The speed of your smile can shape the first impressions others have of you, according to a new research.

But smiling too quickly can lead others to think that you are insincere, while slow grins appear more genuine.
As part of the research, a team of business advisors examined how smiling can give clients a positive impression. They discovered that a smile, which appears too swiftly and does not extend to the eyes can sends signals that you lack sincerity.
They found people should avoid three types of grin:
The Enthusiast: A huge smile showing all of your teeth and wide eyes can be overbearing.
The Big Freeze: A constant, practiced smile that lacks sincerity.
The Robot: A tiny, polite smile that doesn’t display warmth.
“Studies show people perceive a slower, natural smile which floods the entire face to be more genuine,” the Sun quoted Lesley Meechan of the Glasgow-based Go Group as saying.
Psychologist Bridget Hanna added: “Smiling all the time appears over-pleasing and lowers your status.”