The researchers asked people how much they would like to buy objects that had been owned by different celebrities, including popular ones like George Clooney and pariahs like Saddam Hussein. People’s affection for the celebrity did not predict how much value they assigned to the memorabilia — apparently they were not buying it primarily for the pleasant associations.

Nor were they chiefly motivated by the prospect of a profit, as the researchers discovered when they tested people’s eagerness to acquire a celebrity possession that could not be resold. That restriction made people less interested in items owned by villains, but it did not seriously dampen their enthusiasm for relics from their idols.

The most important factor seemed to be the degree of “celebrity contagion.” The Yale team found that a sweater owned by a popular celebrity became more valuable to people if they learned it had actually been worn by their idol. But if the sweater had subsequently been cleaned and sterilized, it seemed less valuable to the fans, apparently because the celebrity’s essence had somehow been removed.