The passive perception of irrelevant actions can facilitate or interfere with the execution of one’s own actions, known as ‘automatic imitation’ (AI). For example, when one is pressing down on a button, reaction times (RTs) are faster when observing a finger depression (compatible action) and slower whilst observing a finger lift (incompatible action). This phenomenon has been attributed to the mirror neuron system and is thought to represent a laboratory model of spontaneous motor mimicry which facilitates social interactions. AI is typically reduced or absent when the observed movement is produced by a non-human agent. However, previous findings suggest that the magnitude of this ‘human bias’ can be modulated by top-down factors, such as attention and prior instructions regarding whether the movement was produced by a human or non-human agent. This thesis aimed to further examine the role of attention and belief regarding stimulus agency in automatic imitation. Participants were required to perform a pre-specified key press or release response to a diffuse yellow flash go signal. This response was either compatible or incompatible with the finger or object movement, which was presented simultaneously. AI was measured by subtracting compatible from incompatible RTs to calculate the compatibility effect. Experiments 1a, 1b, 2 and 7 focused on exploring the role of attention in AI. Experiment 1a revealed that the human bias is dependent on when the go signal occurs. AI was greater for the finger stimulus relative to the object stimulus when the go signal occurred during the movement, but not after the movement. It is suggested that attention to the movement is reduced when the go signal occurs after the movement. This implies that the human bias in AI is dependent on attention being directed towards the movement. Experiments 1b and 2 indicated that AI was removed if a visual dual task was added, but that AI remained and was greater when an auditory dual task was added. This indicates that AI was removed when the visual dual task competed for cognitive resources with action observation. The facilitation of AI when an auditory dual task was added suggests that the additional cognitive load may have occupied cognitive resources required for the inhibition of imitation. These findings highlight that AI is susceptible to attentional load, implying that AI is not a strongly automatic process. Experiment 7 explored whether the spread of attention modulates the magnitude of AI by comparing a ‘diffuse’ go signal to a ‘focused’ go signal which directed attention to the stimulus movement. Significantly larger AI effects were produced for the group of participants who saw the focused flash first, indicating that focusing attention on the spatial location of the movement increased AI, and furthermore that initially observing the focused flash ‘trained’ participants to pay attention to the stimulus movement in the diffuse flash condition. Experiments 3 and 4 examined why AI effects for non-human stimuli are more likely to be significant when trials are presented in separate blocks (e.g. human vs. non-human stimuli) as opposed to randomly mixed trials. It was hypothesised that this pattern of previous results could be due to less attention being drawn to stimulus differences when stimuli are presented separately as opposed to mixed with a block of trials. However, in both experiments, AI effects were present for the object stimulus in the group of participants who observed the block of finger trials first. This suggests that the prior observation of the finger movement caused a carry-over of human agency to the object stimulus. Experiments 5, 6, 8 and 9 directly explored the role of belief regarding stimulus agency in AI by instructing participants that the object movement was generated by a human finger movement. Experiments 5, 6 and 8 provided preliminary evidence that AI is affected by belief instructions, but the effects were weak or confounded by spatial stimulus-response compatibility (SRC) effects (i.e. compatibility effects based on spatial correspondence of the stimulus and response location). Experiment 9 was designed to differentiate imitative compatibility from SRC effects, thus providing a pure measure of imitative compatibility. Imitative compatibility was present for the object stimulus after the belief manipulation. This demonstrates that a human belief regarding stimulus agency of the object modulated imitative compatibility effects due to the top-down knowledge that the movement was human generated, and not due to increased attention and SRC effects. The presented work has provided multiple lines of evidence which demonstrate that so-called ‘automatic’ imitation effects are strongly susceptible to top-down influences, including attention and belief regarding stimulus agency. The current work could be used to evaluate top-down modulation of imitation in autistic populations, as it has been proposed that top-down modulation of the automatic imitation pathway may be atypical in autism.

The aim of this thesis is to examine the cognitive processes of social learning from the bottom up. In the field of comparative psychology, an overemphasis on understanding complex cognitive processes in nonhuman animals (e.g. empathy, imitation), may be detrimental to the study of simpler mechanisms. In this thesis, I report five studies of simple cognitive processes related to social learning. A series of experiments with human children and capuchin monkeys (Sapajus sp.), examined action imitation and identified a possible role for associative learning in the development of this ability. An analysis of observational data from captive capuchins explored a number of lesser-studied social learning phenomena, including behavioural synchrony, the neighbour effect, and group-size effects. The results of this study emphasise the importance of exploring behaviour at a number of levels to appreciate the dynamic nature of social influence. Two final experiments examined social contagion in capuchin monkeys, and highlight the importance of describing the relationship between behaviour and emotion to properly understand more complex social cognition. Together, these studies demonstrate how approaching human and nonhuman behaviour from the bottom up, as well as from the top down, can contribute to a better comparative science of social learning.

Previous studies have established that when a subject’s attention is directed to a specific body part, the subject is able to move that body part faster than a body part their attention was not drawn to. This is known as the body compatibility effect, and it has been shown that this effect only occurs when viewing upright images of the human body. In this study, we presented control subjects and expert acrobats with inverted and upright stimuli. We hypothesized that the amount of time the acrobats spent inverted would result in the acrobats exhibiting body compatibility effects for both upright and inverted stimuli. Compatibility effects were observed in the upright condition for both groups, but neither group exhibited any compatibility effects in the inverted position. Unexpectedly the acrobats responded significantly faster to incongruent trials compared to the control subjects, leading to the conclusion that there must be some form of priming occurring concurrently with the body compatibility task allowing the acrobats to respond faster than the control participants.

Le but de ce travail de thèse était de contribuer à une meilleure compréhension des mécanismes par lesquels nous nous représentons nos propres actions et celles d'autrui. En nous situant notamment dans la perspective de la théorie idéomotrice, nous avons examiné ces questions tout d'abord dans le cadre de l'imitation. Nos résultats indiquent un effet de l'apprentissage idéomoteur sur l'imitation intentionnelle (Etude 1), confirmant la flexibilité des liens perception-action, et démontrant le rôle des associations réponse-effet dans l'imitation. Toutefois, les performances à une tâche d'imitation automatique n'étaient pas influencées par un tel type d'apprentissage (Etude 2), possiblement en raison de processus différents n'ayant pas la même sensibilité à l'apprentissage idéomoteur. Nous avons ensuite étendu nos recherches au cadre des tâches conjointes (Etude 3). Nous montrons qu'une expérience idéomotrice corrélant l'exécution d'une action avec celle d'un agent non-humain conduit à la co-représentation de l'action de cet agent (présence d'un effet Simon social). Ainsi, l'expérience idéomotrice pourrait également permettre de modifier la co-représentation de l'action d'autrui en situation de tâche partagée. Ce travail confirme donc l'approche idéomotrice de la perception et de la représentation des actions d'autrui. / The aim of present work was to better understand the mechanisms by which we represent our own actions and those of others. Within the frame of the ideomotor theory, we first examined these questions in relation to imitation. Our results indicated an effect of ideomotor learning on intentional imitation (Study 1), confirming the flexibility of perception-action links, and demonstrating the role of action-effect associations in imitation. However, automatic imitation was not influenced by this type of learning (Study 2), which may suggest different processes with less sensitivity to learning ideomotor learning. We then extended our research to joint-action tasks (Study 3). We showed that an ideomotor experience, where action execution triggered actions of a non-human agent, induced a subsequent co-representation of this agent's actions (as indexed by social Simon effect). Ideomotor experience therefore seems to influence also the way we represent the actions of others in task-sharing. This work confirms the ideomotor approach to perception and representation of others' actions.