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Graduate Theses & Dissertations
Pages
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- Practicing and Rewarding Task-Relevant Motor Variability to Optimize Motor Performance
- It is universally accepted that human motor performance is variable in both its timing and spatial qualities. However, it is unclear to what extent motor variability impedes performance when learning a new skill and to what extent it enables our ability to learn. The first experiment examined whether performance during a test task depended on whether participants practiced to constrain or vary the task-relevant parameter. Participants used their right hand to make simple point-to-point movements. Results demonstrated the importance of paying attention to test task demands to evaluate which form of practice is most beneficial. The second experiment examined whether levels of variability could be manipulated using a reward-based paradigm to enhance learning when adapting to a perturbation of a simple visually-guided reaching movement. A reward-based feedback task was designed to encourage exploration along the task-relevant dimension, specifically movement direction variability. Overall, I did not find any significant results. Author Keywords: Adaptation, Motor Control, Motor Learning, Reaching
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- Application of One-factor Models for Prices of Crops and Option Pricing Process
- This thesis is intended to support dependent-on-crops farmers to hedge the price risks of their crops. Firstly, we applied one-factor model, which incorporated a deterministic function and a stochastic process, to predict the future prices of crops (soybean). A discrete form was employed for one-month-ahead prediction. For general prediction, de-trending and de-cyclicality were used to remove the deterministic function. Three candidate stochastic differential equations (SDEs) were chosen to simulate the stochastic process; they are mean-reverting Ornstein-Uhlenbeck (OU) process, OU process with zero mean, and Brownian motion with a drift. Least squares methods and maximum likelihood were used to estimate the parameters. Results indicated that one-factor model worked well for soybean prices. Meanwhile, we provided a two-factor model as an alternative model and it also performed well in this case. In the second main part, a zero-cost option package was introduced and we theoretically analyzed the process of hedging. In the last part, option premiums obtained based on one-factor model could be compared to those obtained from Black-Scholes model, thus we could see the differences and similarities which suggested that the deterministic function especially the cyclicality played an essential role for the soybean price, thus the one-factor model in this case was more suitable than Black-Scholes model for the underlying asset. Author Keywords: Brownian motion, Least Squares Method, Maximum Likelihood Method, One-factor Model, Option Pricing, Ornstein-Uhlenbeck Process
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- Utilizing Class-Specific Thresholds Discovered by Outlier Detection
- We investigated if the performance of selected supervised machine-learning techniques could be improved by combining univariate outlier-detection techniques and machine-learning methods. We developed a framework to discover class-specific thresholds in class probability estimates using univariate outlier detection and proposed two novel techniques to utilize these class-specific thresholds. These proposed techniques were applied to various data sets and the results were evaluated. Our experimental results suggest that some of our techniques may improve recall in the base learner. Additional results suggest that one technique may produce higher accuracy and precision than AdaBoost.M1, while another may produce higher recall. Finally, our results suggest that we can achieve higher accuracy, precision, or recall when AdaBoost.M1 fails to produce higher metric values than the base learner. Author Keywords: AdaBoost, Boosting, Classification, Class-Specific Thresholds, Machine Learning, Outliers
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- Sexual consent
- How one identifies their nonconsensual sexual experiences (NSE) and cognitively integrates the experience into their sexual schemas may affect how individuals perceive and negotiate sexual consent. Previous research has demonstrated that both the method of quantifying NSEs and the labels used to describe NSEs yield different results in psychosexual outcomes associated with NSEs. The current study assessed differences in subjectively and behaviourally quantified NSEs, as well as the role of cognitive and affective appraisals of sexuality and sexual interactions, on sexual consent attitudes. While behaviourally measured NSE history did not significantly influence sexual consent attitudes, the subjective identification of NSEs with various labels did influence attitudes toward sexual consent. Cognitive appraisals of rape and affective appraisals of sexuality also significantly predicted sexual consent attitudes. Implications for future research and NSE prevention are discussed. Keywords: Nonconsensual sexual experiences, sexual consent, quantifying NSEs, affective sexuality, cognitive sexuality Author Keywords: identification, nonconsensual sexual experiences, rape, sexual affectivity, sexual assault, sexual consent
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- Tool-use and near-tool effects
- After active tool-use visual stimuli near a tool are processed more quickly and accurately than those farther away from a tool. Can these near-tool effects be modulated by training demands? To investigate this we asked the participants to complete a tool training task followed by a cross-modal interference task. During the training task the participants performed quick and accurate pointing movements to reach a strict or moderate criterion. The results indicated that the strict group made faster movements than the moderate group. During the cross-modal interference task visual distractors were presented along handheld tools in conjunction with vibrotactile stimuli on the hand. No significant compatibility effects were found for visual distractors near the hand or tool tip, and no consistent group differences were found. Our findings demonstrate the importance of using a novel tool during training, and that virtual stimuli may not be effective to elicit near-tool effects. Author Keywords: bimodal neurons, cross-modal interference, near-tool effects, tool training, training demands
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- Childhood Precursors of Adult Trait Incompleteness
- Previous research has suggested that childhood sensory sensitivity may predict adult obsessive compulsive (OC) behaviours. To date, however, research has not addressed how the separate dimensions – harm avoidance and incompleteness - may influence this relationship or why it exists. The current study used a retrospective design to test a) if sensory sensitivity in childhood predicts trait incompleteness in adulthood, as well as b) if emotion regulation variables mediate this relationship. Questionnaires pertaining to OC dimensions and childhood anxieties were completed independently by 172 undergraduate participants and their primary childhood caregiver. Results showed a linear relationship between sensory sensitivity in childhood and incompleteness in adults. Emotion regulation variables failed to mediate this relationship, although a trend for mediation was present. Additionally, exploratory analysis found perfectionism in childhood to be a predictor of trait incompleteness but not harm avoidance, whereas physical anxieties predicted harm avoidance and not incompleteness. Results are discussed in the context of clinical and theoretical implications. Author Keywords: Distress Tolerance, Harm Avoidance, Incompleteness, Obsessive Compulsive Disorder, Sensory Sensitivity, Symmetry
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- Comparing Two Tablet-Based Visuomotor Tasks to Standard Laboratory Versions
- The assessment of visuomotor function can provide important information about neurological status. Several visuomotor tasks exist for testing in the laboratory, although attempts to make these tests portable to allow quick and reliable assessment have been limited. We developed an assessment tool using two laboratory visuomotor tests as a tablet application: the double-step task, and an interception task. Performance was assessed by measuring the participants’ ability to reach toward unpredictably moving targets in each task. Response patterns were compared across equipment types to determine if participants were responding similarly to the moving targets in the standard laboratory and the tablet version of the tasks. On the double-step task, participants adjusted to the displaced target adequately in both the lab and tablet versions. On the interception task, participants intercepted non-accelerating targets, and performed worse on accelerating targets in both versions of the task. These findings suggest that the tablet version of these tasks assesses similar visuomotor processing as the respective laboratory version. Author Keywords: concussion assessment, double-step task, interception task, visuomotor processing, visuomotor system
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- Fathering Experience of the Transition Into Parenthood
- Men who become fathers undergo a transitional period during which they adjust to their new role as the caregiver of a child, a time that is usually viewed as a major life transition (Lamb, 2010). Much of the published literature focuses on fathers with identified issues (e.g., divorced fathers); therefore, there is a need for research that looks at the experiences of more typical fathers in the current Canadian context. To understand how fathers experience this transition, a series of focus groups were conducted with first-time fathers across the Peel Region of Ontario, Canada. Analysis of the focus group transcripts using an interpretative phenomenology framework identified four overarching metathemes: intrapersonal experiences, extrapersonal experiences, father’s role, and supports. Practical implications, theoretical implications, and limitations are discussed. Author Keywords: Fathering, Fathering Experience, First-Time Fathers, Transition Into Parenthood
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- Marital Satisfaction Throughout the Journey of Weight-Loss Surgery
- A mixed-methods’ approach was designed to explore the marital impacts following weight-loss surgery (WLS). In Phase 1, ten individual interviews with spouses of five couples were conducted; two of the couples had the wives preparing for WLS, two of the couples consisted of wives who had WLS, and one couple had both received the surgery. Interviews were transcribed and analyzed using a combination of interpretive phenomenological and grounded theory techniques. Findings demonstrated that WLS does have impacts on marriage regardless of where couples are in their journey. All couples discussed food as a possible source of conflict in their relationship. Interviews also reveled that self-esteem is a major factor contributing to their relationship and support is necessary throughout. In Phase 2 an online survey was developed to quantitatively explore the important constructs deemed important from the participants in Phase 1. Relationships between relationship satisfaction, sexual conflict, self-esteem, depression and body image were examined in 54 participants. Results demonstrate that higher levels of support and self-esteem and lower sexual conflict relate to a more satisfactory relationship in individuals post- WLS. Author Keywords: marital satsifaction, mixed-methods, qualitative, relationship satisfaction, weight-loss, Weight-loss surgery
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- Non-Hippocampal Memory Systems Contributing to Reinstated Context Memory
- Damage to the hippocampus (HPC) typically causes retrograde amnesia for contextual fear conditioning. Reinstating the conditioning over several sessions, however, can mitigate the retrograde amnesic effects. Reinstatements, thus, establish a sufficiently strong memory in non-HPC systems to no longer require the HPC for expression, meaning that it has become HPC independent. This thesis aimed to determine the structures comprising the non-HPC system supporting reinstated context fear memory. The contribution of the perirhinal cortex (PRH) and the anterior cingulate cortex (ACC) were examined because of their established role in context memory. Initially, it was demonstrated that HPC damage indeed causes retrograde amnesia for single session, but not reinstated, contextual fear conditioning. Then, it was demonstrated that combined HPC and PRH damage causes retrograde amnesia for reinstated contextual fear conditioning, whereas combined HPC and ACC damage had lesser effects. Therefore, the PRH is a key structure within the non-HPC memory system for reinstated context fear memory. Author Keywords: anterior cingulate cortex, contextual fear conditioning, hippocampus, memory, perirhinal cortex, retrograde amnesia
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- “Just Say Yes” - Sexual Consent and Boundary Setting On-and Offlinle
- The present study examined the understanding and behaviours relating to sexual consent on, and offline among men who have sex with men (MSM) and heterosexual men internationally using a convergent parallel mixed-methods approach. Men of both sexual orientation groups presented challenges with negotiating sexual consent, and this was especially true if they scored higher on aggressive traits or had previously experienced childhood abuse or an unwanted penetrative sexual act in adulthood. However, from the results as a whole, MSM reported struggle more with regards to consent negotiation for a variety of reasons (e.g. sexual scripts, power dynamics, additional sexual settings, sex-role positioning). Limitations and future directions are discussed. Author Keywords: heterosexual men, men who have sex with men, sexual assault, sexual consent, technology
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- Heavy Rydberg Photo-dissociation Cross-section Calculations and Experimental Progress Towards Cold Collisions in Lithium
- This thesis is divided into two parts, each of which supports constructing and using a lithium magneto-optical trap for cold collision studies: Part I One outgoing channel of interest from cold collisions is the production of ion pairs. We describe an effective method for calculating bound-to-continuum cross-sections for charged binary systems by examining transitions to states above the binding energy that become bound when the system is placed within an infinite spherical well. This approach is verified for ionization of a hydrogen atom, and is then applied to the heavy Rydberg system Li+...I-. Part II A wavemeter previously built in the lab is redesigned for increased reliability and ease of use by replacing the optical hardware with a rocker system, which can be aligned in mere minutes rather than half a day as was previously the case. The new wavemeter has been tested through saturated absorption spectroscopy of lithium. Author Keywords: cross-section, dissociation, lithium, magneto-optical trap, Michelson, wavemeter