Hi Jacob,
I had two friends with "behavioral science" type projects.
Amanda did an economics/math project and was a semifinalist for both Siemens and STS. Her title was "Are Stock Options Congruent with Maximizing Share Holder Value? A Mathematical Derivation."
My friend Ilang is actually not a good example for STS. If I remember correctly she did enter her project into one of the competitions (either Siemens or STS), but wrote her report last minute and didn't end up moving on. She did well at ISEF, however. I know that one of the competitions doesn't accept behavioral science projects, so you should check on that before entering (or perhaps you have already made it to the final round?). Her title was "Quantitative EEG as an Identifier of Learning Modality."
One of the finalists at STS did a project related to an AIBO dog and elderly people, which is sort of like a behavioral science project. He may have measured blood-pressure, etc, though, which may put it in the biology category. There was also a girl who did a political science/economics project. I don't remember what it was about specifically though. You could look at past abstracts for STS finalists and see if there were any projects in your category. I bet they have them available somewhere on the Intel STS site, or you could try a google search.
As for studying for general science, I suppose you could try to go through some of your class notes and remember basic physics formulas, chemistry, bio, etc, but you have no clue what they will ask you so it may be pointless. They seemed to tailor the questions based on each student's knowledge, which was nice because I didn't need to worry about solving crazy math or knowing advanced physics (I was taking AP Physics B at the time). It is more important to get used to talking to 3 judges staring at you while being nervous. You need to talk while figuring out your answer. I'd practice answering random science/logic questions in front of someone that is intimidating. You need to explain your thought process QUICKLY under stressful circumstances, which is not one of my strengths
.
The first part (becoming a semifinalist/finalist) focuses on your research paper and application. The final round of the competition focuses mainly on YOU, your project takes a backseat. There is a short "judging" session with your project on public viewing day, but was pretty casual and I'm not sure how much it contributed to the judges final decisions. They probably made up their mind already, but it's always a good idea to do your best! If you are in the final round, it's a given that they think your project is top-notch, so I wouldn't worry about which category it fits into.
Good luck and let me know if you have any more questions!