TABLE 2

Taxonomy of pain behaviors and associated examples

Type of Behavior	Notation	Preclinical Examples	Clinical Correlates
Unconditioned behavior: US→UR	PS→UR	Stimulation of withdrawal responses, writhing, flinching, grimacing	Same
Unconditioned behavior: US→UR	PS→[US→UR]	Depression of locomotion, feeding, wheel running, burrowing, nesting	Impaired physical functioning
Classically conditioned behavior: CS+US; CS→CR	PS+CS; CS→CR	Conditioned place avoidance; fear conditioning	Avoidance, anxiety, fear
Classically conditioned behavior: CS+US; CS→CR	PS → [US+CS; CS→CR]	Conditioned place preference to putative analgesic treatments	Placebo analgesia
Operant behavior: S^D→R→S^C	PS→R→S^C	Discrimination of a noxious stimulus	Verbal reports of pain intensity or quality
	S^D→R→PS	Punishment with a noxious stimulus	Movement-induced pain
	PS→[S^D→R→S^C]	Depression of operant responding for food or brain stimulation	Impaired physical functioning