In a real smile, a muscle called the orbicularis oculi is activated, creating a hard-to-fake crinkling around the eyes. For example, telling a fake smile from a real one can be difficult, but if the smiler is wearing shades then detecting the sham smile is almost impossible. Not being able to see a person's eyes greatly reduces our ability to infer his or her emotions.

Shades may slightly obscure your view of the world, but they also hide the world's view of how you are feeling. Psychologist Paul Ekman, an authority on facial expressions, says that of the 23 facial expressions relating to human emotion, about one-third involve the eyes. Justice is blind, but the dark glasses help all the same.

Such shades were also popular with China's judges, because they hid any emotional response the judge might exhibit while listening to testimony. Our earliest accounts of sunglasses come from 12th century China, where some individuals from among the aristocratic classes reportedly wore glasses with smoky quartz lenses to protect their eyes from the bright sunlight. Luxottica, the world's largest eyewear company, offers Burberry, Oakley, Ray-Ban and many more sunglass brands the firm's global sales were over $7 billion (Dh25.7bn) last year. It is no coincidence that designer sunglasses have one of the highest profit margins of any product. Worn equally by men and women, shades can simultaneously say we are cool, mysterious, intimidating, anonymous.

Part fashion accessory, part eye protectors, part disguise - sunglasses are ubiquitous. But now I live in the UAE, a land of almost perennial brightness where sunglasses are really a necessity.Д«ut they are also more than a practical accessory: perhaps more than any other item of apparel, sunglasses have a psychological story to tell. When I was growing up in the cloudy north of England, we didn't often need sunglasses.

Alternate word for hiding emotions