Motor Contagion - Hogrefe eContent - Hogrefe Publishing

Research Article

Motor Contagion Goal-Directed Actions Are More Contagious than Non-Goal-Directed Actions Cédric A. Bouquet,1 Thomas F. Shipley,2 Rémi L. Capa,1 and Peter J. Marshall2 1

Centre de Recherches sur la Cognition et l’Apprentissage – CNRS UMR 6234, University of Poitiers, France, 2Department of Psychology, Temple University, Philadelphia, PA, USA Abstract. Recent theories posit a mirror-matching system mapping observed actions onto one’s own motor system. Determining whether this system makes a distinction between goal-directed and non-goal-directed actions is crucial for the understanding of its function. The present study tested whether motor interference between observed and executed actions, which is thought to be an index of perceptual-motor matching, depends on the presence of goals in the observed action. Participants executed sinusoidal arm movements while observing a video of another person making similar or different movements. In certain conditions, elements representing goals for the observed movement were superimposed on the video displays. Overall, observing an incongruent movement interfered with movement execution. This interference was markedly increased when the observed incongruent movement was directed toward a visible goal, suggesting a greater perceptual-motor matching during observation of goal-directed versus non-goal-directed actions. This finding supports an action-reconstruction model of mirror system function rather than the traditional direct-matching model. Keywords: action observation, automatic imitation, motor resonance, motor contagion

More than 100 years ago, James (1890) suggested that every representation of movement awakes in some degree the movement it represents. In line with this, current theories posit that action perception involves a mirror-matching system, such that observed actions are mapped onto their motor representation in the observer’s motor system (Jeannerod, 2001; Prinz, 1997; Rizzolatti & Craighero, 2004). It has been proposed that this mechanism allows action understanding (Iacoboni et al., 1999; Rizzolatti & Craighero, 2004). In addition, though not sufficient for it, such a mirror-matching system is arguably a plausible mechanism for the human ability to imitate (Brass & Heyes, 2005; Iacoboni, 2009; but see Molenberghs, Cunnington, & Mattingley, 2009). In line with this, several lines of evidence suggest that perceiving the actions of other people activates motoric representations in the observer, creating a tendency to perform the observed action (for review, see Hurley, 2008). Indeed, it is well documented that people tend to mimic others’ facial expressions (Dimberg, 1982; Dimberg, Thunberg, & Elmehed, 2000). Studies have also shown that the motor behavior of individuals often unintentionally matches that of others (Chartrand & Bargh, 1999; Shockley, Santana, & Fowler, 2003). It has been suggested that this kind of unintentional imitation of perceived behaviors favors coordination and cooperation with others (Chartrand & Bargh, 1

1999). This human copying tendency, known as ‘‘motor contagion’’ or perceptual induction, is seen as a special case of imitation,1 namely automatic imitation, occurring because the evoked motor representation of action is not inhibited (Knuf, Aschersleben, & Prinz, 2001; Wilson & Knoblich, 2005). Note that in this context, the imitative response refers to actions which are already in the behavioral repertoire. The discovery of mirror neurons in area F5 of the monkey premotor cortex provides a possible neural mechanism for the matching function described above (Rizzolatti, Fogassi, & Gallese, 2001). Mirror neurons fire when a monkey performs object-directed actions, such as grasping or manipulating, but also when the animal observes another individual, either a conspecific or a human experimenter, performing the same class of actions. Importantly, these neurons respond only to transitive – goal-oriented – actions and not to intransitive movements (Rizzolatti & Craighero, 2004; Rizzolatti et al., 2001). In human beings, following the idea that the automatic tendency to imitate results from the activation of a motoric representation in the observer, behavioral studies have used the influence of observed body movements as an index of mirror-matching system functioning. Several recent studies showed that observing a movement primes the execution of that movement, thereby interfering with the execution of another movement (for reviews, see Blakemore & Frith,

In other conceptual frameworks motor contagion would be more related to mimicry rather than imitation (e.g., Tomasello, Kruger, & Ratner, 1993), but functionally, both phenomena can be seen as involving a common process of imitation based on the automatic activation of motor representations by movement observation (Brass & Heyes, 2005; Hurley, 2008).

2010 Hogrefe Publishing

Experimental Psychology 2011; Vol. 58(1):71–78 DOI: 10.1027/1618-3169/a000069

72

C.A. Bouquet et al.: Motor Interference From Goal-Directed Actions

2005; Wilson & Knoblich, 2005). Here the observer’s behavior does not match the observed action but is modified by the observation of a different action. The interference between observed and executed actions can be explained in terms of perceptual-motor matching as follows: The observed action activates the representation of motor commands for that same action within the motor system of the observer, which interferes with the performance of the concurrently executed incongruent action (Blakemore & Frith, 2005; Kilner, Paulignan, & Blakemore, 2003). This motor interference effect, where an observed action interferes with a concurrently executed incongruent action, is thus a particular case of motor contagion which is thought to provide an index of mirror-matching system activity. Several studies have suggested that motor interference reflects mirror-matching system activity, and is not simply due to other factors like increased attentional demands or a spatial-compatibility effect of observing an incongruent movement (e.g., Berthenthal, Longo, & Kosobud, 2006; Kilner et al., 2003; Press, Bird, Flach, & Heyes, 2005). Notably, some studies have successfully dissociated the behavioral effect of observing biological motion from that induced by the observation of nonbiological motion (Bouquet, Gaurier, Shipley, Toussaint, & Blandin, 2007; Kilner et al., 2003; Press, Gillmeister, & Heyes, 2007; Press et al., 2005; Stanley, Gowen, & Miall, 2007). For example, in the Kilner et al. (2003) study, the participants’ movements were subject to interference from an observed incongruent movement executed by a human agent, while their movements were unimpaired by simultaneous observation of incongruent movements executed by a robotic arm. The prevailing interpretation for these effects is that motor interference is restricted to or increased during observation of biological – and potentially imitable – stimuli because the nonbiological stimuli cannot be mapped onto the observer’s own motor representations (but see Jansson, Wilson, Williams, & Mon-Williams, 2007). These results and other related forms of automatic imitation are often cited as a compelling behavioral evidence of mirror-matching system activity (e.g., Blakemore & Frith, 2005; Rizzolatti & Craighero, 2004; Wilson & Knoblich, 2005). Importantly, this motor interference effect has been demonstrated in human beings during the observation of meaningless or intransitive movements (e.g., Blakemore & Frith, 2005; Bouquet et al., 2007; Gowen, Stanley, & Miall, 2008; Kilner et al., 2003; Press, Bird, Walsh, & Heyes, 2008). For example, Press et al. (2008) found evidence of automatic imitation of intransitive actions – hand opening and closing – in a stimulus-response task. Similarly, Kilner et al.’s (2003) results demonstrate that observing Non-goaldirected human arm movements significantly interferes with ongoing executed movements (see also Bouquet et al., 2007; Gowen et al., 2008; Stanley et al., 2007). Thus, it appears that observing intransitive or non-goal-directed movements causes a form of ‘‘motor contagion’’ that interferes with the execution of movements. Thus, while the presence of objects seems to be a necessary condition for activity in the monkey mirror neuron system, studies in human beings suggest that the human mirror-matching system may respond to non-goal-oriented Experimental Psychology 2011; Vol. 58(1):71–78

actions. However, this does not necessarily mean that the human mirror-matching system processes goal-directed and non-goal-directed actions in an identical manner. One way to show this is to demonstrate that motor interference, as an index of perceptual-motor matching, varies with the presence/absence of a target for the observed action. Specifically, if the human mirror-matching system exhibits a greater response to goal-directed actions, thus sharing common properties with the monkey mirror system, motor interference should be larger during observation of goal-directed actions. We tested this prediction by modifying an established paradigm for inducing motor interference (Bouquet et al., 2007; Kilner et al., 2003; Stanley et al., 2007). We had participants make sinusoidal horizontal arm movements while observing different video sequences. In the Incongruent/Non-goal-directed condition, participants observed a video of a human actor making vertical sinusoidal arm movements (see Figure 1). In the Incongruent/Goaldirected condition, participants saw the same video, but with two red dots added at the endpoints of the actor’s vertical arm movements, such that the dots represented visible object goals for the observed movement (the outcome was thus a movement pointing back and forth between the two dots). In the Incongruent/Dot-Only condition, the participants saw the two red dots, but no movement was executed by the actor in the video. This latter condition allowed an estimation of the effects of the observed movement in the two other conditions, with any difference revealing motor interference. In the Congruent conditions, the observed movement executed by the actor was horizontal. We hypothesized that any increased interference effect in the Goal-directed condition, relative to the Non-goal directed condition, could be ascribed to differential mirror-matching system activity, with the condition that the increased effect was not due to an effect of dots per se. Although the contextual processing of visual information during movement execution remains somewhat controversial (Goodale & Haffenden, 1998; Welsh & Elliott, 2005), we had to ascertain that any increased interference effect in the Goal-directed condition, relative to the Non-goal-directed condition, was not due to an effect of the dots per se. In order to evaluate the possible impact of the mere presence of dots on the observer’s behavior, performance in the Dot-Only conditions (where only these dots were present) was compared with performance in a baseline condition where participants executed movements while observing a video sequence of the actor executing no movement, with no dots added. In the Congruent condition, the two dots aligned in the horizontal axis may help the participants to represent a ‘‘virtual’’ horizontal line, favoring movement execution on a straight line (Carrozzo, Stratta, McIntyre, & Lacquaniti, 2002). This may also help participants to code movement endpoints in both egocentric and allocentric frames of references (Ketcham, Dounskaia, & Stelmach, 2006; Krigolson & Heath, 2004), again reducing variability in movement trajectory or endpoint. In contrast, the presence of dots on an axis orthogonal to the executed movements in the Incongruent/Dot-Only condition may interfere with movement execution, since nontarget objects have been found to influence movement trajectory (Welsh & Elliott, 2005). 2010 Hogrefe Publishing


73

Figure 1. Experimental Design. The participants made sinusoidal horizontal movements of the right arm, while observing different video sequences. In the Incongruent/Non-goal-directed and Congruent/Non-goal-directed conditions, participants observed a video of a human being making vertical movements and horizontal movements, respectively. In the Incongruent/Goal-directed and Congruent/Goal-directed conditions, two red dots were added on the video sequence, at the level of endpoints of the actor’s arm movements, such that they represented targets for the observed movement. In the Incongruent/Dot-Only and Congruent/Dot-Only conditions, the participants observed the two red dots, but no movement was executed by the actor on the video. Thus, it was important to quantify the effect of the mere presence of the dots on the observer’s behavior, relative to a baseline condition where no dots and no movement were observed.

Method Participants Twenty-four healthy, right-handed, naive volunteers (12 females; age range 19–25 years) participated. The experiment was approved by the local ethics committee and was conducted in accordance with the Declaration of Helsinki. All participants had normal or corrected-to-normal vision, reported themselves to be right-handed, and were unaware of the experimental goals. Each participant read and signed an informed consent form prior to taking part in the experiment.

(moving from the shoulder). The actor stood upright with the right arm outstretched (see Figure 1). Vertical movements consisted of moving the arm from top to bottom at a rate of 0.5 Hz, such that the resulting amplitude of hand displacement was approximately 80 cm. Horizontal movements involved moving the arm from left to right at a rate of 0.5 Hz such that the resulting amplitude of the hand displacement was approximately 70 cm. Sequences of 10 sinusoidal horizontal movements and 10 sinusoidal vertical movements were filmed using a Sony video camera (CCD-TR515E) with the actor facing the camera. A sequence of the actor being still was also recorded. The video capture did not include the model’s legs. The video sequences were projected onto a 180 · 140 cm screen (using a projector that had a temporal resolution of 60 Hz) such that the projected size of the actor corresponded to his actual size (170 cm high). In the video sequences, the actor’s eyes were covered with a thin black rectangle.

Task and Procedure Motion Capturing Participants wore an infrared light-emitting diode attached to the edge of the right hand at the level of the fifth metacarpus. An Optotrak CertusTM recording system (Northern Digital, Waterloo, Ontario, Canada) recorded three-dimensional coordinates (x, y, and z) of this marker. Data were low-pass filtered at 10 Hz with a second-order Butterworth filter.

Stimuli Participants observed video sequences of an actor making horizontal or vertical movements. The actor was a female experimenter who had been extensively trained to make vertical and horizontal sinusoidal movements of the right arm 2010 Hogrefe Publishing

Participants faced the screen at a viewing distance of approximately 230 cm. Only horizontal movements were executed by the participants. They were required to make sinusoidal horizontal movements of the right arm, as described above for the actor, while observing the video sequences. In the Non-goal-directed conditions, participants observed the basic video sequences described above: In the Incongruent/Non-goal-directed condition, they observed a video sequence of vertical movements; in the Congruent/ Non-goal-directed condition, they observed a video sequence of horizontal movements. In the Goal-directed conditions, participants observed the same video sequences, but a circular red dot (9 cm diameter as displayed) was superimposed on the video at the level of each endpoint of the actor’s arm movements (Figure 1). In the Dot-Only conditions, the observed video sequences were the same Experimental Psychology 2011; Vol. 58(1):71–78

74


as in the previous Goal-directed conditions, with the actor making no movement: The dots that served as goals in the Congruent/Goal-directed condition and those that served as goals in the Incongruent/Goal-directed condition were observed in the Congruent/Dot-Only condition and Incongruent/Dot-Only condition, respectively. The order of these conditions was counterbalanced across participants. Before and after these conditions, the participants executed the arm movements in a baseline control condition where they observed a video sequence of the actor being still, without any dots. Participants performed two identical sessions. Each session consisted of two trials in each condition. One trial consisted of 10 sinusoidal movements. For both the Congruent and Incongruent conditions, participants were further instructed to watch the hand of the actor. Participants were also asked to start their movement when the actor started to move his arm and then to make their movements in time with those of the actor. Before the experimental phase, participants were familiarized with the task and learned the movement patterns. During this training phase, each participant learned the movement patterns first with a metronome providing pulses at a rate of 0.5 Hz. Then, when the participant performed sinusoidal movements at a rate of 0.5 Hz, the metronome was switched off, and the participant was instructed to maintain the same rate.

Dependent Measures and Data Analysis As participants were instructed to move their arm horizontally on a straight line, the variability in the vertical axis (y-deviation) of movement trajectory and movement end-point were used as dependent variables. These two variables reflect different parameters of movement coded by distinct neuron populations within the motor system (Scheidt & Ghez, 2007). To calculate overall variability in movement trajectory, we calculated the sum of squares deviation from the mean for each y-coordinate. To calculate variability of movement endpoints, the data were split into segments of motion. With each trial consisting of 10 sinusoidal movements, this resulted in 10 discrete movements from left to right and 10 discrete movements from right to left. We then calculated the sum of squares deviation from the mean for each endpoint y-coordinate. For each condition the means of the movement trajectory and end-point variances were calculated across all trials and averaged across sessions. To better appreciate the interference effect, we computed an Interference Score (IS) by subtracting the values for Goal-directed and Non-goal-directed congruent performances from the values for performances in Incongruent conditions.

Statistical Analysis All analyses were conducted in Statistica 7.0 (Statsoft; Tulsa, USA). A repeated measures ANOVA with Experimental Psychology 2011; Vol. 58(1):71–78

Congruency (Congruent and Incongruent) and Movement Type (Goal-directed, Non-goal-directed, and Dot-Only) as within-subjects factors was conducted on trajectory and endpoint variability. Significant effects were examined further using planned contrasts. Comparisons with baseline measures and comparisons of IS scores were made using t tests. Corrections (Bonferroni) with respect to multiple comparisons were applied.

Results Preliminary analyses including sex as a between-participants factor indicated no significant sex differences in the following effects.

Trajectory Variability Variability in the Incongruent Dot-Only condition did not differ from baseline control measures, t(23) = .03, p > .97. In contrast, trajectory variability was reduced in the Congruent Dot-Only condition compared to baseline, t(23) = 2.56, p < .05. The repeated measures ANOVA with Congruency (Congruent and Incongruent) and Movement Type (Goal-directed, Non-goal-directed, and Dot-Only) as within-subjects factors revealed a significant effect of Congruency, F(1, 23) = 14.45, p < .0001, g2p = .38, which interacted with Movement Type, F(2, 46) = 3.51, p < .05, g2p = .13. Planned contrasts revealed a significant effect of Movement Type in the Incongruent condition, F(2, 46) = 15.09, p < .0001, g2p = .40, but not in the Congruent condition, F(2, 46) = 1.13, p > .33. For Incongruent conditions, planned comparisons revealed that trajectory variability in the Incongruent/Nongoal-directed condition was larger than in the Dot-Only condition, F(1, 23) = 18.17, p < .001, g2p = .44 and trajectory variability in the Incongruent/Goal-directed condition tended to be larger than that measured in the Incongruent/Nongoal-directed condition, F(1, 23) = 3.66, p = .07, g2p = .14. The amplitude of the IS computed for Goal-directed condition was larger than the IS for Non-goal-directed condition (97 vs. 66), but the difference did not reach significance, t(23) = 1.49, p = .15.

End-Point Variability The Incongruent Dot-Only condition was not associated with variability significantly different from baseline control measures, t(23) = .98, p > .33 (Table 1). In contrast, endpoint variability was significantly lower in the Congruent Dot-Only condition compared to baseline, t(23) = 3.52, p < .01. The repeated measures ANOVA with Congruency (Congruent and Incongruent) and Movement Type (Goal-directed, Non-goal-directed, and Dot-Only) as within-subjects factors revealed a significant effect of Congruency, 2010 Hogrefe Publishing


Table 1. Quality of movement execution in the different conditions indexed by trajectory variability and end-point variability in the vertical axis Trajectory variability

End-point variability

Baseline control

206 (111)

181 (68)

Congruent Transitive Intransitive Dot-Only

206 (107) 209 (110) 183 (106)

157 (75) 175 (77) 152 (71)

Incongruent Transitive Intransitive Dot-Only

303 (158) 275 (136) 207 (101)

268 (93) 227 (71) 170 (59)

Note. Variability is given in mm2 (standard error in parentheses).

F(1, 23) = 28.47, p < .0001, g2p = .55. The effect of Congruency interacted with Movement Type, F(2, 46) = 11.22, p < .001, g2p = .32. The effect of Movement type was modulated by Congruency. Planned contrasts revealed a significant effect of Movement Type in the Incongruent condition, F(2, 46) = 25.18, p < .0001, g2p = .52, but not in the Congruent condition, F(2, 46) = 1.09, p > .34. For Incongruent conditions, planned comparisons revealed a significant increase of end-point variability in the Incongruent/Non-goal-directed condition compared to the Dot-Only condition, F(1, 23) = 51.30, p < .001, g2p = .51, and a significant increase of end-point variability in the Incongruent/Goal-directed condition, compared to the Incongruent/Non-goal-directed condition, F(1, 23) = 6.52, p < .05, g2p = .22. The IS computed for Goal-directed condition was larger than the IS for Non-goal-directed condition (111 vs. 53), t(23) = 3.29, p < .005. Overall, the Incongruent Dot-Only condition decreased variability compared to baseline measures. A closer inspection of the data indicates that in the first session, end-point variability slightly increased in the Incongruent Dot-Only condition compared to baseline (193 vs. 181), t < 1. We thus conducted a more stringent post hoc analysis, restricted to the first session, with the Incongruent Dot-Only minus Baseline difference subtracted from the IS for Incongruent/ Goal-directed condition. This allowed us to test whether the effect was still present, once this effect associated with the Dot-Only condition was subtracted from the IS for Incongruent-Goal-directed condition (note that this analysis was inappropriate in the second session as the end-point variability was decreased in the Incongruent Dot-Only condition compared to baseline). The analysis showed that IS for end-point variability was still larger in the Goal-directed than the Non-goal-directed condition (135 vs. 51), t(23) = 3.46, p < .005.

Discussion This study investigated whether the goal-directed nature of observed movements has an impact on interference between 2010 Hogrefe Publishing

75

perception and action. In line with previous studies (Bouquet et al., 2007; Kilner et al., 2003; Stanley et al., 2007), observing a congruent movement, either goal-directed or non-goaldirected, had no effect on movement execution, while observing an incongruent movement interfered with movement execution. In the congruent conditions, where observed and executed movements were similar, one might have expected the match between observer’s and actor’s behaviors to facilitate movement execution, compared to the Dot-Only condition. A significant facilitation effect might have been counteracted by floor effects or masked by an increased attentional demand associated with synchronization with the observed movements (for a discussion of this result, see Bouquet et al., 2007; Kilner et al., 2003). Our main finding is that the amount of interference between an executed movement and a concurrently observed incongruent movement is modulated by the presence/absence of goals for the observed movement: seeing a goal-directed movement induced a higher level of motor interference than seeing the same movement without a goal. Studies show that when participants are explicitly instructed to imitate what a model did, participants tend to imitate ends (goals) rather than means (movements) (Bekkering, Wohlschla¨ger, & Gattis, 2000; Wohlschla¨ger & Bekkering, 2002). In our study, imitation was not an essential or explicit aspect of the task. Considering that motor contagion reflects the motor representation evoked by the perceived action in the observer, our results suggest that the perceptual-motor matching of an observed action is facilitated when seeing a movement aiming at a visible goal in the environment, compared to seeing only the movement. In the Goal-directed and Non-goal-directed conditions, the participants observed the same movements, but in the Goal-directed condition, two dots were superimposed on the video sequence. Importantly, the Incongruent/Dot-Only condition, where only these dots were present but movement was absent, was not associated with increased movement variability, compared to a baseline control condition where participants observed a video sequence of the actor executing no movement, with no dots added. Thus this suggests that the increased motor contagion in the incongruent Goal-directed condition compared to the incongruent Nongoal-directed condition was not merely due to spatialcompatibility effects induced by the additional presence of dots on an axis orthogonal to the executed movements. Other arguments support this view, including the observation that orthogonal spatial-compatibility effects have been reported in reaction time tasks (Weeks & Proctor, 1990). In the present study, where we focused on trajectory of cyclical arm movements, the potential influence of the dots per se in the Incongruent/Goal-directed condition was instead related to the influence of visual background on feedback-based control of visually guided movements. In fact, nontarget objects have been found to cause a deviation of pointing movements (Welsh & Elliott, 2005), although some studies have shown that a structured visual background can lead to straighter hand paths (Krigolson & Heath, 2004; Toni, Gentilucci, Jeannerod, & Decety, 1996). In addition, the influence of nontarget objects has been found mainly in memory-guided reaching (for review, see Carrozzo Experimental Psychology 2011; Vol. 58(1):71–78

76


et al., 2002). In the present study, the type of executed movement (visually guided, not requiring unexpected readjustments) and the fact that the dots were not potential target locations for the participant (even though they were for the actor in the video) are conditions where nontarget objects do not interfere with the movement (Welsh & Elliott, 2005). Overall, this suggests that the increased motor contagion during the observation of an incongruent movement directed to visible goals was due to the goal-directed nature of the observed movement. Previous work using a similar paradigm to the current study has shown that interference between executed and observed actions is absent or reduced when the observed movement is nonbiological in origin (Bouquet et al., 2007; Kilner et al., 2003), suggesting that motor interference in our task reflects mirror-matching system activity rather than simple spatial-compatibility effects. In fact, the finding that motor interference is increased for the observation of Goal-directed actions compared to Non-goal-directed actions cannot be explained within an interpretative framework of motor interference arising from spatial-compatibility effects (Jansson et al., 2007). Some brain imaging studies have shown that meaningful hand-object interactions are more effective than intransitive actions in activating Broca’s area or parietal cortex (Buccino et al., 2001; Gre`zes, Costes, & Decety, 1998; Johnson-Frey et al., 2003). However, it is unclear whether this activity reflects motor resonance (Hamzei et al., 2003; Johnson-Frey et al., 2003), and contradictory results have been reported (Villarreal et al., 2008). In addition, in brain imaging studies contrasting viewing of transitive movements with viewing of intransitive movements, the two types of movement also differed in term of kinematics (Buccino et al., 2001; Gre`zes et al., 1998; Villarreal et al., 2008). In the present study, participants observed the same movement with or without goals, with the finding that goal-directed actions were more effective than non-goal-directed actions in triggering motor interference. The increased motor interference effect during observation of goal-directed actions can be conceived of as an increased response within the motor system, suggesting that the presence of goals for the observed movement affects the perceptual-motor matching of this movement. The existence in human beings of a neural network with similar properties to monkey mirror neurons is a matter of some debate (e.g., Turella, Pierno, Tubaldi, & Castiello, 2009). Furthermore, evidence of motor contagion during observation of intransitive actions has fueled the hypothesis that the human mirror-matching system differs from the analogous mirror neuron system in monkeys in its sensitivity to both transitive and intransitive actions (Blakemore & Frith, 2005; Press et al., 2008; Rizzolatti & Craighero, 2004). In the present study, we have no direct evidence that the effects were mediated by the fronto-parietal cortical areas – mirror-matching system – previously found to be involved in action execution and perception in human beings (Rizzolatti & Craighero, 2004). Indeed, other systems supporting imitation may also have been involved (see Hickok, 2009). Furthermore, one might question whether, in the present study, the superimposed dots were really perceived as Experimental Psychology 2011; Vol. 58(1):71–78

potential movement targets. However, other results show that the presence of such targets for the observed movement can affect imitation of discrete finger movements (Wohlschla¨ger & Bekkering, 2002). Then, the dots only did not modify movement execution in the Incongruent/ Dot-Only condition, compared to the neutral condition (see above). This thus suggests that this is the Dot + Movement combination that impacted the observer’s behavior in the Incongruent/Goal-directed condition. Finally, neuroimaging results suggest that the modulation of the interference effect by the presence of such superimposed dots may reflect changes in activity in premotor areas (Koski et al., 2002). Whatever the underlying neural networks involved, our results suggest that the system supporting perceptual-motor matching in human beings may exhibit a greater response to goal-directed actions. This may indicate that this system shares common properties with the monkey mirror system (Rizzolatti & Craighero, 2004; Rizzolatti et al., 2001). However, caution is needed, since the goal-directed actions observed in the present study were not object-directed or meaningful actions, like those known to trigger mirror responses in the monkey. In addition, this raises the question of the importance of the target directedness versus transitivity of object-oriented actions in the triggering of mirror system responses in humans versus monkeys (Rizzolatti et al., 2001). In the same way, motor contagion induced by the observation of non-goal-directed and meaningless body movements, as in our Incongruent/Non-goal-directed condition, has been interpreted as evidence that the human mirrormatching system is sensitive to intransitive actions (Blakemore & Frith, 2005; Press et al., 2008). Yet, one must keep in mind that there is some doubt (without challenging the main conclusion of the present study) about what can be considered as an intransitive or meaningless movement in the context of any study investigating the perception of action, because such a movement may become meaningful within the framework of the experiment. The present results have significant implications regarding theories of mirror-matching system function. The directmatching hypothesis of mirror-matching system function posits that viewing an action automatically evokes a motoric representation in the observer of the motor commands necessary to execute that same action, allowing the observer to understand the underlying goals (Iacoboni et al., 1999; Rizzolatti & Craighero, 2004; Rizzolatti et al., 2001). Within the direct-matching framework, since the mapping of kinematics of the observed movement onto an internal motor representation precedes goal understanding, a movement aiming at a visible goal or the same movement without a goal should evoke the same motor representation in the observer’s motor system. Our findings, suggesting that the perceptual-motor mapping of an incongruent movement aimed at a visible goal differs from that of the same movement without a goal, may contradict this hypothesis. Alternatively, they rather support the action-reconstruction hypothesis (Csibra, 2008; Southgate, Johnson, & Csibra, 2008), according to which some understanding of the goal of the observed action precedes the mapping of the observed action onto motor representations in the observer. From this perspective, 2010 Hogrefe Publishing


understanding of the goal of the observed action would be inferred through cognitive processes occurring outside the mirror system itself (Brass, Schmitt, Spengler, & Gergely, 2008; Pelphrey & Morris, 2006), the function of which is to allow action anticipation for coordination with others (see also Wilson & Knoblich, 2005). In summary, in line with other studies on more explicit forms of human imitation, we found that the influence of an observed movement on the observer’s behavior is modulated by the presence or absence of goals in the observed movement. Assuming this motor interference effect is an index of mirror-matching system activity, we interpret these results as evidence that a goal-oriented movement triggers a greater response within the motor system than the same movement without a goal. This result provides support for recent theoretical frameworks of mirror system functioning. Acknowledgments We wish to thank Dr R. Salesse for his help in processing and analysis of the data. We also thank Timothy Welsh and two anonymous reviewers for their comments and advice on this work.

References Bekkering, H., Wohlschla¨ger, A., & Gattis, M. (2000). Imitation of gestures in children is goal-directed. Quarterly Journal of Experimental Psychology A, 53, 153–164. Berthenthal, 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. Blakemore, S., & Frith, C. (2005). The role of motor contagion in the prediction of action. Neuropsychologia, 43, 260–267. Bouquet, C. A., Gaurier, V., Shipley, T., Toussaint, L., & Blandin, Y. (2007). Influence of the perception of biological or non-biological motion on movement execution. Journal of Sports Sciences, 25, 519–530. Brass, M., & Heyes, C. (2005). Imitation: Is cognitive neuroscience solving the correspondence problem? Trends in Cognitive Sciences, 9, 489–495. Brass, M., Schmitt, R. M., Spengler, M., & Gergely, G. (2008). Investigating action understanding: Inferential processes versus action simulation. Current Biology, 17, 2117–2121. Buccino, G., Binkofski, F., Fink, G. R., Fadiga, L., Fogassi, L., Gallese, V., et al. (2001). Action observation activates premotor and parietal areas in a somatotopic manner: An fMRI study. European Journal of Neuroscience, 13, 400– 404. Carrozzo, M., Stratta, F., McIntyre, J., & Lacquaniti, F. (2002). Cognitive allocentric representations of visual space shape pointing errors. Experimental Brain Research, 147, 426–436. 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. Csibra, G. (2008). Action mirroring and action understanding: An alternative account. In P. Haggard, Y. Rosetti, & M. Kawato (Eds.), Attention & performance XXII (pp. 435–459). Oxford, UK: Oxford University Press. Dimberg, U. (1982). Facial reactions to facial expressions. Psychophysiology, 19, 643–647.


77

Dimberg, U., Thunberg, M., & Elmehed, K. (2000). Unconscious facial reactions to emotional facial expressions. Psychological Science, 11, 86–89. Goodale, M. A., & Haffenden, A. (1998). Frames of reference for perception and action in the human visual system. Neuroscience and Biobehavioral Reviews, 22, 161–172. Gowen, E., Stanley, J., & Miall, R. C. (2008). Movement interference in autism spectrum disorder. Neuropsychologia, 46, 1060–1068. Gre`zes, J., Costes, N., & Decety, J. (1998). Top down effect of the strategy on the perception of human biological motion: A PET investigation. Cognitive Neuropsychology, 15, 553–582. Hamzei, F., Rijntjes, M., Dettmers, C., Glauche, V., Weiller, C., & Buchel, C. (2003). The human action recognition system and its relationship to Broca’s area: An fMRI study. Neuroimage, 19, 637–644. Hickok, G. (2009). Eight problems for the mirror neuron theory of action understanding in monkeys and humans. Journal of Cognitive Neuroscience, 21, 1229–1243. Hurley, S. (2008). The shared circuits model (SCM): How control, mirroring, and simulation can enable imitation, deliberation, and mindreading. Behavioral and Brain Sciences, 31, 1–58. Iacoboni, M. (2009). Imitation, empathy, and mirror neurons. Annual Review of Psychology, 60, 653–670. Iacoboni, M., Woods, R. P., Brass, M., Bekkering, H., Mazziotta, J. C., & Rizzolatti, G. (1999). Cortical mechanisms of human imitation. Science, 286, 2526–2528. James, W. (1890). The principles of psychology. London: Macmillan. Jansson, E., Wilson, A. D., Williams, J. H., & Mon-Williams, M. (2007). Methodological problems undermine tests of the ideo-motor conjecture. Experimental Brain Research, 182, 549–558. Jeannerod, M. (2001). Neural simulation of action: A unifying mechanism for motor cognition. Neuroimage, 14, S103– S109. Johnson-Frey, S. H., Maloof, F. R., Newman-Norlund, R., Farrer, C., Inati, S., & Grafton, S. T. (2003). Actions or hand-object interactions? Human inferior frontal cortex and action observation. Neuron, 39, 1053–1058. Ketcham, C. J., Dounskaia, N. V., & Stelmach, G. E. (2006). The role of vision in the control of continuous multijoint movements. Journal of Motor Behavior, 38, 29–44. Kilner, J. M., Paulignan, Y., & Blakemore, S. J. (2003). An interference effect of observed biological movement on action. Current Biology, 13, 522–525. Knuf, L., Aschersleben, G., & Prinz, W. (2001). An analysis of ideomotor action. Journal of Experimental Psychology: General, 130, 779–798. Koski, L., Wohlschla¨ger, A., Bekkering, H., Woods, R. P., Dubeau, M.-C., Mazziotta, J. C., et al. (2002). Modulation of motor and premotor activity during imitation of targetdirected actions. Cerebral Cortex, 12, 847–855. Krigolson, O. E., & Heath, M. (2004). Background visual cues and memory-guided reaching. Human Movement Science, 23, 861–877. Molenberghs, P., Cunnington, R., & Mattingley, J. (2009). Is the mirror neuron system involved in imitation? A short review and meta-analysis. Neuroscience and Biobehavioral Reviews, 33, 975–980. Pelphrey, K. A., & Morris, J. P. (2006). Brain mechanisms for interpreting the actions of others from biological motion cues. Current Directions in Psychological Sciences, 15, 136– 140. Press, C., Bird, G., Flach, R., & Heyes, C. M. (2005). Robotic movement elicits automatic imitation. Cognitive Brain Research, 25, 632–640.

Experimental Psychology 2011; Vol. 58(1):71–78

78


Press, C., Bird, G., Walsh, E., & Heyes, C. (2008). Automatic imitation of intransitive actions. Brain and Cognition, 67, 44–50. Press, C., Gillmeister, H., & Heyes, C. (2007). Sensorimotor experience enhances automatic imitation of robotic action. Proceedings of the Royal Society London B: Biological Sciences, 274, 2509–2514. Prinz, W. (1997). Perception and action planning. European Journal of Cognitive Psychology, 9, 129–154. Rizzolatti, G., & Craighero, L. (2004). The mirror-neuron system. Annual Review of Neuroscience, 27, 169–192. Rizzolatti, G., Fogassi, L., & Gallese, V. (2001). Neurophysiological mechanisms underlying the understanding and imitation of action. Nature Reviews Neuroscience, 2, 661–670. Scheidt, R. A., & Ghez, C. (2007). Separate adaptive mechanisms for controlling trajectory and final position in reaching. Journal of Neurophysiology, 98, 3600–3613. Shockley, K., Santana, M.-V., & Fowler, C. A. (2003). Mutual interpersonal postural constraints are involved in cooperative conversation. Journal of Experimental Psychology: Human Perception and Performance, 29, 326–332. Southgate, V., Johnson, M. H., & Csibra, G. (2008). Infants attribute goals to even biologically impossible actions. Cognition, 107, 1059–1069. Stanley, J., Gowen, E., & Miall, R. C. (2007). Effects of agency on movement interference during observation of a moving dot stimulus. Journal of Experimental Psychology: Human Perception and Performance, 33, 915–926. Tomasello, M., Kruger, A., & Ratner, H. (1993). Cultural learning. Behavioral and Brain Sciences, 16, 495–552. Toni, I., Gentilucci, M., Jeannerod, M., & Decety, J. (1996). Differential influence of the visual framework on the end point accuracy and trajectory specification of arm movements. Experimental Brain Research, 111, 447–454. Turella, L., Pierno, A. C., Tubaldi, F., & Castiello, U. (2009). Mirror neurons in humans: Consisting or confounding evidence? Brain & Language, 108, 10–21.

Experimental Psychology 2011; Vol. 58(1):71–78

Villarreal, M., Fridman, E. A., Amengual, A., Falasco, G., Gerscovich, E. R., Ulloa, E. R., et al. (2008). The neural substrate of gesture recognition. Neuropsychologia, 46, 2371–2382. Weeks, D. J., & Proctor, R. W. (1990). Salient-features coding in the translation between orthogonal stimulus and response dimensions. Journal of Experimental Psychology: General, 119, 355–366. Welsh, T., & Elliott, D. (2005). The effects of response priming on the planning and execution of goal-directed movements in the presence of a distracting stimulus. Acta Psychologica, 119, 123–142. Wilson, M., & Knoblich, G. (2005). The case for motor involvement in perceiving conspecifics. Psychological Bulletin, 131, 460–473. Wohlschla¨ger, A., & Bekkering, H. (2002). Is human imitation based on a mirror-neurone system? Some behavioural evidence. Experimental Brain Research, 143, 335–341.

Received August 23, 2009 Revision received October 24, 2009 Accepted February 16, 2010 Published online May 25, 2010

Ce´dric Bouquet MSHS 99 Avenue du Recteur Pineau 86000 Poitiers France E-mail [email protected]
