Cumulative Record. Chapter 11: Reinforcement Today. Quote 11

The fact that it is the combination of schedule and performance which generates reinforcing contingencies can easily be overlooked. A physiologist once asked to borrow one of our apparatuses to show his class the behavioral effects of certain drugs . . . When one [pretrained] pigeon died through an overdose of a drug, the physiologist simply bought another pigeon and put it into the apparatus. To his surprise, nothing happened. (p. 169)