Contagion Bias

We attribute magical contaminating properties to objects that have been in contact with something repugnant — even when the contact was harmless and the contamination is physically impossible.

• A sweater that once belonged to a convicted murderer, cleaned perfectly, still feels repulsive to almost everyone.
• People refuse to drink juice that has been briefly touched by a thoroughly sterilized cockroach — even knowing it is completely clean.
• A house where a violent murder occurred sells for significantly less than comparable homes — even after full renovation, the 'contamination' persists.