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Rationale: Impulse control deficits are thought to underlie criminal offending. Impulsive choice is a facet of impulse control that refers to a preference for immediate over delayed rewards. This facet of impulse control has been measured empirically using the Iowa Gambling Task (IGT), which provides a metric of overall disadvantageous decision-making, as well as metrics of specific maladaptive decision-making strategies. Purpose: To investigate impulsive choice as a measure of impairment in offenders as reflected by performance on the IGT, and to examine maladaptive decision-making strategies that may mimic real-life decisions to engage in illegal behaviour. Methods: 100 Canadian federal offenders (34% female, mean age = 39.14 ± 9.74) and 89 controls (39% female, mean age = 37.04 ± 10.79) completed the IGT. The IGT involves repeatedly choosing cards from four decks. Two decks are “good” and result in a net gain on the task, and two decks are “bad” and result in a net loss. Decks offer a fixed reward, but vary in loss magnitude and frequency. IGT data were analyzed for net score (number of good choices minus number of bad choices), learning across the task, and deck switching patterns. Other assessments included data on offenders’ current sentence and risk for reoffence level. Results: Offenders performed significantly poorer than controls in terms of net score. Controls learned the advantageous strategy across the task but offenders did not. Offenders also made greater use of a “win-stay/lose-shift” strategy. Low-risk offenders performed significantly better than medium- or high-risk offenders on the IGT. Conclusion: These results suggest that, compared with controls, offenders tend to make riskier choices and use maladaptive decision-making strategies that provide a larger immediate reward but are disadvantageous in the long term. The IGT, as part of a comprehensive assessment of risk, may provide valuable information for preventing criminal offending and recidivism. / Thesis / Master of Science (MSc) / Criminal offending is thought to be related to impulse control problems. Research has linked offending to poor performance on a decision-making task known as the Iowa Gambling Task (IGT). On the IGT, participants repeatedly choose cards from four decks that provide wins and losses of points. Two decks are “good” and result in an overall gain on the task, and two decks are “bad” and result in an overall loss. In this study, 100 Canadian federal offenders and 89 non-incarcerated control participants completed the IGT. Offenders performed worse than the control group overall, and control participants but not offenders learned the best strategy (i.e., choosing from good decks) over the course of the task. Additionally, offenders with a “Low” criminal risk rating did better than those at “Medium” or “High” risk levels. These results suggest that the IGT may provide important information about the cause and prevention of criminal offending.

Investigations on the design of controllable magnetorheological (MR) fluid devices have focused heavily on low velocity and low frequency applications. The extensive work in this area has led to a good understanding of MR fluid properties at low velocities and frequencies. However, the issues concerning MR fluid behavior in impact and shock applications are relatively unknown. To investigate MR fluid properties in this regime, MR dampers were subjected to impulsive loads. A drop-tower test facility was developed to simulate the impact events. The design includes a guided drop-mass released from variable heights to achieve different impact energies. Five drop-heights and two fundamental MR damper configurations were tested. The two configurations were a double-ended piston and a mono-tube with nitrogen accumulator. To separate the dynamics of the MR fluid from the dynamics of the current source, each damper received a constant supply current before the impact event. A total of five supply currents were investigated for each impact velocity. After reviewing the results, it was concluded that the effect of energizing the MR fluid only leads to "controllability" below a certain fluid velocity for the double-ended design. In other words, until the fluid velocity dropped below some threshold, the MR fluid behaved as if it was not energized, regardless of the strength of the magnetic field. Controllability was defined when greater supply currents yielded larger damping forces. For the mono-tube design, it was shown that the MR fluid was unable to travel through the gap fast enough during the initial impact. Consequently, the damper piston and accumulator piston traveled in unison until the accumulator bottomed out. After which, the fluid was forced through the gap. In conclusion, the two designs were compared and general recommendations on designing MR dampers for impulsive loading were made. Possible directions for future research were presented as well. / Master of Science

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

Includes vita. / Title from PDF of title page. / Document formatted into pages; contains 126 pages. / Thesis (Ph.D.)--University of South Florida, 2003. / Includes bibliographical references. / Text (Electronic thesis) in PDF format. / ABSTRACT: Incidence of suicide has been shown to increase dramatically during adolescence. Despite an established pattern of depression and hopelessness leading to suicide in adults, no such pattern emerges in the adolescent literature. Recent investigations suggest that impulsivity may play a key role in adolescent suicide attempts. This study examined the role of impulsivity in adolescent suicidal gestures, as well as the relationships among demographic variables, anger expression, impulsivity, and suicidal behavior. A total of 100 participants (ages 11-17; 71 females and 29 males) were recruited from 2 inpatient crisis centers for children. The Children's Depression Inventory, Hopelessness Scale for Children, Adolescent Behavior Checklist, Pediatric Anger Expression Scale, and Suicide Intent Scale were administered to inpatients, and demographic information was obtained (age, gender, ethnicity, income, and structure of family). / ABSTRACT: It was hypothesized that patterns of depression, anger, hopelessness, and impulsivity would vary by age, gender, ethnicity, and suicidality (e.g., suicidal gesture vs. no gesture). The large majority of hypotheses were not supported. Results are explained in terms of alternative theories for the role of impulsivity in adolescent suicidal gestures. / System requirements: World Wide Web browser and PDF reader. / Mode of access: World Wide Web.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

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