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All organisms, including plants, experience variability in the environment which puts pressure on organisms to evolve flexible responses. The study of these responses by organisms falls into the discipline of behavioural ecology. In this thesis, I am interested in the foraging behaviour of plant roots and I have two goals. First, I will use foraging theory from the animal literature to determine whether plants forage in ways that are similar to animals. Second, I will show how the adoption of foraging theory for plants can lead to a better theoretical understanding of coexistence of plants. I begin with a discussion of the major differences between plants and animals in their foraging behaviour and how this can be incorporated in to a more general predictive framework of plant foraging behaviour. I follow this discussion with two empirical tests of classic foraging models. First, I test a patch use model from the animal literature to determine if it can predict plant foraging behaviour. My results show that plants foraged for patches using the same strategies used by animals. Second, I test a resource choice model from the animal literature. These data indicated that plants select different types of nitrogen using the same resource choice strategies as foraging animals. These two studies reveal some basic foraging abilities of plants, however the experiments were performed in the absence of resource competition, a condition seldom experienced by plants in nature. To overcome difficulties in studying plant roots grown with neighbours I developed a molecular method for the identification of visually indistinguishable plant roots from competition experiments. Finally, I apply the molecular method to examine whether resource patchiness in soil can increase the intensity of competition experienced by foraging plants, and that the presence of neighbours influences the foraging strategies of plants. Together the results presented in this thesis show that plants use the same basic foraging strategies as animals, and that foraging behaviour can be linked to competition and coexistence of plant species. / Ecology

Doctor of Philosophy / Department of Psychological Sciences / Gary L. Brase / Risky decision making occurs in both humans and non-human animals. For a large portion of the history of scientific investigation into human judgment and decision making, risky behavior has been viewed as flawed and irrational. However, the past several decades have seen advances in the view of human rationality. Scientists have suggested that, rather than using probability theory as the metric by which humans are judged as rational or irrational, human minds should be evaluated with respect to specific ecologies (e.g., Gigerenzer & Selten, 2001) with some scientists going further and specifying the ecologies as those which our ancestors evolved; essentially, our minds and their decision processes are adapted to solve specific recurring problems, and to solve those problems in specific environments. Within the domain of risky decision making there are a number of theories and models which are consistent with the hypothesis that human (and non-human) minds are molded for specific behavioral patterns based on environmental cues. One example is the priority heuristic. The priority heuristic is based in the ecological rationality approach—that heuristics are designed for specific ecologies. However, the ecological rationality of the priority heuristic is underspecified. Studies One and Two of the present dissertation compared predictions made by two models of risk-taking from evolutionary biology and behavioral ecology (dominance theory and risk-sensitive foraging) with a variety of predictions made by the priority heuristic. Data clearly showed that risk-sensitive foraging outperforms the priority heuristic (Study One) and that the priority heuristic cannot account for the motivation to acquire a minimum number of resources. Study Two showed mixed results for the priority heuristic when compared to dominance theory. Specifically, choice patterns were consistent with the priority heuristic, but process data in the form of decision times were not consistent with the priority heuristic. Also, the data pointed to a strong effect for desiring higher status when competing against others of varying status. Study Three compared four potential models of risky decision making in an attempt to extend the pattern of results from Studies One and Two showing general risk-sensitivity when attempting to achieve a specified need level (Money for Study One; Status for Study Two). Also, Study Three attempted to clarify the scope of the pattern of general risk-sensitivity by examining differential patterns of results based on whether the models predicted motivations to achieve need levels for money, status, or both. Results from Study Three were consistent with a general model of risk-sensitivity which operated on both monetary need levels and status need levels. This effect was additionally ubiquitous for males and females, contrary to predictions by dominance theory. The data from three studies showed support for a general model of risk-sensitivity consistent with those proposed by others (Mishra, 2010). The concept and implications of this general risk-sensitivity model are discussed, as well as future directions to understand the finer details and potential scope of this particular general risk-sensitivity model.

Major research studies have provided support for information scent based usability evaluation and have increased its parent theory's (Information Foraging theory) credibility in the HCI community. These studies have, directly and indirectly, found significant correlations between good information scent and good usability. We would like to investigate its application to less-studied platforms, such as web pages on PDAs and cell phones. The theory itself is not device specific and it implicitly assumes that information scent's importance is universal. However, all studies on the practical application of Information Foraging theory have been conducted with desktop computers. We would like to examine what role information scent plays in interfaces on mobile devices that are limited in usable screen space. For this project, we performed a controlled study with 28 participants on the BBC News web site and its PDA-optimized version. Various usability and information scent related indicators were measured and compared across devices. Contrary to our expectations, we did not find any statistically significant differences between the information scent indicators of the Desktop and PDA sessions and the paths across the devices were highly correlated. / Master of Science

Tradicionalmente, nichos populacionais são descritos como a somatória de todos os recursos utilizados por uma população. Entretanto, diversos estudos mostram que indivíduos dentro de uma população podem usar recursos de forma distinta. Investigamos três maneiras pelas quais indivíduos podem variar quanto ao uso do recurso. Indivíduos podem apresentar a mesma preferência por presas, mas diferir na propensão à adição de novos itens alimentares em sua dieta (Preferências Compartilhadas); indivíduos podem apresentar a mesma presa preferida mas diferirem em suas presas alternativas (Refúgio Competitivo); ou indivíduos podem apresentar presas preferidas distintas (Preferências Distintas). Estudamos os padrões de interação que emergem sob os pressupostos de cada um dos modelos usando redes de interação entre indivíduos e os recursos que eles consomem. Dessa forma, para derivarmos as previsões de cada um dos modelos de uso de recurso, desenvolvemos modelos simples que geram redes de interação segundo regras que seguem os pressupostos dos modelos e confrontamos essas previsões com dados empíricos, comparando a estrutura dessa redes de interação. Encontramos que o modelo que menos se assemelha ao padrão de uso de recurso observado para as populações estudadas foi o modelo de Preferências Compartilhadas. Para as populações estudadas, a variação intrapopulacional na escolha de presas parece estar mais associada a diferenças nas sequências de preferências por presas entre indivíduos e não à propensão desses indivíduos em adicionarem novos recursos às suas dietas. / Traditionally, a population\'s niche is described as the sum of all resources consumed by a population. However, several studies have highlighted that individuals within a population can use resources differently. We investigate three ways in which individuals can vary in their resource use. Individuals can show the same preference for prey, but differ in their likelihood of adding new prey to their diets (Shared Preferences); individuals can share the same top-ranked prey but differ in their alternative prey (Competitive Refuge); or individuals can have different top-ranked prey (Distinct Preferences). We studied the pattern of interaction that emerges under each model\'s assumption using interaction networks between individuals and the resources they consume. In this sense, to derive the predictions associated with each model of resource use, we developed simple models that generates interaction networks according to a set of rules that represent the assumptions of each model and then confronted these predictions with empirical data on interaction networks, by looking at the structure of these interaction networks. We found that the model that least resembles the pattern of resource use observed in the populations studied was the Shared Preferences model. For the studied populations, intrapopulation variation is not associated with individuals sharing the same rank sequence and differing in their willingness to add new resources to their diets. Instead, it seems that differences in the rank sequence of prey choice are more important in structuring the pattern of resource use in these populations.

<p>Detta arbete har utförts i samarbete med företaget <em>Compute</em> och fokuserar på att utveckla navigationsstöd för webbportaler med bokningssystem. Arbetet har delats upp i tre specifika mål: (1) integrera <em>Information Foraging Theory</em> (IFT) och <em>Graphical User Interface principles</em> (GUI-principer) genom att applicera dessa vid utvecklng av navigation för webbportaler med bokningssystem (2) konkretisera hur navigering kan förbättras på en webbportal med bokningssystem, utifrån ovanstående teroier och (3) arbetet skall resultera i en lista med rekommendationer som kan tillämpas vid utveckling av navigation. För att kunna  integrera IFT och GUI-principer har dessa i kombination med en teroertisk studie tillämpats vid prototyping. Prototyperna användes som verktyg för att konkretisera hur navigationen kunde förbättras på portalen. Prototyperna utvärderades och resulterade i en lista med rekommendationer. Resultaten från utvärderingen påvisade att en integrering av GUI-principer och IFT kan förbättra nvigationsförhållanden på en webbportal. Arbetes främsta bidrag är listan med rekommendationer som skall kunna tillämpas vid navigationsutveckling.</p><p> </p>

This dissertation sought to explain goal achievement at limited traffic “long tail” Web sites using Information Foraging Theory (IFT). The central thesis of IFT is that individuals are driven by a metaphorical sense of smell that guides them through patches of information in their environment. An information patch is an area of the search environment with similar information. Information scent is the driving force behind why a person makes a navigational selection amongst a group of competing options. As foragers are assumed to be rational, scent is a mechanism by which to reduce search costs by increasing the accuracy on which option leads to the information of value. IFT was originally developed to be used in a “production rule” environment, where a user would perform an action when the conditions of a rule were met. However, the use of IFT in clickstream research required conceptualizing the ideas of information scent and patches in a non-production rule environment. To meet such an end this dissertation asked three research questions regarding (1) how to learn information patches, (2) how to learn trails of scent, and finally (3) how to combine both concepts to create a Clickstream Model of Information Foraging (CMIF). The learning of patches and trails were accomplished by using contrast sets, which distinguished between individuals who achieved a goal or not. A user- and site-centric version of the CMIF, which extended and operationalized IFT, presented and evaluated hypotheses. The user-centric version had four hypotheses and examined product purchasing behavior from panel data, whereas the site-centric version had nine hypotheses and predicted contact form submission using data from a Web hosting company. In general, the results show that patches and trails exist on several Web sites, and the majority of hypotheses were supported in each version of the CMIF. This dissertation contributed to the literature by providing a theoretically-grounded model which tested and extended IFT; introducing a methodology for learning patches and trails; detailing a methodology for preprocessing clickstream data for long tail Web sites; and focusing on traditionally under-studied long tail Web sites.

Detta arbete har utförts i samarbete med företaget Compute och fokuserar på att utveckla navigationsstöd för webbportaler med bokningssystem. Arbetet har delats upp i tre specifika mål: (1) integrera Information Foraging Theory (IFT) och Graphical User Interface principles (GUI-principer) genom att applicera dessa vid utvecklng av navigation för webbportaler med bokningssystem (2) konkretisera hur navigering kan förbättras på en webbportal med bokningssystem, utifrån ovanstående teroier och (3) arbetet skall resultera i en lista med rekommendationer som kan tillämpas vid utveckling av navigation. För att kunna  integrera IFT och GUI-principer har dessa i kombination med en teroertisk studie tillämpats vid prototyping. Prototyperna användes som verktyg för att konkretisera hur navigationen kunde förbättras på portalen. Prototyperna utvärderades och resulterade i en lista med rekommendationer. Resultaten från utvärderingen påvisade att en integrering av GUI-principer och IFT kan förbättra nvigationsförhållanden på en webbportal. Arbetes främsta bidrag är listan med rekommendationer som skall kunna tillämpas vid navigationsutveckling.

Tradicionalmente, nichos populacionais são descritos como a somatória de todos os recursos utilizados por uma população. Entretanto, diversos estudos mostram que indivíduos dentro de uma população podem usar recursos de forma distinta. Investigamos três maneiras pelas quais indivíduos podem variar quanto ao uso do recurso. Indivíduos podem apresentar a mesma preferência por presas, mas diferir na propensão à adição de novos itens alimentares em sua dieta (Preferências Compartilhadas); indivíduos podem apresentar a mesma presa preferida mas diferirem em suas presas alternativas (Refúgio Competitivo); ou indivíduos podem apresentar presas preferidas distintas (Preferências Distintas). Estudamos os padrões de interação que emergem sob os pressupostos de cada um dos modelos usando redes de interação entre indivíduos e os recursos que eles consomem. Dessa forma, para derivarmos as previsões de cada um dos modelos de uso de recurso, desenvolvemos modelos simples que geram redes de interação segundo regras que seguem os pressupostos dos modelos e confrontamos essas previsões com dados empíricos, comparando a estrutura dessa redes de interação. Encontramos que o modelo que menos se assemelha ao padrão de uso de recurso observado para as populações estudadas foi o modelo de Preferências Compartilhadas. Para as populações estudadas, a variação intrapopulacional na escolha de presas parece estar mais associada a diferenças nas sequências de preferências por presas entre indivíduos e não à propensão desses indivíduos em adicionarem novos recursos às suas dietas. / Traditionally, a population\'s niche is described as the sum of all resources consumed by a population. However, several studies have highlighted that individuals within a population can use resources differently. We investigate three ways in which individuals can vary in their resource use. Individuals can show the same preference for prey, but differ in their likelihood of adding new prey to their diets (Shared Preferences); individuals can share the same top-ranked prey but differ in their alternative prey (Competitive Refuge); or individuals can have different top-ranked prey (Distinct Preferences). We studied the pattern of interaction that emerges under each model\'s assumption using interaction networks between individuals and the resources they consume. In this sense, to derive the predictions associated with each model of resource use, we developed simple models that generates interaction networks according to a set of rules that represent the assumptions of each model and then confronted these predictions with empirical data on interaction networks, by looking at the structure of these interaction networks. We found that the model that least resembles the pattern of resource use observed in the populations studied was the Shared Preferences model. For the studied populations, intrapopulation variation is not associated with individuals sharing the same rank sequence and differing in their willingness to add new resources to their diets. Instead, it seems that differences in the rank sequence of prey choice are more important in structuring the pattern of resource use in these populations.

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