Nichole R. Lighthall

Acute Stress Increases Sex Differences in Risk Seeking in the Balloon Analogue Risk Task

Background Decisions involving risk often must be made under stressful circumstances. Research on behavioral and brain differences in stress responses suggest that stress might have different effects on risk taking in males and females. Methodology/Principal Findings In this study, participants played a computer game designed to measure risk taking (the Balloon Analogue Risk Task) fifteen minutes after completing a stress challenge or control task. Stress increased risk taking among men but decreased it among women. Conclusions/Significance Acute stress amplifies sex differences in risk seeking; making women more risk avoidant and men more risk seeking. Evolutionary principles may explain these stress-induced sex differences in risk taking behavior.

Gender differences in reward-related decision processing under stress

Recent research indicates gender differences in the impact of stress on decision behavior, but little is known about the brain mechanisms involved in these gender-specific stress effects. The current study used functional magnetic resonance imaging (fMRI) to determine whether induced stress resulted in gender-specific patterns of brain activation during a decision task involving monetary reward. Specifically, we manipulated physiological stress levels using a cold pressor task, prior to a risky decision making task. Healthy men (n = 24, 12 stressed) and women (n = 23, 11 stressed) completed the decision task after either cold pressor stress or a control task during the period of cortisol response to the cold pressor. Gender differences in behavior were present in stressed participants but not controls, such that stress led to greater reward collection and faster decision speed in males but less reward collection and slower decision speed in females. A gender-by-stress interaction was observed for the dorsal striatum and anterior insula. With cold stress, activation in these regions was increased in males but decreased in females. The findings of this study indicate that the impact of stress on reward-related decision processing differs depending on gender.

Both Risk and Reward are Processed Differently in Decisions Made Under Stress

Years of research have shown that stress influences cognition. Most of this research has focused on how stress affects memory and the hippocampus. However, stress also affects other regions involved in cognitive and emotional processing, including the prefrontal cortex, striatum, and insula. New research examining the impact of stress on decision processes reveals two consistent findings. First, acute stress enhances selection of previously rewarding outcomes but impairs avoidance of previously negative outcomes, possibly due to stress-induced changes in dopamine in reward-processing brain regions. Second, stress amplifies gender differences in strategies used during risky decisions, as males take more risk and females take less risk under stress. These gender differences in behavior are associated with differences in activity in the insula and dorsal striatum, brain regions involved in computing risk and preparing to take action.

Risk preferences and aging: The “Certainty Effect” in older adults’ decision making

A prevalent stereotype is that people become less risk taking and more cautious as they get older. However, in laboratory studies, findings are mixed and often reveal no age differences. In the current series of experiments, we examined whether age differences in risk seeking are more likely to emerge when choices include a certain option (a sure gain or a sure loss). In four experiments, we found that age differences in risk preferences only emerged when participants were offered a choice between a risky and a certain gamble but not when offered two risky gambles. In particular, Experiments 1 and 2 included only gambles about potential gains. Here, compared with younger adults, older adults preferred a certain gain over a chance to win a larger gain and thus, exhibited more risk aversion in the domain of gains. But in Experiments 3 and 4, when offered the chance to take a small sure loss rather than risking a larger loss, older adults exhibited more risk seeking in the domain of losses than younger adults. Both their greater preference for sure gains and greater avoidance of sure losses suggest that older adults weigh certainty more heavily than younger adults. Experiment 4 also indicates that older adults focus more on positive emotions than younger adults do when considering their options, and that this emotional shift can at least partially account for age differences in how much people are swayed by certainty in their choices.

Stress modulates reinforcement learning in younger and older adults.

Animal research and human neuroimaging studies indicate that stress increases dopamine levels in brain regions involved in reward processing, and stress also appears to increase the attractiveness of addictive drugs. The current study tested the hypothesis that stress increases reward salience, leading to more effective learning about positive than negative outcomes in a probabilistic selection task. Changes to dopamine pathways with age raise the question of whether stress effects on incentive-based learning differ by age. Thus, the present study also examined whether effects of stress on reinforcement learning differed for younger (age 18-34) and older participants (age 65-85). Cold pressor stress was administered to half of the participants in each age group, and salivary cortisol levels were used to confirm biophysiological response to cold stress. After the manipulation, participants completed a probabilistic learning task involving positive and negative feedback. In both younger and older adults, stress enhanced learning about cues that predicted positive outcomes. In addition, during the initial learning phase, stress diminished sensitivity to recent feedback across age groups. These results indicate that stress affects reinforcement learning in both younger and older adults and suggests that stress exerts different effects on specific components of reinforcement learning depending on their neural underpinnings.

Functional compensation in the ventromedial prefrontal cortex improves memory-dependent decisions in older adults.

Everyday consumer choices frequently involve memory, as when we retrieve information about consumer products when making purchasing decisions. In this context, poor memory may affect decision quality, particularly in individuals with memory decline, such as older adults. However, age differences in choice behavior may be reduced if older adults can recruit additional neural resources that support task performance. Although such functional compensation is well documented in other cognitive domains, it is presently unclear whether it can support memory-guided decision making and, if so, which brain regions play a role in compensation. The current study engaged younger and older humans in a memory-dependent choice task in which pairs of consumer products from a popular online-shopping site were evaluated with different delays between the first and second product. Using functional imaging (fMRI), we found that the ventromedial prefrontal cortex (vmPFC) supports compensation as defined by three a priori criteria: (1) increased vmPFC activation was observed in older versus younger adults; (2) age-related increases in vmPFC activity were associated with increased retrieval demands; and (3) increased vmPFC activity was positively associated with performance in older adults—evidence of successful compensation. Extending these results, we observed evidence for compensation in connectivity between vmPFC and the dorsolateral PFC during memory-dependent choice. In contrast, we found no evidence for age differences in value-related processing or age-related compensation for choices without delayed retrieval. Together, these results converge on the conclusion that age-related decline in memory-dependent choice performance can be minimized via functional compensation in vmPFC.

Gain/Loss Framing Effects on Learning in Economic Decision Making Investigated with Eye Tracking

Previous research has revealed a domain-based bias when people estimate payout likelihoods for probabilistic choice options that minimize losses versus those that maximize gains (Kuhnen, 2015). For instance, in economic boom situations, people overestimate how valuable a low profit stock is. Conversely, in economic recession situations, individuals underestimate stocks that minimize losses. Cognitive neuroscience posits that gain and loss information is processed differently in the brain (Knutson and Bossaerts, 2007; Kuhnen and Knutson, 2005), but the precise mechanisms of these domain differences are still unclear. The current study investigated two potential causes of this domain-based bias. Bias may be driven by a high magnitude effect, owing to greater salience for large gains and losses and subsequent overweighting in probability estimations. This would be evidenced by enhanced attention and memory for stimuli associated with high-magnitude dividend choice options and payouts. Domain-based bias in probability estimations could also be driven by incongruence between objective probabilities and dividend payout valence (e.g., “bad” choice options in the gain domain; “good” choice options in the loss domain; valence incongruence effect). If true, we would expect enhanced estimation errors, reaction times (RT), and attention when there is incongruence between the valence of choice payout probabilities and their payouts. To test these hypotheses, 26 students from the University of Central Florida (UCF) participated in an economic decision-making study. The main task involved choosing between pairs of stocks (probabilistic payouts) and bonds (sure-thing payouts). Choice pairs were embedded in either a gain or loss block, with both choice options paying either positive or negative dividends, respectively. Stocks within a block were pseudorandomly drawn from either the “good distribution” (70% high payouts) or the “bad distribution” (30% high payouts). After choosing a security, the stock payout was shown and participants were then asked to estimate the probability that the current stock was drawn from the good distribution. Performance bonus payments were paid based on accurate stock probability estimates and 10% of the total earned from stock/bond choices. The study was approved by the UCF Institutional Review Board. Eye movements were recorded throughout to measure overt visual attention as a potential mechanism of domainbased bias. Measures included the fixation duration on each stimulus (dwell time) and average number of oscillations between choice options to determine when and where one looks (Carpenter and McDonald, 2007). Interest areas were created a priori around each critical stimulus in the choice and stock payout phases. To test memory for choice and stock payout phases, participants completed an incidental memory test at the end of the experiment. Here memory was assessed for fractal images associated with each stock and bond option, as well as face images associated with each stock payout (“stockbrokers”). The critical dependent variables to measure domain-based bias were estimation error, response time, oscillation between choice stimuli, and stimulus dwell time. The impact of memory, attention, and congruence of information on measures of domain-based estimation bias was examined with 2 x2 domain (gain, loss) by dividend payout (high, low payout) repeated-measures analysis of variance models (ANOVA). Mixed effects modeling was used to examine the power of outcome RT and visual dwell time to predict probability estimate bias. Behavioral results. Consistent with the valence incongruence hypothesis, absolute errors for stock payout probabilities were relatively higher when gain-domain stocks had worse expected values (gain stock was “bad”) than associated bonds and when loss-domain stocks had better expected values than associated bonds (loss stock was “good”). In addition, RT during the choice phase was greater in the loss domain, as participants had to update their estimations the stock came from the “good distribution” even though it only lost money. For stock payout RT, the mixed effects model found an interaction of domain, payout magnitude, and outcome RT where the longer participants spent on gain outcome screens, the more positive their bias and the longer they spent on loss outcome screens, the more negative their bias. Results from the two incidental memory test scores did not reveal any main effects or interactions of domain or dividend payout, lessening support for the high magnitude hypothesis. The data provide support for both attentional effects. Eye tracking data. Greater oscillations between stock and bond options at choice was observed in the loss condition, suggesting greater choice uncertainty when stocks lose money. Stimulus dwell times were higher in the loss domain during the choice phase but did not differ by dividend payout. However, the mixed effects model found an interaction of domain and stock dwell times where the longer participants spent on gain information, the more positive their bias and the longer they spent on loss information, the more negative their bias. The mix of results provide support for both attentional effects. The behavioral results were in line with previous research (Kuhnen, 2015). Together with the eye tracking data, the results support the both the valence incongruence and high magnitude effects. We have evidence that one effect influences overall error rate (incongruence) and the other drives the direction of the error (magnitude). Thus, future interventions should consider both effects when seeking to improve decision making.