Objectives: Sleep has been shown to be involved both in emotion regulation and in the active processing of information. We combined these two concepts and tested if sleep affected the generalization of fear learning.

Methods: In a fear conditioning paradigm, participants were shown images of a small and a big circle where one of them was paired with an aversive sound, making it the CS+. Fear was measured with skin conductance responses. Participants were then randomly divided into a sleep or a wake group. The sleep group took a 2 h nap while the wake group rested for 2 h. Participants were then exposed to the two circles seen before, combined with 8 novel circles that gradually varied in size from the small one to the big one. We looked at how many circle sizes away from the CS+ that participants still exhibited a fear response, and if this differed between the sleep and the wake group.

Results: We found no effect of sleep on the slope of the generalization across the different circles. There was a main effect of circle size, F(1,25) = 10.42, P = 0.01, but no main effect of sleep/wake, F (1,25) = 0.40, P = 0.54, and no interaction between sleep/wake X circle size, F(1,25) = 0.62, P = 0.44.

Conclusions: The fear conditioning manipulation worked, with a gradual increase of fear depending on the stimuli’s similarity to the CS+. However, there was no effect of sleep or wake, which could possibly be explained by that just a 2 h nap not being a sufficient sleep manipulation to detect any differences.