I just read an interesting story about the Kinsey Institute's latest research in the sexual response of women.
Women were first asked in an interview, what "turns them on", and what they did not care about sexually. The researchers then find videos to match what that woman likes and doesn't like, plus other videos. A week later the woman comes back for a test. They insert a glass sensor about the size of a tampon, into her vagina. The sensor measures blood flow. More blood flow means that the woman is aroused.
First, she sees a video of something neutral, such as a documentary, to set a benchmark. Then she watches different kinds of pornographic videos. What was surprising, was that, (for some women), what a woman thinks in her mind, is a "turn on", may not be that arousing to her body. And some things that she thinks that she is neutral about, actually is arousing.
Now Pierre may already know this, but this is a thought for the viewers of his Casting videos. When Pierre asks "Do you like the girls?" She may say no. But if she sees 2 women making love, she might get very aroused. When Pierre is working with a girl, he might be just as surprised as she is, with what really "turns her on".

Where can we see this research or read about it?

I wish I could help you, but can't. I use AOL for emails, and they also have news items, Each news item has links to other news, which has links to other, etc. I read it on one of those links. Its gone now. I Googled The Kinsey Institute. There is a woman heading research into Female Sexual Response. The research is being done at Indiana State University and in Amsterdam. But no details on their web site.
The original story also talked about "foot fetishes". I remembered a recent video on a competing site about casting young models.
The photographers studio was in a garage with furniture moved in. One model's name was Vendula and she was a shy 18 year old, tall, with a slim sexy body. Definitely "Woodman quality". She may have been a virgin because her mother brought her to the studio, and told her "Whatever they ask you to do, if I were you, I would just go for it."
They took a lot of photos and videos of her. The next day, she came without her mother. They talked her into getting naked and into the bed, lying on her back. Then a man came into the room and got naked. He stroked his penis and applied lotion on his erection. As he grabbed her ankles with each hand, I was very aroused, as I expected him to raise her legs, spread them, and mount her. Then slowly force his lubricated penis into her untouched shaved pussy. I was never so disappointed. He just held her ankles, put his penis between her feet, and started thrusting. Maybe some of you are turned on by this, but it does nothing for me.