A size-weight illusion (SWI) occurs when a large object and small object of equal mass but different volume are lifted and the small object is perceived as heavier than the large object. All previous studies of the SWI used similar coloured objects and found that individuals initially use more force to lift the large object, compared to the small object but then use similar forces for the two objects on subsequent lifts. In contrast to the change in lifting forces over trials, the perceptual illusion stays consistent across all trials. The goal of the current study was to determine if introducing different colours for the SWI stimuli could alter participants’ expectations about the masses of the two objects and therefore modify the perceptual SWI. Participants lifted SWI stimuli that were either identical in colour or stimuli of different colour.

Dance is a universal and ancient human behavior; however, our understanding of the basis of this behavior is surprisingly weak. In this dissertation, I explore the cognitive and evolutionary foundations of human dance, providing evidence of two ways in which the production and perception of dance actions are rooted in the functions of more general cognitive systems.In doing so, I aim to both inform our understanding of dance, and use the study of dance to elucidate broader issues in cognition. Chapter 1 demonstrates that the ability to entrain, or move in time with an auditory beat, is not unique to humans. In addition, across hundreds of species, I find that all animals able to entrain can also vocally imitate sound. This supports the hypothesis that entrainment relies on cognitive machinery that originally evolved to support vocal imitation. Chapter 2 investigates the perception of dance-like actions. Previous work shows that we infer the goals of observed actions by calculating their efficiency as a means to external effects, like reaching an object or location. However, dance actions typically lack an external effect or external goal. In two experiments, I show that for dance-like actions, adults infer that the agents’ goal is simply to produce the movements themselves. Furthermore, this inference is driven by the actions’ inefficiency as a means to external goals. This inefficiency effectively rules out external goals, making movement-based goals the best explanation. Thus, perception of both dance and non-dance actions appears to rely the same type of efficiency-based goal inference. Chapter 3 builds on these findings, showing that the inference that the movements are the goal is closely related to our concept of dance. First, I find that participants view movement-based goals as more consistent with dance than with other activities. Second, I find that simply construing actions as having movement-based goals leads participants to view the actions as more dancelike, even when all participants have seen the exact same actions. Thus, even our categorization of actions as dance versus non-dance is rooted in the same cognitive processes as support our understanding of other intentional actions. / Psychology

Micro-affordance effects have been reported for several different components of the reach-to-grasp action during both on-line and off-line visual processing. The presence of such effects represents a strong demonstration of the close relationship between perception, action, and cognition. In this thesis 7 experiments are described, which investigate different aspects of that relationship, with particular attention on the nature of object representations. In 5 behavioural experiments as well as in 1 Transcranial Magnetic Stimulation (TMS) experiment a stimulus-response compatibility paradigm is employed to examine the presence of micro-affordance effects arising during language processing of object names. The power and precision component of the reach-to-grasp action is investigated in relation to the compatibility of an object for grasping with either a power or a precision grasp. Overall, the results of the experiments discussed in the present thesis suggest that: a) object representations activated during language processing of object names are able to potentiate actions arising from the component of the reach-to-grasp action under investigation; b) such representations might be more semantic or „propositional‟ than depictive in nature, therefore more related to stored semantic knowledge of the object and its associated actions than to its detailed visual properties; c) this semantic information about objects seems to be automatically translated into specific motor activity, even in the absence of any intention to act; d) finally, such semantic, non-visual motor potentiation seems to be rapid and relatively short lived.

Imitation is a fundamental way of acquiring knowledge in human development. In their theory of goal-directed imitation (GOADI), Wohlschl&auml / ger et al. (2003) divide the representation of observed movements into hierarchically organized aspects the highest of which is usually the goal. In a face-to-face imitation task young children usually copy the (spatial) goal of the body movement in terms of perceptual mirror symmetry rather than match them conceptually onto their own body, as adults do. We refer to these imitation schemes as &ldquo / mirroring&rdquo / and &ldquo / matching&rdquo / respectively. In the present study, we investigate the effects of age and perspective of the child with respect to the experimenter (0&deg / , 90&deg / , 180&deg / ) in two imitation tasks, a hand-to-ear and a cup-grasping task. Moreover, we evaluate the developmental changes in the imitative behavior of children from a dynamical systems perspective. Children were supposed to imitate the movements of the experimenter. Tasks were conducted on 4.5- to 11-year-old Iranian pre-school and elementary school children (81 female, 84 male). Imitation scores for the spatial goal were analyzed in terms of mirroring or matching. Imitation schemes varied according to age and perspective in both tasks. Overall, older children&rsquo / s imitations of movements were more adult-like as established by an adult Iranian control group than those of the younger ones. They rather matched than mirrored observed movements. In the 180&deg / and 90&deg / conditions the mirroring scheme was predominant, but in 0&deg / matching was predominant. GOADI was confirmed / however it was qualified by the child&#039 / s perspective on the experimenter. Children&rsquo / s imitations showed a non-linear shift from perceptually-based mirroring to conceptually-based matching of observed movements onto their own body. This shift happens between 6 and 8-9 years of age. The amount of matching depends not only on age but also on control parameters such as spatial perspective, task demands, and exposure.

The goal of this dissertation was to understand the issue of load in a more operationally realistic way, while examining underlying segmental relations and postural regulation related to functional capability. The ecological approach provides a foundation for this work, as its approach seeks understanding across nested relations and at the level of the Organism-Environment system. First, a landing task was used to examine transitions from movement to upright stance, evaluating the effects of load on changes relevant to prospective control of action. Greater negative head angles, reductions in the field of regard, and reduced variability in orienting coordination (trunk-head relations) under load all suggest reductions in the postural affordances for visual perception. The heaviest load was not the worst; as the asymmetrically loaded Vest configuration had greater negative effects on postural affordances. This was further supported by the increased power and frequency content in the Center of Pressure dynamics, suggesting much more difficult postural regulation in this configuration. The second study examined the effects of load on dynamic marksmanship performance using large loads on the torso and small loads on the extremities (night vision goggles and extremity armor on the arms) while establishing two different postures determined by target placement. Load and Posture both had negative impacts on the speed-accuracy trade-off, with larger loads affecting gross postural transitions and smaller loads degrading fine-aiming performance. The more challenging posture degraded accuracy on target substantially, suggesting that reorientation of multiple segments may be necessary for assessing the consequences of load on marksmanship performance. Increases in the total coordinative variability of Head-Trunk-Gun relations with load at a high target suggests that increased inertial and interactive forces during movement "push" the system out of the optimal segmental relations. Moreover, the results from Postural-Focal coupling suggest that load "freezes" previously available degrees of freedom, making the system more deterministic and less flexible in goal-directed achievement. The two previous paradigms are joined in the third study to understand perception-action coupling during movement cessation to marksmanship transitions, a ubiquitous task in combat. Increased time to discriminate targets was found with load and was related to peak head velocities and the inability to dissipate energy at the head/eyes under load. Again, Load and Posture had significant effects on the speed-accuracy trade-off, especially at the load most similar to that seen in current missions. Segmental coordination in this effort ballasts the findings in study 2, as significant shifts from optimal Head-Trunk-Gun relations were observed with load as well as increased variability that was detrimental to task performance. This dissertation demonstrates that science can be "Operationalized" in a way that maintains scientific integrity during complex task analysis; providing additional insight into the issue of load across multiple scales of analysis related to functional capability and survivability in combat and others encumbered by load.

L’imitation volontaire est établie comme l’un des modes principaux d’acquisition des habiletés motrices. Il existe également une autre forme d’imitation, automatique et involontaire, étudiée initialement en psychologie sociale du fait de son interaction étroite avec les comportements pro-sociaux. Récemment, et sous l’influence de travaux des années 1990 mettant en lumière des substrats neuronaux communs à l’observation et à l’exécution du mouvement, les recherches scientifiques se sont concentrées sur cette notion d’imitation automatique et ont investigué, via différents paradigmes expérimentaux, les effets de facilitation et d’interférence entre mouvements observés et exécutés. Le travail réalisé dans le cadre de cette thèse vise à améliorer notre compréhension des mécanismes de contagion motrice et à identifier leurs applications possibles au réentraînement moteur. Dans une première étude, nous avons évalué l’impact de l’observation de mouvements de déséquilibre sur le balancement postural d’observateurs jeunes (24,5 ± 5 ans), sans troubles posturaux. Le contrôle de l’équilibre orthostatique fait principalement intervenir des structures sous-corticales pour le maintien du tonus postural et l’intégration multisensorielle. Ces substrats neuronaux seraient, de la même manière que les fonctions végétatives indépendantes du contrôle volontaire, plus facilement contaminés par les mouvements observés. Cependant, l’observation d’un déséquilibre sollicite également des mécanismes de régulation posturale, qui restreignent le balancement de l’observateur et se surajoutent à des processus inhibiteurs prévenant l’imitation compulsive des mouvements observés. Par conséquent, ce paradigme expérimental nous a permis de tester les limites des effets de contagion à partir d’une situation où les processus inhibiteurs et régulateurs de la posture étaient fortement sollicités. Cette étude nous a conduits à mettre en évidence une contamination du balancement postural des sujets par le déséquilibre observé, ce qui a confirmé l’importance et la prédominance des processus d’imitation. Ce résultat soulève des questions importantes en termes d’applications au réentraînement moteur chez les patients souffrant de troubles posturaux, en particulier chez les personnes âgées qui présentent une altération de leurs fonctions de stabilisation. En effet, si l’observation d’un déséquilibre conduit à une réaction de contagion motrice, il est vraisemblable qu’elle sollicite également des fonctions inhibitrices et régulatrices permettant la stabilisation de l’observateur. La visualisation répétée d’un déséquilibre peut-elle alors conduire à une amélioration de la stabilisation chez les personnes à risque ? Pour étudier cette question, il serait nécessaire de répéter ce protocole chez le public cible - les réponses pouvant être modulées par l’âge et les aptitudes motrices des personnes. Notre seconde étude visait à évaluer l’impact du répertoire moteur sur les réactions de contagion motrice. S’il est admis que le système moteur (contraintes biomécaniques, niveau d’expertise) affecte les processus perceptifs, son effet sur les réactions d’imitation automatique a été peu étudié. Nous avons analysé les réactions posturales d’observateurs jeunes (24,2 ± 3,7 ans), sains, face à des séquences de déséquilibre antéro-postérieur et médio-latéral. Les stratégies d’équilibration posturale sont associées à des contraintes différentes selon ces deux axes, avec une symétrie médio-latérale et une asymétrie antéropostérieure – asymétrie résultant d’une position du centre de masse en avant de l’articulation de la cheville, qui induit une sollicitation accrue des muscles du plan postérieur pour la stabilisation posturale. Un impact du système moteur sur le processus de contagion serait donc susceptible de se traduire par des réactions posturales différentes dans nos deux conditions d’observation. etc / Voluntary imitation is known as a major means of acquisition of motor skills. Besides, another form of imitation, automatic and involuntary, was initially more extensively studied in social psychology, perhaps because of its close interaction with prosocial behaviors. Recently, there was a renewal of interest in automatic imitation, following research works of the 1990s that highlighted common neural substrates for movement observation and execution. In this context, scientific studies started, through various experimental paradigms, to investigate facilitation and interference effects between observed and executed movements. Research work presented in this thesis aims to improve our understanding of the mechanisms involved in motor contagion and to identify their possible application to motor retraining. For this purpose, we evaluated, in our first study, the impact of observation of postural imbalance on body sway of young (24.5 ± 5 years), healthy observers. Postural control mainly relies on subcortical structures for maintaining postural tonus and ensuring multisensory integration. Similarly to vegetative functions that are independent of voluntary control, these neural substrates would be more easily contaminated by observed movements. However in response to observed imbalance, postural regulation mechanisms, superimposed to inhibitory processes that prevent compulsive imitation, restrain observers’ disequilibrium. Therefore, this experimental paradigm enabled us to test the limits of contagion mechanisms in a situation highly soliciting inhibitory and regulation processes. Our results led us to highlight a contagion effect of observed imbalance on subjects’ postural sway, which confirmed the importance of imitation processes. These results raise an important question in terms of applications for movement retraining in patients with postural disorders, more specifically in elderly patients with impaired stabilization functions. In effect, if observation of postural imbalance leads to a motor contagion response, it is also likely to solicit regulatory and inhibitory functions for observers’ postural stabilization. Thus, could repeated observation of such disequilibrium movements lead to an improvement of stabilization functions for subjects with postural deficits? To investigate this question, it will be necessary to repeat this protocol with the target population, since observers’ response is likely to vary with age and motor competences. To complete this work, we conducted a second study to assess the impact of the motor repertoire on motor contagion responses. Although it is widely accepted that the motor system (biomechanical constraints, level of expertise) affects perceptual processes, its effect on imitative responses has been little studied. We analyzed postural reactions of young (24.2 ± 3.7 years), healthy observers when presented with sequences of anteroposterior and medio-lateral imbalance. Postural equilibration strategies are associated with different constraints along these two axes, with a medio-lateral symmetry and an anteroposterior asymmetry – this latter asymmetry results from a location of the center of mass ahead of the ankle joint, which induces an increased solicitation of muscles from the posterior plane for stabilization. An impact of the motor system on the contagion process could therefore appear in the form of different postural responses in our two observation conditions. Our results indicated a greater contagion effect during observation of anteroposterior compared to medio-lateral imbalance. Postural contagion is therefore conditioned by observers’ equilibration strategy. In our third study, we considered using this contagion effect for perceptual training aimed at the maintenance and improvement of elderly subjects’ motor performances. The issue of an observational training device is especially relevant when considering people for whom physical exercise is limited due to fatigue or pain.etc

From the start of their lives, infants and young children are surrounded by a tremendous amount of multimodal social information. One intriguing question in the study of early social cognition is how vital social information is detected and processed and how and when young infants begin to make sense of what they see and hear and learn to understand other people’s behavior. The overall aim of this thesis was to provide new insights to this exciting field. Investigating behavior and/or neural mechanisms in early life, the three different studies included in this thesis therefore strive to increase our understanding on perception and processing of social information. Study I used eye-tracking to examine infants´ observations of gaze in a third-party context. The results showed that 9-, 16- and 24-month-old infants differentiate between the body orientations of two individuals on the basis of static visual information. More particularly, they shift their gaze more often between them when the social partners face each other than when they are turned away from each other. Using ERP technique, Study II demonstrated that infants at the age of 4 to 5 months show signs of integrating visual and auditory information at a neural level. Further, direct gaze in combination with backwards-spoken words leads to earlier or enhanced neural processing in comparison to other gaze-word combinations. Study III, also an EEG investigation, found that children between 18 and 30 months of age show a desynchronization of the mu rhythm during both the observation and execution of object-directed actions. Also, the results suggest motor system activation when young children observe others’ mimed actions. To summarize, the findings reported in this thesis strengthen the idea that infants are sensitive to others´ gaze and that this may extend to third-party contexts. Also, gaze is processed together with other information, for instance words, even before infants are able to understand others’ vocabulary. Furthermore, the motor system in young children is active during both the observation and imitation of another person’s goal-directed actions. This is in line with findings in infants, children and adults, indicating that these processes are linked at neural level.

The perception of an action and its production are inextricably linked. This entails that, during development, the skills that children are able to perform influence their perception of others\\\' actions. The present dissertation aimed to investigate the role of children’s experience on the perception of actions in three distinctive areas: manual actions performed by one person (individual action), manual actions performed by two people (joint action), and a conversation between two people. In order to succeed in each of the three areas, children have to acquire new skills and do so successively during their first three years of life. The methodological approach of this work was to measure the gaze behaviour of children, aged 6 months to 3 years, and adults during the observation of visually presented actions, which provided information on whether they were able to anticipate action goals. The findings obtained generally show an influence of experience on the anticipation of action goals in each of the three areas. First, a link between action and perception is not established as soon as an action emerges. There is at least some experience necessary for its development. Second, infants with no coordinated joint-action skills themselves anticipate the goals of joint action less well than those of individual action. Adults with considerable joint-action skills anticipate both equally well. And third, the course of a conversation can only be reliably anticipated by children aged 3 years and adults, whereas younger children shift their gaze between speakers randomly. Furthermore, only at the age of 3 years, did intonation support children’s anticipation of conversations.

No description available.

This thesis is a contribution to the formalisation of the notion of an agent within the class of finite multivariate Markov chains. In accordance with the literature agents are are seen as entities that act, perceive, and are goaldirected. We present a new measure that can be used to identify entities (called i-entities). The intuition behind this is that entities are spatiotemporal patterns for which every part makes every other part more probable. The measure, complete local integration (CLI), is formally investigated within the more general setting of Bayesian networks. It is based on the specific local integration (SLI) which is measured with respect to a partition. CLI is the minimum value of SLI over all partitions. Upper bounds are constructively proven and a possible lower bound is proposed. We also prove a theorem that shows that completely locally integrated spatiotemporal patterns occur as blocks in specific partitions of the global trajectory. Conversely we can identify partitions of global trajectories for which every block is completely locally integrated. These global partitions are the finest partitions that achieve a SLI less or equal to their own SLI. We also establish the transformation behaviour of SLI under permutations of the nodes in the Bayesian network. We then go on to present three conditions on general definitions of entities. These are most prominently not fulfilled by sets of random variables i.e. the perception-action loop, which is often used to model agents, is too restrictive a setting. We instead propose that any general entity definition should in effect specify a subset of the set of all spatiotemporal patterns of a given multivariate Markov chain. Any such definition will then define what we call an entity set. The set of all completely locally integrated spatiotemporal patterns is one example of such a set. Importantly the perception-action loop also naturally induces such an entity set. We then propose formal definitions of actions and perceptions for arbitrary entity sets. We show that these are generalisations of notions defined for the perception-action loop by plugging the entity-set of the perception-action loop into our definitions. We also clearly state the properties that general entity-sets have but the perception-action loop entity set does not. This elucidates in what way we are generalising the perception-action loop. Finally we look at some very simple examples of bivariate Markov chains. We present the disintegration hierarchy, explain it via symmetries, and calculate the i-entities. Then we apply our definitions of perception and action to these i-entities.