The Oxford Dictionary defines the slang word “cool” as fashionably attractive or impressive.

Being called cool is considered a compliment since so many people are hoping to give such an impression.

One area where people try their hardest to “look cool” is in their photographs.

According to University of Arizona Professor Caleb Warren, for many years it was thought that the idea of looking cool always meant looking detached, indifferent or unemotional.

But his new study suggests a nice smile could make the difference in how a person is perceived as “looking cool.”

Warren’s team showed volunteers two pictures of the same person – one smiling the other not smiling.

The researchers then asked their subjects to rate just how cool or “uncool” each version of the photo was to them.

It turns out that their volunteers thought the unsmiling photos appeared less cool than the versions where the subject was smiling.

The study was recently published in the Journal of Consumer Psychology.

So, according to Warren’s findings, if you want to look cool in your selfies – smile!