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Search Results: 1 - 10 of 415 matches for " Raoul Huys "
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Time Scale Hierarchies in the Functional Organization of Complex Behaviors
Dionysios Perdikis ,Raoul Huys,Viktor K. Jirsa
PLOS Computational Biology , 2011, DOI: 10.1371/journal.pcbi.1002198
Abstract: Traditional approaches to cognitive modelling generally portray cognitive events in terms of ‘discrete’ states (point attractor dynamics) rather than in terms of processes, thereby neglecting the time structure of cognition. In contrast, more recent approaches explicitly address this temporal dimension, but typically provide no entry points into cognitive categorization of events and experiences. With the aim to incorporate both these aspects, we propose a framework for functional architectures. Our approach is grounded in the notion that arbitrary complex (human) behaviour is decomposable into functional modes (elementary units), which we conceptualize as low-dimensional dynamical objects (structured flows on manifolds). The ensemble of modes at an agent’s disposal constitutes his/her functional repertoire. The modes may be subjected to additional dynamics (termed operational signals), in particular, instantaneous inputs, and a mechanism that sequentially selects a mode so that it temporarily dominates the functional dynamics. The inputs and selection mechanisms act on faster and slower time scales then that inherent to the modes, respectively. The dynamics across the three time scales are coupled via feedback, rendering the entire architecture autonomous. We illustrate the functional architecture in the context of serial behaviour, namely cursive handwriting. Subsequently, we investigate the possibility of recovering the contributions of functional modes and operational signals from the output, which appears to be possible only when examining the output phase flow (i.e., not from trajectories in phase space or time).
Complex Processes from Dynamical Architectures with Time-Scale Hierarchy
Dionysios Perdikis,Raoul Huys,Viktor Jirsa
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0016589
Abstract: The idea that complex motor, perceptual, and cognitive behaviors are composed of smaller units, which are somehow brought into a meaningful relation, permeates the biological and life sciences. However, no principled framework defining the constituent elementary processes has been developed to this date. Consequently, functional configurations (or architectures) relating elementary processes and external influences are mostly piecemeal formulations suitable to particular instances only. Here, we develop a general dynamical framework for distinct functional architectures characterized by the time-scale separation of their constituents and evaluate their efficiency. Thereto, we build on the (phase) flow of a system, which prescribes the temporal evolution of its state variables. The phase flow topology allows for the unambiguous classification of qualitatively distinct processes, which we consider to represent the functional units or modes within the dynamical architecture. Using the example of a composite movement we illustrate how different architectures can be characterized by their degree of time scale separation between the internal elements of the architecture (i.e. the functional modes) and external interventions. We reveal a tradeoff of the interactions between internal and external influences, which offers a theoretical justification for the efficient composition of complex processes out of non-trivial elementary processes or functional modes.
When Less Is More: Reduced Usefulness Training for the Learning of Anticipation Skill in Tennis
Nicholas J. Smeeton, Raoul Huys, David M. Jacobs
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0079811
Abstract: Participants in this study practiced with feedback to anticipate the left-right direction of forehand tennis shots played by stick-figure players. A technique based on principal component analysis was used to remove dynamical differences that are associated with shots to different directions. Different body regions of the stick-figure players were neutralized with this procedure in the pretests and posttests, and in the practice phases. Experiment 1 showed that training is effective if during practice information is consistently present in the whole body of the player, but not if the information is neutralized in the whole body in half of the practice trials. Experiment 2 showed that training is effective if the variance associated with the direction of the shots is consistently present in one body region but neutralized in others, and that transfer occurs from practice with information in one body region to performance in conditions with information preserved only in other regions. Experiment 3 showed that occlusion has a much larger detrimental effect on learning than the applied neutralization technique, and that transfer between body regions occurs also with occlusion. Discussed are theoretical implications for understanding how biological motion is perceived and possible applications in a type of training referred to as reduced usefulness training.
Distinct Timing Mechanisms Produce Discrete and Continuous Movements
Raoul Huys ,Breanna E. Studenka,Nicole L. Rheaume,Howard N. Zelaznik,Viktor K. Jirsa
PLOS Computational Biology , 2008, DOI: 10.1371/journal.pcbi.1000061
Abstract: The differentiation of discrete and continuous movement is one of the pillars of motor behavior classification. Discrete movements have a definite beginning and end, whereas continuous movements do not have such discriminable end points. In the past decade there has been vigorous debate whether this classification implies different control processes. This debate up until the present has been empirically based. Here, we present an unambiguous non-empirical classification based on theorems in dynamical system theory that sets discrete and continuous movements apart. Through computational simulations of representative modes of each class and topological analysis of the flow in state space, we show that distinct control mechanisms underwrite discrete and fast rhythmic movements. In particular, we demonstrate that discrete movements require a time keeper while fast rhythmic movements do not. We validate our computational findings experimentally using a behavioral paradigm in which human participants performed finger flexion-extension movements at various movement paces and under different instructions. Our results demonstrate that the human motor system employs different timing control mechanisms (presumably via differential recruitment of neural subsystems) to accomplish varying behavioral functions such as speed constraints.
Is Fitts’ Law Continuous in Discrete Aiming?
Rita Sleimen-Malkoun, Jean-Jacques Temprado, Raoul Huys, Viktor Jirsa, Eric Berton
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0041190
Abstract: The lawful continuous linear relation between movement time and task difficulty (i.e., index of difficulty; ID) in a goal-directed rapid aiming task (Fitts’ law) has been recently challenged in reciprocal performance. Specifically, a discontinuity was observed at critical ID and was attributed to a transition between two distinct dynamic regimes that occurs with increasing difficulty. In the present paper, we show that such a discontinuity is also present in discrete aiming when ID is manipulated via target width (experiment 1) but not via target distance (experiment 2). Fitts’ law’s discontinuity appears, therefore, to be a suitable indicator of the underlying functional adaptations of the neuro-muscular-skeletal system to task properties/requirements, independently of reciprocal or discrete nature of the task. These findings open new perspectives to the study of dynamic regimes involved in discrete aiming and sensori-motor mechanisms underlying the speed-accuracy trade-off.
On the junior subjective synonyms of Coullia Hamond, 1973 (Copepoda, Harpacticoida, Laophontidae): an and key to species and related genera
Rony Huys
ZooKeys , 2009, DOI: 10.3897/zookeys.5.64
Abstract: Morphological comparison of the genera Coullia Hamond, 1973 and Phycolaophonte Pallares, 1975 (Copepoda, Harpacticoida, Laophontidae) shows that the latter should be relegated to a junior synonym of the former. The forgotten generic name Eolaophonte Apostolov, 1990, introduced for two species displaying the plesiomorphic condition of P2–P4 endopodal segmentation, is also considered synonymous with Coullia since the taxon it denotes lacks a distinct apomorphy, rendering it paraphyletic exclusive of Coullia. Pesta’s (1959) record of Laophonte sp. from Sorrento (Italy) pertains to Coullia mediterranea (Apostolov, 1990) comb. nov. Keys to the six species currently included in Coullia and to the laophontid genera displaying endopodal size discrepancy (P2 endopod smallest) are presented.
Revisions of the Foundations of Quantum Mechanics Suggested by Properties of Random Walk  [PDF]
Raoul Charreton
Journal of Quantum Information Science (JQIS) , 2011, DOI: 10.4236/jqis.2011.12009
Abstract: A new theorem on random walks suggest some possible revisions of the foundations of Quantum Mechanics. This is presented below in the simplified framework of the description of the evolution of a material point in space. Grossly speaking, it is shown that the probabilities generated by normalizing the square modulus of a sum of probability amplitudes, in the setup of Quantum Mechanics, becomes asymptotically close (under the appropriate limiting conditions) to the probabilities generated by the usual causal processes of Classical Mechanics. This limiting coincidence has a series of interesting potential applications. In particular it allows us to reintroduce the concept of causality within the core of Quantum Mechanics. Moreover, it suggests, among other consequences, that gravitational interaction may not even exist. Even though the interpretations of Quantum Mechanics which follow from this mathematical result may seem to bring some unexpected innovations in the context of theoretical physics, there is an obvious necessity to study its theoretical impact on Quantum Mechanics. The first steps toward this aim are taken in the present article.
The Origin of Gravitational and Electric Forces, the Nature of Electromagnetic Waves  [PDF]
Raoul Charreton
Journal of Quantum Information Science (JQIS) , 2012, DOI: 10.4236/jqis.2012.23014
Abstract: We have proposed a prequantum physics, itself founded on classical mechanics completed by the existence of an universal cloud of tiny particles noted U. These U particle command the mass, variable, of electron, neutron, proton, and atom particles noted M. The “shocks” between U and M particles in the cloud, with screen effect, give birth to electrical forces among charged particles with very small differences between attractive and repulsive forces, and to certain gravitational forces. This cloud with the electromagnetic waves propagating thus recalls an ether, yet much different regarding its effects on the inertial mass of any particle within it. The electromagnetic wave and the photon look like if they were born from a statistical mechanics induced by the universal cloud, and their status, in this regard, may be compared to the status conferred by atomics to a temperature or a pressure. The wave transversality is explained. By the same token, one understands why the photon, a vectorial bearer of a statistical information, may thus describe a particle as well as a wave.
The Lines of Lyman and the Titus-Bode Law Preferred Orbital of a Celestial Body  [PDF]
Raoul Charreton
Journal of Quantum Information Science (JQIS) , 2015, DOI: 10.4236/jqis.2015.53013
Abstract: We have proposed, thanks to a new model of the hydrogen atom [1], some explanation of the lines observed by Lyman in the spectrographic analysis of this atom. The model is based on a prequantum physics, itself founded on classical mechanics completed by the existence of a universal cloud of tiny particles called U. This cloud induces simultaneously and similarly electromagnetic and gravitational effects. This common origin creates a narrow link between how planets are arranged in a solar system, say the Titus-Bode law, and how the electrons are arranged in an atom, say the lines of Lyman. We describe what this link is in the following text and, more generally, what is the preferred orbit of an isolated celestial body.
Corrigenda: Kihara TC & Huys R (2009) A new genus of Ectinosomatidae (Copepoda, Harpacticoida) from sublittoral sediments in Ubatuba, S o Paulo State (Brazil), an updated key to genera and notes on Noodtiella Wells, 1965. ZooKeys 17: 57–88
Terue Kihara,Rony Huys
ZooKeys , 2009, DOI: 10.3897/zookeys.18.249
Abstract: No abstract available
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