As an attorney, I find that a background in psychology is extremely helpful in understanding people and their possible motivations. It is also very useful in mediation and negotiation. Of course, the Duke pedigree is well-respected and I find that people tend to take me more seriously when they learn that I am a Duke alumni.
A psychology background can be applied to almost any field, especially fields involving human interaction. Don’t limit yourself and your course of study. Instead, ask yourself - Does the potential career that I’m contemplating involve human interaction? If so, then a psychology background will probably be useful.