For many years, virtually everyone in the sleep medicine field has been aware of the incongruence of individuals' denial of subjective daytime sleepiness, as opposed to other indicators, such as Multiple Sleep Latency Test results; reports of tiredness, fatigue, or lack of energy; or frequent unintentional sleep episodes. This incongruence has been explained in a number of ways. Some claim that people do not experience themselves as sleepy because it has been years since they experienced adequate restorative sleep. That is, they have habituated to an existence wherein physiologic sleepiness during wakefulness is constantly high and the experience of sustained alertness has long been forgotten. For example, the scenario of a patient with untreated sleep apnea who, upon questioning, denies feeling sleepy but was sleeping in the exam room and has fallen asleep at the wheel on a few occasions during the past month is a common experience of sleep medicine physicians. Some propose that such individuals simply do not remember what it is like to be "wide awake and alert."