1. any action that generates a response that provides the stimulation for repetition of the action, often such that responses increase in intensity and duration. An example is the contraction of a muscle that sends a nerve impulse toward the brain or spinal cord, which in turn sends a nerve impulse back to the muscle to maintain the contraction. Also called circular reflex.

2. in Piagetian theory, repetitive behavior observed in children during the sensorimotor stage, characterized as primary, secondary, or tertiary circular reactions. The primary phase involves ineffective repetitive behaviors; the secondary phase involves repetition of actions that are followed by reinforcement, typically without understanding causation; and the tertiary phase involves repetitive object manipulation, typically with slight variations among subsequent behaviors.

3. in the analysis of crowds and collectives, repetitive behavior that produces behavioral contagion as individuals imitate others’ actions without considering the meaning or consequences of those actions.