Threat of bodily harm has opposing effects on cognition.

Several theoretical frameworks have suggested that anxiety/stress impairs cognitive performance. A competing prediction is made by attentional narrowing models that predict that stress decreases the processing of task-irrelevant items, thus benefiting performance when task-irrelevant information interferes with behavior. Critically, previous studies have not evaluated these competing frameworks when potent emotional manipulations are involved. Here, we used threat of bodily harm preceding a color-word Stroop task to test these claims. We found a basic effect of threat consisting of a slowing down of performance during neutral Stroop trials. Furthermore, both facilitation and interference scores were affected by threat of shock in a way that was consistent with a reduced-distractor effect. Taken together, we interpret our findings in terms of two opposing effects of stress on cognitive performance. Although partly consistent with the attentional narrowing hypothesis, both resource models and cognitive breadth models require revision in order to account for the results.