Sam A. Golden and his team carried anexperiment about the compulsive addiction-like aggressive behavior in mice. Intheir experiment, they trained older mice to lever press for opportunities topunch younger mice. They then tested them for relapse to aggression seekingafter forced abstinence or punishment-induced suppression of aggressionself-administration. In result, these older mice showed strong motivation toacquire operant opportunities to aggress, which means violence is addictive.