Hi Alexandra, I'm assuming you're interested in applied psychology as a researcher as opposed to clinical psychology as a therapist. As a doctoral candidate you are assigned a professor who is your dissertation advisor throughout your doctoral program. This professor must be a professor in the department in which you are seeking your doctorate. As a doctoral student you will not take classes in other disciplines, so you want someone who specializes in your area of study to assist in guiding you. Some schools specialize in gender and sexuality, so that may be an option for you. I hope this is helpful for you and good luck! I suggest you look at the graduate catalog for whichever universities you are interested in and see what their areas of specialization are.