In conditioned suppression, a previously neutral stimulus (e.g., tone, light, etc.) is paired with an aversive US such as an electric shock. After several pairings, the originally neutral stimulus becomes a conditioned aversive stimulus (C-Save). Once the CSave has been conditioned, its onset suppresses ongoing operant behavior. A rat may be trained to press a lever for food. After a stable rate of response is established, the CSave is introduced. When this occurs, the animal's lever pressing is suppressed.