Laugh lines, sometimes called smile lines, are wrinkles or creases in the skin of a person’s face that appear around the outer corners of the mouth and eyes. Various exercises may help a person ...

All smiling involves contraction of the zygomatic major muscles, which lifts the corners of the mouth. But a Duchenne smile is characterised by the additional contraction of the orbicularis oculi ...

But the researchers have found bottlenose dolphins (Tursiops truncates) have an “open mouth” expression that they use to communicate with each other during play, much like a smile in humans.