“The effect of punishment, however, seems reasonably well explained in [The Behavior of Organisms]. When a response is followed by, say, a shock, an emotional reaction to the shock is conditioned according to Type S [Pavlovian] conditioning. Approaching the lever elicits such a reaction, which reduces the strength of lever pressing. I could have added that incompatible behavior would also be strengthened by any reduction in such a conditioned aversive stimulus and would oppose the occurrence of the behavior punished.” (p. 127)
