'Multiplex relationships' are those with a variety of contexts, such as being friends with someone in work, as well as outside of it.
Surveying 168 employees and their performance from an insurance company based in the south east of the USA, the researchers found that those workers with multiplex relationships in the company had higher performance than those who did not.
Possible reasons for this were that workers were more willing to seek advice from a colleague who was also a friend, without feeling intimidated.
Moreover friendships in other departments can provide an informal back channel of information.
Another suggested reason was higher morale.
The study did find some downsides - distraction, while not harming actual productivity, could make it more stressful when some time has been spent on chatting instead of working.
In addition, the emotional effort needed to maintain a friendship can be exhausting, compared to the lack of input needed to maintain an impersonal relationship with a colleague.
Moreover, it can make incidents like 'promotions' more stressful, particularly if we feel envious of a colleague.
Why work friendships are different
Work friendships begin differently to other ones, due to the absence of an excuse to communicate.
According to a paper by co-authored by Arthur Aron of the State University of New York at Stony Brook, breaking down communication barriers and awkwardness in a social context takes roughly 45 minutes.
Not in a work environment, where small talk is skipped over as you discuss work, and this means you can more readily segue into personal stuff, fostering friendship.
According to the Atlantic, having a 'work wife' or 'work husband' can be akin to earning $100,000 USD (£77,500 GBP) more annually. in terms of emotional health.
So it seems, unlike at school where you would be separated from your friends in order to be more productive, bosses should encourage work friendships.