Stress-induced cortisol hampers memory generalization.

Integrative encoding and generalization across past experiences depends largely on the hippocampus, an area known to be particularly sensitive to stress. Yet, whether stress influences the ability to generalize memories is unknown. We exposed volunteers to a stressor or a control manipulation before they completed an acquired equivalence task probing memory generalization. While stress left learning performance intact, it reduced participants' ability to generalize and this deficit was directly linked to the cortisol response to the stressor. These findings show that stress, presumably through the action of glucocorticoids, creates rather rigid memories that are difficult to transfer to novel situations.