The study focused on two fundamental processes in behavioral economics. The first, delay discounting, describes how the perceived value of a reward shrinks as its arrival is pushed into the future. A person with high delay discounting might take fifty dollars today rather than one hundred dollars in six months, effectively trading a larger outcome for immediate gratification. The second, probability discounting, captures how people devalue rewards that are uncertain. Offered a guaranteed fifty dollars or a hundred dollars with only a sixty percent chance of payout, someone with high probability discounting would gravitate toward the smaller, certain option. Both processes have been tied to a striking range of maladaptive outcomes, including tobacco and other substance use, poor adherence to preventive medical care and treatment regimens, and psychiatric conditions such as major depressive and bipolar disorders.

Perceived stress, the psychological variable at the center of the new work, is distinct from a single bad day or an acute laboratory stressor. It reflects the degree to which people experience their lives as unpredictable, uncontrollable, or overwhelming over an extended period, capturing the cumulative burden of multiple stressors. Earlier observational studies consistently found that adults and adolescents reporting greater perceived stress also showed steeper delay discounting, and similar patterns appeared in people recovering from substance use disorders. Yet experimental studies that deliberately induced acute stress, such as through public speaking or cold exposure, generally failed to reproduce the effect, leaving researchers with a puzzling inconsistency. More importantly, both perceived stress and delay discounting are reliably associated with low income and scarcity, making it difficult to tell whether stress genuinely alters decision-making or whether both simply track poverty.

To break that deadlock, the research team, led by Mary J. King of Virginia Tech alongside Michelle Rockwell, John Epling, and Jeffrey S. Stein, turned to a methodological strategy borrowed from epidemiology: restricting the sample. Instead of statistically adjusting for income after the fact, they recruited only participants whose combined household income was at least $100,000 per year, placing them roughly within the top two income quintiles in the United States. By draining most of the variability out of the income variable, the researchers effectively neutralized socioeconomic disadvantage as an alternative explanation. Participants were recruited through the online crowdsourcing platform Prolific and were further limited to adults aged 28 to 75 who worked outside medicine and related fields, because the study doubled as a comparison group for a separate investigation of primary care clinicians.

A total of 247 participants completed the survey in August 2024, with a median completion time of just under six minutes. After excluding ten participants who failed attention checks and fifteen who reported incomes below the pre-screening threshold, 222 participants remained for analysis. The sample had a median age of 48 years, a slight female majority, and a median Perceived Stress Scale score of 14, corresponding to moderate stress. The Perceived Stress Scale, a widely used ten-item instrument asking how often respondents felt nervous, overwhelmed, or in control over the past month, showed excellent internal consistency in this sample.

Discounting was measured with brief, six-trial adjusting tasks administered for two reward magnitudes, $100 and $10,000, in randomized order. In the delay discounting task, participants repeatedly chose between a smaller immediate amount and a larger delayed amount, with the delay adjusted up or down across trials until the point of indifference, expressed as an ED50, was reached. Its inverse, the rate parameter k, indexes how steeply delayed rewards lose value. The probability discounting task worked analogously, adjusting the chance of receiving a larger immediate reward until indifference, yielding the rate parameter h. Because smaller rewards are typically discounted more steeply over time while larger rewards are discounted more steeply under uncertainty, testing both magnitudes provided an internal validity check: the classic magnitude effects were indeed replicated, confirming the tasks behaved as expected.

The results were strikingly selective. For the $100 rewards, perceived stress significantly predicted steeper delay discounting in both univariate and multiple regression models that controlled for age, education, gender, and household income. The same held true for probability discounting at $100, where higher stress scores were associated with greater devaluation of uncertain rewards. At the $10,000 magnitude, however, perceived stress lost its association with both delay and probability discounting entirely. The researchers suggest this magnitude-specific pattern may reflect the more extreme discounting rates observed for large rewards, which can compress the range of individual differences and reduce sensitivity to modest cross-sectional effects. Notably, the association between stress and probability discounting at $100 did not fully survive a sensitivity analysis that retained outlier participants, a caveat the authors acknowledge.

One demographic factor proved more durable than stress. Across both reward magnitudes, female participants showed higher probability discounting than male participants, preferring smaller, guaranteed rewards over larger, uncertain ones. This aligns with prior findings of gender differences in decision-making under uncertainty, although the literature on gender and delay discounting remains less consistent. The persistence of the gender effect at magnitudes where the stress effect vanished underscores that different psychological and demographic influences on risky choice may operate at different scales of reward.

The study’s limitations are worth noting. The cross-sectional design precludes any claim about causality or temporal ordering, and the sample was drawn entirely from a research volunteer platform and restricted to non-healthcare workers with high incomes, limiting generalizability. The brief probability discounting task has received less validation than its delay counterpart, though its successful replication of the magnitude effect lends credibility. The authors also caution that their analyses did not adjust for multiple comparisons, and they call for future longitudinal work across diverse populations, income levels, and geographic regions, where cost of living may translate identical salaries into very different financial realities.

Even with those caveats, the implications are substantial. Health-related decisions, from smoking cessation to medication adherence, hinge on how individuals weigh immediate certainty against delayed or probabilistic benefit. If the everyday experience of stress nudges people toward impatience and risk aversion even in financially secure populations, then stress management could represent an underappreciated target for interventions designed to improve long-term health behavior. What this study establishes is that the well-documented link between stress and impulsive choice is not merely poverty wearing a psychological disguise; it persists where economic hardship is largely absent, provided the rewards on the table are small enough to feel like everyday money.

Subject of Research: The relationship between perceived stress and delay and probability discounting in a high-income adult sample

Article Title: Examining relationships between delay and probability discounting and perceived stress in a high-income online sample

Article References: King, M. J., Rockwell, M., Epling, J., & Stein, J. S. (2026). Examining relationships between delay and probability discounting and perceived stress in a high-income online sample. Journal of Behavioral Medicine. https://doi.org/10.1007/s10865-026-00711-0

Image Credits: AI Generated

DOI: 10.1007/s10865-026-00711-0

Keywords: delay discounting, probability discounting, perceived stress, decision-making, behavioral economics, impulsivity, income, Prolific, health behavior, Journal of Behavioral Medicine, reward magnitude, gender differences

The research, conducted by Christopher J. Petty of the University of Georgia, Mindy Isaman and Linnea R. Freeman of Furman University, and colleagues at Furman and Clemson University, was published in the journal Biology of Sex Differences. The team set out to address two intertwined problems: the persistent excess of severe obesity among women compared with men, and the growing but still murky evidence that the gut microbiome shapes feeding behavior. Individuals with obesity are known to carry an altered gut microbiome, but whether those microbial differences actually drive overeating—or merely accompany it—has remained an open question, particularly with respect to sex differences.

To measure hedonic feeding with real precision, the researchers turned to an approach borrowed from economics rather than simple food-intake counts. Male and female Sprague-Dawley rats were trained in a de-escalating fixed ratio operant task built on behavioral economics principles. In this paradigm, animals work—pressing a lever—to earn high-fat, palatable reward pellets, and the price of those pellets, measured in effort, steadily increases. The design allows researchers to estimate two key parameters. The first is demand elasticity, denoted alpha, which captures how quickly an animal’s demand for the reward falls as the price of obtaining it rises. The second is demand at null cost, or Q0, an extrapolated prediction of how much the animal would consume if the reward required no effort at all. Together, these values describe not just how much an animal eats, but how much it values the food—an economic signature of hedonic drive.

The baseline results were clear and consistent with the team’s earlier work: female rats showed a significantly higher demand at null cost for the high-fat palatable pellets than male rats. In plain terms, when effort was stripped away, females valued and would consume more of the palatable reward than males. Because hedonic feeding is a well-recognized contributor to chronic overconsumption in environments saturated with calorie-dense foods, this kind of sex-linked difference in reward valuation is exactly the sort of biological signal that could help explain why severe obesity disproportionately affects women.

The next question was what might be driving that difference. Emerging evidence suggests the gut microbiome influences feeding behavior through several channels, including the production of short chain fatty acids, metabolites generated when gut bacteria ferment dietary fiber, and through effects on bile acids, molecules synthesized from cholesterol that aid fat digestion and also act as signaling agents in the gut and beyond. The researchers therefore administered an antibiotic cocktail in the rats’ drinking water to disrupt the gut microbiome, then re-ran the behavioral economics task to see whether wiping out the microbial community would change hedonic feeding in either sex.

The outcome was striking in its restraint. Female rats given antibiotics continued to show a higher demand at null cost compared with untreated male control rats, and—critically—the researchers found no statistically significant difference between antibiotic-treated males and females. In other words, disrupting the microbiome did not erase or meaningfully reshape the sex difference in hedonic reward valuation. The antibiotic treatment did do its biological job: when the team characterized the fecal microbiome at the genus level before and after antibiotic administration, they documented clear disruption to the bacterial community, alongside measured changes in fecal short chain fatty acid levels. They also profiled serum short chain fatty acid and bile acid levels at the end of the study, providing a metabolomic snapshot of the systemic consequences of microbial disruption.

What makes the finding conceptually important is what it rules out, or at least renders less likely as a simple explanation. If baseline differences in gut bacterial composition between males and females were the primary engine of the female rats’ stronger hedonic drive, collapsing that composition with antibiotics should have narrowed the gap. It did not. The authors also report that they did not observe striking baseline sex differences in fecal microbiome diversity and composition in the first place, which further weakens the notion that straightforward differences in which bacterial genera dominate the gut could account for the behavioral divergence. The study’s own conclusion is deliberately measured: these results bring into question whether the gut microbiome contributes to sex differences in hedonic feeding at all.

That said, the researchers are careful not to close the book on microbial influence. The gut microbiome is not a single variable but a network of interacting communities and metabolites, and antibiotics are a blunt instrument. The team points to network factors—such as the interplay between the microbiome and bile acids, which themselves show sex differences and can modulate feeding—as avenues requiring further investigation. Serum bile acid profiles measured at the study’s endpoint suggest that downstream signaling pathways, rather than raw bacterial composition, may be where sex-specific microbial effects on appetite ultimately reside, if they exist.

The work also carries a methodological lesson for the field. Behavioral economics approaches like the de-escalating fixed ratio task distinguish between consumption and motivation, two things that simple access-feeding experiments conflate. An animal that eats more of a tasty food at zero cost but gives up quickly when effort increases is economically different from one that persists at high prices, and only the second pattern reflects a genuine shift in reward valuation. By anchoring sex comparisons in demand curve parameters rather than grams consumed, studies of this kind can pinpoint whether the sexes differ in how much they value palatable food, in how sensitive they are to its cost, or both. In this case, the female-male difference lived specifically in the null-cost demand estimate.

For human health, the implications are cautious but meaningful. The finding that female rats place a higher intrinsic value on high-fat palatable food parallels epidemiological patterns in which women face higher rates of severe obesity, and it reinforces the idea that any intervention aimed at curbing pleasure-driven eating may need to account for sex as a fundamental biological variable rather than an afterthought. At the same time, the negative result on the microbiome tempers enthusiasm for microbial therapies—probiotics, targeted antibiotics, or fecal transplants—as quick fixes for hedonic overeating, at least until the relevant mechanisms are better mapped. Obesity, the authors note, remains a pressing public health issue, and hedonic feeding, while not its sole culprit, is one of its major contributing forces. Untangling which biological threads—hormonal, neural, microbial, or metabolic—woven together produce the sex difference in reward valuation will demand the kind of systematic, multi-dimensional profiling this study models: behavior, bacterial census, and metabolites measured in the same animals, before and after perturbation. The microbiome may yet play a role in appetite, but this careful experiment suggests that if it does, it operates through subtler, networked pathways than the simple presence or absence of particular gut bacteria.

Subject of Research: Sex differences in hedonic feeding and the effects of antibiotic-induced gut microbiome disruption in rats

Article Title: Sex differences in hedonic feeding and characterizing the effects of antibiotic-induced microbiome disruption

Article References: Sex differences in hedonic feeding and characterizing the effects of antibiotic-induced microbiome disruption. (n.d.). https://doi.org/10.1186/s13293-026-00970-1

Image Credits: AI Generated

DOI: 10.1186/s13293-026-00970-1

Keywords: hedonic feeding, gut microbiome, sex differences, behavioral economics, obesity, antibiotics, short chain fatty acids, bile acids, operant conditioning, Sprague-Dawley rats, microbiome disruption, food reward