It's no surprise that a smile can go a long way in sales pitches. But apparently, the size of that smile has a lot to do with successfully closing the deal. At least that's the findings reached by researchers out of the University of Kansas (KU).

In their study, the researchers examined a host of Kickstarter campaigns. They found that when the founder was smiling broadly in his or her profile picture, the total amount of cash pledged plunged by over 50 percent. If the founder was smiling a little less enthusiastically, the pledge amount only went down by 30 percent.

The thinking is that while big smiles might convey a sense of warmth to consumers, it also gets across the feeling the the person doing the smiling is less competent. And while this certainly comes into play in Kickstarter campaigns, the researcher found that it affects advertising as well.

After showing study participants a series of marketing images featuring people smiling either broadly or slightly, it was determined that in cases where the service being offered was a more serious enterprise with more potential risk involved (say an investment advisor or lawyer), broad smiles could actually backfire. For those ventures, a slight smile seemed to elicit a better response from potential customers.

"If I see an ad with a heart surgeon who smiles really broadly at me, I might think she is really warm but not choose her to be my doctor because she seems less competent than a surgeon with a slight smile," said Jessica Li, the KU assistant professor who led the research. "If the risk is really low, such as going to the store to get a new shirt, then the competence of the salesperson isn't as important and I respond more positively to the broad smile."

One place where a big beaming smile might just be appropriate? Facebook. According to Li's research, profile photos that had big grins got twice as many shares on the social media platform than those showing only a little smile.

The results of the study by Li and her team have been published in the Journal of Consumer Research.