What advice would you give to a senior or college freshman about picking a major that will define career?

I would say that your major doesn’t actually define your career most of the time. Even if you’re going on to get a higher degree, like a medical degree, the medical schools don’t limit themselves to people who majored in premedical fields like biology.

Even for technical degrees like engineering, the specific field of engineering doesn’t matter all that much. If you get a degree in chemical engineering rather than aerospace engineering you can still go on to work for Boeing or whatever.

So my advice is: Don’t worry about it. Study what makes you passionate. Take lots of electives! If a class excites you, it’s a good class to take.