The ability to recall the past (i.e., episodic memory) and simulate hypothetical events (i.e., episodic simulation) are intrinsically linked, and individuals with diminished episodic memory abilities show similar deficits when imagining potential future events. For instance, age-related declines in episodic memory are mirrored in older adults’ simulations of future events, such that older adults produce fewer episodic details, and more semantic information, than younger adults when both remembering the past and imagining the future. Despite such deficits, recent research suggests that older adults can successfully imagine future scenarios in which they help people in need; however, these findings are limited, and the underlying mechanisms remain unclear. The present thesis examines whether episodic simulation of future helping behaviours differs between younger and older adults under several conditions. Chapter 2 demonstrates that episodic simulation of helping behaviour increases younger and older adults’ willingness to help even in the highly novel scenarios posed by the pandemic. Participants relied more on non-episodic details when imagining COVID-related scenarios for which they had limited similar experiences. Relatedly, in Chapter 3, both episodic simulation and similarity to one’s personal experiences increase willingness to help and phenomenological experiences, but the mechanisms differ between younger and older adults. Scene vividness and perspective-taking mediated the relationship between situation similarity and willingness to help in younger adults, but only perspective-taking had an indirect effect in older adults. Finally, Chapter 4 suggests that time-spent-imagining does not affect older adults’ ability to simulate future helping behaviours. However, time-spent-imagining did affect the number of internal details produced, but the proportion of internal details (correcting for total details produced) was not affected by time. As such, the often-used metric of a count of episodic details alone may not be the best measure to assess episodic simulation abilities in younger and older adults. Taken together, the present studies suggest that episodic simulation of helping similarly increases younger and older adults’ willingness to help, but the underlying mechanisms likely differ across the lifespan. Additionally, both subjective and objective measures of simulated events must be examined to accurately assess simulation abilities across the lifespan.

Face identification involves two tasks: Recognizing an individual even when their appearance changes, and discriminating them from similar-looking individuals. People vary in the accuracy with which they identify unfamiliar faces. Much of the work investigating individual differences in face identification used tightly controlled stimuli (i.e., focused on discrimination). Few studies have used stimuli that incorporate variability in appearance (e.g., focused on recognition). Despite interest in individual differences, and understanding that recognizing a face across instances poses a difficult challenge, many gaps in the literature remain. These include potential predictors, the reliability and convergent validity of face identification tasks, and whether unfamiliar face identification predicts face learning efficiency. I examined a potential predictor of face identification—photography experience (Chapter 2). I recruited photography Experts, Hobbyists and Novices to take part in an unfamiliar face identification task. Photography experience was not a significant predictor of sensitivity in unfamiliar face identification. However, it was a predictor of response bias. I examined the reliability and convergent validity of face identification tasks (Chapter 3). Participants completed four unfamiliar face identification tasks on two days (study 1), or two versions (simultaneous and sequential) of three unfamiliar face identification tasks (study 2). Sensitivity to identity and bias were stable across time and tasks. Response times were fastest on trials that were congruent vs. incongruent with one’s bias, providing preliminary evidence that this reflects decision-making processes. I examined whether unfamiliar face matching predicts face learning efficiency (Chapter 4). Participants completed two unfamiliar face matching tasks and a novel face learning task (which tested recognition four times during learning). Individual differences in the slope of face learning were predicted by unfamiliar face matching ability. These differences appear to be driven by individual differences in recollection, not familiarity. My dissertation provides insights about individual differences in face identification. Individual differences in sensitivity in unfamiliar face identification were stable across time and tasks. They also predict face learning efficiency. My results suggest that face identification is not just a perceptual problem—it is influenced by decision making and other processes. These results have implications for face identification theories and applied settings.

Despite all the advances made in health-related and psychological sciences, advancing age continues to be accompanied by cognitive decline. Aging is usually associated with major changes in the structure and functioning of the brain that lead to impairments in multiple cognitive functions. The trajectories of age-related effects on the brain and cognition exhibit considerable differences across cognitive domains and across individuals, and investigating approaches and factors that might prevent brain and cognitive decline during aging is considered a topic of great scientific and public health relevance. The overall goal of this thesis was to evaluate age-related differences in brain structure and functional connectivity to further our understanding of the neural mechanisms involved in age-related declines in cognition. This thesis also aimed to investigate the influence of lifestyle factors on age differences in cognition, and in that regard, I focused on the effects of sleep quality and physical activity on memory. In Study 1, I assessed the impact of aging on grey matter volume of the medial temporal lobe MTL and prefrontal cortex PFC and compared the relative contributions of MTL and PFC structures to age differences in associative memory. My findings emphasize the critical role of the frontal lobes, and the control processes they subserve, in determining the detrimental effects of age on memory. Additionally, I observed that the relationship between frontal grey matter volume and memory was not moderated by age or sex, suggesting that greater volume in PFC structures relates to better memory performance across the lifespan and in both sexes. In Study 2, I assessed the effects of age on functional brain networks. Given the essential role of the arousal system (ARAS) in cortical activation and previous findings of disrupted ARAS functioning with age, I investigated the hypothesis that age-related changes in ARAS-cortical functional connectivity may contribute to commonly observed age-related differences in cortical connectivity. The findings of this study showed that the arousal system is functionally connected to widespread cortical regions and suggest that age differences in functional connectivity within the cortex may be driven by age-related changes in the brainstem and these altered connectivity patterns have important implications for cognitive health. In Study 3, I investigated the relationship between sleep quality, physical activity, and memory in middle-age and older adults, in addition to assessing the impact of the COVID-19 pandemic on participants’ mood and sleep quality. Our results showed that people who were more active reported better sleep quality and showed better memory, and better sleep quality was associated with better memory. Moreover, our findings also showed that some of the beneficial effects of physical activity on cognition are partially mediated by improved sleep. Additionally, this study indicated that the COVID-19 pandemic had a deleterious effect on people’s sleep quality and overall well-being. Taken together, these studies suggest that aging is associated with disruptive effects on brain structure and function, and that these changes are associated with age-related cognitive decline. Additionally, our study supported the association between lifestyle factors, more specifically, sleep quality and physical activity, and cognitive performance during aging.

Growing evidence supports the evolutionary perspective characterizing aggression as a strategy to achieve proximate adaptive benefits which can indirectly and probabilistically contribute to ultimate evolutionary goals (survival and reproduction). However, aggression may only be adaptive under certain conditions. Therefore, this dissertation investigated various conditions that may affect the adaptiveness of adolescent aggression, namely aggression characteristics (aggressive form, function, and anonymity), target characteristics (power of victim relative to the perpetrator), and perpetrator characteristics (experience of victimization and gender). Study 1 used a person-oriented approach to investigate how proactive and reactive cyber aggression and concurrent experiences of cyber victimization were associated with evolutionarily relevant social advantages and disadvantages in a community sample. Study 2 examined differential associations between aggression involvement and evolutionarily relevant aggressive functions, considering variations in aggressive form, the target’s power relative to perpetrator, and the perpetrator’s gender in a school-based sample. Finally, in a school-based sample, Study 3 investigated (1) how the associations between anonymous perpetration and evolutionary functions of aggression varied by aggressive form and the perpetrator’s gender, (2) how the target’s power and the perpetrator’s gender related to adolescents’ use of anonymous perpetration in each aggressive form, and (3) differential associations between anonymous victimization and victims’ perceptions of harm as a function of aggressive form and gender of the victim. Results suggest that adolescents’ aggression was linked to evolutionarily relevant aggressive functions motivated by competitive (e.g., aggression deterrence, intrasexual competition), impression management (seeking status and mates), sadistic (enjoyment), and reactive (impulsive response to real/perceived threats) functions, and to social advantages (social dominance, dating behaviour) for aggressors who used reactive aggression less frequently. However, aggression involvement was differentially associated with evolutionary motives based on the form, function, or anonymity of aggression, target characteristics, and perpetrator characteristics. Moreover, aggression was associated with costs, especially for cyber aggressor-victims who frequently aggressed reactively, and for victims of anonymous aggression. Thus, adolescents’ aggression may be conditionally adaptive for a narrow range of functions, depending on the characteristics of the aggression, target, and perpetrator. By highlighting the conditional adaptiveness of adolescent aggression, this research may inform efforts to improve interventions addressing aggression.

Future-oriented cognition encompasses a set of key abilities that children must develop for successful functioning in daily life including, saving, prospective memory, episodic foresight, planning, and delay of gratification. These future thinking abilities are supported by memory systems (e.g., semantic, episodic), as well as constructive processes, self-projection, and executive functions. Research primarily measures young children’s future-oriented abilities through behavioural tasks, which have various limitations and may not engage future thinking. The current studies introduce new methods to overcome some of these limitations: developing a parent-report questionnaire and examining children’s open-ended responses. In Study 1 (N = 101; Mazachowsky & Mahy, 2020), 3-to 7-year-old’s future thinking was examined to establish the psychometric properties of a new parent-report measure, The Children’s Future Thinking Questionnaire (CFTQ). The CFTQ detected development of children’s future thinking and is a reliable and valid measure. Study 2 (N = 48; Mazachowsky et al., 2020) examined 3-to 5-year-old children’s episodic foresight using a novel, open-ended version of the Picture-book task. Results showed that children were able to generate items for future use and were more successful with age. Children’s explanations for their generated items were typically present-focused and included both episodic and semantic details. Expanding on Study 2, Study 3 (N = 158; Mazachowsky et al., revisions requested) explored 3-to 5-year-old’s explanations for their item choices on two episodic foresight tasks to determine the degree to which these tasks engaged children’s episodic and future-oriented processes. Children provided more future-oriented explanations on the Picture-book task compared to the Spoon task, but episodicity did not differ between tasks. Further, children’s Picture-book task explanations included more first-person personal pronouns compared to the Spoon task, but explanations did not differ in other pronoun use. Together, these studies show that use of a parent-report measure and examination of children’s open-ended responses offer unique insight into the development of young children’s future thinking and engagement in future-oriented processes.

Several theories of adolescent brain development suggest that adolescence is a sensitive period of development characterized by the onset of internalizing problems, such as anxiety. Sensitivity to threat, a heightened responsiveness to aversive situations, has been suggested to be a precursor to anxiety, highlighting the importance of understanding sensitivity to threat among children and adolescents. Yet relatively little is known about the development of sensitivity to threat. Further, identifying the neural indicators that are associated with heightened sensitivity to threat would help classify which youth are most at risk for anxiety. The primary goals of my dissertation were: 1) to explore whether adolescents, compared to children, have heightened sensitive to threat, 2) assess which neural indicators are associated with heightened sensitivity to threat, and 3) assess whether individual differences (e.g., in consistency of sensitivity to threat across time and situation) help predict which youth are most at risk for anxiety-related problems. Study 1 of my dissertation examined, with concurrent data, whether adolescents have greater neural sensitivity to negative feedback compared to children. Study 2 examined whether children and adolescents differ in their longitudinal trajectories of sensitivity to threat (e.g., consistency across time). I also was interested in whether these trajectories were associated with frontal asymmetry, a neural indicator associated with avoidance motivations. Study 3 extended the findings from Study 2 to examine consistency across threatening situations. While Studies 1 through 3 investigated whether adolescence is a period of heightened sensitivity to threat, Study 4 of my dissertation used a latent class analysis to investigate whether individual differences in sensitivity to threat, impulsivity, and emotion dysregulation are associated with anxiety and/or risk taking. Results indicated that adolescence (especially when defined by pubertal status), may be a normative period for sensitivity to threat. At the same time, not all youth who are sensitive to threat go on to develop anxiety; thus, it may be that for many adolescents, sensitivity to threat is an adolescent-limited phenomenon, meaning that threat sensitivity may peak in adolescence, but then tapers off into adulthood. Importantly, neural indicators associated with threat sensitivity helped identify which youth may have the highest levels of threat sensitivity. Overall, my dissertation shows that while some level of sensitivity to threat is normative, it is less common for youth to be consistently sensitive to threats and importantly, these youth who are consistently sensitive appear to be most at risk. Taken together, the four studies of my dissertation incorporate EEG, longitudinal designs, multiple indicators of development (age and pubertal status), and self-report data to gain a holistic understanding of sensitivity to threat from childhood to adolescence.

Acts of aggression are associated with a variety of negative outcomes. Accordingly, research has aimed to identify the personality traits that give rise to different forms of aggressive behaviour. Recent work has indicated that the factor of Honesty-Humility is associated with a variety of deviant behaviours, including aggression towards others; however, the nuances of these relationships require further investigation. This dissertation aimed to address several gaps in this literature through three main studies. In Study 1, we extended previous findings to younger populations, examining the associations between Honesty-Humility and aggression longitudinally in a large sample of children and youth. These findings demonstrated a bidirectional relationship between Honesty-Humility and aggression over time, such that low levels of Honesty-Humility resulted in higher levels of aggression and vice versa. In Study 2, we explored the specific facets of Honesty-Humility to determine if they differentially predict proactive and reactive aggression. Despite the theoretical link between Modesty and reactive aggression, we found limited support for this association, especially when controlling for proactive aggression. Overall, the Sincerity and Fairness facets were found to strongly predict both forms of aggression. Lastly, Study 3 explored the associations between Honesty-Humility and deviance, aggression, exploitation, and victimization in a workplace context. Robust relationships were found between Honesty-Humility and several deviant behaviours, further emphasizing the importance of this trait. In particular, when provided with the opportunity to aggress, individuals low in Honesty-Humility were more likely to do so, regardless of their level of power in the situation. Collectively, these findings indicate that Honesty-Humility is the strongest predictor of aggressive and deviant behaviour among the broad factors of personality. However, this dissertation extends previous findings by demonstrating the applicability of Honesty-Humility across different contexts and by providing a nuanced understanding of the components responsible for this relationship.

Recognizing facial identity requires two skills: telling a person apart from similar looking people and recognizing them across changes in their appearance. Until recently, the vast majority of studies relied on tightly controlled images to examine face learning and recognition. Research using ambient images (i.e., images that capture within-person variability in appearance) is necessary to assess the true challenge of face learning and recognition in daily life. Only a few studies have examined face learning and recognition using ambient images in children, and, to the best of my knowledge, no studies have examined them in older adults. My dissertation was designed to address these gaps in the literature. In Study 1, children aged 6 to 11 were tested to examine two mechanisms that underlie face learning in young adults: Ensemble coding and the ability to benefit from exposure to variability in appearance in a perceptual matching task. My results revealed that both mechanisms are adultlike by the age of 6. First, children extracted the average of a set of images of an identity, regardless of whether those images were presented simultaneously or sequentially. Second, although their overall accuracy was lower than that of young adults, children showed comparable benefit from viewing multiple images of a to-be-learned identity in a perceptual face learning task. In Study 2, I examined whether younger children (4- and 5-year-olds) benefit from exposure to multiple images when learning a new face in a perceptual task. Although viewing multiple images made young children more sensitive to identity, it also led them to adopt a less conservative response bias, driven both by an increase in hits and an increase in false alarms. This increase in false alarms was not found for older children and adults in Study 1, suggesting that the ability to benefit from exposure to variability in appearance during face learning is not fully refined before the age of 6. In Study 3, I provided the first examination of face learning and recognition in older adults using a battery of tasks. On three of the five tasks, older adults showed comparable learning and recognition to young adults: 1) Older adults recognized a familiar face without error; 2) they showed ensemble coding of facial identity, regardless of whether the images were presented simultaneously or sequentially and 3) despite making more errors than young adults overall, they showed comparable benefit from viewing multiple images of a newly encountered face in the perceptual learning task. In the remaining two tasks, older adults showed a different pattern than young adults: 1) Older adults made fewer hits and more false alarms than young adults when matching images of wholly unfamiliar faces; and 2) after being exposed to low variability in appearance in a face memory task, older adults became more conservative than did younger adults, despite showing comparable benefits in sensitivity. My results reveal that the same abilities that show prolonged development during childhood are those undergo changes in aging. Collectively, my dissertation provides novel insights about learning and recognizing facial identity during childhood and aging and has important implications for understanding models of face processing.

Insufficient sleep has been associated with deficits in emotion processing; sleepy individuals show increased emotional reactivity and decreased emotion regulation. Individual differences that predict performance after sleep loss has remained largely elusive. Concentrations of cortisol, progesterone, and testosterone are candidate predictors for variability in performance following sleep loss. These hormones are associated with emotion functioning under well-rested conditions and show interactions with sleep and circadian rhythms. The central aim of this dissertation was to investigate the interaction of natural sleep and hormones on measures of emotion functioning. Study 1 examined the role of cortisol in the relationship between sleep (across the first three years of university), and self reported emotion functioning in undergraduate students. Poor sleep was associated with worse emotion regulation and reactivity, and greater concentrations of cortisol and cortisol/DHEA-S. Consistently poor sleepers over three years, who had high cortisol, experienced the greatest difficulties with emotion regulation. Study 2 investigated the association between sleep satisfaction and objective measures of sleep on self-reported emotional functioning in a group of children and adolescents. Importantly, in girls who were dissatisfied sleepers, being further though puberty was associated with the greatest difficulties with emotion regulation. Study 3 examined natural sleep, hormones, and menstrual phase on processing emotional stimuli. Participants completed sleep diaries and wore actigraphy watches for 3-weeks and completed measures of emotion perception on two occasions in the laboratory, in different menstrual phases for women. The study supported dynamic relationships between hormone concentrations and various measures of sleep duration and quality on the processing of emotion stimuli. Many relationships emerged for threatening emotions, indicating that high concentrations of testosterone, progesterone or cortisol, combined with poor sleep resulted in increased sensitivity towards threat detection. Together these studies provide evidence that hormones are an important factor in understanding the link between poor sleep and emotion functioning. Hormone concentration plays a role in understanding individual differences in response to sleep loss and can compound with sleep loss to result in worse emotional outcomes. Consideration of hormonal factors may help identify certain at-risk populations for sleep related deficits or timing of interventions.

Psychiatric symptoms following traumatic brain injury (TBI) pose a significant barrier to neurorehabilitation and impact survivor’s life satisfaction following injury. Depressive and somatization symptoms are common clinical presentations postinjury; however, due to the paucity of etiological models to explain these symptoms, treatment approaches are predominately “borrowed” from non-neurally compromised populations with similar clinical presentations. The orbitofrontal cortex (OFC) is particularly vulnerable in TBI, and serves to modulate autonomic arousal states. Varying severities of TBI have been linked to autonomic underarousal as measured by electrodermal activation (EDA). In a series of studies examining persons with mild head injury (MHI), the phenomenological presentation of depressive and somatization symptoms was examined in persons with and without MHI, and the relationship between these symptoms and autonomic underarousal was explored. In study one, MHI were found to be autonomically underaroused, reporting more somatic depressive symptoms relative to their no-MHI cohort, and the relationship between their injury severity and the intensity of their somatic depressive complaints was completely mediated by underarousal. Investigating somatization revealed MHI status as a moderator of the relationship between somatization and post-concussive symptoms, with MHI having a stronger positive association. Autonomic underarousal was found to be a complete mediator between the relationship between injury severity and their somatization symptoms. In study two, we experimentally manipulated autonomic arousal through brief cardiovascular exercise and evaluated whether this concomitantly improved somatic-based psychiatric complaints and neurocognitive functioning in persons with MHI. Study two replicated the somatic depressive mediation model of study one, and revealed that the experimental manipulation was effective in increasing autonomic arousal, and improving somatic-psychiatric complaints and neurocognitive status. Collectively, these findings suggest that depressive and somatization symptoms postinjury are phenomenologically and etiologically different in persons with a history of head injury relative to their non-neurally compromised counterpart, and autonomic underarousal and OFC dysfunction is a strong candidate for continued investigation as an etiological model for psychiatric symptoms postinjury. Reversal of underarousal may serve as an important therapeutic goal. Lastly, we propose the term “somatic underarousal” to describe this symptomatology as a means to avoid confusion with the historical roots of the term somatization.