Cumulative lifetime stressor exposure assessed by the STRAIN predicts economic ambiguity aversion

Human decision-making frequently involves uncertainty. Economists distinguish between risk (known probabilities) and ambiguity (unknown probabilities). While research has explored individual differences in risk preferences, understanding ambiguity aversion remains limited. This study hypothesizes that cumulative lifetime stressor exposure influences ambiguity aversion. The pervasiveness of ambiguity in daily life decisions highlights the importance of understanding its influence on choices with uncertain outcomes. Prior research has established a link between stressor exposure and negative appraisals of ambiguous stimuli, and this study builds upon this by examining the potential for long-term effects of cumulative stressor exposure on ambiguity preferences. Age-related risk aversion has been linked to changes in brain structure, but age doesn't seem to affect ambiguity preferences, suggesting that these two aspects of decision-making are distinct. This study utilizes a novel approach by employing a comprehensive lifetime stressor exposure inventory, the STRAIN, along with a standard economic decision-making task to independently assess risk and ambiguity preferences, aiming to clarify the relationship between cumulative stressor exposure and ambiguity aversion.

Existing research demonstrates that individuals vary significantly in their tolerance for risk and ambiguity, and these preferences are only weakly correlated. While factors influencing risk preferences are relatively well-understood, less is known about psychosocial factors contributing to ambiguity aversion. Studies have shown a link between stress, anxiety, and negative appraisals of ambiguous stimuli. Prior research has explored the impact of proximal effects of stress and anxiety on ambiguity appraisals. However, the literature also suggests that long-term effects of early life stress on cognitive responses to uncertainty are significant. These suggest that cumulative stress exposure may shape how people evaluate ambiguous outcomes, potentially leading to overly pessimistic appraisals and avoidance of uncertain situations. The difficulty in comprehensively assessing lifetime stressors has hindered research in this area. This study addresses this gap by using the STRAIN, a comprehensive interview-based system to quantify lifetime stressor exposure, coupled with an economic decision-making paradigm to disentangle risk and ambiguity preferences.

Two studies were conducted. Study 1 involved 58 healthy young adults (Mage = 25.7), while Study 2 replicated the study with a larger independent sample (n = 188, Mage = 39.81) recruited from Amazon Mechanical Turk. Participants completed a decision-making task involving choices between a certain gain ($5) and a lottery (risky or ambiguous). Risky lotteries had known probabilities (0.25, 0.50, 0.75), while ambiguous lotteries had partially unknown probabilities. Ambiguity was manipulated by occluding a proportion of winning probabilities. The STRAIN, a detailed interview assessing 55 different stressors across 12 life domains, quantified cumulative lifetime stressor exposure. Two primary STRAIN indices were used: total lifetime stressor count and total lifetime stressor severity. Study 2 included additional controls: socioeconomic status, IQ (Raven's Progressive Matrices), and mental health status (Kessler 6-Item Psychological Distress Inventory). Risk and ambiguity attitudes were quantified by calculating the proportion of lottery choices over the certain option, with risk-correction applied to ambiguous choices to account for the influence of risk attitudes. Statistical analyses including Spearman's correlations and multiple linear regression were used to examine the relationships between stressor exposure and risk/ambiguity preferences. In Study 2, multiple linear regression analyses further controlled for IQ, household income, and psychological distress.

Study 1 revealed a significant negative association between total lifetime stressor count and severity and the proportion of ambiguous lottery choices, indicating greater ambiguity aversion with increased stress exposure. This association wasn't observed for risky choices. Multiple regression analyses controlling for age and gender confirmed that lifetime stressor count and severity remained significant predictors of ambiguous choices but not risky ones. Early life stressors were particularly associated with ambiguous choice behavior. Study 2 replicated these findings in a larger sample, while controlling for IQ, socioeconomic status, and mental health status. Multiple linear regressions revealed that lifetime stressor count and severity were significant predictors of ambiguous choice behavior, but not risky choices. Again, early life stressors, particularly those involving interpersonal loss, showed the strongest association with ambiguity aversion. In both studies, the type and timing of stressors played a role in predicting ambiguity aversion, but not risk tolerance.

The findings provide the first direct evidence of a link between lifetime stressor exposure and ambiguity aversion. The consistent results across two independent studies, controlling for various confounding factors, strongly support this association. The significant effect of early life stress suggests that experiences during developmentally sensitive periods may shape the way individuals appraise uncertainty. The preference for known risk over unknown risk is well-established, but the mechanisms underlying ambiguity aversion are less understood. The current research proposes that past experiences with stress, especially during early life development, may bias individuals towards expecting negative outcomes in situations of ambiguity. This might manifest as a heightened avoidance of ambiguous decision contexts, explaining the observed link between lifetime stressor exposure and heightened ambiguity aversion. Future research should investigate the specific mechanisms involved.

This study demonstrates a robust association between cumulative lifetime stressor exposure, particularly early life stress, and increased ambiguity aversion in economic decision-making. The findings highlight the importance of considering psychosocial factors when understanding decision-making under uncertainty. Future research could explore the specific neural mechanisms involved and investigate potential interventions to mitigate the impact of early life adversity on ambiguity preferences.

The correlational nature of the study prevents causal inferences; it's not clear whether stress causes ambiguity aversion or vice versa. The retrospective assessment of lifetime stressor exposure could introduce recall bias. While the STRAIN is robust, it is still a self-report measure. The definition of early life stress (<18 years) may need further refinement. Additional research should use prospective designs and explore the role of individual differences in resilience.