Facebook co-founder and CEO Mark Zuckerberg doesn't wear his signature gray tee simply because he loves the style. Nor does self-made billionaire John Paul DeJoria have a particular affinity for his all-black clothes.
It turns out there's a scientific reason the billionaires routinely wear the same thing. By sticking to a kind of uniform, they're avoiding a phenomenon known as decision fatigue, which describes the way choices become harder and harder as a day goes on and your finite store of energy gets depleted.
As Zuckerberg said during a public Q&A session in 2014, "I really want to clear my life to make it so that I have to make as few decisions as possible about anything except how to best serve this community. ... I feel like I'm not doing my job if I spend any of my energy on things that are silly or frivolous about my life."