The interactive influences of stress, modality of stimuli, and task difficulty on verbal versus visual working memory capacity

Recently, contradictory findings on the influence of stress on verbal and visual working memory (WM) have urged researchers to explore moderators of stress and the two types of WM. This study included perceived task difficulty as a moderator to investigate the interactive effects of stress, different types of stimuli, and perceived task difficulty on verbal and visual WM capacity. In the experimental study, 92 college students were randomly assigned to one of the following groups: high-stress verbal, low-stress verbal, high-stress visual, or low-stress visual. Saliva cortisol level was used as a proxy of stress. The results revealed that (1) stress enhanced visual WM capacity, but not verbal WM capacity; and (2) perceived task difficulty was an important moderator of WM capacity. Under stressful situations, perceived task difficulty may enhance attention, cognitive control, and processing efficiency through the modulation of cortisol responses, which further improves WM, especially visual WM. The findings suggest that interactions between stress, types of stimuli, and task difficulty should be taken into consideration concurrently to maximize the effects of learning.