Top-down social modulation of interpersonal observation–execution

Cyclical upper limb movement can involuntarily deviate from its primary movement axis when the performer concurrently observes incongruent biological motion (i.e. interpersonal observation–execution). The current study examined the social modulation of such involuntary motor interference using a protocol that reflected everyday social interactions encountered in a naturalistic social setting. Eighteen participants executed cyclical horizontal arm movements during the observation of horizontal (congruent) or curvilinear (incongruent) biological motion. Both prior to, and during the interpersonal observation–execution task, participants also received a series of social words designed to prime a pro-social or anti-social attitude. The results showed greater orthogonal movement deviation, and thus interference, for the curvilinear compared to horizontal stimuli. Importantly, and opposite to most of the previous findings from work on automatic imitation and mimicry, there was a greater interference effect for the anti-social compared to pro-social prime condition. These findings demonstrate the importance of interpreting the context of social primes, and strongly support predictions of a comparison between the prime construct and the self-concept/-schema and the top-down response modulation of social incentives.     

Imitative response tendencies following observation of intransitive actions

Clear and unequivocal evidence shows that observation of object affordances or transitive actions facilitates the activation of a compatible response. By contrast, the evidence showing response facilitation following observation of intransitive actions is less conclusive because automatic imitation and spatial compatibility have been confounded. Three experiments tested whether observation of a finger movement (i.e., an intransitive action) in a choice reaction-time task facilitates the corresponding finger movement response because of imitation, a common spatial code, or some combination of both factors. The priming effects of a spatial and an imitative stimulus were tested in combination (Experiment 1), in opposition (Experiment 2), and independently (Experiment 3). Contrary to previous findings, the evidence revealed significant contributions from both automatic imitation and spatial compatibility, but the priming effects from an automatic tendency to imitate declined significantly across a block of trials whereas the effects of spatial compatibility remained constant or increased slightly. These differential effects suggest that priming associated with automatic imitation is mediated by a different regime than priming associated with spatial compatibility.     

Movement observation affects movement execution in a simple response task

The present study was designed to examine the hypothesis that stimulus-response arrangements with high ideomotor compatibility lead to substantial compatibility effects even in simple response tasks. In Experiment 1, participants executed pre-instructed finger movements in response to compatible and incompatible finger movements. A pronounced reaction time advantage was found for compatible as compared to incompatible trials. Experiment 2 revealed a much smaller compatibility effect for less ideomotor-compatible object movements compared to finger movements. Experiment 3 presented normal stimuli (hand upright) and flipped stimuli (hand upside-down). Two components were found to contribute to the compatibility effect, a dynamic spatial compatibility component (related to movement directions) and an ideomotor component (related to movement types). The implications of these results for theories about stimulus-response compatibility (SRC) as well as for theories about imitation are discussed.     

Why does gaze enhance mimicry? Placing gaze-mimicry effects in relation to other gaze phenomena

Eye gaze is a powerful signal, which exerts a mixture of arousal, attentional, and social effects on the observer. We recently found a behavioural interaction between eye contact and mimicry where direct gaze rapidly enhanced mimicry of hand movements ). Here, we report two detailed investigations of this effect. In Experiment 1, we compared the effects of “direct gaze”, “averted gaze”, and “gaze to the acting hand” on mimicry and manipulated the sequence of gaze events within a trial. Only direct gaze immediately before the hand action enhanced mimicry. In Experiment 2, we examined the enhancement of mimicry when direct gaze is followed by a “blink” or by “shut eyes”, or by “occluded eyes”. Enhanced mimicry relative to baseline was seen only in the blink condition. Together, these results suggest that ongoing social engagement is necessary for enhanced mimicry. These findings allow us to place the gaze-enhancement effect in the context of other reported gaze phenomena. We suggest that this effect is similar to previously reported audience effects, but is less similar to ostensive cueing effects. This has important implications for our theories of the relationships between social cues and imitation.     

Attention‐shift vs. response‐priming explanations for the spatial cueing effect in cross‐modal tasks

The task‐irrelevant spatial location of a cue stimulus affects the processing of a subsequent target. This “Posner effect” has been explained by an exogenous attention shift to the spatial location of the cue, improving perceptual processing of the target. We studied whether the left/right location of task‐irrelevant and uninformative tones produces cueing effects on the processing of visual targets. Tones were presented randomly from left or right. In the first condition, the subsequent visual target, requiring response either with the left or right hand, was presented peripherally to left or right. In the second condition, the target was a centrally presented left/right‐pointing arrow, indicating the response hand. In the third condition, the tone and the central arrow were presented simultaneously. Data were recorded on compatible (the tone location and the response hand were the same) and incompatible trials. Reaction times were longer on incompatible than on compatible trials. The results of the second and third conditions are difficult to explain with the attention‐shift model emphasizing improved perceptual processing in the cued location, as the central target did not require any location‐based processing. Consequently, as an alternative explanation they suggest response priming in the hand corresponding to the spatial location of the tone. Simultaneous lateralized readiness potential (LRP) recordings were consistent with the behavioral data, the tone cues eliciting on incompatible trials a fast preparation for the incorrect response and on compatible trials preparation for the correct response.     

The role of emotional context in facilitating imitative actions

In two experiments, we explored whether emotional context influences imitative action tendencies. To this end, we examined how emotional pictures, presented as primes, affect imitative tendencies using a compatibility paradigm. In Experiment 1, when seen index finger movements (lifting or tapping) and pre-instructed finger movements (tapping) were the same (tapping–tapping, compatible trials), participants were faster than when they were different (lifting–tapping, incompatible trials). This compatibility effect was enhanced when the seen finger movement was preceded by negative primes compared with positive or neutral primes. In Experiment 2, using only negative and neutral primes, the influence of negative primes on the compatibility effect was replicated with participants performing two types of pre-instructed finger movements (tapping and lifting). This emotional modulation of the compatibility effect was independent of the participants' trait anxiety level. Moreover, the emotional modulation pertained primarily to the compatible conditions, suggesting facilitated imitation due to negatively valent primes rather than increased interference. We speculate that negative stimuli increase imitative tendencies as a natural response in potential flight-or-fight situations.     

The role of sensorimotor experience in the development of mimicry in infancy

During social interactions we often have an automatic and unconscious tendency to copy or ‘mimic’ others’ actions. The dominant view on the neural basis of mimicry appeals to an automatic coupling between perception and action. It has been suggested that this coupling is formed through associative learning during correlated sensorimotor experience. Although studies with adult participants have provided support for this hypothesis, little is known about the role of sensorimotor experience in supporting the development of perceptual‐motor couplings, and consequently mimicry behaviour, in infancy. Here we investigated whether the extent to which an observed action elicits mimicry depends on the opportunity an infant has had to develop perceptual‐motor couplings for this action through correlated sensorimotor experience. We found that mothers’ tendency to imitate their 4‐month‐olds’ facial expressions during a parent‐child interaction session was related to infants’ facial mimicry as measured by electromyography. Maternal facial imitation was not related to infants’ mimicry of hand actions, and instead we found preliminary evidence that infants’ tendency to look at their own hands may be related to their tendency to mimic hand actions. These results are consistent with the idea that mimicry is supported by perceptual‐motor couplings that are formed through correlated sensorimotor experience obtained by observing one's own actions and imitative social partners.     

Response priming with apparent motion primes

Response priming refers to the finding that a prime stimulus preceding a target stimulus influences the response to the following target stimulus. Typically, responses are faster and more accurate if the prime calls for the same response as the target (i.e., compatible trials), as compared with the situation where primes and targets trigger different responses (i.e., incompatible trials). However, the effect depends on presentational and temporal parameters such as the stimulus onset asynchrony (SOA) of prime and target, or prime duration. Until now, the special role of moving stimuli was largely ignored. In the present research, experiments were conducted using clearly visible moving dots as primes and static arrows as targets. Essentially, with short SOAs up to 200 ms, participants responded faster to compatible targets. In contrast, with SOAs above 200 ms, participants responded faster to incompatible targets. The results were compared with response priming with static primes. Here, a different pattern of results emerged, with faster responses to compatible than incompatible targets at a long SOA of 300 ms. Overall, the experiments provide evidence for the existence of an inhibitory mechanism in action control when (distracting) motion stimuli are present. Results could be explained with slight changes to different accounts of negative response priming effects, as well as theories of attention.     

Automatic imitation of intransitive actions

Previous research has indicated a potential discontinuity between monkey and human ventral premotor-parietal mirror systems, namely that monkey mirror systems process only transitive (object-directed) actions, whereas human mirror systems may also process intransitive (non-object-directed) actions. The present study investigated this discontinuity by seeking evidence of automatic imitation of intransitive actions--hand opening and closing--in humans using a simple reaction time (RT), stimulus-response compatibility paradigm. Left-right and up-down spatial compatibility were controlled by ensuring that stimuli were presented and responses executed in orthogonal planes, and automatic imitation was isolated from simple and complex orthogonal spatial compatibility by varying the anatomical identity of the stimulus hand and response hemispace, respectively. In all conditions, action compatible responding was faster than action incompatible responding, and no effects of spatial compatibility were observed. This experiment therefore provides evidence of automatic imitation of intransitive actions, and support for the hypothesis that human and monkey mirror systems differ with respect to the processing of intransitive actions.     

Sensorimotor fluency influences affect: Evidence from electromyography

Fluency of visual processing induces affective responses, with easier-to-process stimuli being preferred (Winkielman & Cacioppo, 2001). The present study extends this research to the motor domain by investigating the effect of sensorimotor fluency on affective reactions to objects in a categorisation task. In fluent stimulus–response (s–r) trials, grasp-compatible objects were presented on the same side of the screen as the response hand; in non-fluent trials, grasp incompatible objects were presented on the opposite side of the screen to the response hand. Affective responses were measured implicitly using face muscle activity (electromyography). As predicted, participants exhibited greater cheek muscle activity (associated with smiling) in trials with s–r compatible responses compared with incompatible responses. These findings support hedonic models of fluency in which fluent processing elicits direct emotional experience, and suggest that models of hedonic fluency should take into account the integration of the motor system in visual processing.     

Action observation produces motor resonance in Parkinson's disease

Observation of movement activates the observer's own motor system, influencing the performance of actions and facilitating social interaction. This motor resonance is demonstrated behaviourally through visuomotor priming, whereby response latencies are influenced by the compatibility between an intended action and an observed (task‐irrelevant) action. The impact of movement disorders such as Parkinson's disease (PD) on motor resonance is unclear, as previous studies of visuomotor priming have not separated imitative compatibility (specific to human movement) from general stimulus‐response compatibility effects. We examined visuomotor priming in 23 participants with mild‐to‐moderate PD and 24 healthy older adults, using a task that pitted imitative compatibility against general stimulus‐response compatibility. Participants made a key press after observing a task‐irrelevant moving human finger or rectangle that was either compatible or incompatible with their response. Imitative compatibility effects, rather than general stimulus‐response compatibility effects, were found specifically for the human finger. Moreover, imitative compatibility effects did not differ between groups, indicating intact motor resonance in the PD group. These findings constitute the first unambiguous demonstration of imitative priming in both PD and healthy ageing, and have implications for therapeutic techniques to facilitate action, as well as the understanding of social cognition in PD.     

Shaking hands: Priming by social action effects

In a semi‐naturalistic response–effect compatibility paradigm, participants were given the opportunity to learn that hand‐shaking actions would be followed by social effects (human hand‐shaking stimuli from a third‐person perspective) or inanimate effects (block arrow stimuli). Relative to the actions, these effects appeared on the same or the opposite side of the screen (positional compatibility), and pointed towards or away from the response hand (directional compatibility). After learning, response times indicated a positional compatibility effect for both social and inanimate effects, but a directional compatibility effect occurred only for social action effects. These findings indicate that actions can be represented, not only by their effects on the inanimate world, but also by their effects on the actions of others. They are consistent with ideomotor theory, and with the view that actions are represented by bidirectional response–effect associations. They also have implications with respect to the origins and on‐line control of imitation and the systems supporting imitation.     

Tracking hand movements captures the response dynamics of the evaluative priming effect

We tested the response dynamics of the evaluative priming effect (i.e. facilitation of target responses following evaluatively congruent compared with evaluatively incongruent primes) using a mouse tracking procedure that records hand movements during the execution of categorisation tasks. In Experiment 1, when participants performed the evaluative categorisation task but not the non-evaluative semantic categorisation task, their mouse trajectories for evaluatively incongruent trials curved more toward the opposite response than those for evaluatively congruent trials, indicating the emergence of evaluative priming effects based on response competition. In Experiment 2, implementing a task-switching procedure in which evaluative and non-evaluative categorisation tasks were intermixed, we obtained reliable evaluative priming effects in the non-evaluative semantic categorisation task as well as in the evaluative categorisation task when participants assigned attention to the evaluative stimulus dimension. Analyses of hand movements revealed that the evaluative priming effects in the evaluative categorisation task were reflected in the mouse trajectories, while evaluative priming effects in the non-evaluative categorisation tasks were reflected in initiation times (i.e. the time elapsed between target onset and first mouse movement). Based on these findings, we discuss the methodological benefits of the mouse tracking procedure and the underlying processes of evaluative priming effects.     

Mixing location-relevant and irrelevant tasks: Spatial compatibility effects eliminated by stimuli that share the same spatial codes

If compatible and incompatible mappings of left-right stimuli to left-right keypresses are mixed such that participants must maintain both task sets, the typical stimulus-response compatibility (SRC) effect is eliminated. Four experiments examined whether the SRC effect is influenced similarly by inclusion of trials on which stimulus location is irrelevant. The SRC effect for the location-relevant trials was eliminated in Experiments 1 and 3 when those trials shared left-right codes with the location-irrelevant trials. The SRC effect was not eliminated in Experiments 2 and 4, in which the location-relevant stimuli varied along the left-right dimension but the location-irrelevant stimuli were presented in the centre of the screen or in top-bottom locations. The Simon effect for the location-irrelevant trials in Experiments 1 and 3 was positive when the location-relevant mapping was compatible and reversed when it was incompatible. The results are generally consistent with an alternative-routes model, according to which a direct response-selection route is suppressed when compatible trials are mixed with location-irrelevant trials. Repetition analyses suggest that this suppression does not vary on a trial-to-trial basis.     

Seeing how it’s done: matching conditions for observer rats (Rattus norvegicus) in the bidirectional control

In an attempt to increase the reliability of the demonstrator-consistent responding effect produced in the bidirectional control procedure, experiments 1–4 sought conditions that would magnify the matching effect. The aim was to produce a robust demonstrator-consistent responding effect in order that future analytic experiments could investigate the psychological processes responsible for this effect. The joystick responses of observer rats trained using the standard bidirectional control procedure parameters were compared with those of observers subject to conditions identified in the social learning literature as favourable for imitation. Unlike mice, observer rats in experiments 1 a and 1 b tended to push a joystick in the same direction as their demonstrators when the demonstrators were either familiar or unfamiliar males and females. Comparable demonstrator-consistent responding occurred following observation of a standard and a salient joystick response (experiment 2). Experiment 3 showed that the discriminative accuracy of a demonstrator’s responding was important for matching behaviour, and suggested that matching might be enhanced with more than the conventional single observation session. Experiment 4 confirmed that the bidirectional control effect is sensitive to the amount of observational experience; after six observation sessions, demonstrator-inconsistent responding occurs. The results of experiments 1–3 are, and those of experiment 4 are not, compatible with the hypothesis that demonstrator-consistent responding in the bidirectional control is caused by olfactory cues deposited by demonstrators on the joystick. Received: 29 May 2000 / Accepted after revision: 28 August 2000     

Endogenous saccades are preceded by shifts of visual attention: evidence from cross-saccadic priming effects

The present study examines whether endogenous saccades are preceded by shifts of attention. Three experiments are reported in which participants were required to execute a saccadic eye movement to a certain location and to subsequently identify the orientation of a target triangle. Prior to the execution of the saccade a prime was presented, which was compatible or incompatible with the target. A priming effect (faster responses in the compatible condition than in the incompatible condition) occurred only when the prime was presented at the saccade destination, and this effect was larger when the prime was presented during oculomotor programming than when it was presented prior to oculomotor programming. The results indicate that an endogenous shift of attention precedes endogenous saccades, providing further support for theories of visual selection that assume a tight coupling between attention and saccades.     

Effect of prior practice on the stimulus-response compatibility effect in a mixed mapping environment

A stimulus-response compatibility (SRC) effect is obtained when performance is better with compatible mappings than with incompatible mappings. When mappings are mixed within a task, the SRC effect is often eliminated or reversed.The present study examines how 1,600 trials with different practice tasks can affect the response selection process in these mixed mapping environments. Participants were assigned to one of three practice groups: mixed mapping, pure compatible mapping, and pure incompatible mapping. Subsequently, all participants performed an experimental session in which compatible and incompatible trials were mixed.The SRC effect was eliminated in the experimental mixed mapping session, regardless of practice condition. The results suggest that practice does not change the need to suppress the direct response selection route in a mixed mapping task. However, reaction time distributions and sequential analyses were modulated by practice condition, which indicates that the new associations acquired during practice may activate new routes that interact with preexisting ones.     

Farsighted and automatic: Affective stimuli facilitate ultimately compatible approach–avoidance tendencies even in the absence of evaluation goals

Research has shown that affective stimuli automatically trigger responses that ultimately cause a compatible distance change (positive-approach, negative-avoidance), even when this requires an initial movement in the opposite and thus incompatible direction (detour). It is unclear, however, which features of automaticity apply to this effect. The present study investigated whether this effect depends on the goal to evaluate stimulus valence. Participants responded with approach and avoidance movements to affective stimuli. Half of the trials required a detour, i.e., participants initially moved in the direction opposite to the position ultimately intended. The goal of stimulus evaluation was manipulated between participants (present vs. absent). Affective stimuli facilitated ultimately compatible approach–avoidance responses even in the absence of evaluation goals, albeit the effect was larger when evaluation goals were present. The present findings suggest that distance regulation towards and away from affective stimuli is farsighted and automatic at the same time .     

Stimulus and response priming in rapid serial visual presentation: evidence for a dissociation

Two experiments investigated the capacity demands of stimulus and response priming in a rapid serial visual presentation (RSVP) task. Three targets were presented in a stream of visual symbols: The first two (T1 and T2) required an unspeeded manual response at the end of the trial, but the third (T3) called for an immediate,speeded manual response. T2 and T3 either were identical (fully compatible), required the same response (response compatible), or required different responses (incompatible). Priming in the fully compatible condition depended strongly on successful identification of the priming stimulus, whereas response-based priming was observed regardless of whether the prime could be reported or not. These findings suggest that stimulus coding and response coding are automatic processes, unaffected by attentional capacity constraints, followed by capacity-limited stimulus consolidation and response selection. Moreover, even though response codes are activated automatically upon stimulus processing, both types of codes act, and affect behavior, independently.     

Interference and negative priming from ignored distractors: The role of selection difficulty

The relation between distractor interference and negative priming from identical distractors was examined in two experiments. Subjects responded to a target letter, which was indicated by an adjacent bar marker, and attempted to ignore a distracting letter. Onprime trials, distracting letters were either compatible or incompatible with the target, allowing for a measure of interference. On subsequentprobe trials, previously ignored distractors were sometimes presented as targets, allowing for a measure of negative priming. Reducing the spatial separation between targets and distractors on the prime trial increased the magnitude of interferenceand negative priming, but these effects appeared to be independent of each other (Experiment 1). In Experiment 2, the prime target location was precued on some trials, but not on others. Precuing attenuated the magnitude of interference, but not that of negative priming effects. This pattern indicates that measures of negative priming and measures of distractor interference on the immediately preceding trial are independent. The results are discussed in terms of a selective inhibition model of selective attention.