Most children discontinue daytime napping by the age of five. This study investigated the role of nap status and gender in executive functioning of Korean four-year olds, about half of whom have transitioned out of naps. Thirty-seven children living in the Gyeonggi-do area in South Korea participated in this study. A sleep diary filled out by parents was used to identify their nap habits and their executive function was assessed using the Fish Flanker Task involving three phases (standard, reverse, mixed). Looking at speed, reaction-time analyses suggested that girls take longer to warm up on the standard flanker task compared to boys a difference that diminishes by the next phase when children encounter the reverse flanker task. Looking at accuracy, children were slow to warm up. Although there were no differences in initial exposure to the standard flanker task, children were more accurate on congruent than incongruent trials in the the mixed phase regardless of nap status or gender. When shifting from the standard flanker to the reverse flanker task, habitual nappers were more accurate on incongruent trials in the reverse-flanker task compared to non-habitual nappers. There were no statistically significant differences in duration of nighttime sleep for habitual and non-habitual nappers supporting the idea that the advantage in accuracy on incongruent trials for habitual nappers was due to the nap. The results suggest that four-year olds may still receive a cognitive benefit from habitual naps, especially when they must shift between tasks.

The cognitive aging literature contains abundant evidence of the natural vulnerability of the frontal areas of the brain and the associated impact on higher-order cognition. Namely, Executive Functions (EFs) have been repeatedly shown to decline steadily after 60 (Schaie, 2013). These age-related changes are said to impact most aspects of everyday life including quality of life (QoL; Davis et al., 2010), a key variable with regards to health, social service interventions and evidence-based clinical practices. Deepening our understanding of potential moderators of cognitive aging such as QoL is crucial to promoting well-being in the growing older adult population. The overarching aim of this study was to investigate the moderating role of QoL over age-related EFs differences. A seminal taxonomy of EFs (Miyake et. al, 2000, 2012) and the work of the World Health Organization (WHO) on QoL (Power et al., 2005) inspired this endeavor. Six tasks of EFs related to Shifting, Updating, and Inhibiting and self-reported QoL based on the WHOQOL-BREF and -OLD were utilized with 102 community-dwelling, healthy older adults (M = 73.11 years; age range: 60 - 94). A moderation analysis was used to assess if QoL (moderator) buffers the relationship between age (IV) and EFs indicators (DV). Regression and MANCOVA analyses were conducted to evaluate age-related differences in EFs and the following prominent theories: the processing speed theory (Salthouse, 1996), inhibition deficit theory of cognitive aging (Hasher & Zacks, 1988), and dedifferentiation hypothesis (Garrett, 1946). As predicted, age significantly contributed to task performance for most EFs indicators, above and beyond processing speed. As expected, statistically significant moderation interactions were found for several executive indicators and QoL domains, illustrating the buffering role of QoL over age-related differences in EFs. Specifically, QoL items related to the environment, sensory abilities, and social engagement domains, and EFs indicators related to Inhibiting, showed the most notable moderating effects. Implications for these results and the role of covariates were discussed. An emphasis was placed throughout on the importance of investigating QoL variables and other moderating factors of cognitive aging, for the development of prevention and intervention endeavors with older adults. / Graduate

Few studies have researched writing difficulties in individuals with Autism Spectrum Disorder (ASD) and the factors responsible for such difficulties. The current study sought to examine writing difficulties in individuals with ASD and the contribution of working memory (WM) difficulties. The investigation consisted of five youth formally diagnosed with ASD (under DSM-IV-TR, higher functioning Autistic Disorder or Asperger’s Disorder), and five youth with no formal diagnosis. Participants completed a counterbalanced battery of tests that assessed their written expression and WM abilities. Due to challenges in recruiting enough participants for purposes of quantitative research, the study mainly used a case-study analysis. The study showed that participants with ASD (group with ASD) had more difficulty with writing and WM tasks than participates without ASD (traditionally developing [TD] group). Nonparametric analyses revealed that writing and WM were not related; however, these findings are cautionary due to very low participation numbers in the investigation. Case-study analysis showed that the group with ASD had underdeveloped writing skills notably in the areas of word count, vocabulary, spelling and grammar. Regarding WM abilities, the group with ASD showed variable patterns of difficulty; some had strengths in verbal WM while others did not. Unfortunately, the study could not determine if writing difficulties were specific due to WM or other causes, although it does provide useful information for further investigation. Additional studies investigating the relationship between writing and WM, particularly in individuals with ASD, are encouraged. / Graduate

Learner mobility and active school travel (AST) has been proposed to improve school attendance and academic performance. In South Africa, approximately 86% of learners have been reported as walking to and from school. AST in Africa is becoming less common in urban areas, and this may be a contributing factor to the increased risk and frequency of noncommunicable diseases due to decreased physical activity. The aim of this wait-list controlled evaluation was to assess the physiological and cognitive changes of access to a bicycle versus walking on adolescents. Specifically, changes adolescent's physical activity levels and executive function in a South African low-income community. Two schools were recruited, with the evaluation school receiving bicycles and the control a school who were yet to receive bicycles. Significant differences were observed across the physiological and executive function assessments. Most notably in the executive function tests, the evaluation group showed significant time to completion decreases across all three tests (N-Back, Arrow Flanker, WCST: p< 0.001). The results from this study are significant, as they are the first to assess anthropometric, physiological and executive function in South African adolescents from low-socioeconomic regions. It is evident that there are potential improvements in working memory, inhibition and shifting due to cycling as a mode of AST or during leisuretime. Further research needs to determine the specific mechanisms associated with these improvements.

While Attention-deficit/hyperactivity disorder (ADHD) is one of the most common psychological disorders diagnosed during development, adult ADHD remains vastly under recognized and undertreated. In an effort to better understand current issues with adult ADHD assessment, this study examined the relationship between symptoms, impairment, and executive functioning. Results indicate that among individuals who screened negative for ADHD, those higher in executive function reported experiencing significantly less impairment than those lower in executive function. Executive function was shown to have a negative relationship with impairment and ADHD symptomology was shown to have a positive relationship with impairment. Additionally, impairment was significantly predicted by ADHD symptoms and executive function, and there was a significant interaction between executive function and ADHD symptoms in predicting impairment. Understanding the relationship between executive function, ADHD symptoms, and impairment is critically important in better understanding adult ADHD.

Autism Spectrum Disorder (ASD) is a complex neurologically based developmental disorder that can affect an individual’s thinking, feeling, language development and social interactions. The prevalence of ASD in the United States continues to rise and today is identified in approximately 1 in 68 children. The symptoms of ASD interfere with and limit everyday functioning (Centers for Disease Control, 2015), which results in the majority of individuals with ASD remaining dependent on caregivers in the areas of education, habitation, and recreation (Billstedt, Gillberg, and Gillberg, 2005 & 2011). There is growing evidence that executive dysfunction may contribute to the social, cognitive and functional deficits observed in individuals with ASD; however, there is a significant lack of evidence based interventions that address executive functioning skills for emerging adults with ASD. The EFFECT program was developed to address this identified need. It is an 8-week comprehensive program based on research, that facilitates activities of daily living and instrumental activities of daily living by addressing underlying executive functioning skills. A thorough literature review, methods for program implementation, funding, dissemination and program evaluation are described. / 2018-03-03T00:00:00Z

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Both sleep deprivation and loss of situation awareness (SA) have been cited as primary causal factors contributing to the accident and injury rate in the military and civilian sector (e.g., transportation). Despite the numerous references to both factors as causal in nature, much of the literature on the effects of sleep deprivation on executive function is anecdotal. Research has produced mixed results regarding the nature and extent of performance degradation on a variety of lower-level and executive function tasks. Similarly, although SA has been cited as a significant contributor to operational performance, there is still considerable debate over the definition and construct validity of SA. Thus, a 29-hour hour sleep deprivation study was conducted to analyze the effects of sleep deprivation on both lower-order cognitive tasks (e.g., attention and working memory) and executive function tasks (e.g., reasoning, planning, decision making, and SA). In conjunction with the sleep deprivation analysis, the relationships among lower level cognition, executive function, and situation awareness were analyzed to form hypotheses about the SA construct and its relationship to complex task performance. Forty-eight participants were administered a series of cognitive tasks during baseline and sleep deprived testing sessions. Paired t-tests and additional post hoc analyses were conducted to determine the effects of sleep deprivation on cognition. Regression and factor analysis were used analyze the relationship among lower-order cognition, executive function, situation awareness, and complex task performance. Paired t-test results showed degraded vigilance in response to sleep deprivation, but did not indicate degraded executive function. Results of additional post-hoc analyses on executive function data indicated a trend toward degraded decision making and a trend toward increased planning errors in response to sleep deprivation. The results of the regression and factor analyses provided initial support for a dynamic, process definition of SA and illustrated the importance of considering SA as part of information processing as a whole in order to improve performance prediction. Based on the results of this dissertation, engineering recommendations were made for developing an "ideal" SA measurement technique and improving existing SA measurement techniques. Additionally, future sleep deprivation and situation awareness research directions were suggested. / Ph. D.