Several recent studies show that previous experience can influence observers’ search strategy in a way that improves search performance. The purpose of the present study is to investigate how the experience of difficult color discriminability affects search strategies. Two participant groups either experienced difficult color discriminability in a half of the trials (i.e., hard-discrimination group) or experienced easy search in all trials (i.e., easy-discrimination group) in a dual-target search task. Participants were required to respond to the presence of a target (colored T) among distractors (colored pseudo-L). Eye movements were recorded to understand which feature information is used to guide attention, and behavioral performance was measured to compare search efficiency between the two groups. The hard-discrimination group fixated more distractors with target-dissimilar colors than the easy-discrimination group, suggesting the hard-discrimination group used shape information to guide search more than the easy-discrimination group. However, error rates and response times were not significantly different between groups. The results demonstrate that the experience of difficult color discriminability discourages observers from guiding attention by color, and encourages them to use shape information.

Cette thèse est, au départ, une contribution indirecte au problème de la modélisation de l'acquisition des catégories phonétiques chez l'enfant. Les modèles computationnels déjà proposés n'ont encore jamais été testés de manière systématique pour déterminer s'ils sont réellement à même de rendre compte d'une partie conséquente des observations empiriques disponibles. Nous développons une approche permettant une évaluation systématique des modèles sur la base de Mesures de Discriminabilité ABX. Nous montrons l'intérêt de notre approche en l'appliquant à deux problèmes reliés: la traitement des catégories phonétiques à la naissance et à l'âge adulte. La prochaine étape sera bien sûr d'appliquer notre approche aux modèles d'acquisition des catégories phonétiques.L'intérêt des Mesures de Discriminabilité ABX ne se restreint pas au cas particulier de l'évaluation des modèles de traitement des catégories phonétiques. Elle sont utiles dans l'étude de signaux autre que la parole et de catégories autres que les catégories phonétiques, ainsi que dans le cadre de champs disciplinaires autres que les sciences cognitives, comme l'ingénierie, l'exploration des données ou l'intelligence artificielle par exemple. Nous le justifions en étudiant les propriétés de ces mesures dans un cadre abstrait général et en présentant trois grandes familles d'applications: l'évaluation de la capacité de systèmes opérant en l'absence de supervision explicite à représenter une structure catégorielle; la formulation de modèles computationnels simples du comportement dans des tâches de discrimination; la définition de mesures descriptives pour des représentations associées à des données catégorielles. / This thesis constitutes an indirect contribution to the problem of modeling phonetic category acquisition in infancy. Some specific computational models of phonetic category acquisition have been proposed, but they were never tested extensively nor compared quantitatively to see whether they were really able to account for a sizable portion of the available empirical observations. In this thesis, we introduce ABX-Discriminability Measures and we develop a methodology based on these measures that allows to perform such a systematic evaluation. We demonstrate the interest of our framework by applying it to the evaluation of models for two related problems: phonetic category processing at birth and in adulthood. The next step, applying our framework to models of phonetic category acquisition, is left for future work.The interest of ABX-Discriminability Measures is not restricted to the particular problem of evaluating models of phonetic category processing in humans. We argue that their interest generalizes to the study of other signals than speech and other category structures than phonetic categories, as well as to other research fields than cognitive science, like low-resource engineering, data mining and artificial intelligence for example. To make this point, we study the properties of these measures in a general abstract framework and we detail the rationale for three broad family of potential applications: evaluating systems operating without explicit supervision in their ability to represent a category structure; providing simple computational models of behavior in discrimination tasks; providing descriptive measurements for representations of categorical data.

Em experimentos anteriores utilizando tarefa de tempo de reação (TR) vai/não-vai com diferentes estímulos-alvo aparecendo após um estímulo precedente, observamos efeito positivo do estímulo precedente quando o estímulo-alvo era uma linha dentro de um anel, mas não quando era uma cruz dentro de um anel. Este resultado foi atribuído a uma diferença nas discriminabilidades dos dois estímulos em relação ao estímulo negativo, um anel pequeno dentro do anel. A discriminação da cruz seria mais fácil, o que levaria os indivíduos a ignorar o estímulo precedente, resultando em ausência do efeito positivo. O objetivo deste trabalho foi comparar as discriminabilidades da linha e da cruz em relação ao estímulo negativo, o anel, para dar suporte à hipótese considerada, e a partir deste resultado discutir os processos responsáveis pela manifestação ou não de eventuais diferenças de discriminabilidade no comportamento. Nos experimentos 1, 2 e 3 utilizamos tarefas de tempo de reação vai/não-vai sem estímulo precedente, e nos experimentos 4 e 5 utilizamos tarefas com ênfase na acurácia das respostas. No primeiro experimento linha e cruz foram apresentadas em blocos de tentativas diferentes. Nestas condições, os TR à linha e à cruz se igualaram na segunda sessão, mas na primeira sessão o grupo que respondeu primeiro à linha e depois à cruz teve TR menores para a cruz. No segundo experimento, linha e cruz foram apresentadas aleatoriamente nos mesmos blocos de tentativas, para induzir a adoção de estratégia de resposta comum aos dois estímulos. Desta forma evidenciamos uma diferença nos TR, sendo que estes foram menores para a cruz, indicando que esta é mais discriminável que a linha. No terceiro experimento grupos diferentes de voluntários responderam à linha e à cruz. Os TR assim obtidos, iguais para linha e para cruz, indicam que as igualdades nos TR aos dois estímulos-alvo encontradas no primeiro experimento independem da exposição prévia a outro estímulo-alvo. O conjunto destes resultados sugere que linha e cruz têm discriminabilidades diferentes, sendo a cruz mais discriminável que a linha. Esta diferença, no entanto, é evidenciada apenas quando uma mesma estratégia de resposta é adotada para lidar com os dois estímulos. No quarto experimento construímos curvas psicométricas e observamos valores iguais de sensibilidade para a linha e para a cruz. No quinto experimento utilizamos uma tarefa de escolha. Uma análise por meio da Teoria de Detecção de Sinais forneceu medidas do parâmetro sensorial d´ maiores para a linha que para a cruz, indicando que a linha é mais discriminável que a cruz, além de medidas do parâmetro decisional critério iguais para os dois estímulos. Este padrão de resultados, contrário aos obtidos nos experimentos 1 a 3, foi atribuído às diferentes condições de estimulação com cada metodologia: em condições de estimulação supra-limiar como as utilizadas nas tarefas de TR a cruz é mais discriminável (em relação ao anel) que a linha, mas em condições de estimulação próximas do limiar a linha passa a ser mais discriminável. / In a former study in a go/no-go task, we found a reduction in reaction times (RT) at a cued position when the target stimulus was a line inside a ring but not when the target stimulus was a cross inside a ring. We hypothesized that this was due to a difference in the discriminabilities of the target stimuli from the no/go stimulus, a small ring inside a ring. The cross would be more easily discriminated from the no/go stimulus, causing the cue to lose its relevance and to be ignored. The goal of the present study was to compare the discriminabilities of the line and of the cross to support that hypothesis, and to determine the relative contributions of the attentional strategy and of the criterion to prevent such an existing difference from manifesting itself behaviorally. We ran three experiments with a go/no-go RT task with no cue and two experiments in which the accuracy of the responses was the dependent variable. In the first experiment the line and cross were presented in different blocks of trials. RT to both stimuli were equal in the second session of trials, but in the first session the group that responded first to the line (and later to the cross) had smaller RT to the cross. In the second experiment, line and cross were randomized in the same blocks of trials to force participants to respond to both stimuli with the same attentional strategy and/or criterion. This led to faster RT to the cross, indicating that it is easier to discriminate it than the line. In the third experiment the line and the cross were presented to different participants. This led to equal RT to both stimuli, indicating that the equality of RT found in Experiment 1 was not dependent on former experience with a different target stimulus. The results from these three experiments suggest that the cross is in fact easier to discriminate than the line, but this difference can only be expressed behaviorally if participants use the same attentional strategy and/or criterion to handle both stimuli. In the fourth experiment we used the accuracy data to build psychometric functions and we found no difference between responses to the line and to the cross on the slope of the curves or on the points of subjective equality. In the fifth experiment we used a Signal Detection Theory analysis to compare the sensitivity parameter d` and the bias parameter criterion and found bigger d` values to the line and no bias difference. These results are opposite to the RT results, probably because of differing stimulatory conditions. In high intensities such as the ones used in experiments 1, 2 and 3 the cross is more easily discriminated from the negative stimulus than the line, but in near-threshold intensities the line is more easily discriminated.

Em experimentos anteriores utilizando tarefa de tempo de reação (TR) vai/não-vai com diferentes estímulos-alvo aparecendo após um estímulo precedente, observamos efeito positivo do estímulo precedente quando o estímulo-alvo era uma linha dentro de um anel, mas não quando era uma cruz dentro de um anel. Este resultado foi atribuído a uma diferença nas discriminabilidades dos dois estímulos em relação ao estímulo negativo, um anel pequeno dentro do anel. A discriminação da cruz seria mais fácil, o que levaria os indivíduos a ignorar o estímulo precedente, resultando em ausência do efeito positivo. O objetivo deste trabalho foi comparar as discriminabilidades da linha e da cruz em relação ao estímulo negativo, o anel, para dar suporte à hipótese considerada, e a partir deste resultado discutir os processos responsáveis pela manifestação ou não de eventuais diferenças de discriminabilidade no comportamento. Nos experimentos 1, 2 e 3 utilizamos tarefas de tempo de reação vai/não-vai sem estímulo precedente, e nos experimentos 4 e 5 utilizamos tarefas com ênfase na acurácia das respostas. No primeiro experimento linha e cruz foram apresentadas em blocos de tentativas diferentes. Nestas condições, os TR à linha e à cruz se igualaram na segunda sessão, mas na primeira sessão o grupo que respondeu primeiro à linha e depois à cruz teve TR menores para a cruz. No segundo experimento, linha e cruz foram apresentadas aleatoriamente nos mesmos blocos de tentativas, para induzir a adoção de estratégia de resposta comum aos dois estímulos. Desta forma evidenciamos uma diferença nos TR, sendo que estes foram menores para a cruz, indicando que esta é mais discriminável que a linha. No terceiro experimento grupos diferentes de voluntários responderam à linha e à cruz. Os TR assim obtidos, iguais para linha e para cruz, indicam que as igualdades nos TR aos dois estímulos-alvo encontradas no primeiro experimento independem da exposição prévia a outro estímulo-alvo. O conjunto destes resultados sugere que linha e cruz têm discriminabilidades diferentes, sendo a cruz mais discriminável que a linha. Esta diferença, no entanto, é evidenciada apenas quando uma mesma estratégia de resposta é adotada para lidar com os dois estímulos. No quarto experimento construímos curvas psicométricas e observamos valores iguais de sensibilidade para a linha e para a cruz. No quinto experimento utilizamos uma tarefa de escolha. Uma análise por meio da Teoria de Detecção de Sinais forneceu medidas do parâmetro sensorial d´ maiores para a linha que para a cruz, indicando que a linha é mais discriminável que a cruz, além de medidas do parâmetro decisional critério iguais para os dois estímulos. Este padrão de resultados, contrário aos obtidos nos experimentos 1 a 3, foi atribuído às diferentes condições de estimulação com cada metodologia: em condições de estimulação supra-limiar como as utilizadas nas tarefas de TR a cruz é mais discriminável (em relação ao anel) que a linha, mas em condições de estimulação próximas do limiar a linha passa a ser mais discriminável. / In a former study in a go/no-go task, we found a reduction in reaction times (RT) at a cued position when the target stimulus was a line inside a ring but not when the target stimulus was a cross inside a ring. We hypothesized that this was due to a difference in the discriminabilities of the target stimuli from the no/go stimulus, a small ring inside a ring. The cross would be more easily discriminated from the no/go stimulus, causing the cue to lose its relevance and to be ignored. The goal of the present study was to compare the discriminabilities of the line and of the cross to support that hypothesis, and to determine the relative contributions of the attentional strategy and of the criterion to prevent such an existing difference from manifesting itself behaviorally. We ran three experiments with a go/no-go RT task with no cue and two experiments in which the accuracy of the responses was the dependent variable. In the first experiment the line and cross were presented in different blocks of trials. RT to both stimuli were equal in the second session of trials, but in the first session the group that responded first to the line (and later to the cross) had smaller RT to the cross. In the second experiment, line and cross were randomized in the same blocks of trials to force participants to respond to both stimuli with the same attentional strategy and/or criterion. This led to faster RT to the cross, indicating that it is easier to discriminate it than the line. In the third experiment the line and the cross were presented to different participants. This led to equal RT to both stimuli, indicating that the equality of RT found in Experiment 1 was not dependent on former experience with a different target stimulus. The results from these three experiments suggest that the cross is in fact easier to discriminate than the line, but this difference can only be expressed behaviorally if participants use the same attentional strategy and/or criterion to handle both stimuli. In the fourth experiment we used the accuracy data to build psychometric functions and we found no difference between responses to the line and to the cross on the slope of the curves or on the points of subjective equality. In the fifth experiment we used a Signal Detection Theory analysis to compare the sensitivity parameter d` and the bias parameter criterion and found bigger d` values to the line and no bias difference. These results are opposite to the RT results, probably because of differing stimulatory conditions. In high intensities such as the ones used in experiments 1, 2 and 3 the cross is more easily discriminated from the negative stimulus than the line, but in near-threshold intensities the line is more easily discriminated.

La prolifération des réseaux sociaux et des données à caractère personnel apporte de nombreuses possibilités de développement de nouvelles applications. Au même temps, la disponibilité de grandes quantités de données à caractère personnel soulève des problèmes de confidentialité et de sécurité. Dans cette thèse, nous développons des méthodes pour identifier les différents comptes d'un utilisateur dans des réseaux sociaux. Nous étudions d'abord comment nous pouvons exploiter les profils publics maintenus par les utilisateurs pour corréler leurs comptes. Nous identifions quatre propriétés importantes - la disponibilité, la cohérence, la non-impersonabilite, et la discriminabilité (ACID) - pour évaluer la qualité de différents attributs pour corréler des comptes. On peut corréler un grand nombre de comptes parce-que les utilisateurs maintiennent les mêmes noms et d'autres informations personnelles à travers des différents réseaux sociaux. Pourtant, il reste difficile d'obtenir une précision suffisant pour utiliser les corrélations dans la pratique à cause de la grandeur de réseaux sociaux réels. Nous développons des schémas qui obtiennent des faible taux d'erreur même lorsqu'elles sont appliquées dans les réseaux avec des millions d'utilisateurs. Ensuite, nous montrons que nous pouvons corréler les comptes d'utilisateurs même si nous exploitons que leur activité sur un les réseaux sociaux. Ça sa démontre que, même si les utilisateurs maintient des profils distincts nous pouvons toutefois corréler leurs comptes. Enfin, nous montrons que, en identifiant les comptes qui correspondent à la même personne à l'intérieur d'un réseau social, nous pouvons détecter des imitateurs. / The proliferation of social networks and all the personal data that people share brings many opportunities for developing exciting new applications. At the same time, however, the availability of vast amounts of personal data raises privacy and security concerns.In this thesis, we develop methods to identify the social networks accounts of a given user. We first study how we can exploit the public profiles users maintain in different social networks to match their accounts. We identify four important properties – Availability, Consistency, non- Impersonability, and Discriminability (ACID) – to evaluate the quality of different profile attributes to match accounts. Exploiting public profiles has a good potential to match accounts because a large number of users have the same names and other personal infor- mation across different social networks. Yet, it remains challenging to achieve practically useful accuracy of matching due to the scale of real social networks. To demonstrate that matching accounts in real social networks is feasible and reliable enough to be used in practice, we focus on designing matching schemes that achieve low error rates even when applied in large-scale networks with hundreds of millions of users. Then, we show that we can still match accounts across social networks even if we only exploit what users post, i.e., their activity on a social networks. This demonstrates that, even if users are privacy conscious and maintain distinct profiles on different social networks, we can still potentially match their accounts. Finally, we show that, by identifying accounts that correspond to the same person inside a social network, we can detect impersonators.

No description available.

Recently cognitive principles have been discussed for Conceptual Modeling with the aim to increase domain understanding, model comprehension and modeling efficiency. In particular, the principle of Perceptual Discriminability, which discusses the visual differences of modeling constructs, reveals potential for model comprehension if human attention is influenced in a way that important modeling constructs are more easily detected, and can hence faster be processed. Yet, so far no conditions how the human gaze can be influenced have been defined and evaluated for Conceptual Modeling. This dissertation extends Perceptual Discriminability for conditions to attract human attention for those constructs that are important for model comprehension. Furthermore, these conditions are applied to constructs of two different modeling grammars in general as well as to elements of the process flow of Business Process Models. To evaluate the results a laboratory experiment of extended Perceptual Discriminability is described in which significant differences have been identified for process flow comprehension. For the demonstration of the potential of extended Perceptual Discriminability BPMN secondary notation is improved by emphasizing those constructs that are most important for model comprehension. Therefore, those constructs that are important for model comprehension have been identified within a content analysis and have been worked on according to the conditions of extended Perceptual Discriminability for those visual variables that are free for an application in secondary notation.

Cette thèse porte sur la compréhension de textes et plus précisément sur son caractère dynamique. Elle interroge la validité d’une notion qui fait consensus dans les différents modèles de compréhension, celle du modèle de situation qui est la représentation de la situation évoquée par le texte. Construit tout au long de la lecture et permettant l’établissement de la cohérence, ce modèle de situation serait le produit fini obtenu à la fin de la lecture. A travers quatre séries d’expériences, ce travail étudie la répercussion qu’une tâche de compréhension proposée après lecture d’un texte, peut avoir sur la compréhension même du texte. La première série d’expériences examine si la dynamique du modèle de situation, c'est-à-dire sa mise à jour, perdure au-delà de la simple lecture du texte. Les séries d’expériences suivantes s’axent sur l’effet du contexte au moment de la tâche de compréhension. Plus précisément, la deuxième série d’expériences porte sur un effet de discriminabilité au sein des énoncés à juger dans la tâche de compréhension après lecture ; la troisième et quatrième série d’expériences manipulent la fluence conceptuelle et perceptive du traitement. Les résultats tendent à montrer que la réponse du participant n’est pas un acte faisant appel au passé et à une représentation, mais un acte dans le présent et dépendant du contexte situationnel. Ainsi, sa réponse n’est pas contenue dans un schéma pré-stocké que l’on pourrait nommer modèle de situation, mais émerge du présent et de son contexte. / This thesis is about text comprehension and more precisely about its dynamic feature. It questions the validity of a notion which has reached consensus in the various models of comprehension: The notion of situation model which is the representation of the situation evoked by the text. Founded throughout the reading and allowing the establishment of coherence, this situation model would be the final product obtained at the end of this reading. Through four series of experiments, this thesis puts under scrutiny the repercussion a comprehension task, proposed after the reading of a text, could have on the very comprehension of the text. The first series of experiments examines whether the model situation’s dynamic, meaning its updating, is maintained beyond a straightforward reading of the text. The next series of experiments are centred on the context effect when the comprehension task occurred. Much more precisely, the second series of experiments deals with the discriminability effect within the statements which are going to be judged during the comprehension task after reading; the third and fourth series of experiments manipulate the conceptual fluency and the perceptual fluency. The results tend to point to the fact that the participant’s response is not an act referring to the past and a representation, but an act embedded in the present, which depends on the situational context. Thus, the participant’s response is not held in a pre-stocked schema, that we could call situation model but emerges from the present and from its context.

Recently cognitive principles have been discussed for Conceptual Modeling with the aim to increase domain understanding, model comprehension and modeling efficiency. In particular, the principle of Perceptual Discriminability, which discusses the visual differences of modeling constructs, reveals potential for model comprehension if human attention is influenced in a way that important modeling constructs are more easily detected, and can hence faster be processed. Yet, so far no conditions how the human gaze can be influenced have been defined and evaluated for Conceptual Modeling. This dissertation extends Perceptual Discriminability for conditions to attract human attention for those constructs that are important for model comprehension. Furthermore, these conditions are applied to constructs of two different modeling grammars in general as well as to elements of the process flow of Business Process Models. To evaluate the results a laboratory experiment of extended Perceptual Discriminability is described in which significant differences have been identified for process flow comprehension. For the demonstration of the potential of extended Perceptual Discriminability BPMN secondary notation is improved by emphasizing those constructs that are most important for model comprehension. Therefore, those constructs that are important for model comprehension have been identified within a content analysis and have been worked on according to the conditions of extended Perceptual Discriminability for those visual variables that are free for an application in secondary notation.:Preface ii Abstract iii Table of contents iv Table of Figures v List of Tables vi List of Abbreviations vii Part 1 - Summary Paper 1 1. Motivation 2 2. Research design 7 2.1 Research objectives 7 2.2 Scope 9 2.3 Research method 11 3. Structure of the dissertation 13 4. Contribution to theory and practice 17 5. Future Research Ideas 19 Part 2 - Publications 20 Publication 1 21 Publication 2 22 Publication 3 23 Publication 4 24 Publication 5 25 Publication 6 26 Literature 27 Part 3 - Appendix 30

[pt] Baseado na Teoria Cumulativa da Perspectiva, três ensaios são apresentados nessa tese. Todos os três trabalhos estão conectados pelo entendimento aprofundado da Função de Ponderação de Probabilidade e suas conexões cenários de decisão sob risco. O primeiro ensaio é um trabalho empírico utilizando a teoria da perspectiva para analisar o viés do efeito de enquadramento em decisões de investimentos em certos países emergentes: Brasil, China, Russia, México e África do Sul. Em todos os casos, identificamos empiricamente o poder preditivo da teoria da perspectiva para os retornos dos ativos. Também encontramos que a função de ponderação de probabilidade é o fator mais importante para o poder preditivo. O segundo ensaio é um trbalho teórico propondo uma axiomatização da função de ponderação de Goldstein-Einhorn. Desde 1987, a conhecida função de ponderação de Goldstein-Einhorn é largamente utilizada em trabalhos em muitos artigos empíricos e teóricos. Richard Gonzalez e GeorgeWu propuseram uma axiomatização para esta função em 1999. O trabalho que apresentamos analisa a condição de preferência dos autores e encontra uma família maior de funções de ponderação. Fornecemos exemplos úteis e sugerimos uma nova condição de preferência que é necessária e suficiente para a função de Goldstein- Einhorn. Esta nova condição de prefer6encia simula o comportamento das pessoas em situações que envolvem atitutes arriscadas. O terceiro ensaio propõe uma medida para as características psicológicas chamadas de atratividade e discriminabilidade, no contexto das funções de ponderação de probabilidades. Esse conceitos são importantes para nos ajudar a entender como algumas emoções influenciam nosso comportamento. Propomos medidas no sentido absoluto e relativo e as comparamos com alguns exemplos particulares encontrados na literatura. Nossos resultados são consistentes com o entendimento qualitativo encontrado na literatura e fornece um entendimento quantitativo para ele. / [en] Based on Cumulative Prospect Theory, three essays are presented in this thesis. All three works are linked by a deeper understanding of Probability Weighting Functions and its connection with decisions in a risk scenario. The first essay is an empirical work using prospect theory to analyze the narrow framing bias in investment decisions in certain emerging countries: Brazil, China, Russia, Mexico and South Africa. In all cases, we empirically identified the predictive power of prospect theory for stock returns. We also found that the probability weighting function is the most important factor in this predictive power. The second essay is a theoretical work proposing an axiomatization for the Goldstein-Einhorn weighting function. Since 1987, the well known Goldstein- Einhorn Weighting Function is widely used in many empirical and theoretical papers. Richard Gonzalez and George Wu proposed an axiomatization for it in 1999. The present work analyses their preference condition and finds a bigger family of weighting functions. We provide useful examples and suggest a new preference condition which is necessary and sufficient for Goldstein-Einhorn function. This new preference condition simulates the behavior of people in risky attitudes. The third essay propose a measure to evaluate the psychological features of attractiveness and discriminability in the context of probability weighting functions. These concepts are important to help us understand how some emotions drive our behavior. We propose measures in absolute and in the relative sense and compare with some particular cases found in the literature. Our findings are consistent with the qualitative understanding widespread in the literature and provide a quantitative analysis for it.