Social facilitation of responses during a stimulus paired with electric shock.

Key-pecking responses of a pigeon were maintained by a variable-interval schedule of food reinforcement. The responses were suppressed during the occasional presentation of a warning stimulus paired with electric shock. The presence of a second pigeon emitting the same response for food reinforcement reduced the suppression that otherwise occurred during the warning stimulus when the second pigeon was absent. These results reveal that the social facilitation phenomenon can be used to restore behavior that is suppressed by a conditioned aversive stimulus.