The rate of a reinforced response is conceptualized as a composite of engagement bouts (visits) and responding during visits. Part 1 of this paper describes a method for estimating the rate of visit initiations and the average number of responses per visit from log survivor plots: the proportion of interresponse times (IRTs) longer than some elapsed time (log scale) plotted as a function of elapsed time. In Part 2 the method is applied to IRT distributions from rats that obtained food pellets by nose poking a lighted key under various multiple schedules of reinforcement. As expected, total response rate increased as a function of (a) increasing the rate of reinforcement (i.e., variableinterval [VI] 4 min vs. VI 1 min), (b) increasing the amount of the reinforcer (one food pellet vs. four pellets), (c) increasing the percentage of reinforcers that were contingent on nose poking (25% vs. 100%), and (d) requiring additional responses after the end of the VI schedule (i.e., adding a tandem variable-ratio [VR] 9 requirement). The first three of these variables (relative reinforcement) increased the visit-initiation rate. The tandem VR, in contrast, increased the number of responses per visit. Thus, variables that have similar effects on total response rate can be differentiated based on their effects on the components of response rate.Key words: response rate, visits, bouts, relative reinforcement, tandem variable ratio, key poke, ratsThe rate of a reinforced response usually is calculated by dividing the total number of responses by the time available for the response. This method makes most sense if all instances of the response are functionally equivalent. But there are grounds for thinking that they might not be, at least not under some widely studied conditions. According to one tradition, reinforced responding is better thought of as composed of periods of engagement in the reinforced activity (i.e., visits) alternating with periods of disengagement (Blough, 1963;Gilbert, 1958;Mechner, 1992;Mellgren & Elsmore, 1991;Nevin, 1992;Nevin & Baum, 1980;Pear & Rector, 1979;Premack, 1965;Shull, 1991).Although conventional recording equipment typically cannot distinguish visit initiations from responses that occur during the visit (but see Mechner, 1992;Nevin, 1992;Pear & Rector, 1979), these two kinds of reThis research was supported by a grant from the National Science Foundation (IBN-9511934). Portions of these data were presented at the annual meetings of the American Psychological Association (1996) and the Association for Behavior Analysis (1999). Scott Gaynor is now at Western Michigan University.Correspondence concerning this paper should be directed to R. L. Shull, Department of Psychology, Box 26164, University of North Carolina-Greensboro, Greensboro, North Carolina 27402-6164 (E-mail: rlshull@uncg.edu).sponse might nevertheless be controlled by different variables. If so, total response rate would be a composite measure of performance rather than a unitary one. Similar changes in total response rate could res...

This study assessed the treatment specificity and impact on outcome of large, abrupt symptomatic improvements occurring prior to and during cognitive-behavioral, family, and supportive therapy. Eighty-seven depressed adolescents receiving at least 8 therapy sessions were included. Abrupt large decreases in depressive symptoms were identified by changes in weekly Beck Depression Inventory scores. Overall, 28% experienced a pretreatment gain and 39% a sudden within-treatment gain. Both types of gains were associated with superior outcome on self-report and interviewer ratings of depression. Among those participants failing to experience a pretreatment or sudden within-treatment gain, cognitive-behavioral therapy produced the superior outcomes. These findings suggest pretreatment and sudden within-treatment gains are important therapeutic events worthy of further investigation.

Rats obtained food pellets by nose poking a lighted key, the illumination of which alternated every 50 s during a session between blinking and steady, signaling either a relatively rich (60 per hour) or relatively lean (15 per hour) rate of reinforcement. During one training condition, all the reinforcers in the presence of the rich-reinforcement signal were response dependent (i.e., a variable-interval schedule); during another condition only 25% were response dependent (i.e., a variable-time schedule operated concurrently with a variable-interval schedule). An extinction session followed each training block. For both kinds of training schedule, and consistent with prior results, response rate was more resistant to extinction in the presence of the rich-reinforcement signal than in the presence of the lean-reinforcement signal. Analysis of interresponse-time distributions from baseline showed that differential resistance to extinction was not related to baseline differences in the rate of initiating response bouts or in the length of bouts. Also, bout-initiation rate (like response rate) was most resistant to extinction in the presence of the rich-reinforcement signal. These results support the proposal of behavioral momentum theory (e.g., Nevin & Grace, 2000) that resistance to extinction in the presence of a discriminative stimulus is determined more by the stimulus-reinforcer (Pavlovian) than by the stimulus-response-reinforcer (operant) contingency.

The field of clinical behavior analysis is growing rapidly and has the potential to affect and transform mainstream cognitive behavior therapy. To have such an impact, the field must provide a formulation of and intervention strategies for clinical depression, the "common cold" of outpatient populations. Two treatments for depression have emerged: acceptance and commitment therapy (ACT) and behavioral activation (BA). At times ACT and BA may suggest largely redundant intervention strategies. However, at other times the two treatments differ dramatically and may present opposing conceptualizations. This paper will compare and contrast these two important treatment approaches. Then, the relevant data will be presented and discussed. We will end with some thoughts on how and when ACT or BA should be employed clinically in the treatment of depression.