Melbourne School of Psychological Sciences - Theses
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The acute and habitual effects of alcohol consumption on sleep in late adolescents
Adolescence is a critical time period for human development. It is associated with major interrelated changes to the brain and sleep regulatory systems. These changes continue into young adulthood, and often coincide with the onset and acceleration of alcohol use. This is concerning as research suggests alcohol consumption may harm the developing brain and sleep systems. Indeed, sleep is an essential neurophysiological process that is necessary for optimal health, functioning, and development. Disturbances to sleep are associated with adverse physiological and psychological consequences. Alcohol is well-known for its sleep disturbing properties. Research has reliably shown that pre-sleep alcohol ingestion in light-drinking late adolescents leads to characteristic objective sleep disruption. These effects are bi-phasic, manifesting as sedation in the first half of the sleep period, followed by major sleep disruption in the second half. However, there is growing evidence that young people may be less sensitive to the initial sedative effects of alcohol. Critically, the effects of acute alcohol consumption on sleep have not yet been investigated in young people who habitually engage in heavy alcohol use. It is well-established that chronic heavy alcohol use leads to enduring sleep disturbances, such as degradations in slow wave sleep (SWS), that persist into periods of long-term abstinence. This has been investigated exclusively in adults with long-term alcohol use disorders. It is currently unknown whether heavy-drinking young people also suffer disturbances to normal sleep. Due to their ongoing development, it is possible that young people experience unique alcohol-related sleep disturbances. These disturbances could negatively impact physical and mental health. The current study aimed to investigate the effects of acute and habitual alcohol use on sleep quality, architecture, and electroencephalography (EEG) spectral power, in male and female late adolescents, aged 18 to 21 years. Forty-six late adolescents were recruited (mean +/- standard deviation): 9 light-drinking males (20.0 +/- 0.9 years; 13.5 +/- 10.3 standard drinks [10g of ethanol] in the previous 30 days), 13 light-drinking females (19.4 +/- 1.2 years; 12.3 +/- 8.0 standard drinks), 11 heavy-drinking males (20.1 +/- 0.7 years; 133.4 +/- 78.8 standard drinks), and 13 heavy-drinking females (19.2 +/- 0.9 years; 81.9 +/- 25.6 standard drinks). Following an initial adaptation night, participants completed in-laboratory polysomnography under two conditions: pre-bedtime alcohol (peak breath alcohol concentration [BrAC] .10%) and placebo (BrAC .00%) consumption. Experimental nights were non-consecutive and counterbalanced over participants. Participants abstained from alcohol for 48 hours prior to testing. This single-blind, mixed-model study design included two repeated- (acute alcohol vs. placebo consumption, first vs. second half of the sleep period) and two between- (male vs. female, habitual heavy vs. light drinking) measures factors. Sleep quality (sleep onset latency, arousals, wake after sleep onset, sleep efficiency) and architecture (stage N1 sleep, stage N2 sleep, SWS, rapid eye movement [REM] sleep) variables were independently scored using standard American Academy of Sleep Medicine (2007) criteria by two experienced sleep researchers. Discrepancies between scorers were resolved by an independent adjudicator. All scorers were blinded to participant group and experimental condition. Power spectral analysis was conducted for five EEG frequency bands: beta (16 – 30 hertz; Hz), sigma (12 – <16 Hz), alpha (8 – <12 Hz), theta (4 – <8 Hz), and delta (0.5 – <4 Hz) for each sleep stage. Data were analysed using mixed-model analysis of variance and post-hoc t-tests. Correlations between habitual alcohol consumption, and sleep quality and architecture variables, were also performed. Mean BrAC at lights out was .08 +/- .01 percent following pre-sleep alcohol, and .00 +/- .00 percent following placebo consumption. Following acute alcohol consumption, in the first half of the sleep period, both heavy- and light-drinking late adolescents demonstrated fewer arousals (p< .001), less stage N1 sleep (p< .001), more SWS (p= .007), longer REM sleep onset latencies (p< .001), and less REM sleep (p< .001), compared to placebo. There were no differences observed in sleep onset latency (p= .720), wake after sleep onset (p= .850), or sleep efficiency (p= .811). In the first half of the sleep period, alpha EEG spectral power was higher following alcohol consumption in stage N2 sleep (p< .001), SWS (p< .001), and REM sleep (p= .005). Although delta spectral power was higher in SWS (p= .008) and REM sleep (p< .001) in the first half of the sleep period, delta power was lower in stage N2 sleep (p= .006). In the second half of the sleep period, there were more arousals (p< .001), more wake after sleep onset (p< .001), lower sleep efficiency (p< .001), more stage N1 sleep (p< .001), and less SWS (p= .004), following acute alcohol consumption compared to placebo, in both heavy- and light-drinking late adolescents. No differences in EEG spectral power were observed in the second half of the sleep period. By design, heavy-drinking participants had consumed more alcohol in the previous 30 days, and across their lifetimes, than light drinkers (p< .001). There were no differences in objective sleep quality between heavy- and light-drinking late adolescents. However, a correlational analysis showed that, in the placebo condition, higher alcohol consumption in the previous 30 days was associated with higher wake after sleep onset (Spearman's Rho= .312, p= .035), and lower sleep efficiency (Spearman's Rho= -.327, p= .027). Heavy drinkers had less all-night visually scored SWS (p= .026), and more stage N2 sleep (p= .008), than same-aged light drinkers, in the placebo condition. Furthermore, higher previous 30-day alcohol consumption was related to lower SWS (Spearman's Rho= -.261, p= .040) and higher stage N2 sleep (Spearman's Rho= .250, p= .027) percentage, in the placebo condition. Irrespective of experimental condition, heavy drinkers had shorter REM sleep onset latencies, compared to same-aged light drinkers (p= .038). Although there were no differences in all-night REM sleep percentage, heavy drinkers had less REM sleep in the second half of the sleep period compared to light drinkers, irrespective of condition (p= .016). There were no differences in delta spectral power between heavy- and light-drinking late adolescents in any sleep stage. However, heavy-drinking late adolescents had higher sigma spectral power in SWS (p= .029), and stage N2 sleep (p= .021), than same-aged light drinkers, regardless of experimental condition. There was an interaction between sex, acute alcohol use, and habitual alcohol use, for all-night SWS percentage (p= .003). This interaction suggested that heavy-drinking males had higher all-night SWS percentage following alcohol consumption compared to placebo, however, heavy-drinking females had lower all-night SWS. In light-drinking males and females, there were no differences in all-night SWS percentage following alcohol or placebo consumption. The current study demonstrated that both heavy- and light-drinking late adolescents experience substantial sleep disruption following a high dose of alcohol prior to sleep. In contrast to the adult literature, the current investigation reported no differences in sleep onset latency, wake after sleep onset, or sleep efficiency, in the first half of the sleep period. This supports growing evidence that young people may experience less initial physiological sedation following alcohol consumption. However, a direct adult comparison is needed to verify this. This unique physiological response could potentially contribute to higher levels of alcohol use in young people, as it permits them to consume higher doses of alcohol before experiencing sedation. The current study replicated previous findings of higher alpha and delta spectral power following pre-sleep alcohol in young people. This may represent alpha-delta sleep – a potential electrophysiological indicator of sleep disruption. It is possible that these objective sleep disturbances may compromise the restorative properties of sleep and contribute to the alcohol hangover. The current study reported more wake after sleep onset, and less sleep efficiency, following acute alcohol consumption, which may contribute to sleep restriction in young people. Critically, this investigation provided novel evidence that pre-sleep alcohol consumption disrupts sleep in heavy-drinking late adolescents. This indicates that this population may be repeatedly experiencing sleep disruption during the final stages of neural development. Furthermore, these effects may be amplified in heavy-drinking young women, however further research is needed to replicate these novel findings. Finally, the present study uniquely demonstrated that heavy habitual alcohol use in young people is associated with disturbances to normal sleep, irrespective of pre-sleep alcohol consumption. Despite their relatively short drinking histories, the pattern of deficits was similar to those reported in adults with long-term alcohol use disorders, including lower all-night SWS percentage. Furthermore, some sleep abnormalities may be unique to this developing age group, such as elevated sigma spectral power during SWS and stage N2 sleep. Evidence suggests SWS plays a functional role in neurophysiological growth and repair, and learning and memory. Enduring degradations in SWS may be particularly detrimental in young people, as neural development is still ongoing, and academic pressure is high, during this time period. Although longitudinal research is required, the sleep deficits observed in the current investigation may represent alcohol-related changes to the brain and sleep systems, and/or a predisposition to heavy alcohol use. In summary, the current study provided key objective evidence that both acute and habitual alcohol use in late adolescence disrupts sleep. This could have deleterious effects on the health, functioning, and development of young people. It is imperative that action is taken to prevent or reduce alcohol-related sleep disturbances during the final stages of human development. Interventions should aim to delay and reduce alcohol consumption, enhance cognitive function, and improve sleep quality to protect the health and wellbeing of young people.
Characterising the long-term psychosocial outcomes of surgery for temporal lobe epilepsy
Surgery is currently the recommended treatment for patients with drug-resistant epilepsy and a well-localised seizure focus. While the focus is on eliminating seizures, it is well-recognised that a good seizure outcome does not automatically equate to improved psychosocial functioning. Our understanding of the psychosocial outcomes of surgery is supported by a wealth of short- (<2 years) to medium-term (<10 years) research. Relatively less is known, however, about patient experiences and psychosocial outcomes over the longer-term. The current thesis conducted a qualitative exploration of the long-term (15-20 years) psychosocial outcomes of surgery for the treatment of temporal lobe epilepsy (TLE), supported by targeted secondary quantitative analyses. Forty adult patients who had undergone anterior temporal lobectomy (ATL) at the Austin Health Comprehensive Epilepsy Program (CEP) between 1994 and 2001 were recruited. Comprehensive one-on-one interviews elicited patient experiences of their surgery and subsequent psychosocial trajectories, supplemented by well-validated questionnaires assessing mood and quality of life, as well as a novel online survey (Living with Epilepsy) examining patient perceptions of their epilepsy and surgery. Finally, reviews were conducted of patient pre- and post-surgical CEP psychosocial records and of detailed long-term follow-up seizure data. Data were analysed using well-established qualitative and quantitative methodology. Study 1 mapped the achievement of key social milestones over the 15- to 20- year post-surgical period and used thematic analysis to explore these experiences from the patient perspective. A common pattern of milestones emerged as patients progressed through achieving return to driving, education and vocational outcomes and finally, family outcomes. This was felt to resemble a process of psychosocial development, providing a broader theoretical framework for understanding post- surgical social trajectories. Building on this, Study 2 used grounded theory analysis to explore how patients reflected on and made sense of their overall post-surgical psychosocial experiences. The resulting model identified surgery as a major life turning point, which could prompt early post-surgical adjustment difficulties and psychological ‘disequilibrium’. Patients then sought to re-establish a sense of normality, drawing on processes of reframing and meaning making. Meaning making refers to the process of integrating experiences and emotional learning into the self-concept. Given psychosocial development and meaning making are both important processes for identity development, Study 3 characterised personal identity and Study 4, social identity, at long-term follow-up. The majority of patients demonstrated a personal identity profile characterised by a higher level of commitment to, rather than exploration of, psychosocial roles and values. The ability to embrace self-identity development and meaning making (as described in Study 2) was associated with higher health-related quality of life (HRQOL), pointing to a process of positive psychological growth as a result of undergoing surgery. Study 4 further highlighted the powerful role of social identity for patient well-being; identifying as someone without epilepsy post- surgery was associated with higher HRQOL, over and above seizure outcome. In conclusion, this thesis represents the longest qualitative follow-up of the psychosocial outcomes of ATL to date. Findings delineated the complex nature of the longer-term post-surgical psychosocial adjustment process and the importance of understanding the patient experience for promoting well-being. It is hoped that this information can be used to guide the development and refinement of comprehensive pre- and post-surgical counselling and rehabilitation programs.
Chromatic contrast sensitivity functions measured using optokinetic nystagmus and psychophysics
Optokinetic nystagmus (OKN) is a sequence of involuntary eye movements comprising slow phases of tracking a moving stimulus followed by fast saccades to reset the eye position. Although previous studies have studied the relationship between human OKN and functional vision via measurement of the contrast-sensitivity function (CSF), it has not been investigated using colour-varying, red-green, equiluminant patterns. In human vision, spatiotemporal changes in luminance convey a stronger sense of motion than do equiluminant patterns; yet, motion can nevertheless be perceived without luminance cues. The present study used spatial-frequency, band-pass luminance and red-green equiluminant noise patterns to measure OKN, and thus characterise the chromatic input to the mechanisms that drive the optokinetic response. The CSFs of 21 observers with normal vision were recorded using OKN and perceptual report. The results of the study demonstrate that an equiluminant red green stimulus can evoke a robust OKN response. There was a high correlation between OKN and perceptual report, for both luminance and colour stimuli, an indication of a common neural mechanism for defining stimulus direction. In all stimulus conditions tested, OKN can deliver a valid alternate technique for measuring the CSF.
Intelligence analysis in multidisciplinary teams - affordances of the collaborative online SWARM platform for public service and education application
Intelligence analysts from Australian Commonwealth, State and Territory Government agencies and departments regularly work in teams with other roles, referred to in this research as multidisciplinary teams (MDTs). MDTs operate within a ‘framework’, which provides the central mechanism for team coordination and structure. However, there is little available research on intelligence MDT frameworks including challenges. To address this gap and explore potential MDT frameworks, this thesis examines intelligence MDTs and the Hunt Lab’s collaborative software prototype SWARM Platform as a framework to support the functions of intelligence MDTs. The Hunt Lab developed the Platform in 2017 to improve collaboration and quality of reasoning of intelligence analysts. We investigated whether the Platform can move beyond its origins to provide a framework to support the business and training functions of intelligence MDTs, including affordances for managers and educators. As a first step, we developed a maturity model, informed by the intelligence teamwork literature for the purposes of defining and evaluating the key indicators of intelligence MDTs. We detail the development of our maturity model that contains seven pillars against which MDT performance could be evaluated: Mission, Accountability, Agility, Efficiency, Communication, Collaboration and Output. This maturity model formed the central coding mechanism for this research to evaluate MDT performance. We conducted three studies to address our research questions focusing on current MDT workplace application and whether the Platform supports business and training MDT framework functions. Study 1 applied the maturity model to a case study of intelligence MDT performance in the Australian Government, where we identified Mission and Collaboration as a strength but Efficiency as a weakness of their MDT framework. In Studies 2 and 3, we evaluated the Platform as a potential framework to support the business and training functions of intelligence MDTs, first in a small-scale pilot within an Australian Government workplace and then on a larger scale in an analytical competition involving public and intelligence organisation teams. In these two studies, we found the Platform mostly supported key MDT pillars but also identified varying weaknesses across pillars of Accountability, Efficiency and Communication. Despite the Platform’s broad support for the MDT maturity pillars, this research identified technical and cultural issues that prevent adoption of the Platform as a business framework without further prioritised research. Instead, our research indicates the Platform has more immediate benefits in supporting training functions as a computer-supported collaborative learning (CSCL) tool, where research participants reported both cognitive and social learning outcomes in the same studies. This research developed insights relevant to MDT frameworks more broadly including scaffolding strategies to improve multiple maturity model pillars. These strategies include teamwork schema development; launch meetings; accountability practices; and data management. We also developed insights into engaging and researching government with intelligence functions that are an emergent but not unforeseen result from this research. These findings have implications for future collaboration between the tertiary research sector and government with intelligence functions.
Addressing methodological issues in a study of impulsivity and vulnerability for transition to alcohol use disorder
Although large numbers of people consume alcohol, relatively few are diagnosed with alcohol use disorder (AUD). Factors influencing why some individuals transition from alcohol use to AUD remain unclear. Alcohol misuse, especially in adolescence/young adulthood, has been linked to a range of negative outcomes, including increased risk of developing AUD. In addition, a rich literature suggests individuals with AUD have heightened impulsivity. Specifically, they demonstrate increased choice impulsivity and diminished response inhibition. As such, heightened impulsivity, especially in young at-risk drinkers, might be a marker for vulnerability to transition to AUD. Although a number of studies have investigated this proposition, results have been mixed. Various methodological reasons have been posited for these inconsistent findings. Problems related to how to describe/quantify at-risk consumption and/or a reliance on retrospective methods of assessing this intake might be confounding results. Also, such studies typically have relatively modest sample sizes. The overarching aim of research presented in this thesis was to address these methodological limitations. To that end, two studies examined smartphone app development, reliability, and validity. It was proposed use of an app might assist in overcoming difficulties pertaining to empirical definitions and/or measurement of alcohol intake, as well as facilitate data collection from a large, diverse sample. Two studies investigated psychometric properties of online protocols that assess cognition. It was anticipated use of online tools would also enable data collection from a large sample. Finally, two studies concentrated on examining the relationship between alcohol intake and outcomes. Utilising the smartphone app as well as online protocols, the first of these studies explored adverse alcohol use consequences among tertiary students, while the second investigated facets of behavioural impulsivity among individuals who engage in at-risk alcohol intake behaviour. The app-related studies yielded a large representative sample (N = 671). Findings showed i) participants were compliant and demonstrated minimal reactivity to app protocols; and ii) the app is a valid means of assessing alcohol intake behaviour when compared to Timeline Followback. Studies investigating the psychometric properties of online protocols found i) the web-based Stop-Signal Task, when undertaken outside the laboratory as compared to in the laboratory, is a reliable method of assessing response inhibition (N = 166; r = .48); and ii) untimed/timed web-based 12-item versions of the Advanced Progressive Matrices are reliable and, relative to the Wechsler Abbreviated Scale of Intelligence, valid measures of perceptual reasoning and full-scale IQ (Study 1, N = 608, r = .34-.50; Study 2, N = 479, r = .41-.56). Finally, studies examining the relationship between alcohol intake and outcomes showed i) real-time intake of alcohol, age of drinking onset, and drug use predicts severity of alcohol use consequences in tertiary students, as measured by the Brief Young Adult Alcohol Consequences Questionnaire (N = 893; 37.3% of variance); and ii) contrary to expectations, significantly greater impulsivity – that is, either increased choice impulsivity and/or reduced response inhibition – was not apparent in at-risk drinkers, as compared to controls, regardless of the criteria employed to categorise alcohol intake. While this result might be related to the online nature of this research, it is possible more sensitive measures of behavioural impulsivity are required when assessing non-dependent drinkers.
Individual differences in perceptual and cognitive decision-making in response to near identical options
Every day people deal with the “exploration/exploitation dilemma”: Deciding when to stay with the current option or move to a new one. Most research in the literature focuses on the influence that external variables exert on people’s decisions (e.g., punishments/rewards). However, little is known about how people deal with identical or nearly identical options in the absence of external bias. The general assumption present in both human and animal models is that, in the absence of obvious cost, individuals would naturally explore. This thesis directly tests this assumption in six experimental studies by examining people’s behaviour when facing identical or nearly identical options, both in perceptual and behavioural tasks. Despite the obvious differences existing between behavioural and perceptual tasks, people are essentially making similar decisions (to explore a different option; or to exploit the current option). Hence, the broad hypothesis under investigation is that similar tendencies should be found within the same person, across domains. Furthermore, because the impact of external bias was minimal in the tasks used, any differences in people’s explorative tendencies should be attributed to stable factors, such as personality traits. To this end, we individuated two broad personality frameworks (the Big Five Model and the Schizotypy construct). In Study 1-4 we examined how people deal with the trade-off between exploration and exploitation from a perceptual perspective, by using binocular rivalry (where an observer is faced with identical, and equally valid, perceptual solutions). In Study 1 we demonstrated that people high in the Openness to Experience trait significantly differed from other people in the way they flexibly explored and combined basic visual stimuli. In Study 2 we looked at whether differences existed in people’s tendencies to explore perceptual solutions following changes in transient emotional state (i.e., arousal) and found that general changes in one’s mood, but not specific type of mood, have a significant impact. In Study 3 we examined whether changes in alternations (i.e., fast or slow) between perceptual solutions were associated with stable personality traits and found that slower alternations were associated with Conscientiousness, characterised by self-control and determination. In Study 4 we examined whether abnormalities in the way perceptual stimuli are “flexibly” processed in people with schizophrenia can be similarly found in a non-clinical population. We found that increased schizotypy was associated with an increase of mixed percept during binocular rivalry. Study 5-6 examined how people deal with the trade-off between exploration and exploitation from a behavioural perspective, by using the Virtual Environment task, which was designed and developed specifically for this aim. The Virtual Environment task was inspired by the animal literature (i.e., the optomotor maze; van Swinderen, 2011) where flies need to choose between identical turning points to advance in the maze. Study 5 presents the findings from the six pilot task. Each version was sequentially developed to rule out potential confounding variables, which might have been responsible for the “unusual” stereotypical behaviour that emerged. That is, people displayed exclusively exploitative tendencies, with no exploration. Study 6 presents the findings from the virtual environment task. Here people showed variability in their explorative tendencies, however, against our prediction an increase of exploration was linked to those personality traits capturing self-discipline (Conscientiousness), rather than flexibility and the tendency to engage with possibilities (Openness to Experience). This was the first evidence of important similarities between perception and behaviour in the way people deal with the trade-off between exploration and exploitation. For example, in relation to the number of decisions, or sampling, of the environment. Our findings also highlighted two important issues in the exploration/exploitation literature. First, they cast doubt on the assumption that humans have a “natural drive to explore” in the absence of rewards. As shown in the difficulties to design appropriate stimuli to observe a balance between exploration/ exploitation in the first place. Second, because our findings did not replicate data from the animal literature, they represent a cautionary tale in interpreting findings from the animal model to be considered valid for humans.
Evaluating a Universal Social Information Processing Skills Program for Girls: The Friendship Saver Program
This thesis presents an evaluation of the Friendship Saver Program, a universal program designed to be gender-specific, aimed to improve the social information processing skills of girls. Specially, the program aims to teach social information processing skills as defined by the Social Information Processing Model (SIP) (Crick & Dodge, 1994). The 12-week universal program was delivered to 214 middle-primary school age girls, by trained facilitators from their schools. An implementation quality questionnaire was used to track the fidelity of implementation, and indicated satisfactory to very good delivery of the program across the four schools involved. To evaluate program impact multiple measures were included, using a pre- and post-intervention design. An innovative interactive software program What Next? (Ainley & Ainley, 2006) was used to directly measure participants’ social information processing skills, and the widely-used Strengths and Difficulties Questionnaire (SDQ) (Goodman, 1997) was used to measure general social and behavioural functioning as rated by parents and teachers. The What Next? program measured participants interpretation of cues, response construction and response decision after viewing a video scenario of relational aggression. Due to the novel nature of using software and video footage to assess social information processing skills, participant engagement was also assessed. The engagement results offered strong evidence that the participants were highly engaged by the video scenarios, and maintained their engagement throughout their experience with the software. A pre-post intervention comparison indicated that following participation in the Friendship Saver Program, participants identified significantly more subtle cues indicative of hostile intent, and provided more response constructions and response decisions that were adaptive, with fewer maladaptive responses post-intervention. Hence, these results offered evidence of positive change following the Friendship Saver Program on girls’ social information processing skills. Parent and Teacher SDQ ratings indicated that this sample was a high functioning group at commencement of the project. Teacher ratings on the SDQ demonstrated no change in general social or behavioural functioning post-intervention, while parent ratings indicated fewer externalizing problems post-intervention. In concluding, the findings demonstrate the importance of gender-specific programs for teaching social skills to girls, and the advantages of using software and video technology to measure these skills. The results also demonstrate the potential of the SIP model to inform a targeted intervention for girls, and to be a relevant framework for investigating the social skills of girls.
The low statistical power of psychological research: Causes, consequences and potential remedies
This dissertation examines two major issues in psychological research: formal sample size planning and reporting biases. It is organized into three main parts. The first part examines the history of formal sample size planning and reporting biases in the psychology research literature, outlining the history of the dominant approach to statistical analysis (Chapter 2), demonstrating the implications of low statistical power and reporting biases on research literatures (Chapter 3), and examining the history of statistical power analysis as represented in the psychology research literature (Chapter 4). The second part of this dissertation examines psychologists’ research and publication practices. Chapter 5 presents a meta-analysis of previous power surveys and finds that the average statistical power of psychology research at Cohen’s small and medium effect size benchmarks was lower than typical goal levels and that this value remained approximately constant from the 1960s to 2014. Chapter 6 presents an analysis of more than 130,000 effect size estimates from over 9,000 articles published in 5 APA journals from 1985 to 2013 and finds that the average effect size reported in this body of psychological research decreased over time. Together Chapters 5 and 6 suggest that the average statistical power of psychological research remained stable or may even have decreased over time. In order to investigate why this is the case, Chapter 7 presents the results of a survey of researchers from across fields of psychological research about their research planning practices. This survey highlights the most important barriers that prevent researchers from using formal sample size planning during the design phase of their research and shows that while most researchers believe statistical power is important for their research purposes, practical constraints act to limit achieved sample sizes in most studies. The final part of this thesis examines the implications of low statistical power and reporting biases on scientific research and provides suggestions on how research planning methods could be improved. Bringing together all of the previous large-scale replication projects that have been conducted in the behavioral sciences, Chapter 8 shows that effect sizes in replication studies are, on average, considerably lower than those reported in original studies, and quantifies the substantial heterogeneity in this value across replication projects. Finally, Chapter 9 examines sample size planning efforts reported in recent Psychological Science articles and uses this to illustrate a guide to effect size selection for formal sample size planning. Together, this dissertation shows that low statistical power and reporting biases remain serious problems for the behavioral sciences research literature. Contrasting the long history of efforts to improve the statistical power of psychology research with the lack of change in the average power of research from 1962 to 2014, I argue that new methods of avoiding the negative impact of low statistical power and reporting biases are necessary. Several recent publication and methodological developments, namely (a) preregistration, (b) pre-prints and data repositories, (c) the registered reports publication format and (d) the increasing use of large scale collaborative research projects, provide possible mechanisms with which to reduce the negative impact of low statistical power and reporting biases on the published scientific literature.
Contemporary methods for identifying and leveraging expertise in collective decision-making
From company board committees to grand juries to political parties, decision making often involves a group of individuals with differing views on what the best decision may be. Individuals have different views, in part, because some individuals have more knowledge than others. In theory, decision makers can make better decisions by leveraging the expertise of individuals in the crowd by identifying those who have more knowledge than others. Unfortunately, it is often difficult to identify and leverage expertise in practice. Decision makers often have no records of individuals' past performance from which they can estimate expertise, and subjective measures such as confidence and self-ratings of expertise are often considered as unreliable. In this thesis, I demonstrate how individuals' meta-predictions -- predictions about what other individuals will predict -- can be used to identify and leverage expertise in the crowd on 'single-question' problems, where records on individuals' past performance are unavailable. I first examine how a recent algorithm in the literature can be used to distinguish between subsets of high-performing and low-performing individuals in the crowd on binary decision problems. I show that this algorithm is in fact weighting individuals by the absolute difference between an individual's vote and their meta-prediction about the votes of others, and thus this weighting metric can be used to identify and leverage expertise in the crowd. I develop an improved weighting approach that uses individuals' probabilistic forecasts and their meta-predictions about the average probability forecast of others, and show that this outperforms the top alternative probabilistic aggregation approaches in the literature on a large range of decision problems. Furthermore, I demonstrate that this improved weighting approach provides a superior measure of expertise than existing single-question approaches to identifying expertise in the literature. As an additional test, I compare this single-question approach with cross-domain weighting -- weighting by individuals' performance on problems on unrelated domains -- and show that cross-domain weighting is favoured over single-question approaches in cases where it is possible to obtain individuals' past performance on problems -- even if those questions are from unrelated domains. In general, our results demonstrate the potential for using individuals' meta-predictions and performance on problems from unrelated domains to identify expertise in cases where other approaches might be ineffective or unavailable.
Volumetric Measures of the Medial Temporal Structures and their Neuropsychological Correlates in Alzheimer’s Disease
Diagnosing Alzheimer’s disease (AD) in its earliest phases is difficult. A combination of standardised cognitive testing with AD-related biomarkers such as medial temporal atrophy observed on neuroimaging scans has been proposed to improve the diagnostic process of AD detection. The availability of automated volumetric segmentation software presents as a promising avenue for the incorporation of quantitative volumetric measures into routine clinical workup. However, the performance of these automated protocols in a clinical context remains to be clarified. This thesis aimed to examine the use of automated segmentation in a “real-world” clinical setting against the gold standard of manual segmentation, assess the difficulties surrounding reliable automated measurements, and evaluate the relationship between volume, diagnosis, and memory function. Methods utilised to address the research questions included a review of the diagnostic accuracy of various diagnostic tools, in-depth examination of structural variations that could undermine automated segmentation efforts, a series of validation studies, and assessment of medial temporal volumes and memory function in samples of clinical and healthy controls. The results indicate that a multimodal approach to diagnosis that includes a combination of cognitive assessment and other biomarkers would likely yield a more accurate diagnosis. Although automated segmentation of the medial temporal structures was promising for the hippocampus, the entorhinal and transentorhinal cortices were inherently more challenging to delineate and produced much poorer reliability measures. Medial temporal structural volumes contributed little beyond what was already provided by comprehensive memory assessment for distinguishing between the clinical and healthy control samples. Taken altogether, these findings highlight the need for additional refinement of automated algorithms and further investigation into the ideal combination of cognitive testing and other biomarkers.
Organizational Neuroscience with Applications to Stress Management
This thesis was on organizational neuroscience with applications to stress management. Section 1 developed an organizational neuroscience model of occupational stress that integrated the health impairment process of the job-demands resources model of occupational stress with the (biologically-grounded) allostatic load model of stress. In doing so, this section developed a series of propositions that integrated each model through a job demands-allostatic load pathway. Resilience training was discussed as a potential moderator of this pathway with a focus on mindfulness meditation, physical activity, and multi-modal interventions that comprise each of these practices completed concurrently. In Section 2 of this thesis, specific methodological, interpretational, and philosophical concerns that arise when adopting an organizational neuroscience approach to research were discussed across two critical essays. This included a focus on the appropriateness of statistical analyses in organizational neuroscience, the implications of the completeness and transparency of reporting research findings, and what kind of causal inferences can be drawn about organizationally-relevant behavior using neuroscience data. These essays served as the statistical and philosophical framework through which the empirical studies conducted in Section 3 were conducted and interpreted. Finally, Section 3 of this thesis was a conceptual evaluation of the resilience training propositions of the theoretical model developed in Section 1. It was a conceptual evaluation in that the sample was one of convenience rather than a working population, specifically. This included three studies conducted within a pilot and feasibility trial that comprised formal mindfulness psychoeducation and aerobic endurance exercise training, completed concurrently. It has been theorized that interventions of this kind exert salutary effects on mental health outcomes through neurobiological mechanisms. To assess this, this intervention was evaluated at multiple levels of analysis to build a comprehensive understanding of its effect on the mind, brain, and physiology. The primary aim of Study I was to investigate the effect of this intervention on self-reported chronic psychosocial stress, and potential mechanisms involving dispositional mindfulness, adaptive and maladaptive emotion regulation strategies, and maximal and submaximal cardiorespiratory fitness. Notably, participation in this intervention was associated with a reduction in chronic psychosocial stress, and an improvement in wellbeing that is considered clinically meaningful with respect to the scale. The primary aim of Study II was to investigate whether the effects of this intervention on mental health outcomes may occur through neural mechanisms, as predicted by theoretical models. This involved a longitudinal voxel-based morphometry study with a focus on gray matter concentration within the hippocampus. This study provided preliminary evidence that this intervention was associated with increases in gray matter concentration within the hippocampus, as well as within regions associated with stress regulation, memory, and sensorimotor processes. The primary aim of Study III was to investigate whether the aerobic endurance training component of this intervention was associated with exercise-induced adaptations to stress-responsive systems. This is of note because these adaptations have been posited to spill over to heterotypic stressors like psychosocial stress, and confer resilience to adversity more broadly. This was evaluated through measuring the cortisol response to a submaximal steady state exercise bout before and after the training period. In this study it was identified that training was associated with an attenuation of cortisol responses, which was indicative of physiological adaptations that enable submaximal exercise workloads to be conducted with greater efficiency and less strain. Limitations and implications for future research were also discussed.
An investigation of within-dimension stimuli in categorization and change detection
This thesis examined the way in which information is combined in order to make decisions. It focused specifically on within-dimension decision-making with spatially separate stimuli. The primary aim was to characterize the underlying organization of processing over time (i.e., identify the processing architecture; whether information processing proceeds in serial, parallel, or is pooled into a single decision-making channel), stopping rules (i.e., whether the process is exhaustive or self-terminating), and the efficiency of processing (i.e., workload capacity). These attributes were assessed through the analysis of response times (RTs) using Systems Factorial Technology (SFT), the Logical-Rules paradigm, and relevant computational modeling. In the first part of the thesis, results from the categorization experiments showed that for the majority of participants, processing occurs coactively (i.e., is pooled into a single decision process). Workload capacity, however, was shown to be limited. This suggests that a violation of context invariance may have occurred and several theories are considered as potential explanations for this finding. In the second part of the thesis, a novel modeling framework for characterizing the time course of change detection based on information held in visual short term memory was presented. Specifically, we sought to answer whether change detection is better captured by a first-order integration model, in which information is pooled from each location, or a second-order integration model, in which each location is processed independently. We conducted two experiments with both disjunctive OR rules and conjunctive AND rules (across locations) using a double factorial paradigm and a redundant target paradigm. These experiments showed that although capacity is generally limited in both tasks, architecture varies from parallel self-terminating in the OR task to serial self-terminating in the AND task. This novel framework allowed for model comparisons across a large set of models, ruling out several competing explanations of change detection. As a whole, this thesis found both differences and similarities in decision-making using within-dimension stimuli across categorization and change detection tasks. The finding of differences in decision-making strategy across categorization and change detection tasks highlights that different perceptual operations can yield a variety of experimental results. It may be expected that other tasks such as visual search, identification, and detection might also diverge. A finding of limited capacity across both task types, however, points to a potential common bottle neck in processing efficiency at an earlier encoding stage.