I am personally a big believer in majoring in fields outside of design. In industry, you're designing for non-designers but studying design and doing design for 4 years. This will certainly help hone your craft but could narrow your world view. I recently interviewed 15 students in design who mostly, if not all, did not major in design. More at http://www.studentswho.design. Below are some majors, classes and departments that trended from those interviews and that I've found useful:
What better way to design for humans than to learn everything about humans? Learning about the evolution of language and culture is not only interesting, but beneficial to see how current technology patterns will change these traditions.
Understand how a business functions, economic trends, and consumer behavior. While your role is a designer, you function within a business - whether its your own or someone else's. Basic finances can save your own business and carry over to your personal life as well.... See more
Other than the obvious benefits of being able to speak with engineers, computer science teaches you a different way of thinking and rationalizing problems.
Probably the most similar to digital product design, but fine arts (film photography, painting, drawing) forces you to move slowly and be extremely intentional within fine detail. I took a film photography class that I spent about 30+ hours a week on. While tedious, the benefits definitely carry over to my daily work.... See more