Human facial muscles can create ten thousand distinct expressions for social signaling

Humans utilize a sophisticated array of facial muscles, such as the zygomaticus major, which can contract in just 0.1 seconds to lift the mouth. This biological system allows for an incredible 10,000 distinct expressions, a stark contrast to the muscle structures of other mammals. Genuine 'Duchenne' smiles are particularly unique, as they require the involuntary crinkling of the orbicularis oculi muscles, a movement that produces twenty percent more alpha waves in the brain compared to forced expressions.