal can

  be realized by different means. For example, one can open a door by hand or foot. Adam Smith had the concept of emulation in mind when he noted the exemplary role of wealth in capitalist societies. He was not suggesting that we are all inspired to become rich by manufacturing and marketing the same products in the same way, rather that acquiring wealth was a goal to be emulated in diverse ways.

  In the developmental and primate literature, the differ- ence between imitation and emulation becomes extremely significant as a way to decompose cognitive capacities. For example, a monkey that observes an experimenter grasp an object by hand will grasp the object by mouth if its hands are secured. Or if it sees an experimenter turn off a switch by butting it with her head, the monkey will turn it off by hand. Similarly, a child who sees the experimenter hop a toy kangaroo across a table and into a house will reproduce that action, but if the route is blocked will pick the toy up and place it in the right location (Jackson et al. In these cases the action is being emulated, not imitated. Mill should have said: ‘‘the ape-like faculty of emulation.’’

  These cases tell us that (1) emulation is a more basic capacity than imitation; (2) the representation of goals is independent of the representation of means to attain those goals; (3) ‘‘true’’ imitation involves reproducing a move- ment sequence in order to realize a goal. Another way to put this is to say that specific actions rather than mere movement sequences are the object of imitation.

  Imitation, Mind Reading, and Social Learning

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  And these ideas are part of the standard definition of imitation proposed by primatologists and developmental psychologists. On that definition imitation involves:

  Heyes has an elegant solution to this problem, which depends on the idea that imitation is not a modular process. On her view imitation is an instance of associative learning in which association between stimulus and a response that are repeatedly and consistently paired becomes automated (Heyes Heyes et al.

  So one way to solve the problem might be to represent the goal, i.e., to represent the movement sequence qua action. This reduces the range of possible motor instruc- tions to a narrow repertoire. A monkey can only reach by hand or mouth, for example. Note that the more one

  Heyes’ account is designed to solve the correspondence problem and the problem of ‘‘abstraction.’’ Recall that the correspondence problem is the problem of mapping the observed movement to the observer’s own motor instruc- tion. There is nothing intrinsic (one might think) about a perceptual representation of an action that links it to a motor representation of the movement sequence needed to reproduce that action. So imitation presents the would-be imitator with a problem of activating the right movement sequence in herself. Emulation does not present the same problem because the action is goal-driven. The observer just selects an action appropriate to the goal from its repertoire.

  In effect, Heyes is saying that imitation is not a discrete cognitive phenomenon, but a sub-domain of a larger one: associative learning.

  Contiguity refers to temporal proximity. On this view of things, the relation between action observation and repro- duction is like any stimulus–response relationship installed by conditioning.

  As in all cases of associative learning, the stimulus (observed movement) and the response (observer’s repro- duction of the movement) are paired by relations of con- tingency and contiguity. Contingency refers to the fact that one element of the sequence reliably predicts the next.

   ).

  In fact this is only a puzzle if the mirror system if conceived of as the neural substrate of a modular cognitive capacity like language. It would be surprising if a creature had the necessary neural architecture to support a cognitive process but could not perform it when the appropriate elicitors were perceived.

  Novelty. The mere triggering of an automatic movement sequence does not count as imitation. Patients with various frontal pathologies will spon- taneously mimic observed movements, activating and being unable to inhibit, motor plans. But they cannot imitate. (Meltzoff and Decety ; L’Hermitte et. al.

  The puzzle is that macaque monkeys and indeed other monkeys and great apes do not imitate. Or, more accu- rately, their imitative capacities are far more circumscribed than humans’ and are tied to a range of ecologically salient overlearned actions. Thus the presence of a mirror system cannot be a sufficient basis for imitation.

  Mirror neuron activity intuitively seems to be what might be called ‘‘covert’’ imitation. It looks as though the observer is automatically imitating the observed action while inhibiting the motor output. Thus, initially, the mir- ror neuron phenomenon was hypothesized to be an adap- tation for imitation.

  The mirror properties of the motor systems are phylo- genetically preserved in humans. Interestingly, human mirror neurons also have the property of firing for intran- sitive as well as transitive movements.

  These ideas also suggest an interpretation of a puzzle gen- erated by the phenomenon of mirror neurons. ‘‘Mirror neu- rons’’ were discovered in the premotor cortices of macaque monkeys in the 1990s. These cells fire both when an action is observed and when the same action is performed by the observer. Observation and execution of hand and mouth grasping will produce firing of the same premotor neurons involved in grasp. Other neurons in the posterior parietal cortex (area PF) fire when the consequence of an action is perceived. For example, when a monkey hears the experimenter tear open a bag containing peanuts, its ‘‘grasping’’ mirror neurons will fire (Buccino et al. ). These monkey mirror neurons are all transitive: they fire only when the action has a target or object and not when objectless gestures are perceived, although they will fire when observing the last segment of reach to a previously seen but currently occluded target (Kohler et al. ).

  Representation of Ends—Representation of Means These apparently innocuous constraints allow us to dis- tinguish imitation from closely related phenomena of affective and motor contagion, as when smiles, yawns, and postures spread within a group. What we are really seeing here is not imitation per se. That these are not imitative behaviors is shown by the fact that not all classes of action are contagious. An angry expression or vocal tone is not contagious: it will typically produce a variety of responses including defensive or conciliatory posture and vocal tone. This is just a consequence of the fact that evaluation of social stimuli and coordination of response are low-level reflexive phenomena. The ‘‘imitative’’ aspect of social contagion is an instance of affectively driven social coor- dination. Perhaps there is a default setting to mimic pos- tures and expressions but the evidence is equivocal here.

   , p. 330)

  P. S. Gerrans

Author's personal copy abstracts the easier the problem becomes. If the observer understands that the target wants the observer to perform a particular action then it is easier for her to reproduce the action. This level of understanding seems to be one of the large barriers to ape imitation. For example, a dominant male chimp was trained to pull one handle of a two-han- dled barrow while an experimenter pulls the other in order to earn food. An observing chimp introduced after the experimenter left, however, could not pull the other handle to obtain the reward, even when the dominant chimp picked up the other one and ‘‘demonstrated.’’

  If abstraction plays a necessary role in reproducing observed behavior then imitation becomes something more than associate learning, which at its most basic is the detection and reproduction of sequences of events which are not intentional, in the philosopher’s sense of carrying meaning. Pure associative learning allows a subject to associate an observed movement with her own movement. Neither need be intrinsically intentional.

  To characterize a movement as intentional, i.e., as an action, is to abstract. Or as Heyes might put it, to engage in some cognitive ascent: meta-representing an event and applying a concept to it in order to interpret it. Meta-rep- resentation is of course a matter of degree, and some meta- representation may not be very conceptually sophisticated. A monkey might merely need to classify movements as similar along some dimension rather than as implementing a goal, for example. Humans might explicitly represent some words as lies or compliments in order to determine a response. Whether and how to imitate might depend on degrees of meta-representation. Presumably, learning how to play a riff on the piano can be approached in different ways according to whether it is represented as ‘‘this sequence of notes,’’ ‘‘a blues riff,’’ or ‘‘an homage to Professor Longhair.’’ The first is purely associative; the second and third seem to involve higher degrees of con- ceptual sophistication and meta-representation. But there is no doubt that much human imitation involves meta- representation.

  Heyes might agree, but she is concerned to show that pure imitation does not necessarily need this type of abstraction to solve the correspondence problem. For her, the association between observation and action needs to be installed without abstraction.

  Equally she cannot appeal, as ‘‘innate modularists’’ do, to an innate solution to the correspondence problem. This is why she disputes the innatist interpretation of the mirror neuron phenomenon, which has it that the mapping from observation to reproduction of movement is auto- mated, and depends on the maturation of a neural system specialized by evolution for the task. She agrees that mirror neurons solve the correspondence problem because they automate the link between observed and reproduced movement. She also agrees with one stream of the mirror neuron movement that mirror phenomena are a form of ‘‘covert imitation.’’

  According to Heyes, the correspondence problem is not solved by evolution but in development. She points out that the movements and other stimuli to which mirror neurons respond are overlearned. The monkeys in the lab responded to familiar actions with anticipated rewards such as reaching for a peanut. Mirror phenomena are far more elusive for novel stimuli and in fact are strengthened by repeated association. The fact that these associations are intensively ‘‘taught’’ means that the monkey does not need to rely on trial and error to match a motor program to an observed movement. In the highly structured environment of the laboratory the correspondence problem is solved by a wealth of stimulus, or at least sufficient repetition and reinforcement to constrain the domain of possible associations.

  Thus for Heyes the correspondence problem is solved by

  teaching of a movement sequence , which leaves imitation

  as essentially a non-intentional phenomenon. The monkey has no need to meta-represent the sequence, which can be conceived of in non-intentional terms as the matching of observed movement trajectory to performed movement. The price is to make imitation a non-intentional phenomenon.

  Another view is that Heyes is right and mirror neurons are not intrinsically sensitive to the goal of a movement: they mirror movements, not actions. If they ‘‘mirror’’ actions they do so in virtue of upstream computations of the intentional nature of the observed movement. That is to say, when they play a role in imitation, as they do, it is because the problem of abstraction has been solved already. There are neural structures that are sensitive, indeed oversensitive, to goal-directed bodily movements and these form part of the system activated when humans engage in imitation. This view of the matter has been well put by Jeannerod and Jacob as part of an argument that mirror neurons are not part of a system for intention detecting or the attribution of intentional content to movements (Jacob ). A series of experiments have shown that superior temporal sulcus (STS) neurons, which have no motor properties, respond to goal-directed move- ment such as reaching when the actor is looking at the target. That the STS seems to play a crucial role in the detection of purposeful bodily movement is also shown in experiments involving point light displays of human movement and Heider- and Simmel-type experiments in which subjects over-attribute intentions to moving geo- metric shapes. These cases are particularly interesting since no motor or mirror activity is evoked by perception of geometric shapes (the human motor system is indifferent to the trajectories of geometric shapes), and yet the subjects

  Imitation, Mind Reading, and Social Learning

Author's personal copy still attribute goals to the triangles, squares, and circles purely by virtue of their trajectories.

  Thus, provided that the STS is active, the observer has information that what she is looking at is a targeted action, which removes the need for abstraction.

  However, one might still wonder whether the joint action of the mirror system and the STS, no doubt installed by teaching, is sufficient to account for human imitation. I suspect not, and we can see why when we turn from monkeys grasping for peanuts and infants waving back at their parents to the kinds of imitation that might be involved in the transition to human modernity. The making of tools such as adzes and arrowheads is an example. In this case a stone is transformed into a sharpened tool adapted very precisely to a particular task, such as stabbing, cutting, or skinning.

  Typically such skills are acquired in an intensively supervised environment. There is demonstration and cor- rection as well as trial and error.

  Moreover, the process is not merely one of process imitation, or the reproduction of a sequence of movements, but product imitation. The aim of teaching is not for the student to reproduce the teacher’s movements, but to reproduce the final product, a suitably sharp tool.

  In fact it is difficult to see how flints could be turned into adzes by ‘‘pure’’ process imitation. If the student’s flint is harder or has different planes of cleavage, then the iden- tical movement sequence will produce a differently shaped flint than the target. More importantly the flint may be too blunt or misshapen to be any use. Similarly the student may encounter problems, which require her to depart from the demonstrated movement sequence to produce an adequate flint. She may need to turn it upside down to reshape an obstinate surface or even start from a different surface.

  This problem is amplified when we consider other skills such as making fishing nets or arrowheads, which have a complex structure. Often it may be necessary to stop one part of the task and jump ahead to the finish, or to go back to the beginning to refine one component. For example, one might need to unravel part of a fish net to fix a mistake, which only becomes apparent when the components are assembled, or to undo the binding on an arrowhead, and recarve it to make it fit better onto the shaft.

  Furthermore, even more abstract considerations may be extremely relevant. For example, one might need to recall the size of the fish one is catching when making a net or carving bone into a fishhook. Similarly, one might need to bear in mind whether the flint is being used for stabbing, skinning, or cutting. And in fact one can imagine adapting the final goal according to the results of the initial pro- cessing. A flint initially intended to be used for butchering might be adapted for skinning if its planes of cleavage give it a suitable shape.

  These cases suggest that a mere capacity for motor mimicry—the reproduction of movement sequences—is inadequate for the acquisition of worthwhile social knowledge. Heyes notes that in this respect imitation of movement sequences, while it may be useful in some kinds of synchronized activity useful for attachment and social bonding (infants preferentially attend to people who imitate them and engage in games of imitation, and in adulthood in many societies synchronized movement such as dancing combined with chanting in unison or singing are essential mechanisms of social attachment) is unlikely to be the basis for social learning.

  Consequently, as she says: my money is on sequence emulation coming out on top. The cultural wisdom lies in the object transfor- mations rather than the body movements ^… it won’t matter, from the perspective of cultural evolution, how the object movements are effected by the actor’s body. (Heyes in press)

  By sequence emulation Heyes means those movements that effect the necessary final object transformations, for example, the final carving necessary to produce the fishing hook.

  An interesting question here is whether the capacity for sequence emulation alone can suffice for social learning. Heyes implies that it can (at least for things like flints and arrowheads). If this is correct, then imitation need not involve much in the way of abstraction. It will consist in fine-tuning the reproduction of a motor sequence with reference to the represented object end state. Since emu- lation for perceptually represented goals is part of the great ape (and old world monkey for that matter) repertoire this raises the question, ‘‘Why can’t apes imitate?’’ Apes are capable of associative learning and emulation.

  Possibly the answer is the wealth of stimulus provided to human infants in their enriched instructional environments. Apes are not tolerant of juveniles and do not teach skills. This suggests that apes that are intensively taught could learn to imitate, but even here they show limitations. The example of the chimpanzee that could not learn to pull the barrow is an example.

  And those limitations are in the kind of higher-order cognitive capacities unique to humans: mind reading via ‘‘theory of mind’’ inferences, meta-representation, and executive function causal and inductive reasoning. This suite of capacities harnessed in the service of social learning allows a child who is intensively coached to reproduce artifacts and actions. A child who can understand the intentions of her teacher, envision the end product of her sequence copying, meta-represent elements of the sequence in order to adjust, and fine-tune her actions and communicate in language is better placed to learn by imitation.

  P. S. Gerrans

Author's personal copy Like Heyes, I do not think that imitation is a unique cognitive module that provides a breakthrough to sophis- ticated social learning. And like her I suggest that we decompose imitation into components that enable the child to reproduce elements of a sequence using domain-general learning strategies in an enriched environment.

  However, those domain-general strategies also include capacities for abstraction: meta-representation, theory of mind, and causal inference. The development of these capacities both depends on and enables the construction of rich cognitive niches characterized by imitative learning.

  shift is an ontogenetic evolutionary legacy that helps form the basis of cultural transmission through intersubjective

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  Press, Cambridge Catmur C, Walsh V et al (2007) Sensorimotor learning configures the human mirror system. Curr Biol 17:1527–1531 Catmur C, Walsh V et al (2009) Associative sequence learning: the role of experience in the development of imitation and the mirror system. Philos Trans R Soc Lond B 364:2369–2380

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  True imitation is not a modularized capacity that enables this shift, but one of a suite of abilities which co-develop rapidly after infancy as the child’s mind matures within an intensively engineered ecological niche. Imitation is, as Heyes notes, evidence of successful teaching rather than spontaneous unsupervised learning. In humans, teaching and learning of most tasks requires both intensive super- vision and the ability to understand future states and potential purposes of the objects being constructed and the goals, intentions, and mental states of other people.

  , one of the defining features of the human species’’ (Konner p. 288; emphasis added). In particular, the cognitive advances of middle childhood are adaptations for participation in family life. The child now has the ability to be taught how to look after younger children, to help and participate.

  teaching and learning

  tion of Childhood provides an answer: ‘‘the five to seven

  At present it is very difficult to parse the mechanisms of social learning. The functional and neural architectures are not sufficiently well understood. One mechanism may be the mirror system but it cannot be the case that the mirror system evolved to enable imitation. Rather, if it plays a necessary role in imitation (perhaps by solving the corre- spondence problem after suitable training), it does so as part of a larger system. Where I differ from Heyes is in suggesting that those larger systems will include circuitry necessary for abstraction because imitative learning is actually a more complicated task than reproducing an observed movement. To reproduce the movement will typically require the representation of more information than the motor encoding of the movement trajectory.

  I close with a speculation. True imitation is a more cognitively sophisticated phenomenon than motor mim- icry. One reason noted by Sterelny is that childhood is a period of apprenticeship in which social supervised learn- ing plays a crucial role. This is consistent with theories of middle childhood that note a pronounced shift in abilities at this age, evidenced by more abstract and decoupled forms of understanding in many domains, of which mind reading is especially salient. Why? Konner in his epic The Evolu-

  Interestingly, the DLPFC involvement receded as expertise was acquired. This is part of a general feature of skill acquisition. As expertise increases, the tasks becomes more automated, and high-level systems are not recruited. Thus early mirror neuron studies of motor contagion for overlearned associations may have been slightly mislead- ing since, once the association is acquired, the phenomenon is automatic. In the acquisition phase, however, as both Heyes and Sterelny note, supervision and teaching are essential.

  we might expect if imitation requires higher-level super- vision. In particular, the dorsolateral prefrontal cortex (DLPFC) is activated in paradigms requiring high-level cognitive control.

  order supervisory and monitoring operations associated with the prefrontal cortex ’’ (emphasis added). This is what

  resentation of an observed, complex action, as provided by the FPMC, only serves as the ‘raw material’ for higher-

  to account for imitation learning . Rather, the motor rep-

  In an interesting experiment, Higuchi et al. ( p. 1668) asked participants to imitate pictures of hands making chords on a guitar. The contrast with the ‘‘obser- vation’’ condition was in the ‘‘fronto-parietal mirror cir- cuit’’ (FPMC). They concluded that ‘‘a mechanism of automatic perception–action matching alone is insufficient

  

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