I’ve had plenty of jobs with a variety of different dress codes—but only one was truly casual. For the first time in my career, I could wear a T-shirt and shorts on a hot summer day or rock a beanie all through winter. I’ve never tried on yoga pants but according to my female co-workers, they’re incredibly comfortable.

I met my father after work on a particularly schlubby day and he asked “don’t you care about your job?” It got me thinking: Do casual clothes lead to a casual attitude, and in turn, less productivity? If you’re always dressed in “play mode,” is it harder to be focused, alert and productive?

 

Enclothed Cognition

Whenever I’ve worn a suit and tie during my career, I felt more powerful, engaged, and likely to succeed. My actions seemed more decisive and my concentration more focused. Was that just some kind of placebo effect?

Apparently not. Adam Glinsky, professor at the Columbia Business School found that clothing does, indeed, affect performance. He ran a simple experiment giving subjects an attention test. Some were told to wear a white doctor’s lab coat while taking the test, others just wore their normal clothes. The group wearing the lab coat performed much better on the attention test and made half as many errors. He also gave the same coat to another group of participants but called it a painter’s coat. With less gravitas attached to the clothing, the painter’s coat wearers got nowhere near the results that the doctor’s coat wearers did.

Why? It’s what Glinksy calls “enclothed cognition”—clothing influencing performance. If you feel confident in the doctor’s coat, you’re likely to try harder, and perform better, at a specific task.

In another study, a University of Hertfordshire psychology professor asked her students to wear a Superman t-shirt—and they rated their strength and likeability higher than students in a control group. It’s clear, clothing doesn’t just create an impression for the outside world, they affect the wearer too.

 

Business Casual… You Mean Old People Clothes?

Despite the research, the pendulum has swung towards casual dress and doesn’t show signs of stopping. It all started in 1970s and 80s era Silicon Valley, when companies put efficiency above all other metrics.

“It was very inefficient to ask people to work 17-hour days in pantyhose, ties or even a sports coat,” said Deirdre Clemente, associate professor of history at the University of Nevada, Las Vegas and the author of Dress Casual: How College Kids Redefined American Style.

As Silicon Valley churned out hoodie-clad billionaires, casual clothes became part of a successful image. Today, major players like Apple, Google and Quicken Loans have casual dress codes. That’s trickling into traditional companies too as JP Morgan, IBM, BlackRock, Goldman Sachs and General Electric have recently relaxed dress codes restrictions. Why? Because Silicon Valley culture has gone mainstream and relaxed dress codes are a way to attract millennial top talent.

It puts employers in a tough position. They want to give workers the casual environment they crave but still maintain their corporate image.

“They have an idea of how they want their employees to present themselves to the world—and a hoodie and dirty pajama bottoms usually don’t fit into that,” said Clemente. “I feel for employers who struggle to strike balance between keeping their casually dressed employees happy and maintaining what they consider to be a professional environment.”

All experts I spoke with for this story recommended not having a dress code at all. But if you must, be sure to avoid implicit gender bias.

“If they have a laundry list of rules for female-identifying employees but only tell the men to ‘dress professionally,’ that’s a problem,” said Mirande Valbrune an employment lawyer and author of #MeToo: A Practical Guide. If on its face, the policy is equally burdensome on all employees but female employees are the only ones being disciplined for violating the code, that’s another problem.”

 

A Happy Medium

Penji, a graphic design startup in Camden, N.J., may have found a happy medium for its 33 employees. When employees asked for a more casual environment, leadership came up with a great alternative: Dress in what makes you confident. That led plenty of employees to wear T-shirts and jeans. Some women stopped wearing makeup. Still others keep it more formal. One man continues to wear a suit and tie. It’s simple: Do you.

“If you can take away that element of stress they might have throughout their day, we see that as a way to increase productivity,” said Johnathan Grzybowski, co-founder of Penji.

Still, Grzybowski says that companies should be careful to put too much emphasis on dress code. In his view, there are far more important aspects of a company culture.

“If your selling proposition is that you can wear whatever you want, I would argue that there are other areas of your company culture lacking,” said Grzybowski. “I’ve seen recruiters at job fairs talk about the casual dress code before anything else. It’s important, yes, but I think a lot of employees want stability, job growth, moving up in the company and working for a reliable team. That’s more important than the dress code.”