Willingness to wait covaries with endogenous variation in cortisol

Overview

The study tested whether endogenous variation in stress physiology covaries with intertemporal choice preferences within healthy adults. Using a multi-session, within-subject design (N = 34), the investigation compared economic choices between immediate and delayed monetary rewards across short (seconds) and longer (days) temporal horizons. Stress measures included validated questionnaires, serial salivary cortisol assays to index phasic/endogenous fluctuations, and hair cortisol concentrations as a marker of chronic exposure. The principal outcome was the individual discount factor estimated separately for choices presented on second and day time scales, permitting assessment of whether stress markers predict within-subject shifts in willingness to wait.

Methods and approach

Participants completed repeated decision tasks across multiple sessions that interleaved intertemporal choice problems with endogenous sampling of salivary cortisol. Hair samples were collected to quantify long-term cortisol accumulation, and standardized psychosocial stress questionnaires were administered. Intertemporal choice tasks were designed to yield separate estimates of discounting for short (seconds) and long (days) delays using incentive-compatible monetary outcomes. Cortisol assays were processed with established laboratory protocols. Statistical analysis employed mixed-effects regression models to relate within-subject variation in discount factors to contemporaneous salivary cortisol, and between-subject analyses to examine associations with hair cortisol and questionnaire-derived chronic stress indices. Models controlled for session order, time-of-day, and demographic covariates and included robustness checks for nonlinearity and outliers.

Results

Within-subject fluctuations in salivary cortisol were associated with reliable changes in the estimated discount factor on the seconds-scale intertemporal task: higher endogenous cortisol corresponded to reduced willingness to wait (steeper discounting) on the short-delay decisions. This relationship was temporally specific; analogous associations were not observed for discount factors estimated from choices that spanned days. Hair cortisol and questionnaire-based measures of chronic stress showed no consistent relation to discounting in either time scale. Results persisted after adjustment for time-of-day effects, session order, and demographic covariates, and were robust across alternative model specifications.

Implications

The findings indicate that acute, endogenous cortisol dynamics modulate intertemporal choice behavior on very short time scales, whereas longer-horizon preferences appear insensitive to the same endogenous stress fluctuations. This temporal specificity suggests models of economic decision-making should incorporate transient physiological state variables when predicting moment-to-moment variability in patience or impulsivity. From an applied perspective, outcomes tied to short-delay choices—such as micro-purchases or momentary self-control failures—may be particularly susceptible to phasic stress responses even among healthy adults, whereas interventions targeting chronic stress may not directly alter long-horizon discounting.