Browsing by Author "Samanez-Larkin, Gregory R"

Everyday, animals make decisions that require balancing tradeoffs like time delays, uncertainty, and physical effort demands with the prospect of rewards like food or money. The tendency to devalue rewards according to these tradeoffs is also known as discounting and depends on how much subjective value an animal places on a reward. These discounting decisions are supported by different neural systems. The influence of dopamine signaling is well-characterized as a modulator of motivation and decision making. However, the role of dopamine as a marker of interindividual differences of reward sensitivity and valuation is less clearly understood. Using a combination of neuroimaging techniques (functional magnetic resonance imaging and positron emission tomography), behavioral experiments, and meta-analyses, this dissertation identifies how trait-like variation in dopamine function explains the way people differ in their preferences and neural computations of value. Overall, the findings indicate that while dopamine may exert acute influence over reward discounting behavior, these associations may not extend to trait-like differences. Specifically, individual differences in dopamine receptor availability are related to discounting behavior in clinical populations but not healthy adults. Nevertheless, individual differences in dopamine are related to functional brain activation associated with the subjective valuation of rewards—the input to choice behavior. These results highlight that interindividual variation in dopamine is more directly linked to neural computations than observed behaviors and that dopamine-mediated psychopathology does not precisely map on to acute pharmacodynamics.

Humans make a variety of choices every day. Some of these choices are pretty mundane like whether to eat pancakes or oatmeal for breakfast. Others cost a little more, have a little bit of a longer impact, like which vacuum cleaner to buy on Amazon. And finally, there are choices that we don’t make very often—maybe even just once, that have enormous consequences in our lives like whether to choose Duke for graduate school. Deciding to choose one option over a set of alternatives involves imagining the future value that could be obtained by making those choices. Research on value-based decision making has recently begun to assess the impact of memory-related processes in making prospective decisions. Given that remembering the past and imagining the future rely on the same cognitive and neural mechanisms, researchers have investigated how imagining the future and remembering the past shift choice behavior. However, much of this research has focused on relatively abstract choices made in a laboratory setting rather than potentially more impactful long-term decisions that we make in everyday life. Overall, it is unclear to what extent memory-related systems impact a range of choices that humans make in everyday life from minor financial transactions to consequential life choices. Across three studies, I examine the role of the constructive memory process of imagination in decisions between shorter-term monetary rewards available at different temporal delays as well as longer-term consequential life choices like career decisions. Chapter 1 provides a general overview of past research on the role of constructive memory processes in making decisions. In chapter 2 (Study 1), after rehearsal of hypothetical imagined future events, younger adults and older adults made choices between larger-later and smaller-sooner monetary rewards. Some of the trials included a cue that invoked the imagined future event whereas other trials did not include a cue. Younger adults were more likely to choose larger, delayed monetary rewards on trials where the imagined future event was cued compared to trials without a cue. However, older adults did not show an effect of cued imagination. Across age groups, functional neuroimaging data revealed that trials with an imagination cue elicited greater engagement of regions that are part of the default mode network including the posterior cingulate cortex, angular gyrus, and medial prefrontal cortex. This network is commonly engaged during thinking about past memories as well as imagining the future in many studies that did not focus on decision making. Interestingly, this difference in neural activity did not vary across age groups even though the behavioral effect of the cue was limited to younger adults. In Chapter 3, I explore the effects of imagining previous successes and failures on choices between larger-later and smaller-sooner monetary rewards (Studies 2a & 2b). I find no conclusive evidence of differences in decisions based on whether people imagined successes or failures, even when comparing to a non-imagined, emotionally neutral control condition. Finally, in chapter 4, I extend this work into more complex career decision making. In a pilot study (Study 3), greater enjoyment of an imagined future career was associated with increased preference for that career option. Given the small and variable effects of imagining the future on decision making in Studies 1-3, two additional studies (Study 4a & 4b) evaluated the effects on decision making of an individual’s ability to vividly visualize, a different cognitive measure potentially relevant to thinking about and imagining the future. Using multivariate analyses, we found that vividness of visual imagery along with a set of individual difference measures related to future time perspective, self-efficacy, and well-being were associated with a set of variables crucial to career decision making. Together, these studies qualify our understanding of the role of imagination and visual imagery in decision making from choices between small rewards in the laboratory and consequential life choices. Overall various forms of imagination had relatively small and inconsistent effects on both laboratory-based and real-world decisions, whereas visual imagery had a moderate and consistent shared effect on real world decisions. The findings have broad implications for guiding prospective decisions in humans across the life span. For example, educational institutions currently have little to no focus on imagination and imagery in guiding developing students toward their future lives. There are critical opportunities in higher education to integrate imagination and imagery into living and learning communities to support students in their transitions to independent and rewarding careers.

Psychological research on aging typically characterizes it as a period of decline. Numerous studies have reported age-related deficits in episodic memory, sensory perception, and fluid intelligence. These reports only add to society’s negative views of aging, which inevitably have a detrimental impact on older adults’ cognition, health, and general well-being. However, there are several other domains of cognition that remain stable or improve during healthy aging. For example, emotional functioning increases with age: older adults can better regulate their emotions and resist their desires compared to younger adults. Older adults are also more skilled at solving interpersonal problems and display intact implicit and procedural memory. This dissertation highlights two other areas that show improvement with age (i.e., decision making and knowledge) and considers how we can use these positive aspects to offset the negative aspects of aging. Chapter 2 investigates heuristic decision making. While some work suggests that older adults are more reliant on these shortcuts, there is little evidence to support this claim. To clarify this issue, participants from across the adult lifespan solved decision scenarios that tapped each of the following classic heuristics: anchoring, availability, recognition, representativeness, and sunk cost fallacy. Chapter 3 further explores knowledge. While the literature confirms that knowledge increases across the lifespan, it is unclear 1) if people are generally aware of this increase and 2) whether they hold expectations about the scope of younger vs. older adults' knowledge. To address these questions, younger and older participants predicted the knowledge of hypothetical younger and older adults. Chapter 4 focuses on application. While many studies have demonstrated that negative aging stereotypes negatively impact older adults’ memory performance, research on positive aging stereotypes’ influence is still inconclusive. In order to address this gap, older participants demonstrated their memory performance before and after viewing a neutral intervention or positive stereotype intervention about their knowledge advantage. Altogether, I find that older adults continue to use cognitively efficient decision strategies; they are not more reliant on classic heuristics and use them to the same degree as younger adults. Furthermore, I demonstrate that adults of all ages recognize that older individuals have a knowledge advantage over younger individuals, regardless of the difficulty of the information. Critically, if older adults are reminded of this advantage, they remember more words during a memory test. Taken together, this body of work sheds light on the cognitive improvements that accompany healthy aging and considers ways to leverage these positive aspects, with the goal of offsetting age-related deficits and promoting positive self-perceptions of aging.

Emotions infuse each individual’s life with meaning, informing their memories and guiding their future decisions. Previous research has emphasized three important channels of emotion: subjective experience, psychophysiology and neural activity. In addition, research has found that individuals manage their emotions across channels in a diversity of ways. However, most of this research narrowly focuses on a single channel of emotion and misses key aspects of these individual differences. Across 4 studies, this dissertation highlights the immense variability in emotional experiences by integrating channels of emotion. The first empirical chapter (Chapter 2) focuses on subjective channels of emotion and reveals a fundamental aspect of emotion previously unknown—that positive events are actually less complex than negative events, and that individuals evaluate positive events more similarly than negative events. The next chapter (Chapter 3) uses a novel computational approach to identify a whole-brain biomarker of the tendency to suppress negative emotion. The following chapter (Chapter 4) focuses on psychophysiological channels of emotion and investigates the effect of anxiety on how individuals manage their emotions naturally versus when following instructions in the laboratory. Participants report managing their emotions in ways that did not did not reflect how they regulated in the lab—highlighting the importance of conducting research outside the laboratory. Based on this, the final empirical chapter (Chapter 5) uses experience sampling to leave the confines of the laboratory and study people in the wild. Participant responses show that multiple components of emotional health improve with age, including emotional stability, affect, and the ability to resist desire—a finding missing from laboratory-based research. No two individuals are alike in how they experience and manage their emotions. This research emphasizes the vast variability in how individuals experience and manage emotion depending on their goals and the larger context. This holistic framework enhances our understanding of the full spectrum of emotional functioning and brings the field closer to a personalized account of emotion.

Physical activity has many benefits including promoting healthy aging, reducing risk of chronic disease, and supporting general well-being. Despite this, many adults do not get significant amounts of daily physical activity. The effects of interventions promoting physical activity are highly variable and typically modest. Even when behavioral interventions are effective, the understanding of how and why they work is lacking. Understanding the determinants of physical activity behavior change, along with identifying evidence-based behavior change techniques that target these determinants, is critical for developing effective interventions. In this dissertation, across two studies, I examine the role of neural and behavioral determinants of physical activity behavior change. Chapter 1 provides a review of the two prominent theoretical approaches to physical activity behavior change, social cognitive theory and dual-process theory, and highlights how neuroimaging techniques can be utilized to help inform gaps in both theoretical and applied knowledge of physical activity. Chapter 2 (Study 1) evaluates if there are brain regions correlated with physical activity behavior change. In the study, participants wore a pedometer for a week before and after an fMRI session where they read and heard statements about walking. Behavioral analysis demonstrated that participants walked significantly more following exposure to the walking-related messages. Whole-brain analysis examined regions positively associated with walking behavior change and produced two significant clusters in the frontal pole region and the precuneus/posterior cingulate gyrus region. The frontopolar cortex is implicated in pre-commitment, a self-control strategy where people anticipate self-control failures and prospectively restrict their access to tempting alternatives. The precuneus/posterior cingulate cortex region has been found to play a role in self-relevant processing. Both self-control and self-relevant processing are believed to be important for behavior change. Chapter 3 (Study 2) focuses on neural and self-report responses to different types of health messages and their ability to predict physical activity behavior change. In the study, participants completed an fMRI task where they read positively or negatively framed walking-related messages with either social or non-social based content and rated how personally motivating they were as well as other self-reported ratings. Neural activity in regions involved in positive valuation and self-referential processing were measured to evaluate whether sensitivity in these regions to individual messages could predict the effectiveness of those messages when delivered in an intervention weeks or months later. For the next 80 days, participants completed a SMS-based mHealth intervention where they received one of the same walking-related messages from the scanner task daily. We assessed physical activity using a wearable fitness tracker throughout the 80 days and a baseline period. Individual participant ratings on how relevant the message would be to others predicted the effectiveness of the messages. People were more physically active on days when they received messages that were rated as more relevant to others. Brain activation in the regions of interest selected were not associated with message effectiveness during the intervention.

Learning from error is an adaptive process that allows us to correct mistakes, update knowledge, and make better choices. Yet, humans do not always learn from error— motivation, emotion, prior beliefs, and individual differences can all influence learning and memory. In this dissertation, I synthesize diverse evidence from across domains to argue that lingering cognitive and neural states create a context of learning that governs how and what we learn. Here, I report three novel pre-learning interventions that effectively modulate learning from error in humans. First, I show that an imagination exercise enhances subsequent learning from feedback about health risks. Second, I demonstrate that changing beliefs about the value of errors enhances subsequent knowledge updating, especially for individuals with high anxiety. Third, I report that induced motivational states impact both reinforcement learning and subsequent memory. Taken together, these studies demonstrate that pre-learning interventions can have lingering benefits, enhancing subsequent learning from error. These findings offer inspiration for real-world interventions that could improve education, enhance belief updating, drive behavior change, motivate action, or foster curiosity.