Thèses sur le sujet « Representational flexibility »

Karmiloff-Smith (e.g. 1986, 1992) has suggested that 'cognitive flexibility' is the result of a series of three representational redescriptions. These redescriptions are carried out by endogenous metaprocesses operating directly on the representations. Representational redescription accounts only for development beyond 'behavioural success', the stimulus to the redescription being stability at a previous level. Many features of the Representational Redescription theory are criticised, but the underlying idea that cognitive flexibility is associated with representational level is maintained. This point is supported by a review and study of planning development arguing that representational development, rather than process development explains increasing flexibility. Data from children's drawings and block balancing, along with a theoretical analysis of the model indicate that the details of the Representational Redescription theory are not consistent or plausible. In particular the concepts of initial procedural representation, endogenous metaprocesses, behavioural success, stability as the spur to development, and implicit information within representations, are rejected. Removing the constraints of behavioural success suggests a new recursive model, which is proposed as a general developmental mechanism. 'Recursive Re-Representation' views representational redescription as a creative process, and builds on Boden's (1992) computational approach to creativity. Cognitive flexibility is determined by a limited cognitive capacity, the level of 'chunking' in a domain and the possession of an overview of the relevant conceptual space. Chunking is achieved through a re-representation of behaviour and the environment, rather than a direct operation on representations. The BAIRN system (Wallace, Klahr & Bluff, 1987) is suggested as providing the basis for an implementation of Recursive ReRepresentation. It is argued that the Recursive Re-Representation account which views Representational Redecription as a recursive, creative process provides a more parsimonious approach to representational change throughout development.

Representational flexibility is usually assessed in the graphic domain by whether children can innovate canonical drawings. According to the Karmiloff-Smith’s RR Model (RRM 1990), flexibility is acquired with a marked discontinuity at 8-9 years, when routine drawings are overcome once and for all. RRM, though, is inherently recursive, implying that innovation entertains a continuous trade-off with graphic conservatism along development. In this regard, a less recent model by van Sommers (1984) suggests that pictorial conservatism coexist with flexibility, even in adulthood, and that continuity models fit better flexibility development. This study aims at comparing the two models and their ability to predict the relationship between conservatism and flexibility during development. 75 children (5, 7, 9, 11 year-olds) and 20 adults were asked to draw two similar and two different houses (administration order balanced across the sample). Drawings were coded with a 5 point scale for 6 aspects (e.g. house’s structure and details). Results show that linear trends fit flexibility development in all aspects. Adults draw canonical houses more than older children, although score highly in the differentiation task. Results suggest that flexibility coexist with some conservatism even in adults, lending support to van Sommers’s model, in these regards.

This study investigates the development of flexibility and reversibility in a calculus environment that attends to linking multiple representations. Reversibility was studied through Krutetskii’s framework of reversibility of two-way processes and reversibility of the mental process in reasoning. The study was conducted over approximately four months in a high school calculus classroom in an urban school district in a mid-Atlantic state. Instruction attended to linking multiple representations whenever possible. Four types of data were collected: 1) a pre-test, 2) a post-test, 3) daily assessments, and 4) clinical interviews. Twenty-one students completed a pretest and post-test that together assessed development of flexibility over the course of the study. They also completed daily assessments that were collected to provide evidence of the development of reversibility during the course of the study. Six students participated in four clinical interviews each, spread throughout the study. Inferential statistics were used to compare the results of the pre-test and post-test for significant differences and to determine significant differences in the presence of reversibility on the daily assessments over the course of the study. The clinical interviews were analyzed for evidence of students’ thought processes while solving reversible questions. Analysis revealed that over the course of the study, students demonstrated significant increases in both flexibility and reversibility. Two-way reversibility seemed to develop with relative ease for most students and often developed simultaneously with learning a forward process. Developing reversibility of the mental process in reasoning was difficult and tended to develop simultaneously with learning in a forward direction for students with high levels of flexibility. For students who did not develop reversibility simultaneously with forward learning, both two-way reversibility and reversibility of the mental process in reasoning were able to develop through multiple opportunities to solve reversible tasks of similar content. Analysis of the clinical interviews indicated that students typically followed a 4-step thought process when using reversibility to solve problems. Implications and limitations of the study and areas of further research were discussed.

Les travaux présentés dans cette thèse portent sur l'effet d'apprentissages à court et long terme sur le système visuel. Nous avons d'abord montré grâce à des enregistrements Éléctroencéphalographiques que l'apprentissage d'une séquence de stimuli visuels induisait une activité cérébrale spontanée et sélective au prochain stimulus devant apparaitre et que cette activité sélective s'exprimait dans les bandes alpha et beta de l'activité électrique cérébrale. Par la suite nous avons montré grâce à de l'Imagerie par Résonance Magnétique fonctionnelle que lors d'apprentissages longs (trois semaines) les représentations neurales de catégories visuelles associées étaient modulées et devenaient plus similaires après l'apprentissage. Les travaux présentés dans cette thèse ont donc permis de mieux caractériser l'impact d'apprentissages à différentes échelles de temps sur les représentations neurales d'objets visuels
The work presented in this thesis deals with the effect of short- and long-term learning on the visual system. We first demonstrated through electroencephalographic recordings that learning a sequence of visual stimuli induced spontaneous and selective cerebral activity to the next-to-appear stimulus and that this selective activity was expressed in the alpha and beta bands of cerebral electrical activity. Subsequently, we showed through functional magnetic resonance imaging that during long learning (three weeks) the neural representations of associated visual categories were modulated and became more similar due to learning. The work presented in this thesis has thus made it possible to better characterize the impact of learning at different time scales on the neural representations of visual objects

A dynamical system approach is utilized to reduce the representation order of unsteady fluid flows and fluid-structure interaction systems. This approach allows for significant reduction in the computational cost of their numerical simulations, implementation of optimization and control methodologies and assessment of their dynamic stability. In the first chapter, I present a new Lagrangian function to derive the equations of motion of unsteady point vortices. This representation is a reconciliation between Newtonian and Lagrangian mechanics yielding a new approach to model the dynamics of these vortices. In the second chapter, I investigate the flutter of a helicopter rotor blade using finite-state time approximation of the unsteady aerodynamics. The analysis showed a new stability region that could not be determined under the assumption of a quasi-steady flow. In the third chapter, I implement the unsteady vortex lattice method to quantify the effects of tail flexibility on the propulsive efficiency of a fish. I determine that flexibility enhances the propulsion. In the fourth chapter, I consider the stability of a flapping micro air vehicle and use different approaches to design the transition from hovering to forward flight. I determine that first order averaging is not suitable and that time periodic dynamics are required for the controller to achieve this transition. In the fifth chapter, I derive a mathematical model for the free motion of a two-body planar system representing a fish under the action of coupled dynamics and hydrodynamics loads. I conclude that the psicform fish family are inherently stable under certain conditions that depend on the location of the center of mass.
Ph. D.
We present modeling approaches of the interaction between flying or swimming bodies and the surrounding fluids. We consider their stability as they perform special maneuvers. The approaches are applied to rotating blades of helicopters, fish-like robots, and micro-air vehicles. We develop and validate a new mathematical representation for the flow generated by moving or deforming elements. We also assess the effects of fast variations in the flow on the stability of a rotating helicopter blade. The results point to a new stable regime for their operation. In other words, the fast flow variations could stabilize the rotating blades. These results can also be applied to the analysis of stability of rotating blades of wind turbines. We consider the effects of flexing a tail on the propulsive force of fish-like robots. The results show that adding flexibility enhances the efficiency of the fish propulsion. Inspired by the ability of some birds and insects to transition from hovering to forward motion, we thoroughly investigate different approaches to model and realize this transition. We determine that no simplification should be applied to the rigorous model representing the flapping flight in order to model transition phenomena correctly. Finally, we model the forward-swim dynamics of psciform and determine the condition on the center of mass for which a robotic fish can maintain its stability. This condition could help in designing fish-like robots that perform stable underwater maneuvers.

From the Polanyian perspective on the double movement of labour commodification and self-protection of Society, the aim of this study was to examine how unionists perceive and problematise precarious employment and what are their practices for unionising and thereby securing precarious workers. A double case study was conducted in the hotel-restaurant and construction sectors in Sweden with the participation of blue-collar unionists with diverse backgrounds and experiences. The results show that precarious work is associated with labour market segmentation, subcontracting and fragmentation of economic organisations, deskilling of work, loss of autonomy and sometimes over-qualification of workers. Perceived difficulties for unionisation are fear, lack of knowledge of precarious workers about their rights, membership cost, status frustration and lack of interactions with other workers. Reported practices for unionising precarious workers consist of dealing with these barriers in order to build trustful relations and empowering workers through education and inclusion in leadership positions. Actions taken to protect and secure precarious workers are strongly interlinked with their unionisation and seem to rest mainly on negotiations. The main conclusions of the study are that precarious work means a loss of control by workers over their work life stemming from labour commodification and flexibilisation due to increased management control and lack of rights and protections surrounding work. The formation of solidarities needed for unionisation is hindered by the detachment of precarious workers from the work community and by inequality regimes. The domination of fear manifests the prevalence of emotions. Therefore, the care and emotional work of unionists is essential for making workers feel confidence. Unions practices tend to lean also, to some extent, towards organising and community building models. Thereby, union agency appears to be able to engage in an interplay with structures to exert some influence on employment and industrial relations.

Cette thèse s’inscrit au carrefour de la mythocritique, de l’imagologie et des études postcoloniales. Elle a pour ambition d’identifier et d’analyser les images littéraires de la Polynésie du seizième au vingt-et-unième siècles grâce aux mythes bibliques et aux mythes polynésiens qui sont à leurs fondements. L’image la plus connue est celle de l’Éden polynésien qu’ont construit les voyageurs occidentaux et que déconstruisent les auteurs insulaires. Les littératures du Triangle sont en outre habitées par un imaginaire vétérotestamentaire réinterprété mais aussi par les réécritures de mythes traditionnels polynésiens. Se mêlent alors culture biblique d’une région très évangélisée et mise en valeur de la Polynésie pré-contact trop souvent niée ou dépréciée par les missionnaires, colons et écrivains occidentaux. Ainsi, le croisement des disciplines et le recours aux concepts polynésiens ont favorisé l’émergence d’une vision globale du rôle des mythes dans les œuvres littéraires qui participent de la représentation de ce territoire archipélique
This study comes within the scope of mythocritics, image and postcolonial studies. It seeks to identify and analyse literary images from the sixteenth to twenty-first century Polynesia through biblical and Polynesian myths which are at the basis of these representations. The most famous image is obviously the Polynesian Eden, a cliché constructed by Western travellers and deconstructed by Insular writers. Literatures of the Triangle are also tinged with a reinterpreted Old Testament imaginary and with re-written traditional Polynesian myths. The biblical culture of a deeply evangelised region then mingles with the highlighted representation of pre-contact Polynesia which was so often denied or disparaged by missionaries, settlers and Western writers. Crossing disciplines and using Polynesian concepts have favoured a global vision of how myths (inter)act within literary works that take part in this territory of archipelago’s representation

In the model room task, children watch as a miniature toy is hidden somewhere in a scale model of a room and are asked to find the larger version of the toy in the corresponding place in the actual room. Previous work has shown that children under age three often perform very poorly on this task. One prominent theory for their failure is that they lack the ability to understand the model as both a physical object and as a symbolic representation of the larger room. An alternative hypothesis is that they need to overcome weak, competing representations of where the object was on a previous trial, and where it is in the present trial, in order to succeed in their search. Children aged 33-39 months were tested on measures of inhibitory control, cognitive flexibility, recognition memory, and receptive vocabulary, as well as the model room task. Results showed that performance on the model room task was not predicted by measures of inhibitory control, cognitive flexibility or vocabulary, but was predicted by performance on the Delayed Recognition Span Test (DRST), a measure of recognition memory. These findings lend support to the theory of competing representations. Given the predictive nature of the recognition memory task and the task’s sensitivity to lesions in the hippocampus, implications for the development of the hippocampus and its role in success on the model room task are discussed.

Thesis (M.A.)--York University, 2008. Graduate Programme in Psychology.
Typescript. Includes bibliographical references (leaves 61-67). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR51575

Les travaux présentés dans cette thèse portent sur l'effet d'apprentissages à court et long terme sur le système visuel. Nous avons d'abord montré grâce à des enregistrements Éléctroencéphalographiques que l'apprentissage d'une séquence de stimuli visuels induisait une activité cérébrale spontanée et sélective au prochain stimulus devant apparaitre et que cette activité sélective s'exprimait dans les bandes alpha et beta de l'activité électrique cérébrale. Par la suite nous avons montré grâce à de l'Imagerie par Résonance Magnétique fonctionnelle que lors d'apprentissages longs (trois semaines) les représentations neurales de catégories visuelles associées étaient modulées et devenaient plus similaires après l'apprentissage. Les travaux présentés dans cette thèse ont donc permis de mieux caractériser l'impact d'apprentissages à différentes échelles de temps sur les représentations neurales d'objets visuels
The work presented in this thesis deals with the effect of short- and long-term learning on the visual system. We first demonstrated through electroencephalographic recordings that learning a sequence of visual stimuli induced spontaneous and selective cerebral activity to the next-to-appear stimulus and that this selective activity was expressed in the alpha and beta bands of cerebral electrical activity. Subsequently, we showed through functional magnetic resonance imaging that during long learning (three weeks) the neural representations of associated visual categories were modulated and became more similar due to learning. The work presented in this thesis has thus made it possible to better characterize the impact of learning at different time scales on the neural representations of visual objects

Este estudo incide na aprendizagem da Matemática e tem como objetivo compreender o modo como alunos do 6.º ano desenvolvem a proporcionalidade, no contexto de exploração de tarefas de comparação multiplicativa. Mais especificamente, pretende responder a duas questões. A primeira, surge relacionada com a caracterização da evolução da aprendizagem da comparação multiplicativa; e a segunda, aparece ligada às conexões entre a compreensão dos aspetos proporcionais das estruturas multiplicativas, em particular, dos conceitos de razão e de proporção, e a flexibilidade de estratégias de resolução e de representações utilizadas pelos alunos. A fundamentação teórica apresenta três temáticas: estruturas multiplicativas e raciocínio proporcional, representações na aprendizagem matemática e flexibilidade na aprendizagem matemática. Discutem-se, sob diferentes perspetivas, os conceitos de comparação multiplicativa, razão e proporção. Referem-se os modos de representação e a sua ligação à compreensão destes conceitos. Menciona-se a flexibilidade na construção de estratégias, no uso de representações, na criatividade e, em concreto, na resolução de tarefas de comparação multiplicativa. O estudo segue uma metodologia de investigação baseada em design, na modalidade de experiência de ensino conduzida a partir de uma conjetura, concretizada em dois ciclos de experiência. Os participantes são os alunos de duas turmas do 6.º ano de escolaridade e as respetivas professoras. A análise dos dados permite concluir que existe, nos dois ciclos de experiência, evolução na aprendizagem da comparação multiplicativa. O raciocínio dos alunos é desenvolvido somente dentro de um espaço de medida, mas as suas estratégias de resolução permitem marcar um percurso que se inicia na não quantificação e prossegue para a necessidade de quantificar e de utilizar estratégias aditivas e multiplicativas, apoiadas em representações simbólicas de razão (na forma de fração, tabelas e linhas numéricas duplas). Quando usam estratégias e representações adequadas, os alunos não mostram grande apetência para as alterar. No entanto, ao resolverem as tarefas identifica-se o uso de relações numéricas multiplicativas e de propriedades da operação multiplicação que articulam com as estratégias e as representações a que recorrem.
This study focuses on process of learning mathematics and aims to understand how 6th grade students develop proportionality in the context of exploring multiplicative comparison tasks. More specifically, it intends to answer two questions. The first is related to the characterization of the learning trajectory of the multiplicative comparison; and the second is linked to the connections between the understanding of the proportional aspects of the multiplicative structures, the concepts of ratio and proportion, and the flexibility of resolution strategies and representations used by the students. The theoretical framework presents three themes: multiplicative structures and proportional reasoning, representations in mathematical learning and flexibility in mathematical learning. From different perspectives, the concepts of multiplicative comparison, ratio and proportion are discussed. An overview of the modes of representation and their connection to the understanding of these concepts is offered. Moreover, flexibility is discussed in context of construction of strategies, use of representations, creativity, and resolution of multiplicative comparison tasks. The study follows a design-based research methodology, in the modality of teaching experiment conducted from a conjecture, comprised of two cycles of experience. Participants are students from two 6th grade classes and their respective teachers. The analysis of the data allows us to conclude that there is an evolution in the learning of the multiplicative comparison in both cycles of experience. Students' reasoning is only developed within a space of measures, but their resolution strategies make it possible to delineate a path that begins with non-quantification and progresses towards the need to quantify and to use additive and multiplicative strategies, which are supported by symbolic representations of ratio (in the form of fraction, tables and double numeric rows). When using appropriate strategies and representations, students are unwilling to change them. However, when solving the tasks, one identifies the use of multiplicative numerical relations and multiplication operation properties that articulate with the strategies and representations they use.

A relação entre a flexibilidade da gestão de recursos humanos e a precariedade laboral tem gerado crescente controvérsia e análise. Se por um lado, existem cada vez mais empresas a utilizar diferentes modalidades de gestão flexível, por outro lado, verifica-se um aumento de trabalhadores com vínculo precário não só em Portugal, como na Europa. Nomeadamente, as formas de flexibilidade externa parecem implicar precariedade acrescida. No âmbito deste estudo pretendemos contribuir para esta reflexão partindo do pressuposto de que a relação flexibilidade/precariedade se apresenta de modos diferentes atendendo à dimensão das empresas, às actividades que desenvolvem (tipo de serviços ou produtos) e às características das ocupações profissionais envolvidas (mais ou menos qualificadas). Assim, exploramos neste estudo o caso de duas micro empresas, de dois sectores distintos, uma das tecnologias de informação e comunicação e outra das actividades artísticas e culturais, ambas envolvendo trabalhadores qualificados (com ocupações profissionais distintas) com o objectivo de identificar e comparar as estratégias e práticas de flexibilidade e seu impacto na precariedade, bem como mapear e comparar as representações sociais dos trabalhadores das duas empresas sobre a flexibilidade/precariedade.
The relationship between flexibility of human resources management and precarious work has generated further controversy and analysis. On the one hand, there are more and more companies using different methods of flexible management and on the other hand, there is an increase of workers with precarious jobs, not only in Portugal, but in general in Europe. In particular, external flexibility seems to imply increased insecurity and precarious jobs. We intend to contribute to this debate with basis on the assumption that the relationship flexibility/precarious work may assume different patterns in view of the size of the companies concerned, their activities (type of services or products) and characteristics of occupations involved (more or less skilled). Thus, we explore in this study the case of two micro enterprises, of two distinct sectors, one within information and communication technologies sector and the other within the artistic and cultural sector, and both comprising skilled workers with the aim of identifying and comparing strategies and practices of flexibility and their impact on precarious work, and with the aim of mapping and comparing the social representations of the workers (of the two companies) in relation to flexibility/precarious work.