Does stress make us grab smaller rewards now instead of later?
Being put under acute stress did not change how impatient people were on average, but it pushed low-stress-prone people towards smaller immediate rewards and high-stress-prone people towards waiting.
Source
Individual differences in delay discounting under acute stress: the role of trait perceived stress
Study at a glance
- Design
- Human experiment — Between-subjects factorial design crossing acute stress (anticipating a videotaped speech vs a relaxing control) with time orientation (future vs present focus), followed by an adjusting-amount delay and probability discounting task; trait perceived stress measured beforehand and tested as a moderator
- N
- N=113 · 120 male students randomized to four groups; 7 excluded, leaving 113 analysed (111 for cortisol analyses)
- Population
- Male non-smoking undergraduate students at a US university (Rutgers), mean age 20.46 years
- Outcome
- Delay discounting (area under the discounting curve), probability discounting, an immediate-reward bias index, and salivary cortisol and negative-affect change as stress manipulation checks
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What they did
Male students first reported how stressful they generally find their lives (the Perceived Stress Scale). They were then randomly assigned to anticipate giving a judged, videotaped speech about either a future job interview or what they dislike about their body, or to a relaxing control task (listing upcoming nice events or listening to music). They then made a series of choices between smaller-sooner and larger-later amounts of money, and between certain and risky amounts, with one choice paid out for real; saliva cortisol and mood were measured before and after.
What they found
The stress conditions raised negative affect and produced a slightly larger cortisol change than control conditions, but acute stress had no overall effect on delay discounting. Instead, stress interacted with trait perceived stress: under acute stress, men low in perceived stress discounted delayed rewards most steeply, while those high in perceived stress were most willing to wait; without stress, the two groups chose similarly. Risk-taking (probability discounting) was unaffected, and a separate immediate-reward bias measure was highest when a future-focused situation was stressful or a present-focused one was relaxing. Across everyone, larger cortisol increases were weakly associated with steeper discounting.
The limits
What it doesn't show
Only men were tested, so the results cannot be generalized to women, which the authors flag. The average cortisol rise in the stress groups was very small, so the stressor was mild, and negative mood also rose, so stress cannot be separated from mood. The two stress and two control conditions differed in more than time orientation (e.g., speech topic, music versus listing events), and the authors caution that the time-orientation results should be interpreted carefully, especially the immediate-reward bias index, which was noisy and depended on the staircase starting value. The key interaction added only a modest amount of explained variance (an R-squared change of 0.06) and was not tested in a preregistered analysis.
Key terms
- Delay discounting
- The tendency to value a reward less the longer you have to wait for it, leading to choices of smaller-sooner over larger-later rewards.
- Probability discounting
- Valuing a reward less the less likely it is to be received; used here as a measure of risk attitude.
- Area under the curve (AUC)
- A single-number summary of a discounting curve; smaller areas mean steeper discounting, that is, more impatience.
- Indifference point
- The immediate amount at which a person values the immediate and the delayed option equally.
- Trait perceived stress
- A person's general tendency to see life situations as unpredictable, uncontrollable and overloading, measured by the Perceived Stress Scale.
- Moderation
- When the effect of one variable (here acute stress) depends on the level of another (here trait perceived stress).
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Quiz yourself
What was the main effect of acute stress on delay discounting overall?
Common questions
Why might stress make some people more patient rather than less?
The authors suggest people high in perceived stress may see the stressor as a threat, which blunts their response to immediate reward, whereas low-stress people may see it as a challenge and become more drawn to immediate reward.
Why include a risky-choice task as well as a delay task?
Delay and risk discounting are related but distinct; including both showed that stress-related effects appeared for delayed rewards but not for risky ones.
Why were only men tested?
Menstrual cycle and hormonal contraceptives affect cortisol, so many stress studies test only men to simplify hormonal data, at the cost of generalizability.
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