APA Dictionary of Psychology

in classical conditioning, the point at which the conditioned response (CR) elicited by a conditioned stimulus (CS) can lead to a paradoxical reduction in the CR. Hans Eysenck applied this concept of a conditioning threshold in his theory of personality, in which he proposed that introverts should respond more strongly than extroverts to conditions of high arousal (e.g., punishment) but that, depending on the interaction between personality and stimulus intensity, the presence of a TMI may result in lower levels of arousal in introverts than in extraverts.