In a follow-up EEG sleep study, brain signal complexity (Lempel-Ziv complexity, LZC) decreased progressively from wakefulness into deeper non-REM sleep. However, within NREM2 sleep, there was no significant difference in LZC between dream and non-dream awakenings, and no correlation between LZC and subjective ratings of dream vividness, diversity, or perceptual quality. The authors failed to reproduce their earlier finding that posterior LZC increased with more perceptual dream experiences. This raises doubts about whether EEG LZC is a reliable marker of richness of experience within the same sleep stage.
People experiencing depersonalization or derealization often report that the world looks faded, foggy, or dream-like. Two online experiments tested whether these subjective reports reflect genuine changes in visual perception. Participants with varying levels of depersonalization/derealization symptoms rated how real naturalistic images looked (Experiment 1, 200 participants) or adjusted the contrast and saturation of images to match their everyday visual experience (Experiment 2, 125 participants). In both experiments, strong Bayesian evidence supported the null models: symptom severity did not affect realness ratings or vividness adjustments. The results suggest that the altered vividness experience in derealization does not stem from genuine perceptual changes but rather from metacognitive interpretation of those experiences.