orbicularis

Also there is a lot of mimic signals except mouth area muscles tension, especially orbicularis oculi tension, that subconsciously telling that we are smiling.

And even if you can voluntarily contract your orbicularis oculi, you'll need to have the proper onset/offset times and constant intensities for muscle contraction, which are just as hard to fake and easy for a trained observer to spot.

Carrying on with this, I've gone on to train to wiggle my ears, arch eyebrows independently(still can only do it on the left side), and to deliberately control my orbicularis oculi muscles which comes in really handy to make a posed smile look warm and natural..

"Without access to someone's internal mind-state, you cannot reliably tell the difference between a feigned response and a genuine one." Orbicularis oculi.

Interestingly, wikipedia says "In conjunction with orbicularis contraction, the mentalis muscle allows the lips to 'pout.' Externally, mentalis contraction causes wrinkling of the chin skin, as used in expressions of doubt or displeasure.

"But we now know that most people – around 71% - can voluntarily contract the inner portion of the orbicularis oculi." I can't find the source for this anywhere online.

"Without access to someone's internal mind-state, you cannot reliably tell the difference between a feigned response and a genuine one." Orbicularis oculi.

Interestingly, wikipedia says "In conjunction with orbicularis contraction, the mentalis muscle allows the lips to 'pout.' Externally, mentalis contraction causes wrinkling of the chin skin, as used in expressions of doubt or displeasure.

"But we now know that most people – around 71% - can voluntarily contract the inner portion of the orbicularis oculi." I can't find the source for this anywhere online.