Bridging the gap between the other and me: the functional role of motor resonance and action effects in infants' imitation

This paper investigates a two-stage model of infants' imitative learning from observed actions and their effects. According to this model, the observation of another person's action activates the corresponding motor code in the infants' motor repertoire (i.e. leads to motor resonance). The second process guiding imitative behavior results from the observed action effects. If the modeled action is followed by a salient action effect, the representation of this effect (i.e. perceptual code) will be associated with the activated motor code. If the infant later aims to obtain the same effect, the corresponding motor program will be activated and the model's action will therefore be imitated. Accordingly, the model assumes that for the imitation of novel actions the modeled action needs to elicit sufficient motor resonance and must be followed by a salient action effect. Using the head touch imitation paradigm, we tested these two assumptions derived from the model. To this end, we manipulated whether the actions demonstrated to the infants were or were not in the motor repertoire, i.e. elicited stronger or less strong motor resonance, and whether they were followed by salient action effects or not. The results were in line with the proposed two-stage model of infants' imitative learning and suggest that motor resonance is necessary, but not sufficient for infants' imitative learning from others' actions and their effects.     

Methodological issues in measures of imitative reaction times

Ideomotor (IM) theory suggests that observing someone else perform an action activates an internal motor representation of that behaviour within the observer. Evidence supporting the case for an ideomotor theory of imitation has come from studies that show imitative responses to be faster than the same behavioural measures performed in response to spatial cues. In an attempt to replicate these findings, we manipulated the salience of the visual cue and found that we could reverse the advantage of the imitative cue over the spatial cue. We suggest that participants utilised a simple visuomotor mechanism to perform all aspects of this task, with performance being driven by the relative visual salience of the stimuli. Imitation is a more complex motor skill that would constitute an inefficient strategy for rapid performance.     

Relative contributions of goal representation and kinematic information to self-monitoring by chimpanzees and humans

It is important to monitor feedback related to the intended result of an action while executing that action. This monitoring process occurs hierarchically; that is, sensorimotor processing occurs at a lower level, and conceptual representation of action goals occurs at a higher level. Although the hierarchical nature of self-monitoring may derive from the evolutionary history of humans, little is known about this cognitive process in non-human primates. This study showed that the relative contributions of kinematic information and goal representations to self-monitoring differ for chimpanzees and humans. Both species performed aiming actions whereby participants moved a cursor to hit targets. Additionally, a distractor cursor was presented simultaneously, and participants discriminated the cursor under their control from the cursor not under their control. The results showed that chimpanzees found it difficult to determine whether they were controlling the distractor when it moved toward the target, even though the distractor's kinematics and the participant's actions were dissociated. In contrast, humans performed efficiently regardless of any overlap between the presumptive and observed goals of the action. Our results suggest that goal representation, rather than motor kinematics, is the primary source of information for self-monitoring in chimpanzees, whereas humans efficiently integrate both dimensions of information. Our results are consistent with evidence showing species differences during imitation of others' actions, and suggest that humans have evolved the cognitive capacity to monitor motor kinematics in a more flexible manner than have chimpanzees.     

操作表征在被试操作效应中的调节作用：ERPs研究

本研究考察操作表征(operational representation)在被试操作效应中的调节作用。选取结构性/功能性操作表征短语各160个,分析再认判断中的脑电差异。结果表明,动作编码比语词编码诱发更显著的P1、N2pb和N400;在500~700ms时间窗,相比于语词编码,对结构性和功能性操作表征短语进行动作编码均可显著诱发了中央区更负的平均波幅;在700~900ms时间窗,仅对于结构性操作表征短语,动作编码比语词编码诱发了前额叶更正的平均波幅。研究为动作编码的语义反馈加工机制提供了数据支撑,也为动作信息再激活与动作表征观点的整合提供解释方向。     

I don't get you. Action observation effects inverted by kinematic variation

Recent studies have reported an intricate interplay between affordance and mirror effects (the imitation of another agent) when participants attend to the concurrent presentation of an object and another agent interacting with it. In the present paper, we compare two experimental settings in which an observed action was presented as a prime for a task involving the categorization of a graspable object. In experiment 1a, the action depicted a reach and grasp gesture whereas in experiment 1b, only the reach phase was presented. This modification led to very different outcomes. Experiment 1a reflected the traditional imitation effect elicited by human motion. Conversely, experiment 1b showed the facilitation of contralateral responses. Affordance effects were found in experiment 1a only for the RVF. Our results support the view that motor simulation processes underlying imitation or joint actions are extremely sensitive to specific phase kinematics.     

Routes to Actions and their Efficacy for Remembering

Four experiments focused on the influence that different controls of actions have on memory for these actions. A verbal-to-action task in which subjects had to perform actions on verbal command was distinguished from a movement-to-action task in which subjects had to perform the same action that a model had shown (imitation). We expected free recall to be worse for the imitation condition than for the enactment-on-command condition. The following rank order of recall performances was observed: verbal learning << perceiving the model = imitating the watched model < performing on command = performing on command in addition to perceiving the model. The less pronounced effect of imitation on memory is explained by the fact that subjects in this condition could directly use the information provided by perception for enactment without selection and detailed planning of motor actions. In contrast, subjects in the command-to-action condition had to look up the “motor program”. The inefficiency of using two modalities, i.e. perception and action, as compared to using only one is explained by the redundancy of encoded information in the visual and “motor” modality.     

Does how I look at what you're doing depend on what I'm doing?

Previous studies showed that people proactively gaze at the target of another's action by taking advantage of their own motor representation of that action. But just how selectively is one's own motor representation implicated in another's action processing? If people observe another's action while performing a compatible or an incompatible action themselves, will this impact on their gaze behaviour? We recorded proactive eye movements while participants observed an actor grasping small or large objects. The participants' right hand either freely rested on the table or held with a suitable grip a large or a small object, respectively. Proactivity of gaze behaviour significantly decreased when participants observed the actor reaching her target with a grip that was incompatible with respect to that used by them to hold the object in their own hand. This indicates that effective observation of action may depend on what one is actually doing, being actions observed best when the suitable motor representations may be readily recruited.     

Is imitation learning the route to humanoid robots?

This review investigates two recent developments in artificial intelligence and neural computation: learning from imitation and the development of humanoid robots. It is postulated that the study of imitation learning offers a promising route to gain new insights into mechanisms of perceptual motor control that could ultimately lead to the creation of autonomous humanoid robots. Imitation learning focuses on three important issues: efficient motor learning, the connection between action and perception, and modular motor control in the form of movement primitives. It is reviewed here how research on representations of, and functional connections between, action and perception have contributed to our understanding of motor acts of other beings. The recent discovery that some areas in the primate brain are active during both movement perception and execution has provided a hypothetical neural basis of imitation. Computational approaches to imitation learning are also described, initially from the perspective of traditional AI and robotics, but also from the perspective of neural network models and statistical-learning research. Parallels and differences between biological and computational approaches to imitation are highlighted and an overview of current projects that actually employ imitation learning for humanoid robots is given.     

Intention and Motor Representation in Purposive Action

Are there distinct roles for intention and motor representation in explaining the purposiveness of action? Standard accounts of action assign a role to intention but are silent on motor representation. The temptation is to suppose that nothing need be said here because motor representation is either only an enabling condition for purposive action or else merely a variety of intention. This paper provides reasons for resisting that temptation. Some motor representations, like intentions, coordinate actions in virtue of representing outcomes; but, unlike intentions, motor representations cannot feature as premises or conclusions in practical reasoning. This implies that motor representation has a distinctive role in explaining the purposiveness of action. It also gives rise to a problem: were the roles of intention and motor representation entirely independent, this would impair effective action. It is therefore necessary to explain how intentions interlock with motor representations. The solution, we argue, is to recognise that the contents of intentions can be partially determined by the contents of motor representations. Understanding this content‐determining relation enables better understanding how intentions relate to actions.     

Motor imagery during action observation enhances imitation of everyday rhythmical actions in children with and without developmental coordination disorder

Children with developmental coordination disorder (DCD) exhibit deficits both in imitation and motor imagery (MI) compared to typically developing children. Combined action observation and motor imagery (AO + MI) instructions can however enhance automatic imitation in both groups. In the present study we investigated the effects of AO + MI instructions on intentional imitation in children both with (n = 13) and without DCD (n = 12). On each trial participants observed and/or imagined before executing a familiar rhythmical pantomime action. These target actions were either habitually fast (tooth brushing or window wiping) or habitually slow (paint brushing or face washing), in the vertical or horizontal plane. Within each habitual speed, the target action speed was subtly manipulated across trials (fast vs. slow). Instruction condition was manipulated across three blocks of 16 trials: (1) observe before imitating the target action; (2) observe then imagine the action before imitating; (3) observe while imagining the same action before imitating (AO + MI). Kinematic analyses revealed typically developing children imitated the observed cycle times significantly better than children with DCD. A main effect of instruction showed imitation improved for AO + MI compared to the other two instructions. Within-group analyses found a significant advantage in DCD for AO + MI compared to observe then imagine. In typically developing children, imitation was significantly enhanced for AO + MI compared to observe then imitate. Combined AO + MI instructions therefore represent a promising new approach to refining performance of everyday rhythmical actions in children both with and without DCD, with implications for movement therapy and sports training.     

Children's Representation and Imitation of Events: How Goal Organization Influences 3‐Year‐Old Children's Memory for Action Sequences

Children's imitation of adults plays a prominent role in human cognitive development. However, few studies have investigated how children represent the complex structure of observed actions which underlies their imitation. We integrate theories of action segmentation, memory, and imitation to investigate whether children's event representation is organized according to veridical serial order or a higher level goal structure. Children were randomly assigned to learn novel event sequences either through interactive hands‐on experience (Study 1) or via storybook (Study 2). Results demonstrate that children's representation of observed actions is organized according to higher level goals, even at the cost of representing the veridical temporal ordering of the sequence. We argue that prioritizing goal structure enhances event memory, and that this mental organization is a key mechanism of social‐cognitive development in real‐world, dynamic environments. It supports cultural learning and imitation in ecologically valid settings when social agents are multitasking and not demonstrating one isolated goal at a time.     

Exploring memory in infancy: deferred imitation and the development of declarative memory

Imitation is an important means by which infants learn new behaviours. When infants do not have the opportunity to immediately reproduce observed actions, they may form a memory representation of the event which can guide their behaviour when a similar situation is encountered again. Imitation procedures can, therefore, provide insight into infant memory. The deferred imitation paradigm requires a modelled action to be reproduced following a delay, without prior motor practice. As such, deferred imitation procedures have been proposed to tap declarative memory abilities in non‐verbal populations such as infants. Contrary to the popular belief that infants form sparse or ill‐defined memories, deferred imitation research reveals that infants store and retrieve highly detailed memory representations. The specificity of detail encoded into the representation can, however, cause memory retrieval to fail at young ages. Developing the ability to identify event components which are central (the target stimulus) versus details which are peripheral (the exact context in which learning occurred) is therefore an important aspect of memory development. Using deferred imitation procedures to study the transition from constrained to flexible memory representations can thus facilitate our understanding of the development of declarative memory during the infancy period. Copyright © 2006 John Wiley & Sons, Ltd.     

Understanding the flexibility of action–perception coupling

The idea that observing an action triggers an automatic and obligatory activation of an imitative action in the motor system of the observer has recently been questioned by studies examining complementary actions. Instead of a tendency for imitation, cooperative settings may facilitate the execution of dissimilar actions, resulting in a relative disadvantage for imitative actions. The present study aimed at clarifying the contribution of associative learning and interference of task representations to the reversal of congruency effects. To distinguish between the two, an experiment was designed, in which we increased the effects of associative learning and minimized the effects of task interference. Participants completed a series of imitation and complementary action runs, in which they continuously imitated or complemented the actions of a virtual co-actor. Each run was alternated with a test run showing the same actions but including color-cues, and the participants were instructed to respond to color instead of the actor’s posture. Reaction times to test runs showed no reversal of facilitation effects between the imitation and complementary action conditions. This result strongly argues that associative learning cannot adequately account for reversed facilitation effects. Our study provides additional support for action–perception models that allow flexible selection of action–perception coupling and challenges the existing models purely based on stimulus–response associations.

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The case for motor involvement in perceiving conspecifics

Perceiving other people's behaviors activates imitative motor plans in the perceiver, but there is disagreement as to the function of this activation. In contrast to other recent proposals (e.g., that it subserves overt imitation, identification and understanding of actions, or working memory), here it is argued that imitative motor activation feeds back into the perceptual processing of conspecifics' behaviors, generating top-down expectations and predictions of the unfolding action. Furthermore, this account incorporates recent ideas about emulators in the brain-mental simulations that run in parallel to the external events they simulate-to provide a mechanism by which motoric involvement could contribute to perception. Evidence from a variety of literatures is brought to bear to support this account of perceiving human body movement.     

Bio-inspired cognitive model of motor learning by imitation

Learning, and even more so by imitation, is an essential Cognitive Functions because it is carried out throughout life and allows us to adapt our behaviors from other beings through observation. In this work, we propose a model, and implementation of the cognitive function of imitation motor learning (IML), based on psychological and neuroscientific evidence. According to the evidence, learning by imitation includes imitation of action and imitation of action over an object sub-processes. The imitation of action consists of the movement of the limbs. The imitation of action over an object consists of the interaction with an object within the environment. We achieve an implementation of the proposed model for IML and endow a virtual entity with it. In order to validate the proposal, we use a case study to analyze the sub-processes performance. From results, we conclude that both imitation of action and imitation of action over an object sub-processes play an essential role in getting the agent to interact with stimuli within the environment.     

Mental representations of magnitude and order: A dissociation by sensorimotor learning

Numbers and spatially directed actions share cognitive representations. This assertion is derived from studies that have demonstrated that the processing of small- and large-magnitude numbers facilitates motor behaviors that are directed to the left and right, respectively. However, little is known about the role of sensorimotor learning for such number–action associations. In this study, we show that sensorimotor learning in a serial reaction-time task can modify the associations between number magnitudes and spatially directed movements. Experiments 1 and 3 revealed that this effect is present only for the learned sequence and does not transfer to a novel unpracticed sequence. Experiments 2 and 4 showed that the modification of stimulus–action associations by sensorimotor learning does not occur for other sets of ordered stimuli such as letters of the alphabet. These results strongly suggest that numbers and actions share a common magnitude representation that differs from the common order representation shared by letters and spatially directed actions. Only the magnitude representation, but not the order representation, can be modified episodically by sensorimotor learning.     

从动作模仿到社会认知：自我-他人控制的作用

在社会互动中, 人们具有自动模仿他人动作的倾向。尽管这种自动模仿有利于个体理解他人动作的感受, 但有时也会与自身的动作意图产生冲突。因此我们需要将自身动作意图与他人动作进行区分并调控二者之间的冲突。这种能力被称为自我-他人控制(self-other control, SOC)。与动作模仿控制相同, 心理理论、观点采择和共情等更高级的社会认知同样涉及对自我和他人信息的加工。很多证据表明, SOC可能是一种领域普遍的(domain-general)加工机制, 即在动作模仿控制和其他社会认知中, 大脑对自我和他人双方信息的区分和冲突调控共用同一套SOC系统。最近一些研究发现, 相比于抑制自身优势反应的抑制控制(inhibitory control), SOC是社会认知中一个更为关键的影响因素, 抑制控制对社会认知的作用受到SOC的调节。此外, SOC的领域普遍性提示我们, 未来可以通过简单的动作模仿控制训练, 来为社会认知受损个体(如孤独症和述情障碍者)进行康复训练。     

The influence of action observation on action execution: Dissociating the contribution of action on perception,perception on action,and resolving conflict

For more than 15 years, motor interference paradigms have been used to investigate the influence of action observation on action execution. Most research on so-called automatic imitation has focused on variables that play a modulating role or investigated potential confounding factors. Interestingly, furthermore, a number of functional magnetic resonance imaging (fMRI) studies have tried to shed light on the functional mechanisms and neural correlates involved in imitation inhibition. However, these fMRI studies, presumably due to poor temporal resolution, have primarily focused on high-level processes and have neglected the potential role of low-level motor and perceptual processes. In the current EEG study, we therefore aimed to disentangle the influence of low-level perceptual and motoric mechanisms from high-level cognitive mechanisms. We focused on potential congruency differences in the visual N190 ? a component related to the processing of biological motion, the Readiness Potential ? a component related to motor preparation, and the high-level P3 component. Interestingly, we detected congruency effects in each of these components, suggesting that the interference effect in an automatic imitation paradigm is not only related to high-level processes such as self-other distinction but also to more low-level influences of perception on action and action on perception. Moreover, we documented relationships of the neural effects with (autistic) behavior.     

Role of Timing of Visual Monitoring and Motor Rehearsal in Observational Learning of Action Patterns

This experiment tested the hypothesis that observational learning is enhanced by visual monitoring of enactments that is optimally timed for conception-action matching and by motor rehearsal that serves to refine the cognitive representation. Subjects observed a modeled action pattern, after which they enacted it with either concurrent, delayed, or no visual monitoring. They then engaged in motor rehearsal or did not rehearse the action pattern. Development of the cognitive representation of the modeled action was also measured. Concurrent visual monitoring of enactments greatly facilitated observational learning, whereas delayed visual monitoring did not affect the acquisition process. Rehearsal aided cognitive representation and behavioral reproduction. The more accurate the cognitive representation of the modeled action pattern, the more skilled were the subsequent reproductions of it. After gaining proficiency in converting conception to action, subjects showed no decline in reproduction accuracy when modeling and visual monitoring were withdrawn.     

Role of timing of visual monitoring and motor rehearsal in observational learning of action patterns

This experiment tested the hypothesis that observational learning is enhanced by visual monitoring of enactments that is optimally timed for conception-action matching and by motor rehearsal that serves to refine the cognitive representation. Subjects observed a modeled action pattern, after which they enacted it with either concurrent, delayed, or no visual monitoring. They then engaged in motor rehearsal or did not rehearse the action pattern. Development of the cognitive representation of the modeled action was also measured. Concurrent visual monitoring of enactments greatly facilitated observational learning, whereas delayed visual monitoring did not affect the acquisition process. Rehearsal aided cognitive representation and behavioral reproduction. The more accurate the cognitive representation of the modeled action pattern, the more skilled were the subsequent reproductions of it. After gaining proficiency in converting conception to action, subjects showed no decline in reproduction accuracy when modeling and visual monitoring were withdrawn.