When we’re sleep deprived, our bodies try to compensate by activating the stress response—doses of adrenaline and cortisol to help us survive the temporary stressor of too little sleep—which masks the fatigue and impairment. The result is that sleep deprivation can act a little like alcohol; just as a person who has been drinking may be too impaired to know how impaired they are (“I’m fine, gimme the keys!”), a person who isn’t rested may be too sleep deprived to be aware of how sleep deprived they are.
