Cumulative Record. Chapter 49: Pigeons in a Pelican. Quote 4

Something happened during the brief life of Project Pigeon which it has taken a long time to appreciate. The practical task before us created a new attitude toward the behavior of organisms. We had to maximize the probability that a given form of behavior would occur at a given time … We had to discover all relevant variables and submit them to experimental control whenever possible. (p. 646)