How is nighttime acth secretion related to expected sleep duration? humans secrete increasing amounts of adrenocorticotropic hormone (acth) during the late stages of normal sleep, with the peak secretion occurring at the time of spontaneous waking. because acth is released in response to stressful stimuli, scientists hypothesize that acth secretion prior to waking might be an anticipatory response to the stress associated with transitioning from sleep to a more active state. if so, an individual’s expectation of waking at a particular time might influence the timing of acth secretion. how can such a hypothesis be tested? in this exercise, you will examine how researchers designed a controlled experiment to study the role of expectation. researchers studied 15 healthy volunteers in their mid-twenties over three nights. each night each subject was told when he or she would be awakened: 6: 00 or 9: 00 a. m. the subjects went to sleep at midnight. subjects in the "short" or "long" protocol group were awakened at the expected time (6: 00 or 9: 00 a. m., respectively). subjects in the "surprise" protocol group were awakened at 6: 00 a. m., three hours earlier than expected, under the pretense of a technical problem. at set times, blood samples were drawn to determine plasma levels of acth. to determine the change (δ) in acth concentration post-waking, researchers compared samples drawn at waking and 30 minutes later.