On-line games featuring virtual worlds could become a venue for medical and sociological experiments which bypass regulations on human research subjects. Recently, education researchers at UCLA wanted to study how a disruptive event affected an on-line community. They released a virtual epidemic with a virtual disease called Whypox. It swept through an educational online site for 8 to 16-year-olds called Whyville, which supposedly has 2.7 million participants.

A more full-blooded experiment took place in the violent game World of Warcraft. A deadly virus dubbed Corrupted Blood left millions of corpses strewn over the virtual landscape. Characters fled the scene, taking the disease with them.

A recent article in the leading journal Science highlighted games' "great potential as sites for research in the social, behavioural, and economic sciences, as well as in human-centred computer science". In the past, many experiments used to be done without seeking the consent of participants, but "those days are gone," says author William Sims Bainbridge. But now scientists might be able to use on-line worlds to understand how humans react in crises.

Naturally, these environments are far from ideal for scientific surveys -- the stakes in the game are so low that participants can behave recklessly and most of them are men. However, scientists are hopeful. University of Indiana economist Edward Castronova, one of the first to study on-line games in depth, says that they could model government policies. "Down the road, you might have a situation where every government maintains a whole bunch of virtual worlds, trying out variations on its policies to see how they work."