When far becomes near: Shared environments activate action simulation

It has been proposed that one means of understanding a person's current behaviour and predicting future actions is by simulating their actions. That is, when another person's actions are observed, similar motor processes are activated in the observer. For example, after observing a reach over an obstacle, a person's subsequent reach trajectory is more curved, reflecting motor priming. Importantly, such motor states are only activated if the observed action is in near (peripersonal) space. However, we demonstrate that when individuals share action environments, simulation of another person's obstacle avoiding reach path takes place even when the action is in far (extrapersonal) space. We propose that action simulation is influenced by factors such as ownership. When an “owned” object is a potential future obstacle, even when it is viewed beyond current action space, simulations are evoked, and these leave a more stable memory capable of influencing future behaviour.     

Priming of reach trajectory when observing actions: Hand-centred effects

When another person's actions are observed it appears that these actions are simulated, such that similar motor processes are triggered in the observer. Much evidence suggests that such simulation concerns the achievement of behavioural goals, such as grasping a particular object, and is less concerned with the specific nature of the action, such as the path the hand takes to reach the goal object. We demonstrate that when observing another person reach around an obstacle, an observer's subsequent reach has an increased curved trajectory, reflecting motor priming of reach path. This priming of reach trajectory via action observation can take place under a variety of circumstances: with or without a shared goal, and when the action is seen from a variety of perspectives. However, of most importance, the reach path priming effect is only evoked if the obstacle avoided by another person is within the action (peripersonal) space of the observer.     

The predictive mirror: interactions of mirror and affordance processes during action observation

An important question for the study of social interactions is how the motor actions of others are represented. Research has demonstrated that simply watching someone perform an action activates a similar motor representation in oneself. Key issues include (1) the automaticity of such processes, and (2) the role object affordances play in establishing motor representations of others' actions. Participants were asked to move a lever to the left or right to respond to the grip width of a hand moving across a workspace. Stimulus-response compatibility effects were modulated by two task-irrelevant aspects of the visual stimulus: the observed reach direction and the match between hand-grasp and the affordance evoked by an incidentally presented visual object. These findings demonstrate that the observation of another person's actions automatically evokes sophisticated motor representations that reflect the relationship between actions and objects even when an action is not directed towards an object.     

Predicting others' actions via grasp and gaze: evidence for distinct brain networks

During social interactions, how do we predict what other people are going to do next? One view is that we use our own motor experience to simulate and predict other people's actions. For example, when we see Sally look at a coffee cup or grasp a hammer, our own motor system provides a signal that anticipates her next action. Previous research has typically examined such gaze and grasp-based simulation processes separately, and it is not known whether similar cognitive and brain systems underpin the perception of object-directed gaze and grasp. Here we use functional magnetic resonance imaging to examine to what extent gaze- and grasp-perception rely on common or distinct brain networks. Using a 'peeping window' protocol, we controlled what an observed actor could see and grasp. The actor could peep through one window to see if an object was present and reach through a different window to grasp the object. However, the actor could not peep and grasp at the same time. We compared gaze and grasp conditions where an object was present with matched conditions where the object was absent. When participants observed another person gaze at an object, left anterior inferior parietal lobule (aIPL) and parietal operculum showed a greater response than when the object was absent. In contrast, when participants observed the actor grasp an object, premotor, posterior parietal, fusiform and middle occipital brain regions showed a greater response than when the object was absent. These results point towards a division in the neural substrates for different types of motor simulation. We suggest that left aIPL and parietal operculum are involved in a predictive process that signals a future hand interaction with an object based on another person's eye gaze, whereas a broader set of brain areas, including parts of the action observation network, are engaged during observation of an ongoing object-directed hand action.     

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.     

Self produced and observed actions influence emotion: the roles of action fluency and eye gaze

Affective responses to objects can be influenced by cognitive processes such as perceptual fluency. Here we investigated whether the quality of motor interaction with an object influences affective response to the object. Participants grasped and moved objects using either a fluent action or a non-fluent action (avoiding an obstacle). Liking ratings were higher for objects in the fluent condition. Two further studies investigated whether the fluency of another person’s actions influences affective response. Observers watched movie clips of the motor actions described above, in conditions where the observed actor could be seen to be looking towards the grasped object, or where the actor’s head and gaze were not visible. Two results were observed: First, when the actor’s gaze cannot be seen, liking ratings of the objects are reduced. Second, action fluency of observed actions does influence liking ratings, but only when the actor’s gaze towards the object is visible. These findings provide supporting evidence for the important role of observed eye gaze in action simulation, and demonstrate that non-emotive actions can evoke empathic states in observers. This research was supported by Economic and Social Research Council grant RES-000-23-0429 awarded to S. P. Tipper and A. E. Hayes.     

Bend it like Beckham: Embodying the motor skills of famous athletes

Observing an action activates the same representations as does the actual performance of the action. Here we show for the first time that the action system can also be activated in the complete absence of action perception. When the participants had to identify the faces of famous athletes, the responses were influenced by their similarity to the motor skills of the athletes. Thus, the motor skills of the viewed athletes were retrieved automatically during person identification and had a direct influence on the action system of the observer. However, our results also indicated that motor behaviours that are implicit characteristics of other people are represented differently from when actions are directly observed. That is, unlike the facilitatory effects reported when actions were seen, the embodiment of the motor behaviour that is not concurrently perceived gave rise to contrast effects where responses similar to the behaviour of the athletes were inhibited.     

Bend it like Beckham: embodying the motor skills of famous athletes

Observing an action activates the same representations as does the actual performance of the action. Here we show for the first time that the action system can also be activated in the complete absence of action perception. When the participants had to identify the faces of famous athletes, the responses were influenced by their similarity to the motor skills of the athletes. Thus, the motor skills of the viewed athletes were retrieved automatically during person identification and had a direct influence on the action system of the observer. However, our results also indicated that motor behaviours that are implicit characteristics of other people are represented differently from when actions are directly observed. That is, unlike the facilitatory effects reported when actions were seen, the embodiment of the motor behaviour that is not concurrently perceived gave rise to contrast effects where responses similar to the behaviour of the athletes were inhibited.     

Authorship effects in the prediction of handwriting strokes: Evidence for action simulation during action perception

Does the action system contribute to action perception? Recent evidence suggests that actions are simulated while being observed. Given that the planning and simulating system are the same only when one observes one's own actions, it might be easier to predict the future outcomes of actions when one has carried them out oneself earlier on. In order to test this hypothesis, three experiments were conducted in which participants observed parts of earlier self- and other-produced trajectories and judged whether another stroke would follow or not. When the trajectories were produced without constraints, participants accomplished this task only for self-produced trajectories. When the trajectories were produced under narrow constraints, the predictions were equally accurate for self- and for other-generated trajectories. These results support the action simulation assumption. The more the actions that one observes resemble the way one would carry them out oneself, the more accurate the simulation.     

Moral Testimony and its Authority

A person sometimes forms moral beliefs by relying on another person's moral testimony. In this paper I advance a cognitivist normative account of this phenomenon. I argue that for a person's actions to be morally good, they must be based on a recognition of the moral reasons bearing on action. Morality requires people to act from an understanding of moral claims, and consequently to have an understanding of moral claims relevant to action. A person sometimes fails to meet this requirement when she relies on another person's moral testimony, and so there are moral limits on such reliance.     

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.     

Sex differences in components of imagined perspective transformation

We explored the impact of motor experience on the interaction between implicit motor simulation and language-processing. In an action familiarity judgment task, expert volleyball players, fans and novices were presented with semantically correct sentences describing possible and not possible motor actions, all as negative or positive contexts, e.g., "Don't shank!" or "Assist!". As processing negated action-phrases is known to reduce simulation states, exposure to negative or positive contexts was used here to test how simulation varies according to motor feasibility (possible, impossible) and experience (experts and fans). A significant group×stimulus×context interaction showed that athletes and fans, took longer to process negative than positive contexts for possible actions, compared to action-impossible sentences. In addition, experts were significantly faster and more accurate than fans and, in turn, they were both more accurate than novices. Thus, implicit motor simulation impacts on action-verb processing depending on (i) the domain-relevant expertise, (ii) the feasibility of the actions, and (iii) on whether scenes are presented in a negated context. These results suggest that the implicit triggering of motor representations is modulated by the context and it is tuned to people's motor repertoire, even when actions are described linguistically.     

镜像神经元的意义

镜像神经元是一种感觉–运动神经元。它的典型特征是在动作观察和动作执行两个阶段皆被激活。多年来, 由于研究伦理的限制, 研究恒河猴时使用的单细胞电极植入方式无法应用于人类, 因而不能确定人类大脑皮层是否也存在着具有同样功能的神经细胞。但是通过脑成像技术, 神经科学家确定人类大脑皮层存在着具有相同或类似功能的脑区, 称为“镜像神经系统”。文章对镜像神经元及其人类镜像神经系统的意义进行了深入分析, 指出：(1)由于镜像机制把动作知觉和动作执行进行匹配, 观察者仅仅通过他人行为的知觉, 就激活了执行这一动作的神经环路, 产生了一种他人动作的具身模拟, 因而可以直接把握他人的行为意图; (2)镜像神经元所表现出来的那种动作知觉与动作执行的双重激活功能支持了身心一体说, 从方法论上证明了身心二元论的缺陷, 为身心的整体观提供了神经生物学的证据; (3)镜像神经机制把他人的动作与自己的运动系统相匹配, 以自身动作的神经环路对他人的动作做出回应, 促进了人际理解和沟通, 成为社会沟通的“神经桥梁”。     

Kinematic cues in perceptual weight judgement and their origins in box lifting

When accepting a parcel from another person, we are able to use information about that person’s movement to estimate in advance the weight of the parcel, that is, to judge its weight from observed action. Perceptual weight judgment provides a powerful method to study our interpretation of other people’s actions, but it is not known what sources of information are used in judging weight. We have manipulated full form videos to obtain precise control of the perceived kinematics of a box lifting action, and use this technique to explore the kinematic cues that affect weight judgment. We find that observers rely most on the duration of the lifting movement to judge weight, and make less use of the durations of the grasp phase, when the box is first gripped, or the place phase, when the box is put down. These findings can be compared to the kinematics of natural box lifting behaviour, where we find that the duration of the grasp component is the best predictor of true box weight. The lack of accord between the optimal cues predicted by the natural behaviour and the cues actually used in the perceptual task has implications for our understanding of action observation in terms of a motor simulation. The differences between perceptual and motor behaviour are evidence against a strong version of the motor simulation hypothesis. A. F. de C. Hamilton and D. W. Joyce have contributed equally to this work.     

Observed reach trajectory influences executed reach kinematics in prehension

Previous studies have demonstrated that the observation of action can modulate motor performance. This literature has focused on manipulating the observed goal of the action, rather than examining whether action observation effects could be elicited by changing observed kinematics alone. In the study presented here, observed reach trajectory kinematics unrelated to the goal of the action were manipulated in order to examine whether observed movement kinematics alone could influence the action of the observer. Participants observed an experimenter grasp a target object using either a normal or an exaggeratedly high reaching action (as though reaching over an invisible obstacle). When participants observed the experimenter perform actions with a high reach trajectory, their own movements took on aspects of the observed action, showing greater wrist height throughout their reaching trajectory than under conditions in which they observed normal reaching actions. The data are discussed in relation to previous findings which suggest that kinematic aspects of observed movements can prime action through kinematic or intention based matching processes.     

Observed reach trajectory influences executed reach kinematics in prehension

Previous studies have demonstrated that the observation of action can modulate motor performance. This literature has focused on manipulating the observed goal of the action, rather than examining whether action observation effects could be elicited by changing observed kinematics alone. In the study presented here, observed reach trajectory kinematics unrelated to the goal of the action were manipulated in order to examine whether observed movement kinematics alone could influence the action of the observer. Participants observed an experimenter grasp a target object using either a normal or an exaggeratedly high reaching action (as though reaching over an invisible obstacle). When participants observed the experimenter perform actions with a high reach trajectory, their own movements took on aspects of the observed action, showing greater wrist height throughout their reaching trajectory than under conditions in which they observed normal reaching actions. The data are discussed in relation to previous findings which suggest that kinematic aspects of observed movements can prime action through kinematic or intention based matching processes.     

Eye movements may cause motor contagion effects

When a person executes a movement, the movement is more errorful while observing another person’s actions that are incongruent rather than congruent with the executed action. This effect is known as “motor contagion”. Accounts of this effect are often grounded in simulation mechanisms: increased movement error emerges because the motor codes associated with observed actions compete with motor codes of the goal action. It is also possible, however, that the increased movement error is linked to eye movements that are executed simultaneously with the hand movement because oculomotor and manual-motor systems are highly interconnected. In the present study, participants performed a motor contagion task in which they executed horizontal arm movements while observing a model making either vertical (incongruent) or horizontal (congruent) movements under three conditions: no instruction, maintain central fixation, or track the model’s hand with the eyes. A significant motor contagion-like effect was only found in the ‘track’ condition. Thus, ‘motor contagion’ in the present task may be an artifact of simultaneously executed incongruent eye movements. These data are discussed in the context of stimulation and associative learning theories, and raise eye movements as a critical methodological consideration for future work on motor contagion.     

The influence of environmental context in interpersonal observation–execution

Cyclical upper-limb movements involuntarily deviate from a primary movement direction when the actor concurrently observes incongruent biological motion. We examined whether environmental context influences such motor interference during interpersonal observation–execution. Participants executed continuous horizontal arm movements while observing congruent horizontal or incongruent curvilinear biological movements with or without the presence of an object positioned as an obstacle or distractor. When participants were observing a curvilinear movement, an object located within the movement space became an obstacle, and, thus, the curvilinear trajectory was essential to reach into horizontal space. When acting as a distractor, or with no object, the curvilinear trajectory was no longer essential. For observing horizontal movements, objects were located at the same relative locations as in the curvilinear movement condition. We found greater involuntary movement deviation when observing curvilinear than horizontal movements. Also, there was an influence of context only when observing horizontal movements, with greater deviation exhibited in the presence of a large obstacle. These findings suggest that the influence of environmental context is underpinned by the (mis-)matching of observed and executed actions as incongruent biological motion is primarily coded via bottom-up sensorimotor processes, whilst the congruent condition incorporates surrounding environmental features to modulate the bottom-up sensorimotor processes.     

A question of intention in motor imagery

We examined the question—is the intention of completing a simulated motor action the same as the intention used in processing overt actions? Participants used motor imagery to estimate distance reachability in two conditions: Imagery-Only (IO) and Imagery-Execution (IE). With IO (red target) only a verbal estimate using imagery was given. With IE (green target) participants knew that they would actually reach after giving a verbal estimate and be judged on accuracy. After measuring actual maximum reach, used for the comparison, imagery targets were randomly presented across peripersonal- (within reach) and extrapersonal (beyond reach) space. Results indicated no difference in overall accuracy by condition, however, there was a significant distinction by space; participants were more accurate in peripersonal space. Although more research is needed, these findings support an increasing body of evidence suggesting that the neurocognitive processes (in this case, intention) driving motor imagery and overt actions are similar.