Tesis Doctorales

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Text-based link prediction in social networks
(Universidad del Desarrollo. Facultad de Gobierno, 2022) Toledo Román, Ignacio Galvarino; Fábrega Lacoa, Jorge
This thesis aims to contribute to the literature on text-based link prediction methods in scientific collaboration networks with two original works. First, in Chapter I we present a comprehensive survey on text-based link prediction methods in social networks. And second, in Chapter II we introduce a simple but effective approach to improve the performance of text-based link prediction models.
Evolutionary determinants and hormonal underpinning of men's mating strategies: Correlational and experimental evidence from Chilean samples”
(Universidad del Desarrollo. Facultad de Gobierno, 2022) Fajardo Rodríguez, Gabriela Paz; Polo, Pablo
Humans show a wide variety of mating strategies, from promiscuous mating to the establishment and maintenance of long-lasting pair-bonds, with variation between sexes, within sexes, and within-individuals. The following thesis focuses on men’s mating strategies, from an evolutionary and a proximate approach, presenting the results from two studies. The first one takes the evolutionary perspective, that proposes the variation on mating strategies can be partially explained by phenotypical, social, and environmental factors. We aimed to investigate the traits associated with men’s predisposition to invest in long-term mating to understand the selective pressures that shape the cost-benefit balance that favors men’s parental investment. We obtained that socioeconomic status is the main predictor for long-term mating orientation, while strength is highly associated with short-term orientation in men. The second study considers a proximate approach, where testosterone and immediate social context play a major role in regulating individuals’ mating strategies. We investigated the testosterone-related and social mechanisms involved in the calibration of long and short-term mating strategies, obtaining that the most relevant factor to explain these strategies is the inclusion of a female confederate in the immediate context where the session was carried out. This manuscript brings together approaches from the ultimate and proximate causes for a better understanding of human mating strategies in men.
Neurobiological coding of value and prediction error in stable and volatility uncertainty contexts in human decision making
(Universidad del Desarrollo. Facultad de Gobierno, 2022-10) Valdebenito, Gabriela; Billeke, Pablo
Los neurocientíficos que estudian el proceso de toma de decisiones económicas se han centrado en investigar cómo los seres humanos, y otras especies animales, eligen entre diferentes opciones guiadas por refuerzo. El cálculo de la probabilidad de obtener una recompensa y el valor de las opciones disponibles son elementos que deben ser estimados con precisión para obtener buenos resultados. Sin embargo, en el contexto de la vida cotidiana, este proceso puede tener diferentes grados de complejidad dependiente del nivel de información que poseamos desde las experiencias previas y que nos entrega el ambiente. La estimación de los factores que afectan una elección implica un proceso de aprendizaje que está mediado por la capacidad de diseñar y actualizar un modelo interno del valor de las probabilidades de las opciones a través de la detección de la magnitud del error de la predicción. Se han investigado extensamente los mecanismos neurobiológicos que subyacen al proceso de toma de decisiones en diferentes contextos de incertidumbre. Para la condición de ambigüedad se ha observado la presencia de actividad en la corteza parietal cuyo rol aún no está claro y es el centro de esta investigación. En la presente tesis se presenta el estudio de la toma de decisiones en diferentes contextos de incertidumbre (estable y volátil) para evaluar los mecanismos neurobiológicos de la computación de la incertidumbre. Para esta investigación se han diseñado dos tareas experimentales con diferentes condiciones que afectan directamente al grado de información que reciben los jugadores para hacer una predicción. Las hipótesis que se evalúan en esta investigación son: (i) La corteza parietal contribuye causalmente en la valorización de la información ambigua durante la toma de decisiones en contextos de incertidumbre estable. (ii) La corteza parietal participa en la detección del cambio de las contingencias en contexto de incertidumbre volátil. Para testear nuestras hipótesis se realizaron dos experimentos: 1. Sesenta y seis participantes resolvieron una tarea de toma de decisiones probabilísticas (PDM) en dos sesiones experimentales. En primera instancia, los sujetos realizaron el experimento bajo resonancia magnética funcional para medir los cambios de la señal BOLD. Nuestro análisis se centró en observar la actividad neurobiológica y conductual asociada a la construcción del valor de las probabilidades en contexto de ambigüedad. Los resultados mostraron una importante activación de la corteza parietal posterior y el surco intra parietal, también se observó actividad en el giro frontal inferior asociado al valor absoluto del error en la predicción. En concordancia con el objetivo de evaluar nuestra hipótesis, en una segunda sesión experimental, los participantes realizaron la misma tarea bajo la medición de la actividad electri siológica y la estimulación inhibitoria previo al feedback en los dos focos de la corteza parietal para perturbar el procesamiento cognitivo y conductual de la probabilidad. Los resultados revelaron que la estimulación de la corteza parietal afectó la construcción de la probabilidad ambigua. Además, se observó una disminución en la actividad theta de la corteza frontal inferior asociado al error en la predicción demostrando un rol causal de la corteza parietal en la computación de la ambigüedad. 2. Treinta participantes resolvieron una tarea de toma de decisiones en contexto de incertidumbre estable y volátil (DMUV). La actividad cerebral fue medida bajo resonancia magnética funcional. Los análisis se centraron en calcular el valor de la función de aprendizaje en cada contexto del experimento y la actividad neurobiológica durante el periodo del feedback. Los resultados mostraron un aumento de la señal BOLD en la corteza parietal asociado a la función de aprendizaje en el contexto de alta incertidumbre volátil.
Using experimental game theory to measure cooperative relations in elementary school classrooms to understand its relationship with academic performance and school climate
(Universidad del Desarrollo. Facultad de Gobierno, 2022-05) Landaeta Torres, Víctor; Rodríguez-Sickert, Carlos
Cooperation has been key to our success as a species. Cooperative behavior on multiple levels and the structures that emerge from those interactions have been extending over different domains and scopes, from small food-sharing networks among hunter-gatherers to global trade and the generation and diffusion of knowledge and technology worldwide. Groups and societies have been creating and changing increasingly complex social mechanisms and institutions to allow, promote, and support cooperation and its scaling. All these efforts have boosted and expanded the benefits of cooperation but also have increased our interdependence between different actors, which also implies higher systemic risks. Cooperative Networks in small groups are the essential building blocks to sustain and promote large-scale cooperation. Moreover, large-scale cooperation is possibly our best chance to face today’s most significant global challenges and threats, such as climate change and global pandemics. Schools are crucial for human development. Here, we first face peers and learn how to cooperate with strangers. The school’s main goals are socialization, the transmission of culture, and teaching knowledge and skills. Classrooms, in many ways, have a similar tribe-like structure and a nested and controlled general situation, so dynamic cooperative networks emerge and mutate. Two main challenges for schools nowadays are about learning and well-being. In specific, how can we improve learning and achievement? And, how can we make school a safer, bullying-free place? Cooperative learning literature has consistently found that creating more cooperative learning environments has causal effects on increased academic achievement and decreased bullying behavior. However, no precise mechanism is known. So, our main research question over this work is the following: How cooperative networks in the classroom relate with other educational outcomes, particularly Academic Achievement and Bullying Behavior? But, how can we measure cooperation in the class, and elicit these networks? We propose that we can use experimental Game Theory, specifically implementing in the field an adaptation of a lab game-theoretic social dilemma, which try to reproduce with ecological similarities the tension between individual interests and social efficiency that students face in real life everyday interactions in the classroom. The essential concept is External Validity. We expect that the student’s behavior in the game will reflect their day-to-day behavior and classroom structure. The dyadic social dilemma we implement is a modified version of the Prisoner’s dilemma. A major adjustment is that in this game, students are aware of the partner’s identity that has been matched to them each round, i.e., the game is non-anonymous. Thereby, their choices when playing again each other are not only the result of intrinsic prosocial dispositions (or their absence), but also the result of their history and the perceptions they have about each other. In the first chapter, our first draft paper tackles the relationship between cooperative network topology and academic performance. We measured the cooperative centrality of students by quantifying their deviations from the average level of reciprocal cooperation in each interaction and found that students that engaged in high levels of reciprocal cooperation have significantly higher GPAs. In the second chapter, our second draft paper characterized the relationship between cooperative network topology and bullying subtypes. We categorized students on their bullying involvement in four different social categories: bully, bully-victim, victim, and non-involved students. Then, we use the data from the experiment combined with a self-report instrument and using multilevel modeling, we study how bullies, victims and bully-victims differ in their access to the elicited cooperative network. We found that bully/victims and victims tend to receive less tokens than non-involved students. Both articles have important policy implications to the extent that they can inform the design of interventions in the early phases of education to improve both academic achievement and social coexistence.
The chilean constituent process: A Computational Social Science approach.
(Universidad del Desarrollo. Facultad de Gobierno, 2022-01) Raveau Morales, María Paz; Couyoumdjian, Juan Pablo
In October 2015, the government of Chile started a constitution-making process, which allowed citizen participation. During the participatory phase, citizens gathered in local selfconvoked encounters to debate on four dimensions: constitutional values, rights, duties, and institutions. For each one of these four dimensions, participants collectively selected seven concepts from a list provided by the government or added new ones. For each concept, they wrote down a short argument explaining why this concept should be included in the new constitution. Although this process did not result in a new Constitution, the citizen consultation resulted in a valuable and unique source of information about people’s social and political preferences. The first objective of this work is related to the constitutional process itself and the citizen participation. The Chilean process exhibited two critical design weaknesses we analyze here. The first one is representativeness: the voluntary nature of the encounters increased participation biases, as those citizens who support the acting government were more likely to participate in the consultation. We study the determining factors of citizen participation in ELAs by setting up various regression models at the municipality-level. We found that engagement in politics and support for the government increases participation, which suggests that citizen involvement in the constitutional process may have been ideologically driven. The second weakness is the group deliberation quality. For a public deliberation to produce epistemic superiority, all the participants should have access to relevant and accurate information and evidence. Then, we analyze the written arguments for each selected concept, using structural topic modeling and natural language processing. We show that the emergent content can be ideologically differentiated, and that groups from municipalities with higher socioeconomic index, on average, produce higher-quality deliberation compared to groups from less developed municipalities. The second object of study comes from the data. The dataset gathered in the local participatory phase provides a rich source of information about people’s political preferences. To map the political ideology, we built co-occurrence networks where the nodes represent the constitutional concepts, and the links represent the association among them. Then, we aim to discover the structure of the ideology by examining the resulting networks, and identifying clusters - highly connected groups of concepts - inside them. The communities we found are consistent with the political conglomerates existing in Chile in 2016. Finally, using natural language processing techniques, we extracted psycho-linguistic features from the argument texts. These features are “internal factors”, for they respond to the intrinsic psychological, emotional, attitudinal or cognitive state of the subject, which affects their political ideology. Next, we set up a discrete choice model to study the effect of those features in cluster membership. We find that the progressive-left cluster shows a more propositive and non-agentic attitude when referring to values, as opposed to the traditional left. Regarding the dimension of rights, the right-wing cluster displays a more valorative attitude, suggesting that first-generation rights may also play the role of values. Throughout all chapters, and by the methods we use, this work attempts to contribute to the field of computational social science.

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