Figure 2. The 3 addiction-like criteria.

A. Persistence to response. Non-reinforced active responses during the pellet free period (10 min), when the box is illuminated and signaling the unavailability of pellet delivery, are used to evaluate the persistence of food-seeking. B. Motivation. The progressive ratio test is used to evaluate the motivation for chocolate-flavored pellets. The responses to earn a single pellet increase exponentially. The maximal number of responses that the animal performs to obtain one pellet is the last event completed, referred to as the breaking point. C. Compulsivity. The total number of shocks in the session of shock test, when each pellet delivered is associated with punishment, is used to evaluate compulsivity-like behavior.