Majors in Admissions

I’m fairly new to CC and I see on numerous threads where people say that for many top20-30 schools, showing an intended major of science/medicine or business would hinder your chances because those schools have many of those students. My question is, does it really make that much of an impact for these schools? What would happen if you intended on a science or med degree but purposely listed something else as intended major such as Art or Philosophy and if accepted, were to simply switch your major to your truly favored one. Does your major actually make a big factor on your application to these schools?

Some schools don’t allow you to just switch your major. And there is no Med major as an undergrad. You can major in anything you want as long as you take the premed classes.