The assignment was what made me come up with the idea. I've only photographed one person before this. It was for a portrait assignment in Intermediate Photography. There is also this photography meetup (meetup.com) I go to every once in a while and the friends I've made from there are all telling me that I should work on the things I don't prefer to photograph, namely people. So, I figured this project was my chance. I've never photographed nudes and I've only photographed one person before this. heh. I ran the idea by my professor before I embarked on posting ads up at tribe.net and asking friends if they knew anyone who'd volunteer.
So far, most of the people interested want to hear about my project and what I plan to do. Basically, what I tell them is the project is very open ended with very few requirements. 1) I must purchase two condoms from a store on my own and somehow include both into my project. 2) One must be opened, but not used. 3) The project must convey at least two topics from my textbook with art. 4) The art must be accompanied by a journal entry explaining in detail how the project conveys topics from the textbook. I also tell them that I think the main topic I wish to convey is the Masters and Johnson stages of sexual response a) arousal b) plateau c) orgasm and d) resolution. And, the fact that I'm photographing a couple makes me actively a voyeur, which is another topic mentioned in the textbook. I will probably also include in my journal the sexual positions (there's a whole chapter on that) and whatever other foreplay is practiced during the shoot.
As for the shoot, I told my models to pretend like I'm not there and to do whatever it is they most enjoy, preferrably something that at least someone has an orgasm. I didn't want to be a director; I hate posed shots. I have a decent amount of experience photographing animals, so I figured I'd apply the same general concepts of getting good animal pics to people. The two general rules I've decided help me most for animals are to keep shooting because 1 or 2 seconds might make or break the photo. With animals, you can't predict what they're going to do, so you have to sit, wait, watch, and shoot when you think you see something good. To answer your question more directly, I didn't ask them about their changes of state because sound was a pretty good indicator.
As for my state of mind, the couple was hot and playful with a sense of humor, so I had fun. The guy in the couple said I was very professional, so I think that's a good thing.