Parasites brainwashing their hosts — it sounds like something straight out of science fiction. But this is no zombie movie, this is a fascinating new field of study. Scientists have collected hundreds of examples of brain-manipulating parasites. Researchers are starting to untangle how these parasites have evolved to control their victims, whether caterpillars, fish, birds, rats, cats — or humans! And at least one scientist hypothesizes that a parasitic infection may explain some of the differences between different human cultures.