They’re aversive. They’re arousing. They’re fairly well-remembered. They’re negative political ads, and one researcher has found scientific evidence that they do have a physiological and psychological effect on voters. American voters should get ready to feel uncomfortable and remember a lot of mudslinging sentiments — even if they’re incorrect, according to the researcher. “The question was simple.” he said “Are negative political ads unpleasant enough to engage a person’s emotional circuitry? The data show that negative ads do indeed engage emotional circuits involved in helping humans avoid unpleasantness.”