If you like X, you also like to hear Y
Never before has a person's identity been more important than in the age of the internet and the "war on terror". And never before has it been questioned so often. That's why researchers are constantly developing new variants of how we can prove that we really are us. For example with the music collection on our MP3 player.
In truth, of course, the physicists Renaud Lambiotte and Marcel Ausloos from the University of Liège did not intend to develop identity checks based on musical taste. But who knows whether their results might one day fall into the hands of overzealous security ministers and give them musically stupid ideas. After all, in the age of MP3 players with gigabytes of memory, users create individual collections of tracks that they have downloaded from the Internet and the combination of which would give most other people a cold ringing in their ears. A musical signature, so to speak - and something like that is in demand in certain circles.
The Belgian researchers were more concerned with the question of how interconnected the sounding cosmos actually is and whether its individual parts can actually be classified in the classic categories such as pop, rock or jazz. Material galore provided them with a website where users can set up a personal virtual music closet with whatever they like. As an added service, the site sometimes suggests pieces from other users' closets that might somehow suit the surfer's tastes. In January 2005, which the scientists were allowed to use, data came from 35,916 users and 617,900 music groups. For chart enthusiasts, it should be said straight away: Radiohead, Nirvana, ColdPlay, Metallica and the Beatles were at the top.
Lambiotte and Ausloos analyzed this mess using the methods of the theory of complex networks. First, they connected all users who had at least one piece of music by the same artist in their list. They then ran an increasingly strict filter over this highly ramified network. The criterion was how similar the total collections of the people were.
The result was a kind of tree structure with dense tufts that were connected by areas with few connections. It is quite easy to read trends in music consumption from this, even if each user ultimately had their very own mix. And that was mostly more variable than one would expect from the gut. It went right through funk, rock, heavy metal and pop. Against this background, the music industry should ask itself whether dividing it into fairly rigid categories makes any sense at all. In the computer, a pure voice mixes with a crunching guitar anyway.
If you listen to Uriah Heep while driving, you might be able to end the day with Bach at home. Given such combinations, it might be difficult to read a person's character from their "record collection". Checks at the airport will probably continue to rely on face and fingerprints in the future.