Stress prompts habit behavior in humans.
Level 2 - randomized trial
Controlled laboratory experimental study with stress versus control conditions
PubMed 19494141 · doi:10.1523/JNEUROSCI.0979-09.2009
What was done
Participants were exposed to acute stress (socially evaluated cold pressor test) or a control condition prior to learning two instrumental actions paired with two distinct food outcomes. Following training, one food outcome was selectively devalued by feeding subjects to satiety on that food. Participants were subsequently tested on the instrumental actions in extinction to evaluate whether responding remained goal-directed or became habitual, and explicit knowledge of action-outcome contingencies was assessed.
What was found
The abstract reports no numerical values, exact sample sizes, or test statistics. Qualitatively, pre-training stress rendered participants insensitive to outcome devaluation during extinction (promoting habit-based performance) and reduced explicit awareness of action-outcome relationships relative to the control condition.
Why it matters
This study provides experimental evidence in humans that acute stress impairs goal-directed action-outcome processing and promotes habitual stimulus-response behavior during instrumental learning.
Limits
The abstract provides no participant numbers, demographic characteristics, or quantitative effect sizes. The findings reflect acute laboratory stress using a cold pressor task and food devaluation, which may not fully represent chronic stress states or complex real-world habit formation.