What’s the deal with “morning wood”? My psychology of human sexuality teacher said that erections are not uncommon in males during REM sleep and so if a male is woken up during REM sleep, he may still have an erection. I disagree with this explanation. I think that it has something to do with the blood flow in your body when you come out of sleep. I also think it might have to do with the position of your body in relation to your blood flow. I might be going into too much detail here, but speaking from personal experience, if I have an erection when I wake up and I sit up, it goes away. Then if I lie down again, it comes back. Okay, sorry you had to read that, but anyways, can anyone explain morning wood?