The Structure of Random Ratio Responding in Humans

Four experiments explored the rate and structure of human responding on random ratio (RR) schedules of reinforcement, using 3 different methods of analysis. All experiments demonstrated that responding on RR schedules was higher with intermediate ratio Values rates being higher on an RR-30 schedule than on either a RR10 or RR-60 schedule. All experiments identified 2 distinct types of responding generated by RR schedules: "response initiation" responding and "within-burst" responding. In contrast to overall rates, response initiation responding was greatest on RR I)) schedules, and less pronounced as the ratio value increased, hut response rates did not vary greatly within the burst (being higher on longer ratio schedules when there was a difference). These findings are consistent with previously obtained data from nonhumans, and suggest human schedule performance should be considered as a joint product of 2 different aspects of responding: response initiation responding which is sensitive to rates of reinforcement; and within(burst responding which is less sensitive to the molar characteristics of the schedule in operation. The presence of 2 distinct forms of responding may require reinterpretation of many human schedule-controlled phenomena that rely on assumptions about the similarity of all responses to one another.