Many entrepreneurs are unaware of the sales power and influence that arise from conveying a genuine smile. Poet Emily Dickinson nailed it more than a century ago when she wrote, “They might not need me -- yet they might -- I’ll let my Heart be just in sight -- A smile so small as mine might be precisely their necessity.”

Though she was a poet and not an entrepreneur, Dickinson understood the power of the smile. She may have not understood the science that makes smiling such a valuable business asset, but she no doubt observed good things when she expressed a genuine smile.

Related: Smiling Is Contagious. Customers (and Your Business) Thrive on It.

About 100 years after Dickinson’s death, scientists began to formally study the power that a smile confers on the closing of a deal. Researchers have conducted many studies over the years and repeatedly have found a strong correlation between smiling and positive business outcomes. Scientists have named this phenomenon the emotional contagion.

In a business setting, emotional contagion means a prospect might be influenced by the emotion of another person. In other words, if an entrepreneur is making a pitch and genuinely smiling, his or her positivity and warmth will be conveyed to the other party, improving the odds for closing a deal.

Understanding this gives additional weight to the phrase “put on your game face.” Armed with this information, entrepreneurs conducting face-to-face meetings might be able to positively influence outcomes by being certain to port a genuine smile throughout their entire interaction with a prospect.

Unfortunately, not just any smile will suffice. Researchers found that emotional contagion occurs when the person smiling displays a genuine smile, also known as a Duchenne smile.

“The Duchenne smile involves both voluntary and involuntary contraction from two muscles: the zygomatic major (raising the corners of the mouth) and the orbicularis oculi (raising the cheeks and producing crow's feet around the eyes),” according to Adoree Durayappah in Psychology Today. “A fake smile or, as I like to call it, a ‘Say Cheese’ smile involves the contraction of just the zygomatic major since we cannot voluntarily contract the orbicularis oculi muscle.”

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Therefore, an entrepreneur can aim to induce the wrinkles at the corner of the eyes that produce the crow’s feet effect. This improves the odds of achieving the meeting's objective.

But entrepreneurs should be forewarned: Emotional contagion works in many ways. Studies have also found that individuals frowning or exhibiting indifference will struggle to close a deal. Just as a genuine smile warms a prospect’s heart, a frown or other adverse facial expression has the opposite effect.

Guy Kawasaki addresses emotional contagion in his book Enchantment: “Smiling sends a very clear message about your state of mind, not smiling creates an opening for many interpretations, including grumpiness, aloofness, and anger.” In essence, a genuine smile tells a prospect that you are happy to visit, know what you’re talking about and love what you’re doing!

Kawasaki offers a simple tip for generating the Duchenne smile: Think pleasant thoughts. Those who struggle to generate a genuine smile prior to a meeting should think of a positive mood changer: a kiss from a spouse, a hug from a child, scoring the winning run in a softball, or anything else that induces a warm and fuzzy feeling. That feeling generates the genuine smile that will warm up a prospect and improving the odds of closing the deal.

A June study published in the Proceedings of the National Academy of Sciences of the United States of America documented similar outcomes for communicating on social networks. Specifically, the researchers found after observing Facebook users that “emotional states can be transferred to others via emotional contagion, leading people to experience the same emotions without their awareness.”

So not only should entrepreneurs genuinely smile when meeting people face-to-face, but they should also express themselves positively on social networks and the Internet to warm prospects' hearts.

Smiling during a sales call is common sense. At times, however, a personal or professional issue might get the best of an entrepreneur.

But a business executive must do everything in his or her power to generate a genuine smile when meeting with prospects. Failing to do so could compromise a deal -- and that's nothing to smile about.

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