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The following experiments looked at how encoding information and available cues at test can influence context effects. More specifically, the present experiments investigated the overshadowing and outshining hypotheses. Experiment 1 established a new method for attaining robust reinstatement effects by using movie scenes. Experiment 2 found support for the outshining hypothesis. So, if verbal and contextual cues were encoded and verbal cues were present at test, then context reinstatement through the reinstatement of the movie scenes would have little effect on memory. However, in the absence of verbal cues at test, significant context effects were found showing that the verbal cues were able to outshine the context (i.e., the movie scenes). Experiment 3 extended the outshining hypothesis by showing that strengthening the association between the verbal cues and the target items led to greater outshining of the movie scenes by the verbal cues. Experiment 4 looked at the overshadowing hypothesis and showed that if the context (i.e., the movie scenes) was not encoded well, but the verbal cues were then the context was overshadowed by the verbal cues. Further, if the association between the verbal cue and target items was encoded, then the overshadowing effect was greater as compared to cases where the association between the two items was not encoded. Finally, Experiment 5 found that if context was well encoded but verbal cues were not well encoded then the verbal cues were overshadowed by the context. It was also found that encoding the association between the context and target led to a more robust overshadowing effect as compared to cases where the association was not encoded.

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Categorizing knowledge into different disciplines and units may block knowledge within separate “folders”, which could limit its later retrieval and transfer to new contexts. To test this hypothesis, two experiments had been conducted. In one experiment, participants memorized a list of words with or without cuing which category these words belonged to. One week later, they were asked to recall all the positive adjectives, which required them to retrieve words that came from different categories. In the other experiment, participants read exactly the same story but embedded in two different subject domains or no context. A survey report was presented to test whether people from different contexts would have different transfer effect. The current study replicated previous results that successful transfer was hard to observe in the laboratory settings without explicit prompts. The memory test and transfer task in this study were too difficult and resulted into to the poor performance of the participants. The initial hypothesis had been neither supported nor rejected. To test the hypothesis, future studies could reduce the time interval between study and test, and modified the transfer task to lower the difficulty of the experiment. / text

This research examines a possible relationship between intentional memory and possible phonologic cues in the human voice. Specifically, if someone has told us something in the past, does hearing that same voice at the time of recall affect our ability to remember what was said? Also, if voice cues do affect memory, is the effect voice-specific? Since most standardized assessments of student learning and tests of human memory rest their conclusions about human learning solely on non-aural tests, it is necessary to determine if student performance changes with test modality. Via a computer program, ninety-five adults each listened to a male voice read a one-minute story and were then randomly assigned to take one of three different tests consisting of multiple-choice and fill-in-the-blank items. In the first test, the male voice from the story read all questions and possible answers. The second test used a different male voice to read while the third test was text-only. All tests contained identical content and gave single-modality cues only, text or speech. Results show no significant difference in long-term recall or recognition with respect to test-modality. Further research in this area is encouraged to determine if conclusions are generalizable to wider populations and hold for longer memory intervals. / Ph. D.

The purpose of this study was to examine the effect of encoding specificity on learning in a multimedia environment. Based upon the theory of encoding specificity there should be a relationship between the modality for which a learner encodes information into memory and the modality used to assess the learner's knowledge. Modality attributes for purposes of this study included visual (animation) and verbal information (narration and text). Two-hundred and fifteen students viewed a computer animation on lighting formation which was presented in one of three different modalities (animation with narration, animation with text, text only). Following the instruction students were assessed in one of three modalities (animation with narration, animation with text, text only) on recall and transfer. A 3 Encoding/Study x 3 Retrieval/Test (animation with narration, animation with text, text only) full-factorial post-test only design was used to assess the effects of matched and mismatched encoding and retrieval modalities in a multimedia environment. Encoding specificity suggests that there is an interaction between the conditions at encoding and retrieval such to say that the to-be-remembered item will not be as effective during retrieval unless the cue was specifically encoded at time of storage. Unfortunately, the present study did not find much to support the claim of encoding specificity based upon modality. The use of modality in both encoding and retrieval condition to support encoding specificity was found only in the AT-AT matched recall group versus the mismatched groups. Furthermore, significance was not found in any of the matched mismatched transfer conditions. / Ph. D.

The principle of competitive exclusion holds that the strongest competitor for a single resource can exclude other species. Yet in many systems, more similar species appear to stably coexist than the small number of limiting resources. Understanding how and when similar species can stably coexist has taken on new urgency in managing biological invasions and their ecological impacts. Recent theoretical advances emphasize the importance of predators in determining coexistence. The effects of predators, however, can be mediated by behavioral changes induced in their prey as well as by their lethality. In this dissertation, I ask how considering multiple trophic levels changes our understanding of how a grass invasion (Pennisetum ciliare) affects species diversity and dynamics in southeastern Arizona. In considering interactions with plant consumers, and with the predators of those consumers, this research reveals more general ecological processes that determine species diversity across biological communities. I first present evidence from a grass removal experiment in the field that shows increased emergence and short-term survival of native perennial plants without grass. This is consistent with Pennisetum ciliare causing the observed concurrent decline in native plant abundance following invasion. I then present results from greenhouse and field studies consistent with that suppression of native plants being driven primarily through resource competition rather than increased rodent granivory. Granivorous rodents do not solely function as consumers, however, because they cache their harvested seeds in shallow scatter-hoards, from which seeds can germinate. Rodents thus act also as seed dispersers in a context-dependent mutualism. The primary granivores in areas invaded by Pennisetum ciliare are pocket mice (genus Chaetodipus), which have a well-studied tendency to concentrate their activity under plant cover to avoid predation by owls. Because the dense canopy of the grass may provide safer refuge, I hypothesized the pocket mice may be directly dispersing native seeds closer to the base of the invasive grass. Such a behavior could increase the competitive effect of the grass on native plant species, further driving the impacts of the invasion. By offering experimental seeds dusted in fluorescent powder and tracking where the seeds were cached, I show that rodents do preferentially cache experimental seeds under the grass. This dispersal interaction may be more general to plant interactions with seed-caching rodents across semi-arid regions that are experiencing plant invasions. Finally, I ask how the predator avoidance behavior exhibited by these rodents affects their ability to coexist with one another. Not only could their diversity affect that of the plant community, but the effects of plant invasions can cascade through other trophic levels. Theoretical understanding of how similar predator avoidance strategy alters coexistence had not yet been developed, however. Instead of a field study, therefore, I modified a general consumer-resource model with three trophic levels to ask whether avoidance behavior by the middle trophic level alters the ability of those species to coexist. I found that more effective avoidance behavior, or greater safety for less cost, increased the importance of resource partitioning in determining overall niche overlap. Lowering niche overlap between two species promotes their coexistence in the sense that their average fitness can be more different and still permit coexistence. These results provide novel understanding of behavioral modifications to population dynamics in multi-trophic coexistence theory applicable to this invasion and more broadly.

Activation in the hippocampus (HC) and prefrontal cortex (PFC) is critical to accurately retrieve overlapping sequences. Experiments 1 and 2 tested the hypotheses that activation in and interaction between HC and PFC increases as overlap between sequences increases in a non-spatial task. Experiment 3 tested the hypothesis that theta oscillations are involved in orchestrating interactions between HC and PFC in a spatial task with overlapping elements. In the first two studies, 17 participants (aged 18-34; 11 female) learned sequences consisting of a picture frame, face, and scene. Conditions varied by degree of overlap. Using fMRI, Experiment 1 tested how degree of overlap affected HC and PFC activation. In overlapping sequences, middle and posterior HC were active when predictability of the correct response increased, dorsolateral PFC was active when participants were able to ascertain the correct set of sequences, and ventrolateral PFC was active when inhibition of interfering associations was required. Experiment 2 examined functional connectivity of HC and PFC during disambiguation. Low- and high-overlap conditions were associated with increased connectivity in separate regions at different times indicating that retrieval under the two conditions used different neural networks and strategies. Low-overlap trials were associated with increased connectivity between HC and prefrontal and parietal regions. High-overlap trials showed increased connectivity between lateral PFC and visual areas, indicating that imagery may be necessary for accurate performance. Using EEG recording, Experiment 3 examined theta activity during retrieval of well-learned, overlapping and non-overlapping mazes in 17 participants (aged 18-34, 11 female). Theta activity increased in overlapping mazes during the first of four hallways, suggesting participants were looking ahead to upcoming turns in the maze. Theta activity increased at the beginning and choice point of the third overlapping hallway, possibly in response to interference from the paired, overlapping maze. These studies provide evidence that (1) overlapping associations in non-spatial sequences elicit interactions between hippocampus and lateral prefrontal cortex, (2) increasing the degree of overlap changes the neural processes required to perform the task, and (3) theta power increases in response to increased cognitive demand and maintenance of sequence information needed to differentiate between overlapping spatial routes.

Questions pertaining to the unique structure and organisation of language have a long history in the field of linguistics. In recent years, researchers have explored cultural evolutionary explanations, showing how language structure emerges from weak biases amplified over repeated patterns of learning and use. One outstanding issue in these frameworks is accounting for the role of context. In particular, many linguistic phenomena are said to to be context-dependent; interpretation does not take place in a void, and requires enrichment from the current state of the conversation, the physical situation, and common knowledge about the world. Modelling the relationship between language structure and context is therefore crucial for developing a cultural evolutionary approach to language. One approach is to use statistical analyses to investigate large-scale, cross-cultural datasets. However, due to the inherent limitations of statistical analyses, especially with regards to the inadequacy of these methods to test hypotheses about causal relationships, I argue that experiments are better suited to address questions pertaining to language structure and context. From here, I present a series of artificial language experiments, with the central aim being to test how manipulations to context influence the structure and organisation of language. Experiment 1 builds upon previous work in iterated learning and communication games through demonstrating that the emergence of optimal communication systems is contingent on the contexts in which languages are learned and used. The results show that language systems gradually evolve to only encode information that is informative for conveying the intended meaning of the speaker - resulting in markedly different systems of communication. Whereas Experiment 1 focused on how context influences the emergence of structure, Experiments 2 and 3 investigate under what circumstances do manipulations to context result in the loss of structure. While the results are inconclusive across these two experiments, there is tentative evidence that manipulations to context can disrupt structure, but only when interacting with other factors. Lastly, Experiment 4 investigates whether the degree of signal autonomy (the capacity for a signal to be interpreted without recourse to contextual information) is shaped by manipulations to contextual predictability: the extent to which a speaker can estimate and exploit contextual information a hearer uses in interpreting an utterance. When the context is predictable, speakers organise languages to be less autonomous (more context-dependent) through combining linguistic signals with contextual information to reduce effort in production and minimise uncertainty in comprehension. By decreasing contextual predictability, speakers increasingly rely on strategies that promote more autonomous signals, as these signals depend less on contextual information to discriminate between possible meanings. Overall, these experiments provide proof-of-concept for investigating the relationship between language structure and context, showing that the organisational principles underpinning language are the result of competing pressures from context, cognition, and communication.

O presente trabalho desenvolve um modelo capaz de descrever preferências dependentes de contexto, buscando superar as limitações impostas pela abordagem da preferência revelada. O espaço informacional no ato da escolha é ampliado através da incorporação de uma segunda dimensão, na forma de um novo tipo de utilidade, dita social ou moral, representativa do contexto no qual a escolha é realizada. As dimensões são assumidas incomensuráveis entre si, uma característica típica de escolhas que envolvem questões morais. A impossibilidade de comparação entre duas alternativas, cada qual superior à outra em uma dimensão distinta, é resolvida através de uma simetria rotacional capaz de preservar a relação sujacente entre ambas utilidades. O modelo é baseado, fundamentalmente, nos trabalhos de Amartya Sen (1974, 1977, 1993, 1997) e Amitai Etzioni (1986), incorporando conceitos de utilidade moral (ETZIONI, 1986), dependência de contexto no ato da escolha (SEN, 1993, 1997), inescapabilidade ou urgência da escolha (SEN, 1997), auto-imposição de limites à escolha (SEN, 1997; ETZIONI, 1986), commitment, entendido como divisão entre escolha e bem-estar (SEN, 1977) e flexibilidade cognitiva dos indivíduos (ARIELY, 2012). / In this work, we develop a model that is able to describe context-dependent preferences, trying to overcome the limitations given by the revealed preference approach. The informational space in the act of choice is broadened by incorporating a second dimension, as a new type of utility, called social or moral, representing the context within the choice is made. The dimensions are deemed incommensurable, a typical characteristic of moral-related choices. The impossibility of comparison between two alternatives, where each alternative is the superior one in a different dimension, is resolved through a rotational symmetry able to preserve the underlying relationship between the two utilities. The model is fundamentally based on the works of Amartya Sen (1974, 1977, 1993, 1997) and Amitai Etzioni (1986), making use of the concepts of moral utility (ETZIONI, 1986), context-dependency in the act of choice (SEN, 1993, 1997), inescapability or urgency of the choice (SEN, 1997), self-imposing limits to choice (SEN, 1997; ETZIONI, 1986), commitment, understood as a wedge between choice and welfare (SEN, 1977) and the cognitive flexibility of the individuals (ARIELY, 2012).