The results of this study are no surprise to those who study body language. People who adopt a smile, particularly a true smile consistent with joy (Duchenne Smile), have lower heart rates and lower anxiety levels - both during and after the stressor. The multiple images of the people shown during the 0:36 - 0:46 segment are genuine, sincere smiles characterized by the cardinal nonverbal signs of partial eyelid closure, a concave up dynamic furrow on the lower eyelids, only the upper teeth visible and a relaxed forehead.
The same study showed that laughter has the added effect of boosting the immune system and relieving pain. Although this particular study was new, these and other similar benefits of adopting positive body language have been well described for decades.
Few people can call up a sincere smile on command (how good are you?) - but it's value is tremendous. For while everyone knows those who are joyful smile, this and other studies show us that the reverse is true - a sincere smile can alter our physiology and lead to true happiness.
Secret # 702: Mouth of Fear, Trying to Smile and Forehead of Pain
Secret # 133: Surprise or Smile or Neither?
Analysis # 2: Body Language of Blake Lively and Penn Badgley Strongly Suggests an Impending Break-up in Near Future
Nonverbal Communication Analysis # 2203: A Body Language Metric of Intimacy and Affection - How Do YOU cuddle?