Comments on the 1950s applications and extensions of Skinner's operant psychology.

These comments address Laties', Dewsbury's, and Rutherford's papers on the extension and application of Skinner's operant psychology during the 1950s. I begin by reflecting on the papers' overall theme-that the success of behavior analysis lies in its practical applications-and add some comments on Planck's principle. I then turn to the three papers and address such topics as (a) other applications and extensions (e.g., the U.S. space program), (b) relations between the research and researchers at the Yerkes Laboratories of Primate Biology (e.g., a Yerkes' researcher in Skinner's laboratory), and (c) human schedule performance (e.g., continuity and discontinuity with nonhuman behavior). I end with a discussion of the fundamental reason for the success of the extensions and applications of behavior analysis-the experimental analysis of behavior.