(campbell and tobler, 1984; tobler, 1989). there is little reason to believe that the human sleep/wake system would evolve in a fundamentally different manner. that people often do not exhibit such sleep organization in daily life merely suggests that humans have the capacity (often with the aid of stimulants such as caffeine or increased physical activity) to overcome the propensity for sleep when it is desirable, or is required, to do so. a 2021 review found no evidence supporting the benefits of polyphasic sleep but instead adverse physical, mental and performance effects. the effectiveness of alternative sleeping schedules to achieve more time awake each day is disputed.