A fake smile actually uses different muscles than a real smile. Since a real smile is involuntary and a fake smile is deliberate, different portions of the brain control the muscles used for each. The muscle responsible for drawing the corners of the mouth outwards, zygomaticus major, is active in both a real and a fake smile, but additional muscles are involved in real smiles. When a person genuinely smiles, the orbicularis oculi and the pars orbitalis contract in addition to zygomaticus major, causing the cheeks to raise and the skin around the eyes to crease.