Observer (OB) and demonstrator (DM) mice are placed in separate chambers and allowed to adapt to the new environment for 5 minutes. Soon afterward, the DM mouse shows pain and panic reactions due to repeated mild foot shocks. OB does not receive the shocks, but witnesses the DM's behavior through the transparent plastic wall that separates the two cages, and starts to behave in the same way empathetically. Panic is expressed by immobility (freezing in place). The next day, when the OB mouse is placed in the same chamber it continues to express its fear, even in the absence of the DM. This type of social fear test is correlated to human affective empathy.