Psychologists at the University of Toronto have found that immoral behaviour triggers the same physiological reactions that enabled early humans to stay away from poisonous foods and infection. The study–published this week in the journal Science—is one of the first to discover that morality has biological roots linked to primitive survival. The study asked participants to drink foul-tasting liquids and look at pictures of filthy toilets, feces or injuries while the disgust and repulsion in their facial expressions were measured by electronic sensors. The volunteers were equally disgusted when they were cheated in games involving money. While researchers say moral disgust doesn’t actually taste bad, it does affect the same neural circuitry as when you taste something foul.