Well, the problem with this is brief time involved. You aren't going to learn a whole lot of the medicine involved in any specialty in one to three months. All you can do is get a mild flavor of it. There's a reason residencies are 3-7 years, it's because that's about how long it takes to be trained in these fields, working up to 80 hours/week in them. So no med student is going to come out of a surgery rotation knowing a substantial amount of surgery (a 5 year residency), nobody is going to learn IM (a 3 year residency), and nobody trying their hand at learning radiology (a 4 year residency, after prelim year) is going to learn how to read films to any significant degree, etc. And if as you suggest we even tuck in other residencies (optho, ortho, PM&R, anesthesiology etc) into the cores, then you really aren't going to actually learn the medicine. All of these things take 3+ years to learn, and the med student will get a couple of weeks exposure to them. There just isn't time. When people are spending 3-7 YEARS trying to "actually learn the medicine" in that field, it's laughable for some med students to expect to "actually learn the medicine" in a matter of weeks. So no, I don't think it's about a sorority rush so much as it's a "you are here for three weeks and we cannot possibly teach you this subject in that time period, so help out the residents and see if you like it, because realistically that's all that we can do in this timeframe." I also disagree with your notion that med students already have an inkling of what they are going into independent of the things forced on them. Most med students change their mind at least once during med school, and I know many many people who were impressed enough by a core to switch their interest to that field.