Design has to be done for people, so yes it requires Psychology, Business, Marketing and a lot of other things. I don't we can do an equation like this.
I suspect business and marketing, whose main purposes are to improve income (by various means) shouldn't be as much a part of the UX Design puzzle as the business sector tries to make them. They certainly have little to no part of open source UX.
By "psychology," I'm not just referring to the academic field, but to the larger set of understanding how humans think, behave, and respond, as well as the broad spectrum of needs they may have while interacting.
So, while it may not be the entire equation, I still say that the majority of UX design is "what looks good" plus "what does the user need"? Ergo, design + psychology.
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