Interactions in multiple avoidance schedules

From a discussion of theories of behavioral contrast, it was concluded that earlier theoretical treatments of the topic, such as Reynolds' reinforcement frequency hypothesis, Terrace's response suppression hypothesis, and Bloomfield and Premack's preference theory of contrast were insufficient. A more recent theory, additivity (or response summation)theory was considered to put too much emphasis on pigeons as subjects. The first experiment therefore attempted to obtain behavioral contrast using another species,(rats)another response(two-way shuttle)and another type of reinforcement(negative). Behavioral contrast was not observed, but the obtained negative induction could be explained by an additivity theory. An attempt was then made to determine under what conditions of relative shock density behavioral contrast would occur. Although day to day variations were high, obscuring long-term trends, neither behavioral contrast nor negative induction were suggested by the results, despite both increases and decreases in shock rate in the S1 component being used. The original studies showing multiple schedule interactions with negative reinforcement were then discussed, and it was concluded that a recent demonstration of contrast by de Villiers may well be a misinterpretation of the results obtained. The significance of the findings for the field of behavioral contrast was discussed, with implications for future research pointed out