Impulsive behavior can be viewed as selecting the less beneficial option when multiple choices are presented. This type of sub-optimal decision-making behavior has been demonstrated to be a basic behavior process that is not unique to humans. In recent years, a large body of research has surfaced analyzing the sub-optimal decision-making of animals, generating models that are analogous to impulsive human behavior. This literature attempts to investigate the factors that influence the choice-making of organisms and lead organisms to choose less reinforcement over more reinforcement in some circumstances. Research has shown that reinforcement contingencies alone do not account for all of the behavior produced, especially when organisms fail to optimize their receipt of reinforcement when given a choice. The current study sought to replicate the recent animal research on sub-optimal behavior with humans. Specifically, the current study investigated the choice-making behavior of three young boys with autism using a concurrent-chains schedule of reinforcement. Results replicated previous research with the finding that two of the three participants indicated an increasing preference for the least optimal choice while a third participant maximized his reinforcement throughout the study. Implications for future research are discussed.

Doctor of Philosophy / Psychological Sciences / Kimberly Kirkpatrick / Risky decisions are inherently characterized by the potential to receive gains and losses from these choices, and gains and losses have distinct effects on global risky choice behavior and the likelihoods of making risky choices depending on the outcome of the previous choice. One translationally-relevant phenomenon of risky choice is loss-chasing, in which individuals make risky choices following losses. However, the mechanisms of loss-chasing are poorly understood. The goal of two experiments was to illuminate the mechanisms governing individual differences in loss-chasing and risky choice behaviors. In two experiments, rats chose between a certain outcome that always delivered reward and a risky outcome that probabilistically delivered reward. In Experiment 1, loss processing and loss-chasing behavior were assessed in the context of losses-disguised-as-wins (LDWs), or loss outcomes presented along with gain-related stimuli. The rats presented with LDWs were riskier and less sensitive to differential losses. In Experiment 2, these behaviors were assessed relative to the number of risky losses that could be experienced. Here, the addition of reward omission or a small non-zero loss to the possible risky outcomes elicited substantial individual differences in risky choice, with some rats increasing, decreasing, or maintaining their previous risky choice preferences. Several reinforcement learning (RL) models were fit to individual rats’ data to elucidate the possible psychological mechanisms that best accounted for individual differences in risky choice and loss-chasing behaviors. The RL analyses indicated that the critical predictors of risky choice and loss-chasing behavior were the different rates that individuals updated value estimates with newly experienced gains and losses. Thus, learning deficits may predict individual differences in maladaptive risky decision making. Accordingly, targeted interventions to alleviate learning deficits may ultimately increase the likelihood of making more optimal and informed choices.

Doctor of Philosophy / Department of Psychological Sciences / Gary L. Brase / Risky decision making occurs in both humans and non-human animals. For a large portion of the history of scientific investigation into human judgment and decision making, risky behavior has been viewed as flawed and irrational. However, the past several decades have seen advances in the view of human rationality. Scientists have suggested that, rather than using probability theory as the metric by which humans are judged as rational or irrational, human minds should be evaluated with respect to specific ecologies (e.g., Gigerenzer & Selten, 2001) with some scientists going further and specifying the ecologies as those which our ancestors evolved; essentially, our minds and their decision processes are adapted to solve specific recurring problems, and to solve those problems in specific environments. Within the domain of risky decision making there are a number of theories and models which are consistent with the hypothesis that human (and non-human) minds are molded for specific behavioral patterns based on environmental cues. One example is the priority heuristic. The priority heuristic is based in the ecological rationality approach—that heuristics are designed for specific ecologies. However, the ecological rationality of the priority heuristic is underspecified. Studies One and Two of the present dissertation compared predictions made by two models of risk-taking from evolutionary biology and behavioral ecology (dominance theory and risk-sensitive foraging) with a variety of predictions made by the priority heuristic. Data clearly showed that risk-sensitive foraging outperforms the priority heuristic (Study One) and that the priority heuristic cannot account for the motivation to acquire a minimum number of resources. Study Two showed mixed results for the priority heuristic when compared to dominance theory. Specifically, choice patterns were consistent with the priority heuristic, but process data in the form of decision times were not consistent with the priority heuristic. Also, the data pointed to a strong effect for desiring higher status when competing against others of varying status. Study Three compared four potential models of risky decision making in an attempt to extend the pattern of results from Studies One and Two showing general risk-sensitivity when attempting to achieve a specified need level (Money for Study One; Status for Study Two). Also, Study Three attempted to clarify the scope of the pattern of general risk-sensitivity by examining differential patterns of results based on whether the models predicted motivations to achieve need levels for money, status, or both. Results from Study Three were consistent with a general model of risk-sensitivity which operated on both monetary need levels and status need levels. This effect was additionally ubiquitous for males and females, contrary to predictions by dominance theory. The data from three studies showed support for a general model of risk-sensitivity consistent with those proposed by others (Mishra, 2010). The concept and implications of this general risk-sensitivity model are discussed, as well as future directions to understand the finer details and potential scope of this particular general risk-sensitivity model.

Individuals experience risk ubiquitously, but measuring risk taking is difficult. The balloon analogue risk task (BART) was developed in order to assess risk taking through having subjects press a key that accrues reward but also risk losing all reward with each press. In humans, greater responding in this task is associated with other maladaptive risk taking behaviors. The present research modeled this relationship in pigeons due to their previously shown propensity towards risk taking behavior. Experiment 1 used an unsignaled balloon task in which losing could only occur after 5 pecks. Results showed below optimal performance with greater pecks associated with faster acquisition of risk taking in the suboptimal choice task and evidence of modulation by delay discounting measures. Experiment 2 signaled the number of pecks with colors and tested multiple hoppers as a reinforcement modality to increase performance. Results showed only signaling the number of pecks improved performance and was related to performance in the high risk BART task. Both the low and high risk variants were associated with slower suboptimal choice acquisition and again had evidence of modulation by delay discounting measures. Potential shared underlying mechanisms are discussed.

Master of Science / Department of Psychological Sciences / Kimberly Kirkpatrick / The present experiments examined the effect of different uncertain-reward magnitudes (i.e., gains and losses) on global and local probabilistic choice behavior in rats. In two experiments, rats were given a choice between a variable-amount certain outcome that delivered 2 or 4 pellets and a variable-amount uncertain outcome that probabilistically delivered a larger reward. In Experiment 1, the larger uncertain outcome was always 11 pellets and different groups received 1, 2, or 4 pellets for the uncertain small reward. In Experiment 2, the uncertain small reward was always 4 pellets and different groups received 6, 9, or 11 pellets for the uncertain large reward. In both experiments, the rats increased their uncertain choice behavior with the probability of uncertain food. In Experiment 1, the magnitude of the uncertain small outcome affected choice behavior; there was no such effect of the uncertain large reward magnitude in Experiment 2. The group differences in choice behavior suggest that the expected value of the certain choice served as a reference point distinguishing uncertain gains and losses, and that the rats exhibited differential sensitivities to such outcomes. As some extant theoretical frameworks of choice behavior seem unable to account for all of the present data, a possible mechanism for the present results is proposed. These results emphasize the importance of identifying the choice outcomes that constitute gains and losses in animals such that the effects of prior uncertain gains and losses on subsequent choice behavior can be adequately and comprehensively understood.

Adolescence is a unique developmental period where substantial brain development and social independence can result in higher risk-taking behavior. Researchers have spent the last several decades trying to understand at a neurological level why adolescents are more likely to take risks that often have extreme consequences (e.g., car accidents, drug use, etc.). The resulting research has found mixed and often inconsistent findings and scientists have posited that this could be due to differences in experimental tasks; where some are more description-based (e.g., Wheel of Fortune tasks) and others are more experience-based (e.g., Stop Signal tasks). Research examining the way adults learn about risk reveals that individuals make different decisions when information is learned via description or experience – a phenomenon known as the Description-Experience Gap. The present work aims to bridge research in adolescent development and judgement and decision-making to identify the neural processes associated with the Description-Experience gap in adolescents and adults. Across two studies, I examined the neural mechanisms associated with learning via description and experience in adolescents and adults and their subsequent impact on risky choice to find that adolescents and adults utilize information from description and experience differently. In adults, similar neural mechanisms involved with memory and deliberation are implicated at different points of the decision process. Adolescents displayed distinct neural activation associated with risk-taking and reward sensitivity when learning via experience. Both studies demonstrate the significance of memory and learning-relevant processes in risk-taking across development. / Psychology

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Under de senaste 20 åren har värdet på de svenska privata hushållens bostadslån ökat med i genomsnitt 8,1 % per år. Som en konsekvens av att bostadspriserna ökat i högre takt än inflationen har hushållen tvingats belåna sig i en högre grad, vilket bidragit till att både skuldkvoten och belåningsgraden ökat. Hushållen har på grund av detta blivit mer exponerade för risker i form av ränteförändringar eller i form av bostadsbubblor. Ett bostadslån är för majoriteten av den svenska befolkningen den största och mest riskfyllda investering som görs under dess livstid och kan ge bekymmersamma konsekvenser vid fel beslut. Vid ett bolån står låntagaren inför ett val mellan rörlig och bunden ränta, där den bundna räntan ses som det säkra valet. Bolånetagare kan också välja att dela upp ränta med en del rörlig och en del bunden ränta vilket då kan tolkas som ett säkrare val än rörlig ränta men mer osäkert än bunden ränta. Tidigare forskning konstaterar dock att många bolånetagare har svårt att förstå risken och följden av valen mellan olika räntebindningstider och på grund av komplexiteten med räntor inte fatta rationella beslut. Syftet med studien är att undersöka hur vissa utvalda faktorer påverkar valet mellan bunden och rörlig räntebindningstid och koppla detta till ekonomiska teorier. Studien använder sig av en multinomial logistisk regression och faktorerna som analyseras är: ålder, låneobjektet, belåningsgraden, skuldkvoten, inkomsten, antalet låntagare i hushållet, räntedifferensen (mellan rörlig och bunden 2 år) och förändringar under pandemin covid-19 under perioden 2016 - 2021.  Resultatet av studien är av intresse för både svenska beslutsfattare och banker, då resultatet visar vad som driver bolånetagare riskexponering. Vidare konstaterar studien att bolånetagarna har en minskad riskaversion med en ökad förmögenhet, samt att bolånetagare med högst skuldkvot och belåningsgrad är de hushåll som väljer rörlig ränta i högst utsträckning. Där med konstaterar studien att de svenska bolånetagare som är mest exponerade för risk också är de bolånetagare som i lägst utsträckning binder sin ränta och är där med mest risksökande i deras val av ränta. / Over the past 20 years, the value of Swedish private households' housing loans has increased by an average of 8.1% per year. Because of house prices rising at a higher rate than inflation, households have been forced to borrow to a greater extent, which has contributed to an increase in both the debt-to-income ratio and the loan-to-value ratio. As a result, households have become more exposed to risks, as interest rate changes or housing bubbles. For most of the Swedish population, a housing loan is the largest and most risky investment made during its lifetime and can have worrying consequences in the event of a wrong decision. In the case of a mortgage, the borrower is faced with a choice between variable and fixed interest rates, where the fixed loan is seen as the safe choice. Mortgage borrowers can also choose to divide interest with some variable and some fixed interest, which can then be interpreted as a safer choice than variable interest but more uncertain than fixed interest. Previous research finds, however, that many mortgage borrowers find it difficult to understand the risk and consequences of the choices between different fixed interest periods and, due to the complexity of interest rates, do not make rational decisions.  The purpose of the study is to investigate what influences the choice between fixed and variable interest rate periods and link this to economic theories. The study uses a multinomial logistical regression, and the factors analyzed are age, loan object, loan-to-value ratio, debt ratio, income, number of borrowers in the household, the interest rate differential (between variable and fixed rate 2 years), and changes during the covid-19 pandemic during the period 2016 - 2021.  The results of the study are of interest to both Swedish decision-makers and mortgage banks, as the results show what drives mortgage borrowers' risk exposure. Furthermore, the study states that mortgage borrowers have decreased risk aversion with increased wealth and that mortgage borrowers with the highest debt ratio and loan-to-value ratio are the households that choose variable interest rates to the greatest extent. Thus, the study states that the Swedish mortgage borrowers who are most exposed to risk are also the mortgage borrowers who to the least extent tie their interest rate, consequently, mortgage borrowers with the highest loan-to-value ratio are also the most risk-seeking group in their choice of interest rate.

「風險決策」行為非常普遍的存在於吾人之日常生活中，而選項所帶來的風險和獎勵是吾人進行決策時的重要考量因素。風險選擇的適當與否，對於個體的生存扮演著相當重要的角色。在以往的文獻中，對於決策的行為歷程已有所關注及探討，但對於風險選擇行為的神經生理機制迄今未明。本研究藉由大白鼠於T字迷津中，選擇確定之低酬賞或高不確定性之高酬賞的行為表現，進行風險選擇行為的探討。本研究中以兩項主要實驗，探討風險選擇行為之神經行為機制。實驗1a中，確定之低酬賞端固定呈現1顆食物粒，而高不確定性之高酬賞端則同時操弄酬賞物機率(50%、25%及12.5%)以及酬賞物的量(2、4及8顆)，以系統性地檢驗期望值(0.5、1和2)於此風險選擇行為中扮演的角色。行為結果顯示當風險較低時，大白鼠會選擇高不確定性之高酬賞端；而風險較高時，則轉為選擇確定之低酬賞端。實驗1b中，系統性地施打不同劑量之安非他命，探討多巴胺系統在此風險選擇行為中之機制。實驗結果顯示施打安非他命後，大白鼠表現出相對地追求風險之行為，亦即選擇高不確定之高酬賞端之比例顯著高於控制組。實驗2中，藉由毀除大腦特定部位(依核、背外側之紋狀體、眶前額皮質、內側之前額皮質)，檢驗風險選擇行為之神經基礎。毀除後之結果顯示，僅有依核受到毀除之大白鼠表現出相對地趨避風險之選擇行為。綜合以上結果，本研究建立之風險選擇行為與多巴胺有關，而依核在此行為歷程中扮演重要的調節角色。 / Many decisions people make every day involve uncertainty where both risks and rewards associated with each option need to be considered. Behavioral performance associated to risk-based choice appears wildly over the lifespan, and the fitness of risky choice behavior plays an important role in individual survival. Despite a growing body of research has focused to investigate the neurobiology of decision making, little is known about the neurobehavioral mechanisms of risky choice behavior. Based on a pilot work, this study used a T-maze to study decision under a probability-based risk in the rat. The subject was assessed on making choice to obtain either a large reward associated with risk of non-reward “empty” or a small reward ensured for every entry. Two experiments were conducted in this project to investigate neurobehavioral mechanisms of probabilistic risky choice behavior. In Experiment 1a, probabilistic risky choice behavior was systemically assessed under three expected values (0.5, 1.0, and 2.0) by manipulating the probabilities of reward presence (50%, 25%, and 12.5%) and the reward magnitude (2, 4, or 8 pellets) in the probabilistic high reward (PHR) arm. Behavioral data showed that the subject chose the probabilistic high reward in a lower risk condition but would shift to the choice of certain low reward (CLR) as the risk is increased. In Experiment 1b, the dose effects of amphetamine on this probabilistic risky choice task was tested to verify whether the dopaminergic mechanism was involved. Amphetamine, presumably activating brain dopamine systems, produced a relatively risk-seeking effect on the present behavioral task. In Experiment 2, the excitoneurotoxic lesion was conducted in the nucleus accumbens, the dorsolateral striatum, the orbitofrontal cortex, and the medial prefrontal cortex to examine the neural substrates for this probabilistic risky choice behavior. The results showed that the lesion of the nucleus accumbens significantly produced a relatively risk-averse effect on the present behavioral task, as compared to the lesions made on the other three brain areas. In conclusion, the probabilistic risky choice behavior established in the present study is dopamine dependent. And, the nucleus accumbens plays a major role of mediating this behavioral processing.

The purpose of this research is to determine if loss aversion is replicable as an overt behavioral response to potential gains and losses in complex, recurring, uncertain, and risky choice with real gains and losses of money and food. Cognitive methods used to determine the effect of loss have primarily measured verbal response to hypothetical choice scenarios in which participants cognitively predict their behavior in a series of bets or situations involving imagined monetary gains and losses. Less has been done using behavioral methods that measure overt behavioral response to gains and losses of actual commodities. The present study uses the experimental analysis of behavior to measure the asymmetrical effect of loss in multiple choice domains. A series of four experiments investigated four factors likely to affect the expression and degree of loss aversion: (a) learning and experience with consequences of choice; (b) real gains and losses instead of hypothetical quantities or imagined commodities; (c) gains and losses of a non-quantitative, primary reinforcer (food); and (d) the menstrual cycle. Participants played one of two computer games in which they earned or lost coins or food tokens exchanged for real food. Participants (N = 27, 15 women) played several 18-minute sessions in gains-only conditions and 16 sessions in 36-minute gains+punishment conditions. Recurring, complex, uncertain, and risky choice was simulated in the games by using 6-ply interdependent concurrent variable interval schedules of reinforcement (gains) and punishment (losses). Choice behavior with real gains and losses of money and food was modeled using the generalized matching law, allowing for the quantification of the effects of potential loss, relative to gains, as a change in bias and sensitivity. Loss aversion was operationalized as gain-loss asymmetry ratios derived from bias estimates produced in unpunished and punished choice conditions. Gain-loss asymmetry was replicated in both women and men in complex, recurring, uncertain, and risky choice with potential gains and losses of real money and food. Average gain-loss asymmetry ratios were 3 to 6 times greater in choice with money and 4 to 16 times greater in choice with food than those reported in the cognitive and behavioral literature. Although individual differences in response to loss were striking, the asymmetrically larger behavioral effects of loss, relative to gains, were nearly ubiquitous. Marked disruption in sensitivity to reinforcement was observed in punished choice for most participants, but for 33% of participants in choice with money and 42% in choice with food, sensitivity to reinforcers increased. No evidence was found for behavioral choice varying with the menstrual cycle.