TIME AND RATE MEASURES IN CHOICE TRANSITIONS

Three experiments with pigeons studied the relation between time and rate measures of behavior under conditions of changing preference. Experiment 1 studied a concurrent chain schedule with random-interval initial links and fixed-interval terminal links; Experiment 2 studied a multiple chained random-interval fixed-interval schedule; and Experiment 3 studied simple concurrent ran-dom-interval random-interval schedules. In Experiment 1, and to a lesser extent in the other two experiments, session-average initial-link wait-time differences were linearly related to session-average response-rate differences. In Experiment 1, and to a lesser extent in Experiment 3, ratios of session-average initial-link wait times and response rates were related by a power function. The weaker relations between wait and response measures in Experiment 2 appear to be due to the absence of competition between responses. In Experiments 1 and 2, initial-link changes lagged behind terminal-link changes. These findings may have implications for the relations between fixed- and variable-interval procedures and suggest that more attention should be paid to temporal measures in studies of free-operant choice. Key words: choice, changeover time, interresponse time, interval schedules, conditioned reinforce-ment, wait time, key peck, pigeons Organisms can be trained to choose be-tween sources of primary reinforcers (con-current schedules) or between stimuli that signal the occurrence of primary reinforcers (concurrent chain schedules). In terms of re-sponse- and reinforcer-rate measures taken across sessions, results from concurrent schedules are relatively straightforward: In the steady state, relative response rate ap-proximately matches relative (primary) rein-forcer rate, the well-known matching law (Herrnstein, 1961, 1997; see review in Davi-son & McCarthy, 1988). The results with con-current chain schedules are more complex, and several theories have been proposed, such as a version of the matching law (Herrn-stein, 1964), delay-reduction theory (Fantino, 1969), context theory (Grace, 1994), incen