In general, L2 learners have great difficulty mastering aspects of grammar in the second language. For example, Chinese-speaking ESL learners often fail to mark past tense in their speaking and writing (Aaronson & Ferres, 1987; Bayley, 1991; Bean & Gergen, 1990; Jia & Fuse, 2007; Krashen & Pon, 1975; Lardiere, 1998; Wei, 2000), and there are some suggestions in the literature that Chinese learners of English never master English tense (Lardiere, 1998). One question that arises is whether the failure to learn to use the past tense is due to a failure of competence or a failure of performance. If the former, then Chinese-speaking ESL learners should show such failures in all tasks including comprehension tasks.However, little research has investigated L2 comprehension of tense marking in reading. The studies (Gass, 2001; Guillelmon & Grosjean, 2001; Jiang, 2004, 2007) have showed that late L2 learners are not sensitive to certain types of grammatical marking. They have poor inflectional comprehension. It is possible that Chinese English-language learners are insensitive to grammatical violation involving tense during reading. This dissertation tests this idea.A group of English-proficient college students from Fu-Jen University in Taiwan was tested in a number of tasks. In paper-and-pencil tests, Chinese English-language learners showed knowledge of the past tense forms and the appropriate contexts for their usage. This suggests that past tense marking is learnable. Chinese English-language learners can acquire this knowledge. Does the relative mastery of past tense show up in comprehension in a similar L2 population? A reading comprehension test that measured reading time to sequential segments of a sentence indicated that unlike native speakers of English who were tested, Chinese English-language learners were insensitive to grammatical violation involving tense. This finding is consistent with the other studies, indicating that L2 learners are insensitive to grammatical marking during reading.Overall, it appears that high-functioning Chinese English-language learners can learn almost the proper way to use tense, but fail to do so during performance.

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No description available.

During viral infections, CD8+ T cells only respond to a select few epitopes derived from the respective foreign pathogen. These epitopes can be organized into a hierarchy, based on their ability to induce T cell priming. Such phenomenon is known as immunodominance. Cytotoxic T cells can be primed through the direct pathway, or the cross-priming pathway. The latter involves exogenously derived viral epitope presentation by uninfected professional antigen presenting cells. It has been previously reported that Lymphocytic Choriomeningitis nucleoprotein expressed in HEK cells (HEK-NP) could be cross presented to CD8+ T cells. In these studies we have used this same HEK-NP model to study the effects of LCMV-NP cross priming on the LCMV immunodominance hierarchy following viral challenge. Our results provide strong evidence that cross priming is an efficient route with which to induce cell-mediated immunity. We also highlight a regulatory role for cross priming in immunodominance by showing that a single dose of HEK-NP can completely shift the immunodominance hierarchy of a typical LCMV infection. Furthermore, we see that the induction of LCMV-NP cross priming boosts anti-viral immunity to subsequent LCMV infections. This work provides strong support for the physiological role that cross priming plays in normal cell-mediated immune responses. It may also provide relevant information to the realm of immunotherapy. / Thesis (Master, Microbiology & Immunology) -- Queen's University, 2007-07-10 14:33:18.115

The primary aim of this dissertation is to address an important issue of individual susceptibility to false memories. Specifically, what is the role inhibitory control (IC) in children’s and adult’s propensity to producing false memories? Inhibitory control within the context of the current study is defined on the basis of performance on selective attention tasks. Inhibitory control is discussed within this dissertation as it is reflected in two selective attention tasks, Stroop and Negative Priming. While the false memory effect, as reflected in the Deese/Roediger and McDermott paradigm (Roediger & McDermott, 1995), is one of the most widely studied memory phenomenon, the current study is important as it provides some insights into the relation between attention and memory. An interesting finding in the DRM false memory effect is that participants often report having a clear false memory of having seen or heard the non-presented critical lure item (CL item). Such memory illusions have been informative on how memory works. The current study adds to this body of research by providing converging evidence of how individual differences in the sensitivity to the false memory effect may occur, and how this sensitivity may reflect the same IC mechanisms involved in selective attention tasks. The basic notion examined within this dissertation is that when recognition memory is tested in the DRM paradigm, individuals have to select information that was studied and simultaneously inhibit highly activated yet non-presented information in memory, in order to correctly reject the CL item. If the notion that individual differences in sensitivity to the false memory effect is indeed related to a basic IC mechanism, then a relationship should be found between measures of IC in selective attention tasks and rates of false memories in the DRM test. The current study incorporates three experiments. Experiments 1 and 2 are broken down into parts ‘a’ and ‘b’, with each part varying in respect to the IC measure. In part a, participants were assigned to an inhibitory control group (IC group) on the basis of Stroop interference. In part b, participants are assigned to IC groups on the basis of a combined measure of inhibitory control that is, Stroop and Negative Priming. The third experiment assigned participants on the basis of a combined measure of IC, and then considered the relation between the duration of IC over a number of DRM word-lists presented simultaneously prior to the recognition test. Experiment 3 also compared the robust effect of IC on the propensity to produce false memories across all three experiments. The results of this study can be summarized as follows. In each experiment there was clear evidence of a relation between IC estimates and proportion of false memories. As predicted, individuals assigned to a Less IC group produced a higher proportion of false memories than those assigned to the More IC group. Inhibitory control differences did not modulate differences in correct or incorrect recognition in general (hits and false alarms to unrelated distractors). This second finding is important because it suggests a specific effect of IC in false memories, rather than a general breakdown in memory processes. The IC effect in false memories occurred in children (8-year olds and 10-year olds) as well as adults. Furthermore, the IC effect appeared to be additive with age; i.e., all groups produced a similar pattern across all three experiments. Last, the combined estimate of IC was found to be a more sensitive measure of false memories than a single index of IC; however, this was found in relation to adults but not for children. A number of additional manipulations and measures of interest were also included. Experiment 2 found clear evidence of an effect of IC on remember responses, not only were Less IC individuals more likely to produce false alarms to critical lure items, they were also more likely to distinctly respond they “remembered” the CL item as opposed to only “knowing” the CL had been presented. Examination of reaction times (RTs) to false alarms as a function of IC group found the Less IC group were faster to make false alarm responses to CL items, whereas the More IC group were slower to make false responses CL items. As predicted the relation between IC and the false memory effect was modulated by the random versus blocked presentation manipulation in Experiment 3. Specifically, decreased rates of false memories were found in the random presentation format compared to the blocked format. Interestingly however, a small effect of IC group in false memories was found even in the random condition. From this study it can be concluded that individual susceptibility to the false memory effect is in part modulated by inhibitory control. Individuals who demonstrate less effective IC show a greater propensity to false memories than those who demonstrate more effective IC. The IC effect of false memories was found to be robust, with converging evidence found across all three experiments. In relation to the development of inhibitory control, consistent with the research of Pritchard and Neumann (2004, 2009), and Lechuga and colleagues (2006), the results of this study suggest IC is fully developed in young children. However, their ability to accurately encode, retain and retrieve information would appear to develop at a different rate than IC. Specifically, it may be that while younger children are able to utilize IC in memory processes, they have yet to fully develop a richly interconnected semantic network. On the other hand, older children and adults would appear to have a more fully developed semantic network. This series of experiments presents a novel demonstration of the relation between inhibitory control and false memories. As such, this study has the potential to provide new insight into a cognitive mechanism that may be responsible for both developmental trends and for individual differences in the regulation of false memories. Moreover, if the mechanism responsible for mediating false memories is causally linked to performance on selective attention tasks in the systematic way that is proposed, it may be possible in the future to utilize IC measures to assist in identifying individuals who have an exaggerated propensity to form false memories, as well as those more prone to resist them.

As the popularity of digitally based communication devices increases, so does the propensity for individuals to find clever ways to convey messages in a shorter amount of space and time. Often, individuals use word or phrase shortening techniques known collectively as text-speak. A majority of investigations into the topic of text-speak have only focused on the potential impact text-speak may have on literacy or scholastic achievement (Crystal, 2008; Pinker 1994; Thurlow, 2003). However, there is a void in empirical investigation into how individuals create text-speak and more importantly how they process it (Farrell & Lyddy, 2012). The primary aim of this dissertation is to systematically investigate text-speak using various methodological techniques to gain a better understanding of how people create text-speak and explore how it elicits meaningful comprehension. An additional aim of this dissertation is to determine whether processing text-speak comes at a cognitive cost.

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Emotionally charged stimuli have been reported as efficient distractors during visual search (e.g., Eastwood, Smilek, Merikle, 2001; Hansen & Hansen, 1988; Öhman, 2002; Öhman, Flykt, & Esteves, 2001; Öhman & Soares, 1993). The extensiveness and specificity of the influence of such distractions for attention and performance beyond the context of their presentation were currently investigated. Of interest was whether prior experiences of distraction from such stimuli influence spatial attention during a subsequent visual event. General and location-specific bases of such effects and the role of memory in modulating these were investigated. Over a series of trials, participants performed a target localization task during a prime event involving exposure to an emotionally charged distractor, or only neutral distractors. Subsequently, performance at the same task was measured when only neutral distractors were presented during a probe event. During each event, one of four shapes had to be identified and responded to as a target. Distractor images were presented within each shape outline. Whether or not the shapes were the same or different across the prime and probe event of a trial was manipulated as a test of the role of memory in modulating effects across the events of a trial. Earlier findings of immediate impairments to attention based in exposure to emotionally charged stimuli were replicated. The current study also revealed the occurrence of robust performance impairments during the probe event subsequent to the disruption of attention during the prime event. Evidence was limited in suggesting that the impairments depended on which location the emotional stimulus occupied during the prime event. Strong evidence, however, was observed for global impairments on attention across visual events, conditional on task demands being similar during both. An account of the findings which incorporates memory was suggested, whereby retrieval processes engaged during the probe event support access to the interaction history with emotionally charged stimuli during the prime event. Consistent experience with emotional stimuli requiring no response produced a prominent cognitive refraction period at the time of the probe event, requiring that attention be re-centered to the task. Less consistent experiences produced a briefer refractory period.

Early during an immune response, dendritic cells (DC) interact closely with CD4+ T cells, and cross-talk between these cells can come in the form of tumour necrosis factor (TNF) superfamily ligand-receptor interactions. These signals are critical for the maturation, function and survival of DC, and thereby dictate the capacity of DC to prime a robust T cell response. Among these cues, helper T cell-expressed CD40L interaction with DC-expressed CD40 is required to fully mature DC for cross-priming of help-dependent CD8+ T cell responses. The lymphotoxin-beta receptor (LTβR) is another TNF family receptor on DC, and it’s ligands LTα1β2 and LIGHT are expressed on activated T cells. Since abrogated LTβR signaling impairs T cell immunity, we have examined whether LTαβ represents another possible helper T cell-derived cue for full DC maturation. However the LT pathway controls lymphoid tissue organization and DC homeostasis, a second possible mechanism explaining the necessity of LTβR signaling for T cell immunity. Here we dissect the role of helper T cell-expressed LTβR ligands and DC-intrinsic LTβR signaling, independent of DC homeostasis or lymphoid organization, in DC function and T cell immunity. Absence of LTα1β2 and not LIGHT on helper T cells results in compromised T cell priming by DC ex vivo, and LTβ-/- CD4+ T cell responses are impaired in vivo. Ag-specific CD4+ T cell-expressed LTα1β2 and DC-intrinsic LTβR signaling are required for an optimal cytotoxic T lymphocyte (CTL) response in vivo. While CD40 induces IL-12 and is required for CTL function, DC-intrinsic LTβR signaling is necessary for CTL activation and expansion, early up-regulation of CD86 and IFNα/β production. Our results reveal non-redundant roles for distinct TNF family receptors in enabling DC to program different features in Ag-specific CD8+ T cells.

This project investigated the statistical learning of musical expectancy. As a secondary goal, the effects of the perceptual properties of tone set familiarity (Western vs. Bohlen-Pierce) and textural complexity (melody vs. harmony) on the robustness of that learning process were assessed. A series of five experiments was conducted, varying in terms of these perceptual properties, the grammatical structure used to generate musical sequences, and the methods used to measure musical expectancy. Results indicated that expectancies can indeed be developed following statistical learning, particularly for materials composed from familiar tone sets. Moreover, some expectancy effects were observed in the absence of the ability to successfully discriminate between grammatical and ungrammatical items. The effect of these results on our current understanding of expectancy formation is discussed, as is the appropriateness of the behavioural methods used in this research.