We have had an operant-conditioning rat lab associated with either our Experimental or Introductory Psychology course at Western Michigan University since 1964. Many students report that the rat lab is very exciting and that they find it the best feature of our course. It has been our impression however that this lab has an even more important effect. The experience of directly modifying the behavior of another organism is a primary factor in demonstrating to students the power and validity of the basic principles of behavior.