Blue light influences negative thoughts of self.

Darkness is equated with sadness. This study explored how light that differentially impacts non-visual photoreception (blue-enriched vs. blue-depleted light) affects how we feel about ourselves. In a repeated-measured design, 35 participants (22 female participants, 13 male participants, Mage = 20.29, SD = 2.09) completed the self-referential encoding task (SRET) under both blue-enriched or blue-depleted light conditions, with light conditions randomized and counterbalanced between sessions. The SRET involved participants deciding whether positive (e.g. "good") and negative (e.g. "terrible") words were self-descriptive. Trial-by-trial performance analysis using logistic mixed effects models revealed that blue-enriched light significantly increased the likelihood of rejecting negative words as self-descriptive. A hierarchical drift-diffusion model (HDDM) further examined latent decision-making processes and found evidence accumulation to be faster under blue-enriched light when rejecting negative descriptors, suggesting rejecting negative self-descriptors was easier under blue-enriched light. We find light can acutely influence self-perception, with blue-enriched light decreasing negative self-thoughts.