You must have heard about Duchenne smile, also known as genuine smile. It was discovered by a French physician Guillaume Duchenne, who studied the physiology of facial expressions and found that a genuine smile involves contractions of the zygomatic major muscle, which raises the corner of your mouth when you laugh or smile. He also found that there is a contraction of muscles around the eyes known as orbicularis oculi, which crinkles the eyes making crow’s feet around them. This kind of smile has a better effect on the brain and produces better feelings.
In Laughter Yoga, we laugh on purpose as an exercise, which has its own benefits, but with my experience, I found that if you crinkle your eyes while laughing, you can enjoy the laughter in a much better way. I deliberately cultivated this laughter, which over a period of time became a part of my conditioned reflex. If you try crinkling your eyes deliberately while doing laughter exercises, you will notice a better effect.
I have named this laughter as Duchenne Laughter although there is no official terminology like this. To see the demonstration of this laughter, have a look at this video: