Dr Tehrani, who has previously studied cultural change over generations in areas such as textiles, debunked theories that the tale emerged in China, arriving via the Silk Route.
Lakes, ponds, parks and shopping centers are denoted, and the Web site shows additional information on several downtown areas that the index has previously studied, including libraries, bars and restaurants.
Brown has always been interested in the meanings of objects and their cultural values – she has previously studied Tupperware and the idea of the housewife – so "sunglasses seemed like an ideal next project", she says.
Harrison, who has previously studied the evolutionary origins of mass murder, began by compiling a list of American female serial killers, which she defined as women who had killed three or more people with at least a week between each death.
Lena Edlund, an economist at Columbia University who has previously studied how the Trivers-Willard hypothesis fits with social status, says Pollet's methods are sound and that wife rank seems to be a good measure of women's status.
Space agency Nasa has previously studied the phenomenon and has announced plans to install a light-colour changing system of its own into the International Space Station (ISS) in 2016.
