Toward human-like pathfinding with hierarchical approaches and the GPS of the brain theory

Pathfinding for autonomous agents and robots has been traditionally driven by finding optimal paths. Where typically optimality means finding the shortest path between two points in a given environment. However, optimality may not always be strictly necessary. For example, in the case of video games, often computing the paths for non-player characters (NPC) must be done under strict time constraints to guarantee real time simulation. In those cases, performance is more important than finding the shortest path, specially because often a sub-optimal path can be just as convincing from the point of view of the player. When simulating virtual humanoids, pathfinding has also been used with the same goal: finding the shortest path. However, humans very rarely follow precise shortest paths, and thus there are other aspects of human decision making and path planning strategies that should be incorporated in current simulation models. In this thesis we first focus on improving performance optimallity to handle as many virtual agents as possible, and then introduce neuroscience research to propose pathfinding algorithms that attempt to mimic humans in a more realistic manner.In the case of simulating NPCs for video games, one of the main challenges is to compute paths as efficiently as possible for groups of agents. As both the size of the environments and the number of autonomous agents increase, it becomes harder to obtain results in real time under the constraints of memory and computing resources. For this purpose we explored hierarchical approaches for two reasons: (1) they have shown important performance improvements for regular grids and other abstract problems, and (2) humans tend to plan trajectories also following an topbottom abstraction, focusing first on high level location and then refining the path as they move between those high level locations. Therefore, we believe that hierarchical approaches combine the best of our two goals: improving performance for multi-agent pathfinding and achieving more human-like pathfinding. Hierarchical approaches, such as HNA* (Hierarchical A* for Navigation Meshes) can compute paths more efficiently, although only for certain configurations of the hierarchy. For other configurations, the method suffers from a bottleneck in the step that connects the Start and Goal positions with the hierarchy. This bottleneck can drop performance drastically.In this thesis we present different approaches to solve the HNA* bottleneck and thus obtain a performance boost for all hierarchical configurations. The first method relies on further memory storage, and the second one uses parallelism on the GPU. Our comparative evaluation shows that both approaches offer speed-ups as high as 9x faster than A*, and show no limitations based on hierarchical configuration. Then we further exploit the potential of CUDA parallelism, to extend our implementation to HNA* for multi-agent path finding. Our method can now compute paths for over 500K agents simultaneously in real-time, with speed-ups above 15x faster than a parallel multi-agent implementation using A*. We then focus on studying neurosience research to learn about the way that humans build mental maps, in order to propose novel algorithms that take those finding into account when simulating virtual humans. We propose a novel algorithm for path finding that is inspired by neuroscience research on how the brain learns and builds cognitive maps. Our method represents the space as a hexagonal grid, based on the GPS of the brain theory, and fires memory cells as counters. Our path finder then combines a method for exploring unknown environments while building such a cognitive map, with an A* search using a modified heuristic that takes into account the GPS of the brain cognitive map.El problema de Pathfinding para agentes autónomos o robots, ha consistido tradicionalmente en encontrar un camino óptimo, donde por óptimo se entiende el camino de distancia mínima entre dos posiciones de un entorno. Sin embargo, en ocasiones puede que no sea estrictamente necesario encontrar una solución óptima. Para ofrecer la simulación de multitudes de agentes autónomos moviéndose en tiempo real, es necesario calcular sus trayectorias bajo condiciones estrictas de tiempo de computación, pero no es fundamental que las soluciones sean las de distancia mínima ya que, con frecuencia, el observador no apreciará la diferencia entre un camino óptimo y un sub-óptimo. Por tanto, suele ser suficiente con que la solución encontrada sea visualmente creíble para el observado. Cuando se simulan humanoides virtuales en aplicaciones de realidad virtual que requieren avatares que simulen el comportamiento de los humanos, se tiende a emplear los mismos algoritmos que en video juegos, con el objetivo de encontrar caminos de distancia mínima. Pero si realmente queremos que los avatares imiten el comportamiento humano, tenemos que tener en cuenta que, en el mundo real, los humanos rara vez seguimos precisamente el camino más corto, y por tanto se deben considerar otros aspectos que influyen en la toma de decisiones de los humanos y la selección de rutas en el mundo real. En esta tesis nos centraremos primero en mejorar el rendimiento de la búsqueda de caminos para poder simular grandes números de humanoides virtuales autónomos, y a continuación introduciremos conceptos de investigación con mamíferos en neurociencia, para proponer soluciones al problema de pathfinding que intenten imitar con mayor realismo, el modo en el que los humanos navegan el entorno que les rodea. A medida que aumentan tanto el tamaño de los entornos virtuales como el número de agentes autónomos, resulta más difícil obtener soluciones en tiempo real, debido a las limitaciones de memoria y recursos informáticos. Para resolver este problema, en esta tesis exploramos enfoques jerárquicos porque consideramos que combinan dos objetivos fundamentales: mejorar el rendimiento en la búsqueda de caminos para multitudes de agentes y lograr una búsqueda de caminos similar a la de los humanos. El primer método presentado en esta tesis se basa en mejorar el rendimiento del algoritmo HNA* (Hierarchical A* for Navigation Meshes) incrementando almacenamiento de datos en memoria, y el segundo utiliza el paralelismo para mejorar drásticamente el rendimiento. La evaluación cuantitativa realizada en esta tesis, muestra que ambos enfoques ofrecen aceleraciones que pueden llegar a ser hasta 9 veces más rápidas que el algoritmo A* y no presentan limitaciones debidas a la configuración jerárquica. A continuación, aprovechamos aún más el potencial del paralelismo ofrecido por CUDA para extender nuestra implementación de HNA* a sistemas multi-agentes. Nuestro método permite calcular caminos simultáneamente y en tiempo real para más de 500.000 agentes, con una aceleración superior a 15 veces la obtenida por una implementación paralela del algoritmo A*. Por último, en esta tesis nos hemos centrado en estudiar los últimos avances realizados en el ámbito de la neurociencia, para comprender la manera en la que los humanos construyen mapas mentales y poder así proponer nuevos algoritmos que imiten de forma más real el modo en el que navegamos los humanos. Nuestro método representa el espacio como una red hexagonal, basada en la distribución de ¿place cells¿ existente en el cerebro, e imita las activaciones neuronales como contadores en dichas celdas. Nuestro buscador de rutas combina un método para explorar entornos desconocidos mientras construye un mapa cognitivo hexagonal, utilizando una búsqueda A* con una nueva heurística adaptada al mapa cognitivo del cerebro y sus contadores

From Placebo to Panacea: Exploring the Influence of Price, Suspicion, and Persuasion Knowledge on Consumers’ Perception of Quality

Consumers’ associate higher prices with higher levels of quality. Nevertheless, the relationship between price and objective quality (i.e., real quality) in the marketplace is not always strong or even positive. This seemingly paradoxical phenomenon could be explained by either consumers’ lack of access to the product information (which is unlikely as we live in the age of information) or their reluctance/inability to assimilate the available information and modify their price-quality judgments. The current research is built on this latter assumption and attempts to answer two substantive questions that remain to be fully addressed in the pricing literature: First, how can we alter consumers’ price-quality judgments? Second, what is the effect of gender on consumers’ price-quality perceptions? Essay 1 attempted to answer these questions using 12 main studies that employed survey research, experimental research, and observational research methods to achieve methodological triangulation. Samples included a student sample, adult samples, and real-world data and varied from 72 respondents to 222,600 product/day observations in size. Cumulative evidence in Essay 1 suggested that provoking suspicion against a specific brand could undermine consumers’ reliance on price to judge the quality of that brand. Whereas, activating persuasion knowledge is likely to elicit a general suspicion against marketing and subsequently increase consumers’ tendency to make price-quality judgments. Furthermore, Essay 1 offered empirical evidence that gender influences consumers’ thinking style, price-quality perceptions, and the actual prices that they pay for comparable products in the marketplace. Given the counterintuitive findings in Essay 1 regarding the positive effect of persuasion knowledge on consumers’ tendency to make inaccurate price-quality judgments, Essay 2 attempted to explore the underpinning mechanisms of the persuasion knowledge. In Essay 2, the author synthesized the extant literature on persuasion knowledge and proposed an integrative, process-based framework of consumers’ persuasion knowledge (CPK). This framework points out the key role that emotions play in the development and activation processes of persuasion knowledge, which is likely to account for the counterintuitive effect of persuasion knowledge on the accuracy of the price-quality perceptions

Relationship between Teachers’ Experience and Their Talk Richness: A Case Study of Iranian EFL Teachers

The purpose of the present study is to address the relationship between teachers' experience and the richness of their talk in an EFL classroom context. The participants were four male EFL teachers who were divided into two groups, namely inexperienced and experienced. To collect the required data for this study, the researcher observed the classrooms as a non-participant and made audio-recordings from one lesson of each teacher. Using the above-mentioned method, seven hours of naturally occurring data was obtained from the four teachers participating in this study. The measure of lexical variation which is a type-token ratio was used to assess the lexical richness of teachers talk. The findings showed that experienced teachers used less number of types and tokens in their talk in comparison to their inexperienced counterparts which is attributed to reasons such as different approaches of experienced and inexperienced teachers toward communicative approach, the teachers' own language learning experiences and background knowledge, the various teaching history of teachers, and different type of relationship between teachers and students

A Quantitative Action Research on Promoting Confidence in a Foreign Language Classroom: Implications for Second Language Teachers

Research has revealed that second language learners often seem passive and reticent in language classrooms. In the age of globalization, however, there is an urgent need for English as a Foreign Language (EFL) teachers to enhance their reticent students\u27 confidence to help them take part more actively in classroom oral activities. In line with this trend, the present study reports on an action research on increasing the EFL students\u27 confidence in speaking. A second aim was to find out about the beneficial consequences of doing an action research for second language teachers in their specific classroom contexts. Participants involved in this study were 16 Iranian male university students who had participated in a general English classroom in a private English language institute. The students had an upper-intermediate level of English. In order to increase the students\u27 confidence, thirty minutes of each session were devoted to interview technique during 8 successive weeks. Insights into the students\u27 confidence development were gained through quantitative analysis of their confidence questionnaire. The findings indicated that the students\u27 confidence increased because of incorporating additional speaking activities into the classroom and encouraging them to collaborate with their peers. In addition, this study showed that action research has a great potential to help second language teachers become autonomous

Does “Experience” Bring about Any Significant Difference in EFL Teacher Talk?

The rationale for the present study is based on the fact that understanding the teaching pro-cess and the development of teachers is incomplete unless the teachers' classroom behavior, especially their talk, is objectively explored. To this end, four male teachers offering Eng-lish as a foreign language (EFL) were recruited and divided into two groups, namely inex-perienced and experienced. To secure the objectivity in data collection they were observed in their classes and one lesson of each teacher was audio-recorded. The audio-recordings were then fully transcribed and analyzed through micro structural approach of schema theo-ry. The approach is based on the assumption that any word uttered by the teacher represents a specific concept commonly known as a schema. The schema enters into a hierarchical re-lationship with other schemata to constitute species, genera and semantic, syntactic and parasyntactic domains of language. The teachers’ talks were thus parsed into their constitut-ing schema types, species, genera and domains and certain codes were assigned to them to run statistical analyses. The findings showed that the inexperienced teachers significantly outnumbered their experienced counterparts in all schema categories and thus challenged “experience” as an effective variable in EFL teachin

The effect of exercises rehabilitation program in stable and unstable surfaces on balance and muscles strength of the lower limbs in patients with Multiple Sclerosis

Background and aims: The aim of the present study was to investigate the effect of ten-week exercises rehabilitation in stable and unstable surfaces on balance and muscles strength of the lower extremity in women with multiple sclerosis. Methods: In this quasi-experimental study, thirty patients were divided randomly into two exercise groups. Training program for groups was carried out in ten weeks, three times per week and each session one hour. Muscles strength was measured with a hand-held dynamometer. One-legged standing and timed get up and go tests were used to assess static and dynamic balance, respectively. The data were analyzed using analysis of ANOVA with repeated measures and independent and dependent t-test. Results: The results showed that there was a significant increase for all diameters of measuring in both exercise groups. Exercise group in unstable surface showed significantly larger improvement in muscles strength and static and dynamic balance compered to exercise group in stable surface. Conclusion: Generally, it can be stated that exercise in stable and unstable surfaces will result in considerable improvements in muscles strength and balance in patients with multiple sclerosis. Thus, the respective specialists can use these exercise as a complementary treatment along with the drug therapy for patients with multiple sclerosis

The Relationship between Loneliness and High-risk Behaviors among Adolescents of Bojnourd

Background: High-risk behaviors are increasing among adolescents, and consequently, risk and preventive factors have been highlighted and investigated. The aim of this study was to investigate the relationship between loneliness as a risk factor and high-risk behaviors among adolescents of Bojnourd, Iran. Methods: In this cross-sectional study, 455 adolescents (aged 15-19 years) were selected based on the age and gender by using quota sampling method. Data were collected by using demographics checklist, high-risk behaviors checklist, and the SELSA-S loneliness Questionnaire. Finally, data were analyzed using descriptive and inferential statistics like t-test, ANOVA, and Pearson’s correlation coefficient. Results: The results show that there was a significant and direct relationship between the feeling of loneliness and high-risk behaviors (r=0.147, P=0.002). In addition, there was a significant and direct relationship between the feeling of loneliness and violence (r= 0.148, P= 0.002), suicide (r=0.278, P< 0.001), and drug abuse (r= 0.124, P= 0.008). High-risk behaviors was more common among male rather than female (P= 0.005). Conclusion: This study show that there is a relationship between the feeling of loneliness especially loneliness in families and high-risk behaviors. Therefore, prevention programs for improving the relationships and interactions in families, can be very effective in preventing high-risk behaviors among adolescents

Assessing impacts of climate change on Kansas water resources: rainfall trends and risk analysis of water control structures

Doctor of PhilosophyDepartment of Biological & Agricultural EngineeringStacy L. HutchinsonPrecipitation impacts hydrologic structures, agricultural production, water resources management, and recreational activities, all of which significantly affect a state’s economy. Water control structure design is based on the maximum runoff rate resulting from storms with a specific return period and duration. The Rainfall Frequency Atlas (National Weather Service Technical Paper 40, 1961) (TP-40) provided statistical rainfall analysis as the basis for hydrologic structure design until the information was updated for Kansas in February 2013 (National Oceanic and Atmospheric Administration Atlas 14, volume 8) (Atlas-14). With growing concern about the effects of global climate change and predictions of more precipitation and extreme weather events, it is necessary to explore rainfall distribution patterns using the most current and complete data available. In this work, the changes in rainfall patterns were studied using the daily rainfall data from 23 stations in Kansas and 15 stations from adjacent states with daily rainfall data of 1890 through 2012. Analysis showed an increase in extreme precipitation events in Kansas with increase in magnitude from the northwest to southeast part of the state. A comparison of results of the TP-40 analysis to period 1980–2009, showed that approximately 84% of the state had an increase in short-term rainfall event magnitudes. In addition, trend analyzes on the total annual rainfall indicated a gradual increase at 21 out of 23 stations, including eight statistically significant trends. A change-point analysis detected a significant sudden change at twelve stations as early as 1940 and as recently as 1980. The increasing trend, particularly after the significant change-points, is useful in updating water management plans and can assist with agricultural production decisions such as crop selection and new plant variety development. A comparison between 10-yr, 24-hr storms from TP-40 and Atlas-14 indicated a change of -12% to 5% in Kansas. However, the number of exceedances from the 10-yr, 1-, 2-, 3-, 4-, 7-, and 10-day storms demonstrated a tendency towards more exceedances, particularly in the last five decades. Results of this study are useful for hydrologic structure design and water resources management in order to prevent accepting additional risk of failure because of the current changing climate