Inclusion Criteria:  Participants are physically and mentally healthy (assessed with BMI and 'General Health Questionnaire-12)'. Participants accept to comply to the protocol (retain regular bed- and wake times before the simulated shifts). Refrain from alcohol and maintain regular nicotine and caffeine usage during participation. Norwegian as primary language/proficiency in Norwegian language.  Exclusion Criteria:  Neurological, psychiatric or sleep related disorders ('Bergen Insomnia Scale, 'Global sleep assessment questionnaire'). Extreme 'morning-eveningness' type ('Horne-Östberg). Use of medication that affect sleep or cognitive performance. Pregnancy.