Pleasure

Positive emotional states in humans are measured by facial/vocal displays (e.g., Duchenne smiling and laughter), approach behavior, and subjective self-report of feeling states. In laboratory animals, only facial vocal displays along with approach/avoidance behavior can be measured. Conditioned place preference is a sensitive measure of positive affective states in animals. In laboratory rats, frequency-modulated 50-kHz ultrasonic vocalizations (USVs) indexes an appetitive pro-social positive affective state, and hedonic taste reactivity indexes consummatory pleasure. Offensive aggression, predation, and exercise have also been shown to induce positive affective states in laboratory animals as measured by conditioned place preference.