Cheerful people are trustful - this is something already recognized.

But now a new research said that, in a few cases, individuals may truly be less trusting of others when they are happy.

Robert Lount, author of the study and assistant professor of management and human resources at Ohio State University''s Fisher College of Business said, "A person's mood may determine how much they rely on subtle - or not so subtle -- cues when evaluating whether to trust someone."

In five separate trials, Lount discovered that people in an optimistic mood were more likely than those in a neutral mood to follow signals or stereotypes when deciding whether they should faith someone.

If you are predisposed to faith an unfamiliar individual - as he belongs to the same society as you, or he has a "honest" face -- a joyful mood makes you even more likely to faith him completely.

However, if you are predisposed to not faith him, a happy mood will make you even more suspicious than usual.

Lount said, "I think the assumption is that if you make someone happy, they are going to be more likely to trust you. But that only works if they are already predisposed to trust you."

"If you''re a professional meeting new clients, you may think if you buy them a nice lunch and make them happy, you''re building trust. But that can actually backfire if the client has some reason to be suspicious of you," he said.

The results of the research appeared in the March 2010 issue of the Journal of Personality and Social Psychology.

All 5 trials involved undergraduate pupil who participated in different scenarios in which they were put into optimistic or neutral moods, and were then given the chance to show faith or doubt toward an outsider.

The outcomes were impressing: partakers in a happy mood assessed the person with the trusty features as more trustable than did those in a neutral mood.

On the other hand, the joyful people were more suspicious of the person with unreliable features than were those in the neutral mood. (With Input from Agencies)