Cognitive deficits are highly prevalent in multiple sclerosis (MS) and have a negative impact on daily life. Impairments in information processing speed are among the most commonly reported deficits in MS and are generally assessed by evaluating mean-level performance on time-limited tests. However, this approach to assessing performance ignores potential within-subject differences that may be useful for characterizing cognitive difficulties in MS. An alternative method of measuring performance on timed cognitive tasks is to examine the degree of within-subject variability, termed intraindividual variability (IIV). IIV provides information about the characteristics of an individual’s performance and may provide novel information about cognitive functioning in MS and other neurodegenerative disorders. The research presented in this dissertation examined IIV in performance as an indicator of cognitive functioning in persons with MS and explored the relations of performance variability to measures of neuronal connectivity derived from resting state functional magnetic resonance imaging (rsfMRI). Individuals with MS were found to be both slower and more variable on tests of information processing speed and attention. This variability was observed even when controlling for sensorimotor confounds and other systematic variables that may influence variability, such as practice and learning effects. IIV in performance was found to better distinguish MS patients from matched groups of healthy control subjects when compared to common clinical measures of cognitive performance or average response speed. These differences in IIV were also found consistently across six monthly assessments in a group with MS who remained clinically stable over this period. This stability in IIV suggests its feasibility as a measure of changes in longitudinal cognitive or clinical status. Using rsfMRI, greater stability in performance (i.e., lower IIV) was associated with greater functional connectivity between frontal lobe regions (i.e., ventral medial prefrontal cortex and frontal pole) in persons with MS. This increased connectivity appears to represent potential compensatory processes within mildly affected MS individuals. Together the findings demonstrate that IIV is an important characteristic of cognitive performance that may provide new insights into the cognitive deficits present in MS.

To characterize the relationship between dispersion-based intra-individual variability (IIVd) in neuropsychological test performance and brain volume among HIV seropositive and seronegative men and to determine the effects of cardiovascular risk and HIV infection on this relationship. Magnetic Resonance Imaging (MRI) was used to acquire high-resolution neuroanatomic data from 147 men age 50 and over, including 80 HIV seropositive (HIV+) and 67 seronegative controls (HIV-) in this cross-sectional cohort study. Voxel Based Morphometry was used to derive volumetric measurements at the level of the individual voxel. These brain structure maps were analyzed using Statistical Parametric Mapping (SPM2). IIVd was measured by computing intra-individual standard deviations (ISD’s) from the standardized performance scores of five neuropsychological tests: Wechsler Memory Scale-III Visual Reproduction I and II, Logical Memory I and II, Wechsler Adult Intelligence Scale-III Letter Number Sequencing. Total gray matter (GM) volume was inversely associated with IIVd. Among all subjects, IIVd -related GM atrophy was observed primarily in: 1) the inferior frontal gyrus bilaterally, the left inferior temporal gyrus extending to the supramarginal gyrus, spanning the lateral sulcus; 2) the right superior parietal lobule and intraparietal sulcus; and, 3) dorsal/ventral regions of the posterior section of the transverse temporal gyrus. HIV status, biological, and cardiovascular disease (CVD) variables were not linked to IIVd -related GM atrophy. IIVd in neuropsychological test performance may be a sensitive marker of cortical integrity in older adults, regardless of HIV infection status or CVD risk factors, and degree of intra-individual variability links with volume loss in specific cortical regions; independent of mean-level performance on neuropsychological tests.

Insufficient sleep duration is associated with poor physical and mental health outcomes, and many Americans report that they are not meeting sleep duration recommendations. Many individuals choose to restrict their own sleep, yet little is known about the source of this sleep deficit. Recent research efforts have used the Theory of Planned Behavior (TPB) to predict sleep health behavior. However, this research is limited in that it fails to measure volitional sleep behavior and focuses exclusively on between-person differences. This study addressed these limitations by using an intensive longitudinal design to test how constructs of the TPB relate to nightly sleep opportunity. Healthy college students (N=79) completed a week long study in which they completed 4 ecological momentary assessment signals per day that measured their attitudes, perceived norms, perceived behavioral control (PBC), and intentions relating to their nocturnal sleep opportunity. Participants wore an actiwatch each night of the study to measure their sleep opportunity. Analyses revealed between- and within-day variability of attitudes, perceived norms, PBC, and intentions. Further, there were significant between- and within-day trajectories of these constructs. Mixed linear models demonstrated that both intentions and PBC were significant predictors of subsequent sleep opportunity, and that PBC was the strongest predictor of future intentions. The between-and within-day patterns of these constructs highlight important considerations for their measurement, and provide insight into the potential refinement of sleep promotion efforts. Results also demonstrate that within-person changes in PBC and intentions predict subsequent sleep opportunity, demonstrating the need for a daily framework when using the TPB to predict sleep health behavior.

Traditionally, reaction time (RT) was conceived of as an average speed of a number of responses made by an individual, or mean RT. Increasingly, however, intraindividual variability in reaction time (RT IIV) – the consistency of responses by a single person across trials – is used as an additional or even alternative measure. RT IIV is often found to be elevated in a number of conditions that affect the central nervous system functioning, such as traumatic brain injury or neurodegenerative diseases. It can predict change in cognitive performance in ageing, progression from normal ageing to mild cognitive impairment, and even death. Therefore, RT IIV may be of great practical importance. However, RT IIV and mean RT are correlated; therefore it is often problematic to draw conclusions about unique associations between these and other variables. One objective of the work presented in this thesis was to investigate determinants and correlates of simple and choice RT IIV and to test which associations may be accounted for by the individual differences in mean RT. The first investigation was concerned with age differences in RT IIV. Following a systematic review of literature, a series of meta-analyses demonstrated that older individuals (aged 60 years and above) have greater RT IIV than young or middle-aged adults in simple and choice RT tasks. The effects were reduced but still significant when RT IIV was adjusted for mean RT. The next study was a cross-sectional investigation of the associations between age and RT IIV, as well as of sex differences in RT IIV, across the lifespan in participants ranging in age from 4 to 75. Non-linear effects of age were found for RT IIV measures, such that variability decreased with age in children and increased with age in older adults. A novel finding from this study was that sex differences in RT IIV were present among adults but not children, suggesting that there might be an age threshold at which sexes diverge in their RT IIV trajectories. The results also indicated that findings regarding RT IIV may differ depending on the variability measure used (that is, whether and how mean RT is controlled). The second study on the same sample investigated variability on a trial-by-trial basis. Specifically, it tested the hypothesis that sex differences in variability are due to females being disproportionately slower at the first trial which inflates their overall RT IIV. This hypothesis was not supported. Another investigation used longitudinal data from the West of Scotland Twenty-07 study. Three cohorts of individuals aged approximately 15, 35 and 55, were followed up for 20 years and had RT data collected at four occasions. Analyses confirmed non-linear effects of age on RT IIV found in the earlier cross-sectional investigation. The final study investigated the effect of high altitude on RT IIV. It found that altitude-related increase in RT IIV is fully accounted for by general slowing of RT at high altitude. The overall pattern of results obtained from the investigations suggests that RT IIV increases with age in adults and that not all of the increase is due to general slowing. Moreover, the results show that sex differences in RT IIV are not uniform across the lifespan. Finally, whereas associations of RT IIV with some variables, for example age, are relatively robust to controlling for mean RT, others are fully attenuated by such practice.

<p>Elevated levels of anxiety are a common response to stressful competitive sports situations, are known to moderate athletic performance and are referred to as an unpleasant emotional state associated with perceptions of situational threat. The empirical studies in this dissertation considered primarily psychometric, methodological and conceptual issues of relevance for the study of anxiety and sports performance. In Study I, athletes were followed across a full competitive season to explore patterns of inter- and intra-individual variability of anxiety and self-confidence in relation to performance. The findings imply intra-individual anxiety and self-confidence variability to affect performance differently than the specific intensity level and are discussed in relation to more stable personality dispositions such as private self-consciousness. Study II evaluated the psychometric properties of the 27-item Competitive State Anxiety Inventory-2 (CSAI-2) and alternative versions of this scale. General support for a 17-item version (CSAI-2R) was found, but there are also psychometric limitations future research needs to resolve. Study III investigated assessment of intensity and directional ratings on single anxiety items with reference to the conceptualisation of anxiety symptoms as interpreted on a debilitative-facilitative continuum. The findings question the importance and rationale of assessing anxiety direction and revealed serious concerns with assessment procedures and statistical techniques applied in previous research. These concerns were also supported in Study IV, which explored athletes’ idiosyncratic experiences of debilitative and facilitative anxiety symptoms in terms of intensity and emotional valence. The findings are discussed and summarised in a model in order to increase conceptual clarity and provide implications for future research regarding anxiety and related emotional performance states.</p>

Elevated levels of anxiety are a common response to stressful competitive sports situations, are known to moderate athletic performance and are referred to as an unpleasant emotional state associated with perceptions of situational threat. The empirical studies in this dissertation considered primarily psychometric, methodological and conceptual issues of relevance for the study of anxiety and sports performance. In Study I, athletes were followed across a full competitive season to explore patterns of inter- and intra-individual variability of anxiety and self-confidence in relation to performance. The findings imply intra-individual anxiety and self-confidence variability to affect performance differently than the specific intensity level and are discussed in relation to more stable personality dispositions such as private self-consciousness. Study II evaluated the psychometric properties of the 27-item Competitive State Anxiety Inventory-2 (CSAI-2) and alternative versions of this scale. General support for a 17-item version (CSAI-2R) was found, but there are also psychometric limitations future research needs to resolve. Study III investigated assessment of intensity and directional ratings on single anxiety items with reference to the conceptualisation of anxiety symptoms as interpreted on a debilitative-facilitative continuum. The findings question the importance and rationale of assessing anxiety direction and revealed serious concerns with assessment procedures and statistical techniques applied in previous research. These concerns were also supported in Study IV, which explored athletes’ idiosyncratic experiences of debilitative and facilitative anxiety symptoms in terms of intensity and emotional valence. The findings are discussed and summarised in a model in order to increase conceptual clarity and provide implications for future research regarding anxiety and related emotional performance states.

Mild Traumatic Brain Injury (mTBI), often called concussion, has become a growing public health concern, prevalent in both athletic and military settings. In response, many researchers have explored cognitive outcomes post-mTBI, with a plethora of meta-analyses summarizing these findings; however, these meta-analyses examine solely mean performances on cognitive tasks, ignoring intra-individual variability (IIV) in cognitive performance that may elucidate neuropsychological impairment following mTBI. The current thesis involved two studies, responding to both the growing meta-analytic research and limited IIV findings. Study 1: Many meta-analyses have amalgamated individual study results on post-mTBI neuropsychological outcomes. With the abundance of meta-analyses, a systematic review of meta-analyses stands as the next logical step. Method: A systematic literature search yielded 11 meta-analyses meeting inclusion criteria (i.e., English-language systematic reviews/meta-analyses covering post-mTBI observational cognitive research on late adolescents/adults), with their findings qualitatively synthesized based on moderator variables (i.e., cognitive domain, time since injury, past head injury, participant characteristics, comparison group, assessment technique, and persistent symptoms). Results: The overall effect sizes ranged for both general (range: .07-.61) and sports-related mTBI (range: .40-.81) and differed both between and within cognitive domains, with executive functions appearing most sensitive to multiple mTBI. Cognitive domains varied in recovery rates, but overall recovery occurred by 90 days post-injury for most individuals and by seven days post-injury for athletes. Greater age/education and male gender produced smaller effects sizes, while high school athletes suffered the largest deficits post-mTBI. Control-group comparisons yielded larger effects than within-person designs, while assessment techniques had limited moderating effects. Conclusions: Overall, meta-analytic review quality remained low with few studies assessing publication or study quality bias. Meta-analyses consistently identified adverse acute mTBI-related effects and fairly rapid symptom resolution. Study 2: The long-term outcomes of executive functions and IIV following mTBI are unclear due to inconsistent and limited research, respectively. Further, the relationship between physical activity (PA) and cognitive performance at young adulthood remains almost fully unexplored. In turn, the current study aimed to (a) assess the diagnostic utility of both executive functions and IIV at predicting mTBI history and (b) evaluate the interaction between PA levels and mTBI on both of these cognitive metrics. Method: Altogether 138 self-identified athletes (Mage = 19.9 ± 1.91 years, 60.8% female, 19.6% 1 mTBI, 18.1% 2+ mTBIs) completed three executive-related cognitive tasks (i.e., N-Back, Go/No-go, Local-Global). Ordinal logistic regression analyses examined the joint effect of person-mean and IIV as predictors of mTBI status. Multi-level models examined mTBI and PA levels as predictors of trial-to-trial changes in performance. Results: Only mean response time (RT) for the Local-Global task predicted mTBI status, while no IIV variables reached unique significance. PA levels predicted subtle within-task decreases in RT across Local-Global trials. Conclusions: IIV research on mTBI remains limited; however, the preliminary results do not indicate any additional predictive value of IIV indices above mean performances. For executive functions, shifting appeared most affected, with past researchers identifying post-mTBI impairment in attentional processing. Higher PA levels minutely benefited within-task shifting and mean inhibitory performance, although these finding require cautious interpretation. / Graduate / 0622 / jkarr@uvic.ca

In risk assessment of risk chemicals, variability in susceptibility in the population is an important aspect. The health hazard of a pollutant is related to the internal exposure to the chemical, i.e. the target dose, rather than the external exposure. The target dose may be calculated by physiologically based pharmacokinetic (PBPK) modeling. Furthermore, variability in target dose may be estimated by introducing variability in the physiological, anatomical, and biochemical parameters of the model. Data on these toxicokinetic model parameters may be found in the scientific literature. Since the early seventies, a large number of experimental inhalation studies of the kinetics of several volatiles in human volunteers have been performed at the National Institute for Working Life in Solna. To this day, only very limited analyses of these extensive data have been performed. A Bayesian analysis makes it possible to merge a priori knowledge from the literature with the information in experimental data. If combined with population PBPK modeling, the Bayesian approach may yield posterior estimates of the toxicokinetic parameters for each subject, as well as for the population. One way of producing these estimates is by so-called Markov-chain Monte Carlo (MCMC) simulation. The aim of the thesis was to apply the MCMC technique on previously published experimental data. Another objective was to assess the reliability of PBPK models in general by the combination of the extensive data and Bayesian population techniques. The population kinetics of methyl chloride, dichloromethane, toluene and styrene were assessed. The calibrated model for dichloromethane was used to predict cancer risk in a simulated Swedish population. In some cases, the respiratory uptake of volatiles was found to be lower than predicted from reference values on alveolar ventilation. The perfusion of fat tissue was found to be a complex process that needs special attention in PBPK modeling. These results provide a significant contribution to the field of PBPK modeling of risk chemicals. Appropriate statistical treatment of uncertainty and variability may increase confidence in model results and ultimately contribute to an improved scientific basis for the estimation of occupational health risks.

Affective intra-individual variability (IIV) and affective psychological flexibility (PF) are both types of within-person variability. Affective IIV is defined as the range of emotions experienced by an individual assessed at multiple time points. PF is defined as the ability to vary one’s responses in a contextually dependent manner in order to appropriately meet situational demands. Currently, there are no comparisons between affective IIV and PF demonstrating how these constructs might be uniquely different from each other. The current study proposed to examine affective IIV and PF in order to establish discriminant and convergent validity, and stability data for each construct. The National Study of Daily Experiences (NSDE) waves 1 and 2, an 8-day daily diary portion of the Midlife Development in the United States (MIDUS I) and MIDUS II surveys was used for this study (n =793 adults completed both waves of the NSDE). Affective IIV was related to higher mean NA and neuroticism, and lower perceived control. Affective PF was related to lower mean NA, neuroticism, and higher mean PA and perceived control. Higher affective IIV was associated with more psychological distress when assessed concurrently at both waves and predicted more psychological distress and physical ill-health 10 years later. Higher affective PF was related to less psychological distress and physical ill-health when assessed concurrently at wave 1 and less psychological distress and physical ill-health 10 years later. When situational context is included in the calculation of emotional variability, changes in emotional response may represent emotional complexity and increased control rather than emotional lability and are related to better psychological and physical outcomes.

Cette thèse porte sur l’évaluation du leadership par une approche multi-évaluateurs (dite à 360 degrés). Tout d'abord les différents modèles du leadership, allant d'une conception unitaire, à une conception interractionniste puis à une définition en termes d'effet, sont détaillés. Puis en étudiant la question de la mesure, on met en évidence qu'avec la popularité croissante de leurs modèles, certains outils d'évaluation sont devenus des questionnaires psychométriques à part entière. Pourtant, du fait des limites de l’auto-évaluation, une nouvelle approche du leadership à vu le jour: l'évaluation à 360°. Elle évalue les qualités d'un manager en interrogeant les personnes travaillant avec lui (subordonnés, collègues, supérieurs...) et en comparant leurs évaluations avec la propre évaluation du manager. Un des points central de notre recherche a été d’étudier les apports et les limites de cette méthode. Tout d'abord on a vérifié dans quelle mesure les caractéristiques souvent utilisées pour expliquer la variabilité entre les catégories d'observateurs permettaient réellement de comprendre les écarts observés. Ces analyses ont montré que malgré des résultats significatifs, ces variables n’expliquent que très partiellement la variance existante. De par ces conclusions l’accent a été mis, non plus sur les différences inter-groupes, mais sur l'accord et le désaccord au sein des groupes d'observateurs. Enfin, la dernière partie revient aux bases méthodologiques et théoriques de la mesure en cherchant à proposer un modèle psychométriques qui conviendrait aux résultats de questionnaires à 360°, permettant de donner un cadre conceptuel au recours à des évaluateurs multiples. / This thesis is centered on leadership assessment through multi-rater evaluation, commonly known as 360 degrees assessment. First, leadership models were presented, and then, we discussed the measurement aspects of leadership, wherein we observed that some tools became full fledged psychometric assessments owning to the growing popularity of their underlying theory. Nevertheless, the concerns over the inherent limitations of self-report measures continued to be a major challenge in leadership assessment. This led to a new assessment approach called 360 degrees in which the characteristics of leaders are assessed by people working with them (subordinates, colleagues, superiors...) and compared with the leaders' self-appraisals. The focal point of this thesis was to study the advantages as well as the limitations of this approach. The study started with examining how well the variables which are supposed to explain the inter-rater variability were actually helpful in understanding the observed variance among observers. Those analysis yielded significant results despite the fact that those variables could explain only a very limited amount of variance. Following these observations, the study switched its focus from inter-group differences to intra-group / inter-rater agreement and disagreement. Finally, the last part of this thesis gets back to methodological and theoretical basics of measurement theory and proposes a psychometric model that would suit the 360 degrees assessments followed by a conceptual framework for the studies using multi-rater techniques.