More fascinating facts you never knew about smiling:
One smile can give the same level of brain stimulation as 2000 bars of chocolate.
Smiling can be as stimulating as receiving £16,000 in cash.
When you smile others think you are more competent.
Unborn babies smile.
Your smile can be a predictor of how long your marriage lasts.
Read more from Ron Gutman on the power of the smile.