Quantitative acquisition of preference studies with nonhumans essentially began in the early 1980’s (e.g., Commons, Woodford, Boitano, Ducheny, & Peck, 1982;Hermstein, 1982; Hermstein& Vaughan, 1980;Myerson&Mizzen, 1980). In preference studies, organisms select among schedules of reinforcement by

either responding on one operandum (key) more often than on others or by responding on an operandum that selects one of the schedules. The reinforcement schedules deliver reinforcers (SR+) to the organisms based upon some rule, for example, following the first response (R) after one minute has elapsed since the last reinforcer had been delivered (Fixed Interval, FI). In the late 1980s there have been a few such studies (Myerson & Hale, 1988; Vaughan & Hermstein, 1987). Preference experiments, in which organisms make real choices and experi­ ence real outcomes form an even smaller subclass of such studies (e.g., Bailey, 1988; Bailey & Mazur, submitted; Commons, Woodford, Boitano, Ducheny, & Peck, 1982; Myerson & Mizzen, 1980). Corresponding theories and experimental results are so few that a fairly detailed history of them is possible.