According to a study, the first things people notice when meeting someone are their smile (47%), eyes (31%), smell (11%), clothes (7%), and hair (4%). There are two types of smiles: a posed or social smile which is static, sustained, and voluntary without squinting of eyes, and an emotional smile which is dynamic, not sustained, and involuntary with squinting of eyes present. Important smile characteristics include the smile arc, lip line, buccal corridors, frontal occlusal plane, gingival display, gingival margin levels, dental alignment, tooth color, gingival shape, and symmetry.