The current study investigated the nature of executive function (EF) abilities in preschoolers using confirmatory factor analysis; potential antecedents and outcomes were examined as well. Executive function refers to higher order cognitive abilities necessary to consciously and deliberately persist in a task; these abilities are associated with a wide variety of important developmental outcomes. Within the developmental literature, studies on EF development in early childhood have focused most often on the constructs of working memory (WM) and inhibitory control (IC). Whether WM and IC are dissociable cognitive abilities is an unresolved issue within the literature; accordingly, performance on a battery of EF tasks at ages 2 and 4 was assessed to determine if EF structure at these ages is best described by a single factor or two factors consisting of working memory and inhibitory control. At both ages, a unitary model fit the data well. Longitudinal relations between attention in infancy, preschool EF, and school readiness and social competency at age 4 were also examined. Although infant attention measures failed to significantly predict later EF, pathways between age 4 EF (but not age 2 EF) and all age 4 outcomes were significant and in the expected direction. Understanding the nature of EF and the factors associated with optimal regulatory abilities is necessary for both theoretical and practical purposes, and given the considerable improvements that happen to EF abilities during this time period in early childhood, longitudinal studies such as this one are necessary to address issues of developmental change. / Ph. D.

The focus of this project falls largely within the realm of investigating the development of brain-cognition relations from a developmental cognitive neuroscience perspective. There were two main goals of this study. First, this study focused on the regional differences in baseline-to-working memory task brain electrical activity and specifically investigated the hypothesis that there would be an increasing specificity of task EEG power between 3½ and 4½ years of age. The second goal of this study was to investigate the sources of variability in working memory function and to specifically examine the contributions of task-related EEG, the regulatory dimensions of temperament, and linguistic ability to the prediction of working memory performance. This second study objective included an investigation of the relation between working memory and each of these variables (1) separately, (2) in conjunction with age, and (3) collectively to examine any multivariate contributions to the explanation of variance in working memory function in early childhood. The results of this study provided some support to the increasing specificity of baseline-to-task EEG power hypothesis. Specifically, an increase in brain electrical activity was found for four scalp regions at age 4 and only two regions at age 4½. These findings coupled with previous work indicating an increase in task brain electrical activity for only one region at age 4½ suggest that cortical specialization is occurring during the early childhood years. With regard to the investigation of sources of variability working memory function, age, brain electrical activity, temperament, and linguistic functioning were all found to be meaningful variables in the explanation of variance in working memory. However, linguistic functioning " and specifically language receptivity " was found to be the strongest and most meaningful associate of working memory function. Additional findings of interest included the differential associations demonstrated between working memory and temperament for each age group and also an increase in the strength of the relation between working memory and language across the three ages. / Ph. D.

Seventy-three children participated in an investigation of inhibitory control (IC) at 3 years of age. Child IC was measured under various conditions in order to determine the impact that nonverbal and/or motivational task demands had on child IC task performance. Furthermore, task performance was examined with respect to measures of language, temperament, and psychophysiology. Tasks showed different patterns of relations to each of these variables. Furthermore, performance on the Hand Game, our measure of nonverbal IC, was explained by frontal EEG activity and, surprisingly, by language abilities. In contrast, performance on two other IC tasks, Day-Night and Less is More, was not related to measures of language or frontal EEG, perhaps because children performed at chance level on these tasks, indicating that these tasks may be too difficult for 3-year-old children. Implications of these findings are discussed. / Master of Science

Inhibitory Control (IC), a vital facet of childhood development, involves the ability to suppress a dominant response, as well as the ability to suppress irrelevant thoughts and behaviors. This ability emerges during the first year of life and develops rapidly during the preschool years. A variety of tasks have been developed to measure IC in this age group and, recently, research has demonstrated important differences in task performance according to various distinctions among these tasks. One under-researched distinction is that of whether an IC task requires the child to give a verbal or a motoric response. Therefore, the purpose of this study was to examine, in 4-year-old children, the differences and similarities among IC tasks requiring either a verbal or a motoric response. Differences were explored with respect to the contributions to verbal and motoric IC performance of language, intelligence, temperament, and frontal encephalography, as well as with respect to social and school readiness outcomes. IC was best described by a two-component model, distinguishing verbal and motoric IC. Both baseline and task electrophysiology contributed to task performance in the verbal Yes-No task as well as the motoric IC composite. Language and intelligence, too, were associated with both verbal and motoric IC, although nonverbal intelligence was less strongly correlated with verbal IC than it was with motoric IC. All laboratory measures of IC related to parent report of children’s IC as well as to other parent-reported temperament scales and factors. Children’s verbal and motoric IC were associated, too, with children’s social development, surprisingly showing the most consistent associations with social inhibition. Asocial behavior positively correlated more strongly with motoric IC than with verbal IC. Children’s laboratory IC positively correlated with their school readiness, even when controlling for their intelligence although children’s emergent literacy more positively related to their motoric, rather than verbal, IC. An interaction of intelligence and IC contributed to social variables, but not to school readiness. This research supports the important distinction between verbal and motoric IC, and demonstrates the utility of including an array of measures of both in early childhood research. / Ph. D.

Selective attention towards alcohol-related cues (i.e., “attentional bias”) is thought to reflect increased incentive motivational value of alcohol and alcohol cues acquired through a history of heavy alcohol use, and as such attentional bias is considered to be a clinically relevant factor contributing to alcohol use disorders. This dissertation consists of two studies that investigated specific mechanisms through which attentional bias might serve to promote alcohol abuse. Study 1 compared magnitude of attentional bias in heavy (n = 20) and light (n = 20) drinkers following placebo and two doses of alcohol (0.45 g/kg and 0.65 g/kg). Heavy drinkers displayed significantly greater attentional bias than did moderate drinkers following placebo. However, heavy drinkers displayed a dose-dependent decrease in response to alcohol. Individual differences in attentional bias under placebo were associated with both self-reported and laboratory alcohol consumption, yet bias following alcohol administration did not predict either measure of consumption. These findings suggest that attentional bias is strongest before a drinking episode begins, and as such might be most influential in terms of initiation of alcohol consumption. Study 2 addressed theoretical accounts regarding potential reciprocal interactions between attentional bias and inhibitory control that might promote excessive alcohol consumption. Fifty drinkers performed a measure of attentional bias and a novel task that measures the degree to which alcohol-related stimuli can increase behavioral activation and reduce the ability to inhibit inappropriate responses. As hypothesized, inhibitory failures were significantly greater following alcohol images compared to neutral images. Further, heightened attentional bias was associated with greater response activation following alcohol images. These findings suggest that alcohol stimuli serve to disrupt mechanisms of behavioral control, and that heightened attentional bias is associated with greater disruption of control mechanisms following alcohol images. Taken together, these studies provide strong evidence of an association between attentional bias in sober individuals and alcohol consumption, suggesting a pronounced role of attentional bias in initiation of consumption. Further, findings show that attention to alcohol cues can serve to disrupt mechanisms of inhibitory control that might be necessary to regulate drinking behavior, suggesting a potential means through which attentional bias might promote consumption.

Dual Processing theory proposes that the ability to over ride associative (System 1) in favour of analytical (System 2) processed in deductive reasoning may depend on inhibitory control. The present study applies this association to a spatial reasoning task by adapting a mental rotation task to a multichoice format including System 1 (mirror) and System 2 (rotated image) responses. Fifty undergraduate volunteers from the University of Canterbury responded to a Stroop task as a measure of inhibitory control that was compared with System 1 and System 2 responding from a spatial and a deductive reasoning task. It was expected that people with weaker inhibitory potential would make more System 1 and fewer System 2 responses in both deductive and visual-spatial reasoning tasks. Contrary to expectation System 2 responding dominated for both tasks and correlations between both reasoning tasks and measures of inhibitory control were non-significant. The differing idiosyncratic demands of each task may have obscured any common variables associated with inhibitory control. This research initiated a test for the presence of System 1 and System 2 in spatial reasoning.

Introduction: Impaired inhibitory control, one of the core executive functions, is common among individuals with mental illness. However, inhibitory control is essential for successful treatment and recovery. Inhibitory control is extremely vulnerable to developmental disruption during adolescence, a time when mental illness is first diagnosed. An acute bout of exercise has been shown to improve inhibitory control in healthy adolescents, however, to our knowledge there are no studies evaluating this effect in adolescents with mental illness. Purpose: The primary goal of this project was to examine the effect of an acute bout of high-intensity interval training on inhibitory control immediately, and 30 minutes following exercise in adolescents hospitalized for mental illness. The secondary goal was to assess the feasibility of using this type of exercise as an adjunct to current treatment. Methods: Participants were recruited through the inpatient mental health unit at the Children’s Hospital of Eastern Ontario. They performed exercise and control conditions in a randomized, counterbalanced manner. The Colour-Word Stroop Task was assessed pre, post, and 30-minutes-post on both days. The exercise condition included a 12 minute HIIT circuit, consisting of body weight exercises performed in a 1:1 work to rest ratio. The control condition involved reading magazines. Repeated-measures ANOVA evaluated changes in Interference Cost, the reaction time cost of responding to trials where the ink and colour do not match, and overall accuracy. Feasibility was assessed through recruitment and completion rates, as well as changes in affect and acceptability of the high-intensity interval training. Results: There was a significant interaction between condition and time for the Interference Cost measure, F(1.6,43.3)=13.6, p<.0001, η2=.34. Interference Cost was similar for both conditions at baseline (Mdiff = 12.4±11.11, p=.28). Interference Cost was significantly reduced immediately (Mdiff = 78.8±14.91, p<.001) and 30-minutes post-exercise (Mdiff = 59.6±15.14, p=.001) compared to control. Response accuracy did not differ by time, F(2,54)=.14, p<=.87, η2=.01 nor condition, F(1,27)=2.25, p=.15, η2=.08. After exercise, participants increased positive affect (mean difference = 4.3±8.09, p=.009) and were willing to perform the exercise before therapy sessions (rating = 6.4±2.75 out of 10). Conclusion: These findings suggest that high-intensity interval training could be used to improve inhibitory control in adolescents with mental illness, which has the potential to enhance the efficacy of their treatment. Future research should determine the impact of individual factors, such as diagnosis, medication, age of illness onset, length of hospitalization, and treatment history, on inhibitory control improvement after exercise.

Fear and stigmatization are often used to motivate overweight individuals to engage in healthy behaviors, but these strategies are often counterproductive and can lead to undesirable outcomes. In the present study, I examined the impact of weight-based stigma on cognitive ability (i.e., inhibitory control) and food selection (i.e., calories selected) in individuals who consider themselves to be overweight. I predicted that participants higher in perceived weight stigma would perform more poorly on an inhibitory control task and order more calories on a menu task when they read about discrimination against the overweight versus discrimination against a self-irrelevant out-group. Additionally, I expected that inhibitory control would mediate the relationship between perceived weight stigma and calories ordered for participants who read about discrimination against the overweight, but not for control participants. Participants completed online prescreen measures assessing whether or not they considered themselves to be overweight and their perceptions of weight stigma. Those individuals who considered themselves overweight were then invited into the laboratory to complete tasks to (1) manipulate weight-based discrimination, (2) measure inhibitory control, and (3) measure food selection. As predicted, participants higher in perceived weight stigma performed more poorly on the inhibitory control task and ordered more calories when they read about discrimination against the overweight, but not when they read about discrimination against an out-group. Conversely, inhibitory control did not mediate the relationship between perceived weight stigma and number of calories ordered by participants. Importantly, the present findings provide evidence that perceptions of weight stigma are critical in our understanding of the impact of weight discrimination. Additionally, these results have theoretical and practical implications for both understanding and addressing the psychological and physical consequences of weight-based stigma.

Alcohol research has shown that alcohol-related stimuli can disrupt behavioral control and attract more attention in alcohol drinkers. Stimuli typically used in tasks assessing these mechanisms are likely representative of an individual's history. Responses to visual stimuli that no longer closely resemble an individual's history may help shed light on whether these behaviors are due to classical conditioning or processes such as semantic priming. Hypotheses were tested using typical visual stimuli and modified, abstract versions in these tasks. 41 participants were exposed to these stimuli types while using a visual dot probe task. The difference in degree of attentional bias between real and modified stimuli was determined using gaze time. Individuals participated in two versions of the attentional bias-behavioral activation (ABBA) task. Proportion of inhibitory failure differences between versions was examined for the effects of stimuli modification on behavioral control. Results demonstrated that the sample did not exhibit an attentional bias to alcohol. Visual probe results yielded no differences between real and modified stimuli on attentional bias. ABBA performance indicated no differences as a result of image abstraction or stimuli type. Reasons for these findings and comparisons to similar research inquiries using the tasks the current thesis utilized were explored.

Children with traumatic brain injury (TBI) often experience difficulties with inhibitory control (IC), manifest in both neurocognitive function (poor performance on the stop signal task, SST) and behavior (emergence of de novo attention-deficit/hyperactivity disorder, or secondary ADHD, S-ADHD). IC allows for the regulation of thought and action, and interacts with reward to modify behaviour adaptively as environments change. Children with developmental or primary ADHD (P-ADHD) exhibit poor IC and abnormalities when responding to rewards, yet the extent to which S-ADHD is similar to and different from P-ADHD in terms of these behaviours is not well-characterized. The cancellation and restraint versions of the SST were used to examine the effects of rewards on 2 distinct forms of IC in children and adolescents divided into 4 groups (control, TBI, S-ADHD, and P-ADHD). The SST requires participants to respond to a “go signal” and inhibit their responses when encountering a “stop signal”. Rewards improved performance similarly across groups, ages, and cancellation and restraint IC tasks. Adolescents exhibited better IC and faster and less variable response execution relative to children. Significant IC deficits were found in both tasks in the P-ADHD group, with participants with S-ADHD exhibiting intermediate cancellation performance relative to the other groups. Participants with TBI without S-ADHD were not impaired on either task. The relationship between neurocognitive and behavioral IC was examined by comparing multi-informant ratings of IC across groups, and examining the relationship between ratings and IC performance on the SST. Participants in the control and TBI groups were rated within the typical range, and exhibited fewer problems than either of the ADHD groups, who differed from each other (the P-ADHD group was rated as more inattentive than the S-ADHD group). Moderate to high concordance was found between parent and teacher reports, each of which was poorly concordant with self-reports. The P-ADHD and S-ADHD groups were unaware of their own deficits. Poorer IC predicted parent and teacher classification of participants into ADHD subtypes, although IC did not predict rating concordance. Despite similar clinical presentations, S-ADHD and P-ADHD differ in the phenotypic expression of behaviour and manifestation of IC across contexts.