Dream content and slow waves benefit prey against predator in a video game confrontation

Every studied animal species exhibits some form of sleep, a state evolved under the sustained influence of prey and predator behaviors. Dreams have been proposed to have evolved as offline mental simulations able to warn against impending threats from the environment, such as predators. To assess how the ecological roles of prey and predator interact with sleep and dreaming, we used a first-person shooter game as a proxy for predator-prey confrontations. Electroencephalographic (EEG) and electrocardiographic (ECG) signals were simultaneously recorded from 30 human adult pairs while (1) playing a video game round against each other, (2) taking a nap, (3) reporting dreams and/or thoughts, and (4) playing another round. We found that the participants in the prey role were highly affected by sleep and dreaming. Their score gains were positively correlated with slow wave activity during the nap, with how much the dreams were related to the game, and with heart rate variability during the first round. In contrast, no significant correlations were found for participants in the predator role. The results suggest that slow wave activity and task-related dream content predict the post-sleep performance of individuals under stressful, low-agency, prey-like situations.