Nonverbal communication of affects was studied experimentally in rhesus

monkeys. A group of monkeys was conditioned to avoid an electrical shock by pressing a bar as soon as the stimulus monkey was seen through a one-way screen. This conditioned response was then extinguished. Later the test animal was again exposed to the stimulus animal but this time the stimulus animal received the electric shock and the test animal could stop it by pressing its own bar. Observing the affective response of the stimulus animal caused the test animal to respond as if frightened and to react appropriately by pressing the bar. This resulted from the memory of its own previous experience coupled with the visual stimulation of an affect; thus it could be shown conclusively that a communication of affect between the animals had occurred. This type of behavior relates to the phenomenon of empathy as conceived by Freud.