Before 2012, most online dating services matched people according to their autobiographical information, such as interests, hobbies, future plans, among other things. But the advent of Tinder that year meant that first impressions could play a crucial role. For social scientists studying human courtship behavior, Tinder offers a much simpler environment than its predecessors. In 2016, Gareth Tyson of the Queen Mary University of London and his colleagues published a paper analyzing the behavior of Tinder users in New York City and London. In order to minimize the number of variables, they created profiles of white heterosexual people only. For each sex, there were three accounts using stock photographs, two with actual photographs of volunteers, one with no photos whatsoever, and one that was apparently deactivated. The researchers pointedly only used pictures of people of average physical attractiveness. Tyson and his team wrote an algorithm that collected the biographical information of all the matches, liked them all, then counted the number of returning likes.