La loi de Fitts, qui relie le temps de mouvement MT dans une tache de pointage aux dimensions de la cible visée D et W est usuellement exprimée à partir d’une imitation de la formule de la capacité de Shannon MT = a + b log 2 (1 + D/W). Toutefois, l’analyse actuelle est insatisfaisante: elle provient d’une simple analogie entre la tache de pointage et la transmission d’un signal sur un canal bruité sans qu’il n’y ait de modèle explicite de communication.Je développe d’abord un modèle de transmission pour le pointage, où l’indice de difficulté ID = log 2 (1 + D/W) s’exprime aussi bien comme une entropie de source et une capacité de canal, permettant ainsi de réconcilier dans un premier temps l’approche de Fitts avec la théorie de l’information de Shannon. Ce modèle est ensuite exploité pour analyser des données de pointage récoltées lors d’expérimentations contrôlées mais aussi en conditions d’utilisations réelles.Je développe ensuite un second modèle, focalisé autour de la forte variabilité caractéristique du mouvement humain et qui prend en compte la forte diversité des mécanismes de contrôle du mouvement: avec ou sans voie de retour, par intermittence ou de manière continue. À partir d’une chronométrie de la variance positionnelle, évaluée à partir d’un ensemble de trajectoires, on remarque que le mouvement peut-être découpé en deux phases: une première où la variance augmente et une grande partie de la distance à couvrir est parcourue, est suivie d’une deuxième au cours de laquelle la variance diminue pour satisfaire les contraintes de précision requises par la tache.Dans la deuxième phase, le problème du pointage peut-être ramené à un problème de communication à la Shannon, où l’information est transmise d’une“source” (variance à la fin de la première phase) à une “destination” (extrémité du membre) à travers un canal Gaussien avec la présence d’une voie de retour.Je montre que la solution optimale à ce problème de transmission revient à considérer un schéma proposé par Elias. Je montre que la variance peut décroitre au mieux exponentiellement au cours de la deuxième phase, et que c’est ce résultat qui implique directement la loi de Fitts. / Fitts’ law, which relates movement time MTin a pointing task to the target’s dimensions D and Wis usually expressed by mimicking Shannon’s capacityformula MT = a + b log 2 (1 + D/W). Yet, the currentlyreceived analysis is incomplete and unsatisfactory: itstems from a vague analogy and there is no explicitcommunication model for pointing.I first develop a transmission model for pointing taskswhere the index of difficulty ID = log 2 (1 + D/W) isthe expression of both a source entropy and a chan-nel capacity, thereby reconciling Shannon’s informa-tion theory with Fitts’ law. This model is then levera-ged to analyze pointing data gathered from controlledexperiments but also from field studies.I then develop a second model which builds on thevariability of human movements and accounts for thetremendous diversity displayed by movement control:with of without feedback, intermittent or continuous.From a chronometry of the positional variance, eva-luated from a set of trajectories, it is observed thatmovement can be separated into two phases: a firstwhere the variance increases over time and wheremost of the distance to the target is covered, follo-wed by a second phase where the variance decreasesuntil it satisfies accuracy constraints. During this se-cond phase, the problem of aiming can be reduced toa Shannon-like communication problem where infor-mation is transmitted from a “source” (variance at theend of the first phase), to a “destination” (the limb ex-tremity) over a “channel” perturbed by Gaussian noisewith a feedback link. I show that the optimal solution tothis transmission problem amounts to a scheme firstsuggested by Elias. I show that the variance can de-crease at best exponentially during the second phase,and that this result induces Fitts’ law.

Speed-accuracy tradeoffs, velocity profiles, and physiological tremor are fundamental characteristics of human movement. The principles underlying these phenomena have long attracted major interest and controversy. Each is well established experimentally but as yet they have no common theoretical basis. It is proposed that these three phenomena occur as the direct consequence of a movement response planning system that acts as an intermittent optimal controller operating at discrete intervals of ~100 ms. The BUMP model of response planning describes such a system. It forms the kernel of adaptive model theory which defines, in computational terms, a basic unit of motor production or BUMP. Each BUMP consists of three processes: (i) analysing sensory information, (ii) planning a desired optimal response, and (iii) executing that response. These processes operate in parallel across successive sequential BUMPs. The response planning process requires a discrete time interval in which to generate a minimum acceleration trajectory of variable duration, or horizon, to connect the actual response with the predicted future state of the target and compensate for executional error. BUMP model simulation studies show that intermittent adaptive optimal control employing two extremes of variable horizon predictive control reproduces almost exactly findings from several authoritative human experiments. On the one extreme, simulating spatially-constrained movements, a receding horizon strategy results in a logarithmic speed-accuracy tradeoff and accompanying asymmetrical velocity profiles. On the other extreme, simulating temporally-constrained movements, a fixed horizon strategy results in a linear speed-accuracy tradeoff and accompanying symmetrical velocity profiles. Furthermore, simulating ramp movements, a receding horizon strategy closely reproduces experimental observations of 10 Hz physiological tremor. A 100 ms planning interval yields waveforms and power spectra equivalent to those of joint-angle, angular velocity and electromyogram signals recorded for several speeds, directions, and skill levels of finger movement. While other models of response planning account for one or other set of experimentally observed features of speed-accuracy tradeoffs, velocity profiles, and physiological tremor, none accounts for all three. The BUMP model succeeds in explaining these disparate movement phenomena within a single framework, strengthening this approach as the foundation for a unified theory of motor control and planning.

Empirical studies show that similar patterns emerge from a large number of different biological systems. For example, the group size distributions of several fish species and house sparrows all follow power law distributions with an exponential truncation. Networks built by ant colonies, slime mold and those are designed by engineers resemble each other in terms of structure and transportation efficiency. Based on the investigation of experimental data, we propose a variety of simple stochastic models to unravel the underlying mechanisms which lead to the collective phenomena in different systems. All the mechanisms employed in these models are rooted in the concept of selective reinforcement. In some systems the reinforcement can build optimal solutions for biological problem solving. This thesis consists of five papers. In the first three papers, I collaborate with biologists to look into group formation in house sparrows  and the movement decisions of damsel fish.  In the last two articles, I look at how shortest paths and networks are  constructed by slime molds and pheromone laying ants, as well as studying  speed-accuracy tradeoffs in slime molds' decision making. The general goal of the study is to better understand how macro level patterns and behaviors emerges from micro level interactions in both spatial and non-spatial biological systems. With the combination of mathematical modeling and experimentation, we are able to reproduce the macro level patterns in the studied biological systems and predict behaviors of the systems using minimum number of parameters.

Although research has highlighted the importance of decisions when learning and performing motor actions, few studies have focused on individuals’ ability to choose between potential motor actions. To help bridge this gap, this thesis presents a series of studies that investigate the behaviour of able-bodied individuals when attempting to choose movements based on a speed-accuracy tradeoff. In the first study, a two-alternative forced-choice task was used to determine whether people are consistent with Fitts’s law when choosing the movement they perceive to require the least movement duration. Participants performed almost perfectly when clear visual cues were available—when one of the targets was closer, wider, or both. Contrary to Fitts’s law, however, participants showed a preference for closer targets when visual cues were not informative—when one of the targets was closer and narrower. This study demonstrates that motor decisions are not always optimal, especially when participants are naïve at the task. To determine the basis of individuals’ preference for closer targets, a pair of studies explored the relation between motor decisions, imagined movements, and visual perception. Participants showed a similar deviation from Fitts’s law when imagining movements—believing that movement duration increased with distance within the same index of difficulty. Participants did not behave similarly, however, in a perceptual version of the decision task. These results suggest that imagined movements and motor decisions are linked, but they are not always based on veridical representations of actual movement. To further probe the origin of individuals’ erroneous belief about movement duration, the final study of this thesis measured movement duration for movements made at speeds other than ‘as fast as possible’. Movements made at more natural movement speeds shared important similarities with decisions and imagined movements. This study suggests that the biases seen in naïve motor decisions might originate from participants considering movements for which they have more experience, such as target-directed movements made at a naturally-selected pace. Together, the findings presented in this thesis may help to identify the ways that motor decisions can deviate from optimal, suggesting how those decisions must change with practice to better accomplish a task.

Although research has highlighted the importance of decisions when learning and performing motor actions, few studies have focused on individuals’ ability to choose between potential motor actions. To help bridge this gap, this thesis presents a series of studies that investigate the behaviour of able-bodied individuals when attempting to choose movements based on a speed-accuracy tradeoff. In the first study, a two-alternative forced-choice task was used to determine whether people are consistent with Fitts’s law when choosing the movement they perceive to require the least movement duration. Participants performed almost perfectly when clear visual cues were available—when one of the targets was closer, wider, or both. Contrary to Fitts’s law, however, participants showed a preference for closer targets when visual cues were not informative—when one of the targets was closer and narrower. This study demonstrates that motor decisions are not always optimal, especially when participants are naïve at the task. To determine the basis of individuals’ preference for closer targets, a pair of studies explored the relation between motor decisions, imagined movements, and visual perception. Participants showed a similar deviation from Fitts’s law when imagining movements—believing that movement duration increased with distance within the same index of difficulty. Participants did not behave similarly, however, in a perceptual version of the decision task. These results suggest that imagined movements and motor decisions are linked, but they are not always based on veridical representations of actual movement. To further probe the origin of individuals’ erroneous belief about movement duration, the final study of this thesis measured movement duration for movements made at speeds other than ‘as fast as possible’. Movements made at more natural movement speeds shared important similarities with decisions and imagined movements. This study suggests that the biases seen in naïve motor decisions might originate from participants considering movements for which they have more experience, such as target-directed movements made at a naturally-selected pace. Together, the findings presented in this thesis may help to identify the ways that motor decisions can deviate from optimal, suggesting how those decisions must change with practice to better accomplish a task.

Speed-accuracy tradeoffs, velocity profiles, and physiological tremor are fundamental characteristics of human movement. The principles underlying these phenomena have long attracted major interest and controversy. Each is well established experimentally but as yet they have no common theoretical basis. It is proposed that these three phenomena occur as the direct consequence of a movement response planning system that acts as an intermittent optimal controller operating at discrete intervals of ~100 ms. The BUMP model of response planning describes such a system. It forms the kernel of adaptive model theory which defines, in computational terms, a basic unit of motor production or BUMP. Each BUMP consists of three processes: (i) analysing sensory information, (ii) planning a desired optimal response, and (iii) executing that response. These processes operate in parallel across successive sequential BUMPs. The response planning process requires a discrete time interval in which to generate a minimum acceleration trajectory of variable duration, or horizon, to connect the actual response with the predicted future state of the target and compensate for executional error. BUMP model simulation studies show that intermittent adaptive optimal control employing two extremes of variable horizon predictive control reproduces almost exactly findings from several authoritative human experiments. On the one extreme, simulating spatially-constrained movements, a receding horizon strategy results in a logarithmic speed-accuracy tradeoff and accompanying asymmetrical velocity profiles. On the other extreme, simulating temporally-constrained movements, a fixed horizon strategy results in a linear speed-accuracy tradeoff and accompanying symmetrical velocity profiles. Furthermore, simulating ramp movements, a receding horizon strategy closely reproduces experimental observations of 10 Hz physiological tremor. A 100 ms planning interval yields waveforms and power spectra equivalent to those of joint-angle, angular velocity and electromyogram signals recorded for several speeds, directions, and skill levels of finger movement. While other models of response planning account for one or other set of experimentally observed features of speed-accuracy tradeoffs, velocity profiles, and physiological tremor, none accounts for all three. The BUMP model succeeds in explaining these disparate movement phenomena within a single framework, strengthening this approach as the foundation for a unified theory of motor control and planning.

No description available.

Neste estudo foi analisado o efeito de distância, velocidade, tamanhos do disco e do alvo, e massas do disco e da manopla, sobre o desempenho motor em movimentos requisitando rapidez e precisão. Para tanto, foram analisadas as características cinemáticas da tarefa de projetar um disco a um alvo com movimento de contato balístico, empunhando uma manopla. Os movimentos foram desempenhados sobre uma base plana e filmados com câmera optoeletrônica de alta freqüência. O estudo foi conduzido em seis experimentos com um grupo único de participantes. Os resultados indicaram que os modelos de controle motor que têm sido empregados para analisar a relação velocidade-precisão em tarefas mais simples não foram apropriados para explicar o comportamento da tarefa utilizada. O controle motor na tarefa demonstrou ser dinâmico e flexível, frente às diferentes restrições de movimento. As seguintes estratégias de controle foram sugeridas na explicação dos resultados: sincronização da maior velocidade e do instante de contato manopla-disco, manutenção na proporção entre as fases aceleração-desaceleração, maior inércia e menor impacto para aumentar a estabilidade de movimento, e o controle da velocidade e da precisão em dimensões independentes. A análise das ações articulares demonstrou as particularidades das estratégias utilizadas pelo sistema no movimento em função das variáveis manipuladas. Em conjunto, esta seqüência de experimentos permitiu uma compreensão mais ampla das estratégias de controle motor empregadas em movimentos com alta demanda de velocidade e de precisão / In this study it was analyzed the effect of distance, velocity, disc and target width, disc and manipulandum mass, over motor control of a rapid and accurate movement. For such, it was analyzed the kinematic characteristics of the task of launching a disc to a target using a ballistic movement, performed with a manipulandum. Movements were performed on a flat surface and filmed with a high frequency optoelectronic camera. The study was conducted through six experiments with a single group of participants. Analysis of results indicated that models of motor control that has been used to analyze speed-accuracy tradeoff in simpler tasks were not appropriate to explain the observed behavior in the task used. Motor control in the task showed to be dynamic and flexible, regarding the several constraints manipulated. The follow strategies of control were suggested to explain the results: synchronization of the peak velocity and the instant of disc-manipulandum contact, maintenance of the proportion between the acceleration-deceleration phases, greater inertia and minor impact to increase movement stability, and control of velocity and accuracy of independent dimensions. The prediction of Analysis of joint actions showed the particularities of the strategies used by the system on movement as a function of the manipulated variables. Together, this study sequence of experiments allowed for a deeper comprehension of the control strategies used in the control of rapid and accurate movements

Ce travail doctoral, centré sur l'étude des processus de contrôle d'un périphérique d'interaction de type joystick, poursuivait un double objectif. D'une part, ce travail visait à comprendre comment l'utilisateur d'un périphérique adapte son comportement pour faire face à l'ensemble des contraintes qu'il rencontre. En particulier, nous avons manipulé les contraintes relatives à la tâche à réaliser (l'indice de difficulté et le comportement de l'objet déplacé) et les propriétés physiques du périphérique. D'autre part, d'un point de vue appliqué, comprendre comment le comportement du sujet émerge d'un ensemble de contraintes nous renseigne sur la façon dont un contrôle plus intuitif des périphériques, et par la même une meilleure performance, peuvent être favorisés. Pour cela, un cadre d'analyse qui permet de manipuler l'ensemble des contraintes dans des conditions de contrôle qui se rapproche de situation réelle d'interaction (chirurgie vidéoassistée, aéronautique ou contrôle industriel) a été proposé. L'analyse comportementale à deux niveaux (niveau local et niveau global) qui est utilisée nécessitait l'intégration des concepts, moyens et méthodes des sciences comportementales (contrôle moteur) d'une part, et de la biomécanique d'autre part. Au regard des résultats obtenus, l'étude des processus de contrôle d'un périphérique d'interaction constitue une voie d'entrée sur une compréhension plus générale du comportement perceptivo-moteur. / This doctoral work focused on the study of the process involved in the control of a joystick-type device of interaction and had a double objective. First, this work was aimed to understand how the user of a device adapts its behavior to face a set of encountered constraints. In particular, the constraints inherent to the task (the index of difficulty and behavior of the object displaced) and the physical properties of the device (joystick or rotorcraft stick) have been manipulated. Second, understanding how the subject's behavior emerges from the influence of this set of constraints informed us about how we can access to a more intuitive control of the device and a better performance level. To achieve this goal, an analysis framework allowing the manipulation of all the constraints in conditions that are close to real situations of control (e.g. video-assisted surgery, aeronautics and industrial control) has been proposed. The behavioral analysis at two levels (local level and global level) that is used required the integration of concepts, means and methods from behavioral sciences (motor control) and from biomechanics. Taking all the results together, the study of the control process of a device of interaction allows a more general understanding of the perceptual-motor behavior.

Neste estudo foi analisado o efeito de distância, velocidade, tamanhos do disco e do alvo, e massas do disco e da manopla, sobre o desempenho motor em movimentos requisitando rapidez e precisão. Para tanto, foram analisadas as características cinemáticas da tarefa de projetar um disco a um alvo com movimento de contato balístico, empunhando uma manopla. Os movimentos foram desempenhados sobre uma base plana e filmados com câmera optoeletrônica de alta freqüência. O estudo foi conduzido em seis experimentos com um grupo único de participantes. Os resultados indicaram que os modelos de controle motor que têm sido empregados para analisar a relação velocidade-precisão em tarefas mais simples não foram apropriados para explicar o comportamento da tarefa utilizada. O controle motor na tarefa demonstrou ser dinâmico e flexível, frente às diferentes restrições de movimento. As seguintes estratégias de controle foram sugeridas na explicação dos resultados: sincronização da maior velocidade e do instante de contato manopla-disco, manutenção na proporção entre as fases aceleração-desaceleração, maior inércia e menor impacto para aumentar a estabilidade de movimento, e o controle da velocidade e da precisão em dimensões independentes. A análise das ações articulares demonstrou as particularidades das estratégias utilizadas pelo sistema no movimento em função das variáveis manipuladas. Em conjunto, esta seqüência de experimentos permitiu uma compreensão mais ampla das estratégias de controle motor empregadas em movimentos com alta demanda de velocidade e de precisão / In this study it was analyzed the effect of distance, velocity, disc and target width, disc and manipulandum mass, over motor control of a rapid and accurate movement. For such, it was analyzed the kinematic characteristics of the task of launching a disc to a target using a ballistic movement, performed with a manipulandum. Movements were performed on a flat surface and filmed with a high frequency optoelectronic camera. The study was conducted through six experiments with a single group of participants. Analysis of results indicated that models of motor control that has been used to analyze speed-accuracy tradeoff in simpler tasks were not appropriate to explain the observed behavior in the task used. Motor control in the task showed to be dynamic and flexible, regarding the several constraints manipulated. The follow strategies of control were suggested to explain the results: synchronization of the peak velocity and the instant of disc-manipulandum contact, maintenance of the proportion between the acceleration-deceleration phases, greater inertia and minor impact to increase movement stability, and control of velocity and accuracy of independent dimensions. The prediction of Analysis of joint actions showed the particularities of the strategies used by the system on movement as a function of the manipulated variables. Together, this study sequence of experiments allowed for a deeper comprehension of the control strategies used in the control of rapid and accurate movements