Roger went to see his doctor with complaints of erectile dysfunction (ed). his doctor has him participate in a sleep disorder study to determine the cause of his ed. the cause of his ed was determined to be psychological. why?

During our sleep, the human body goes through cycles in which erections are possible to be attained. If Roger was able to achieve tumescence while he was asleep, then this shows that the problems he was having doing so while awake were not physiological in nature.