The dampened smile is an attempt to control an automatic, happy one and exists because some muscles, such as the ones controlling the mouth, are easier to suppress than others. “The cheeks will be raised but we pull the corners of the mouth downwards or press the lips together, like “I shouldn’t be smiling”,’ says Zara Ambadar, a cognitive psychologist at the University of Pittsburgh.

This is thought to explain why in Japan, where etiquette dictates that emotions are stifled in public, there’s a greater emphasis on smiling with the eyes. Intriguingly, this discrepancy even stretches to the way smiles are typed: vertically, with a flat mouth and squinting eyes, as opposed to dotted eyes with a curved mouth. This ^_^ instead of this : ).

The urge to smile may be universal, but when it’s acceptable to – and how it is interpreted – depends on cultural rules. As usual, Darwin hit the nail on the head, remarking that though facial expressions have been hardwired by evolution, ‘once acquired, such movements may be voluntarily and consciously employed as a means of communication.’

Embarrassed smile

The ‘embarrassed smile’ is identical, though the two are easily distinguished – if not by the flushed cheeks, then the uncomfortable situation which usually precedes it. Another tell-tale sign is moving the head downwards and slightly to the left.

Qualifier smile

From the check-out assistant who watched you queue for 10 minutes, only to tell you sweetly that ‘returns are only available on the fourth floor’, to the receptionist who explains that the next available appointment is in a year’s time, the ‘qualifier smile’ aims to take the edge off bad news.

It begins abruptly, raising the lower lip slightly, and is occasionally accompanied by a slightly downwards and sideways tilt of the head. It’s perhaps the most irritating of all the smiles, since it often traps the recipient into smiling back.