The empirical support for the SCM is mixed. We review recent results from our own lab and others supporting a central claim of SCM that mirroring occurs at multiple levels of representation.  By contrast, the model is silent as to why human infants are capable of showing imitative behaviours mediated by a mirror system.  This limitation is a problem with formal models that address neither the neural correlates nor the behavioural evidence directly

Bennett I. Bertenthal

Bertenthal

Bruner

Matthew R. Longo

Stengel

English

Crossref

Flexibility and development of mirroring mechanisms

The empirical support for the shared circuits model (SCM) is mixed. We review recent results from our own lab and others supporting a central claim of SCM that mirroring occurs at multiple levels of representation. By contrast, the model is silent as to why human infants are capable of showing imitative behaviours mediated by a mirror system. This limitation is a problem with formal models that address neither the neural correlates nor the behavioural evidence directly

Longo, MR

Bertenthal, BI

UCL Discovery

Flexibility and development of mirroringmechanismsdoi: 10.1017/S0140525X07003226Matthew R. Longoa and Bennett I. BertenthalbaInstitute of Cognitive Neuroscience and Department of Psychology, UniversityCollege London, London WC1N 3AR, United Kingdom;bDepartment ofPsychological and Brain Sciences, College of Arts and Sciences, IndianaUniversity, Bloomington, IN 47405.m.longo@ucl.ac.uk bbertent@indiana.eduhttp://www.homepages.ucl.ac.uk/~ucjtml0/Abstract: The empirical support for the shared circuits model (SCM) ismixed. We review recent results from our own lab and others supportinga central claim of SCM that mirroring occurs at multiple levels ofrepresentation. By contrast, the model is silent as to why human infantsare capable of showing imitative behaviours mediated by a mirrorsystem. This limitation is a problem with formal models that addressneither the neural correlates nor the behavioural evidence directly.Hurley’s shared circuits model (SCM) is an ambitious attempt tosystematize a large body of recent research. One key prediction isthat mirroring should occur at multiple grains, or levels of rep-resentation in the motor hierarchy. Recent results from ourown lab, as well as others, conﬁrm this prediction. Severalstudies have shown that mirroring is dependent on the presenceof the observed action in one’s own motor repertoire (e.g., Calvo-Merino et al. 2005). We recently used this ﬁnding to examine thelevel of abstraction at which mirroring occurs, and whether thiscan be manipulated by instructions (Longo et al., in press).We used a paradigm developed previously (Bertenthal et al.2006) in which participants observe a video image of a hand atrest with ﬁngers spread apart. The hand is shown from the per-spective of someone else facing the participant; the participantresponds by pressing a button with the right index ﬁnger if thestimulus ﬁnger appearing farther to the left moves, and withthe right middle ﬁnger if the ﬁnger father to the right moves.With a left hand as the image, the stimulus and responseﬁngers match anatomically (e.g., index ﬁnger response to anindex ﬁnger movement); with a right hand, the stimulus andresponse ﬁngers differ anatomically (e.g., index ﬁnger responseto a middle ﬁnger movement). Responses are faster when thereis an anatomical match between the stimulus and responseﬁngers than when there is not, reﬂecting mirroring, or automaticimitation, of the perceived ﬁnger movements.We used this paradigm to investigate the representational levelof abstraction at which mirroring occurs by presenting images ofa computer-generated model of a hand, the joints of which couldbe conﬁgured ﬂexibly, enabling us to present ﬁnger actions whichwere either biomechanically possible or impossible. Importantly,the impossible actions were impossible only in terms of themanner in which they were performed (i.e., the joints bent inimpossible ways), but were perfectly possible in terms of whatwas performed (i.e., tapping a surface). Thus, these actions areimpossible at one level of the motor hierarchy (i.e., movements),but possible at a higher level (i.e., goals).In a ﬁrst experiment, in which no mention was made of differ-ent types of movements, comparable automatic imitation of poss-ible and impossible actions was observed, though participantsgenerally were aware of the difference between the stimuli.This suggests that mirroring involves a common representationat the level of goals. In a second experiment, in contrast, inwhich attention was explicitly drawn to the manner in whichthe actions were performed by mentioning the two types ofmovements during instructions, automatic imitation was comple-tely eliminated for the impossible, but not possible, movements.This latter result suggests that actions were being coded at thelevel of movements. Together, these results demonstrate thatmirroring can occur at more than one level of the motor hierar-chy, either in terms of goals or in terms of movements – whatRizzolatti et al. (2002) referred to as high-level resonance andlow-level resonance, respectively.Similar relations between mirroring and motor ability as thosejust described have been observed in young infants (e.g., Longo& Bertenthal 2006; Sommerville et al. 2005). These developmen-tal ﬁndings are also relevant to our evaluation of the SCMbecause Hurley acknowledges evidence of mirroring by humaninfants, but her model remains agnostic as to its origins and pre-requisites. By contrast, we contend that the evidence reveals thatmirroring or imitation is present from birth, but limited to actionsalready available to infants.We (Longo & Bertenthal 2006), for example, used the Piage-tian A-not-B error to examine mirroring in 9-month-old infants.This error reﬂects the tendency of infants at this age to perseve-rate in searching to a location where they have previously found ahidden object (A), even after having seen it hidden at a newlocation (B). We found that infants “perseverated” in reachingto the A location, even when they had merely observed an exper-imenter retrieve the object there, but had not reached them-selves. Furthermore, infants were signiﬁcantly more likely toperseverate when the experimenter had reached ipsilaterally(without crossing the body midline), than when they hadreached contralaterally (across the midline). This pattern reﬂectsthe difﬁculty infants of this age show in performing contralateralreaches – what Bruner (1969) referred to as the “mysteriousmidline barrier” – and demonstrates that mirroring ininfants – as in adults – is systematically related to motor skilllevel. Whereas our results show an effect of action observationon motor performance, the ﬂip side of mirroring is reported bySommerville et al. (2005), who show that manipulating infants’ability to perform actions alters their perception of thoseactions when performed by another agent.Although such results show that mirroring mechanisms areoperative quite early in human ontogeny, strong inferencesregarding the origins of such abilities must come from studiesof younger infants still. In this light, the numerous experimentsdemonstrating imitation of facial and manual gestures byhuman neonates are key, suggesting that the neural circuitsnecessary for mirroring are present at birth. Indeed, giventhe reported lack of imitation in adult chimpanzees andmonkeys, the ﬁnding of neonatal imitation in neonates ofboth species (e.g., Myowa-Yamakoshi et al. [2004] and Ferrariet al. [2006], respectively) is especially striking. Such neonatalimitation disappears over the ﬁrst few months of life inhumans as well as primates, suggesting that rather than reﬂect-ing a precocial social-communicative ability, overt mimicry rep-resents an inability to inhibit automatic priming of motorrepresentations. This pattern highlights the fact that at leastsome forms of imitation are not abilities reﬂecting long-termlearning over time, but are rather automatic tendencies whichmust be inhibited in order to interact effectively with theenvironment.Thus, there is a clear developmental progression of inhibitorycontrol over mirroring responses. Whereas neonates show overtautomatic imitation, reﬂecting very weak inhibitory control,older infants do not compulsively imitate, but are biased intheir overt search behaviour by previously observed action. Mir-roring in adults is more implicit still, generally manifesting itselfin priming of motor responses, rather than their overt imitation(though overt imitation has been reported when attention isdiverted [e.g., Chartrand & Bargh 1999; Stengel 1947]). Thispattern suggests that much of the development of mirroringresponses reﬂects changes in inhibitory control, rather thanchanges in mirroring representations, per se.In conclusion, the model proposed by Hurley is in the traditionof competence versus performance models. The difﬁculty withsuch a model is that it provides a mere skeletal structure thathas to be ﬂeshed out in greater detail. Until some critical massof details has been provided, the validity and usefulness of thismodel will remain an issue.Commentary/Hurley: The shared circuits modelBEHAVIORAL AND BRAIN SCIENCES (2008) 31:1 31

Longo, Matthew R.

Bertenthal, B.I.

Name not available

   BIROn - Birkbeck Institutional Research Online  Enabling open access to Birkbeck’s published research output    Flexibility and development of mirroring mechanisms  Journal Article  http://eprints.bbk.ac.uk/5426   Version: Accepted (Refereed)  Citation:         © 2008 Cambridge Journals    Publisher version   ______________________________________________________________  All articles available through Birkbeck ePrints are protected by intellectual property law, including copyright law. Any use made of the contents should comply with the relevant law. ______________________________________________________________  Deposit Guide  Contact: lib-eprints@bbk.ac.uk Birkbeck ePrints Longo, M.R., Bertenthal, B.I. (2008) Flexibility and development of mirroring mechanisms –  Behavioral and Brain Sciences 31(1) Flexibility and Development of Mirroring Mechanisms  Abstract:  The empirical support for the SCM is mixed. We review recent results from our own lab and others supporting a central claim of SCM that mirroring occurs at multiple levels of representation.  By contrast, the model is silent as to why human infants are capable of showing imitative behaviours mediated by a mirror system.  This limitation is a problem with formal models that address neither the neural correlates nor the behavioural evidence directly.    Hurley’s SCM is an ambitious attempt to systematize a large body of recent research.  One key prediction is that mirroring should occur at multiple grains, or levels of representation in the motor hierarchy.  Recent results from our own lab as well as others confirm this prediction.  Several studies have shown that mirroring is dependent on the presence of the observed action in one’s own motor repertoire (e.g., Calvo-Merino et al., 2005).  We recently used this finding to examine the level of abstraction at which mirroring occurs, and whether this can be manipulated by instructions (Longo, Kosobud, & Bertenthal, in press).  We used a paradigm developed previously (Bertenthal, Longo, & Kosobud, 2006) in which participants observe a video image of a hand at rest with fingers spread apart.  The hand is shown from the perspective of someone else facing the participant who responds by pressing a button with the  right index finger if the stimulus finger appearing farther to the left moves, and with the right middle finger if the finger father to the right moves.  With a left hand as the image, the stimulus and response finger match anatomically (e.g., index finger response to an index finger movement); with a right hand, the stimulus and response fingers differ anatomically (e.g., index finger response to a middle finger movement).  Responses are faster when there is an anatomical match between the stimulus and response fingers than when there is not, reflecting mirroring, or automatic imitation, of the perceived finger movements.  We used this paradigm to investigate the representational level of abstraction at which mirroring occurs by presenting images of a computer-generated model of a hand, the joints of which could be configured flexibly, allowing us to present finger actions which were either biomechanically possible or impossible.  Importantly, the impossible actions were impossible only in terms of the manner in which they were performed (i.e., the joints bent in impossible ways), but were perfectly possible in terms of what was performed (i.e., tapping a surface).  Thus, these actions are impossible at one level of the motor hierarchy (i.e., movements), but possible at a higher level (i.e., goals).   In a first experiment in which no mention was made of different types of movements, comparable automatic imitation of possible and impossible actions was observed, though participants generally were aware of the difference between the stimuli.  This suggests that mirroring involves a common representation at the level of goals.  In a second experiment, in contrast, in which attention was explicitly drawn to the manner in which the actions were performed by mentioning the two types of movements during instructions, automatic imitation was completely eliminated for the impossible, but not possible, movements.  This latter result suggests that actions were being coded at the level of movements.  Together, these results demonstrate that mirroring can occur at more than one level of the motor hierarchy, either in terms of goals or in terms of movements, what Rizzolatti et al. (2002) referred to a high- and low-level resonance, respectively.  Similar relations between mirroring and motor ability as described above have also been observed in young infants (e.g., Longo & Bertenthal, 2006; Sommerville, Woodward, & Needham, 2005).  These developmental findings are also relevant to our evaluation of the SCM model because Hurley acknowledges evidence of mirroring by human infants, but her model remains agnostic as to its origins and prerequisites.  By contrast, we contend that the evidence reveals that mirroring or imitation is present from birth, but limited to actions already available to infants. We (Longo & Bertenthal, 2006), for example, used the Piagetian A-not-B error to examine mirroring in 9-month-old infants.  This error reflects the tendency of infants at this age to perseverate in searching to a location where they have previously found a hidden object (A), even after having seen it hidden at a new location (B).  We found that infants “perseverated” in reaching to the A location, even when they had merely observed an experimenter retrieve the object there, but had not reached themselves.  Furthermore, infants were significantly more likely to perseverate when the experimenter had reached ipsilaterally (without crossing the body midline), than when they had reached contralaterally (across the midline).  This pattern reflects the difficulty infants of this age show in performing contralateral reaches, what Bruner (1969) referred to as the “mysterious midline barrier”, and demonstrates that mirroring in infants – as in adults – is systematically related to motor skill level.  While our results show an effect of action observation on motor performance, the flip side of mirroring is reported by Sommerville and colleagues (2005) who show that manipulating infants’ ability to perform actions alters their perception of those actions when performed by another agent.  While such results show that mirroring mechanisms are operative quite early in human ontogeny, strong inferences regarding the origins of such abilities must come from studies of younger infants still.  In this light, the numerous experiments demonstrating imitation of facial and manual gestures by human neonates are key, suggesting that the neural circuits necessary for mirroring are present at birth.   Indeed, given the reported lack of imitation in adult chimpanzees and monkeys, the finding of neonatal imitation in neonates of both species (e.g., Myowa-Yamakoshi, Tomonaga, Tanaka, & Matsuzawa, 2004; and Ferrari et al., 2005, respectively) is especially striking.  Such neonatal imitation disappears over the first few months of life in all three species, suggesting that rather than reflecting a precocial social-communicative ability, overt mimicry represents an inability to inhibit automatic priming of motor representations.  This pattern highlights the fact that at least some forms of imitation are not abilities reflecting long-term learning over time, but are rather automatic tendencies which must be inhibited in order to interact effectively with the environment. Thus, there is a clear developmental progression of inhibitory control over mirroring responses.  While neonates show overt automatic imitation, reflecting very weak inhibitory control, older infants do not compulsively imitate, but are biased in their overt search behavior by previously observed action.  Mirroring in adults is more implicit still, generally manifesting itself in priming of motor responses, rather than their overt imitation (though overt imitation has been reported when attention is diverted [e.g., Chartrand & Bargh, 1999; Stengel, 1947]).  This pattern suggests that much of the development  of mirroring responses reflects changes in inhibitory control, rather than changes in mirroring representations, per se. In conclusion, the model proposed by Hurley is in the tradition of competence vs. performance models.  The difficulty with such a model is that it provides a mere skeletal structure that has to be fleshed out be details.  Until some critical mass of details has been provided, the validity and usefulness of this model will remain an issue.   References Bertenthal, B. I., Longo, M. R., & Kosobud, A. (2006). Imitative response tendencies following  observation of intransitive actions. Journal of Experimental Psychology: Human Perception and Performance, 32, 210-225. Bruner, J. S. (1969). Eye, hand, and mind. In D. Elkind & J. H. Flavell (Eds.), Studies in cognitive development: Essays in honor of Jean Piaget (pp. 223-235). Oxford: Oxford University Press. Calvo-Merino, B., Glaser, D. E., Grèzes, J., Passingham, R. E., & Haggard, P. (2005). Action  observation and acquired motor skills: An fMRI study with expert dancers. Cerebral Cortex, 15, 1243-1249. Chartrand, T. L., & Bargh, J. A. (1999). The chameleon effect: The perception-behavior link and social interaction. Journal of Personality and Social Psychology, 76, 893-910.  Ferrari, P. F., Visalberghi, E., Paukner, A., Fogassi, L., Ruggiero, A., Suomi, S. J. (2006). Neonatal imitation in rhesus macaques. PLoS Biology, 4, e302. Longo, M. R., & Bertenthal, B. I. (2006). Common coding of observation and execution of action in 9-month-old infants. Infancy, 10, 43-59. Longo, M. R., Kosobud, A., & Bertenthal, B. I. (In press). Automatic imitation of biomechanically possible and impossible actions: Effects of priming movements vs. goals. Journal of Experimental Psychology: Human Perception and Performance. Myowa-Yamakoshi, M., Tomonaga, M., Tanaka, M., & Matsuzawa, T. (2004). Imitation in neonatal chimpanzees (Pan troglodytes). Developmental Science, 7, 437-442. Rizzolatti, G., Fadiga, L., Fogassi, L., & Gallese, V. (2002). From mirror neurons to imitation: Facts and speculations. In A.N. Meltzoff & W. Prinz (Eds.), The imitative mind: Development, evolution and brain bases (pp. 247-266). Cambridge: Cambridge University Press. Sommerville, J. A., Woodward, A. L., & Needham, A. (2005). Action experience alters 3-month- old infants' perception of others' actions. Cognition, 96, B1-B11. Stengel, E. (1947). A clinical and psychological study of echo-reactions. Journal of Mental Science, 93, 598-612. 

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A clinical and psychological study of echo-reactions.

Action experience alters 3-monthold infants' perception of others' actions.

Action observation and acquired motor skills: An fMRI study with expert dancers.

Flexibility and development of mirroring mechanisms

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