Cumulative Record. Chapter 10: The Experimental Analysis of Behavior. Quote 17

By differentially reinforcing high rates of responding, pigeons have been made to respond as rapidly as 10 to 15 responses per second. Here technical problems become crucial . . . The excursions of head and beak become very small, and it is doubtful whether any single “response” can be properly compared with a response at a lower rate. (p. 141)