Upon Further Reflection. Chapter 11:Can the Experimental Analysis of Behavior Rescue Psychology?. Quote 9

Another source of misunderstanding of the relation between operant conditioning and natural selection is the strong inclination to look inside a system to see what makes it tick. Those who use operant conditioning are criticized when they refuse to do so . . .  I am sure there are mechanisms, but they belong to a different discipline – physiology. (p. 170)