An individual must be continually monitored to ensure that sleep does not occur. One nearly universal aspect of sleep deprivation in humans and animals is that it becomes more difficult to keep an organism awake as the period of sleep deprivation lengthens. Puppies become progressively more difficult to keep awake the longer they are sleep deprived. It becomes harder to keep puppies awake in periods of rest, while it is somewhat easier in periods of physical inactivity, or when the attention of the dog was captivated. However, after 3 or 4 days of deprivation, puppies showed a loss of interest in the environment, and made continual attempts to sleep.
Human subjects are capable of lying awake in bed during the first night of sleep deprivation.
During and after the second night, it becomes virtually impossible to keep a sleep-deprived person awake if he or she is in bed. Because of this, one of the challenges that experimenters researching sleep deprivation initially faced was to be able to separate any observable effects as owing to sleep deprivation or the activity that was necessary to produce the sleep deprivation. Sleep deprivation may exacerbate any pre-existing condition or tendency. One case study of a man who had a history of nervous disorders, but who was stable going into the sleep deprivation period. Performance Research Tech.