Mark Zuckerberg: Glad to be grey / AP

Facebook's Mark Zuckerberg wears the same T-shirt every day to avoid wasting time on 'silly' decisions. Could we all unlock extra brain power this way, asks Simon Usborne

Search for photos of Mark Zuckerberg and a shot from his family album leaps out of a sea of grey. The five-year-old proto-billionaire sits, grinning at the camera, wearing a brightly patterned short-sleeve shirt, trousers held up with braces and a broad pink tie. As the Facebook founder ages, however, the colour fades to a now familiar grey.

Zuckerberg has talked about his uniform of jeans and T-shirt before, praising the makers of The Social Network, the Oscar-winning film about him, for their attention to at least this detail. But after revealing that he had been hurt by other "made-up stuff" in the film, the 30-year-old has explained for the first time the thinking behind his lazy wardrobe.

"You'll be happy to know that there are multiples of the same shirt," he said at a Q&A at Facebook HQ in California (in 2012, he said he kept about 20 of the T-shirts in a drawer). "It's a simple question but it actually speaks to how we think about our duty to the community here… I'm in this really lucky position where I get to wake up every day and help serve more than one billion people, and 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."

Zuckerberg, whose estimated net worth of $33bn (£20bn) is more than double the global annual sales at Gap, where he may or may not buy his T-shirts, went on to say that making even small decisions about the little things – what we wear or have for breakfast – "makes you tired and consumes your energy."

Turns out he's right, and far from the only successful figure who saves valuable brain space by dismissing trivial decisions. For some, including Steve Jobs (polo neck), Bono (sunglasses), Tom Wolfe (white suit), and Homer Simpson (white T-shirt, blue trousers), sartorial monotony becomes part of a personal brand. For others, including Zuckerberg, it's a business plan.

Scientists have devoted a lot of decision-making time to the study of choice, and how it affects performance. Kathleen Vohs, an associate professor of marketing at the University of Minnesota, asked shoppers a series of questions about the decisions they had made that day. She found that the more time given to decision making, the worse they did in a simple maths test.

Barry Schwartz, a professor of psychology and the author of the 2004 book The Paradox of Choice: Why More Is Less has likened the brain to a muscle. "The mere act of thinking about whether you prefer A or B tires you out," he told the Los Angeles Times. "So if I give you something else that takes discipline, you can't do it – you'll quit faster. If I have lifted weights in a gym, later trying to lift a 30lb weight is impossible."

President Barack Obama is of the Zuckerberg school, and cited some of the above research in a 2012 interview in Vanity Fair. "You'll see I wear only grey or blue suits," he explained. "I'm trying to pare down decisions. I don't want to make decisions about what I'm eating or wearing. Because I have too many other decisions to make."

Albert Einstein is widely reported to have worn the same grey suit for similar reasons, although photos of him in his dotage reveal his discovery of the grey sweatshirt.

If time is money, then dressing up rarely pays. Zadie Smith once said that Virginia Woolf had joked that "the amount of time women spent getting dressed... they could learn Greek". Or lead Germany, perhaps. Angela Merkel is rarely seen wearing anything but the same trouser suit, albeit in a selection of colours. In 2011, she presented a framed copy of a front page of the Frankfurter Allgemeine newspaper to the then US Secretary of State, Hillary Clinton. A photo revealed a below-neck glimpse of the women alongside each other, wearing comparable outfits, alongside the text, "Which one is Merkel and which one is Clinton?"

These giants of public life are concerned about decision fatigue, as it's known. And it can be more than bad for business or the state of a nation. A study of more than 1,000 court cases in Israel conducted jointly by a university in the country and Stanford University in America showed that judges gave prisoners parole 70 per cent of the time early in the day, but only 10 per cent of the time later in the day (when tiredness subconsciously compelled them to take the easier route – to let the prisoner go).

Yet judges presumably spend very little time considering what they wear before they go to court. And while saving our brains for the big stuff can only help, will it lead us to riches or the White House? Would Obama still be smoking marijuana on a beach on Hawaii had he not pared down his wardrobe? Would Zuckerberg be a dot-com dropout had he kept wearing that pink tie? It's a question that neither man could answer.