BOUTS OF RESPONDING: THE RELATION BETWEEN BOUT RATE AND THE RATE OF VARIABLE-INTERVAL REINFORCEMENT

By nose poking a lighted key, rats obtained food pellets on either a variable‐interval schedule of reinforcement or a schedule that required an average of four additional responses after the end of the variable‐interval component (a tandem variable‐interval variable‐ratio 4 schedule). With both schedule types, the mean variable interval was varied between blocks of sessions from 16 min to 0.25 min. Total rate of key poking increased similarly as a function of the reinforcer rate for the two schedule types, but response rate was higher with than without the four‐response requirement. Analysis of log survivor plots of interresponse times showed that key poking occurred in bouts. The rate of initiating bouts increased as a function of reinforcer rate but was either unaffected or was decreased by adding the four‐response requirement. Within‐bout response rate was insensitive to reinforcer rate and only inconsistently affected by the four‐response requirement. For both kinds of schedule, the ratio of bout time to between‐bout pause time was approximately a power function of reinforcer rate, with exponents above and below 1.0.