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Examination of responding under various schedule arrangements is a core component of many analyses of operant behavior. Much of the pioneering work in applied behavior analysis was bred from laboratory research involving the exposure of nonhuman subjects to a variety of schedule arrangements. For example, Reynolds (1961) described a multiple-schedule arrangement in which one component consisted of reinforcement for not responding for a specific period of time (i.e., differential reinforcement of other behavior [DRO]). Exposure to the DRO schedule resulted in generally low rates of responding. Since the initial publication of the basic DRO schedule arrangement, DRO procedures have been frequently employed in the treatment of destructive behavior (e.g., Cowdery, Iwata, & Pace, 1990; Mazaleski, Iwata, Vollmer, Zarcone, & Smith, 1993).
Hodos (1961) described a schedule arrangement in which the requirement to access reinforcement increased on a trial-by-trial basis within the course of a single session. That is, the subject would initially emit a predetermined number of responses before reinforcement delivery (e.g., 20 responses). Following reinforcer delivery, the subsequent response requirement would increase by some increment (e.g., another 10 responses; referred to as a step size) such that in the next trial the subject would be required to complete more responses than in previous trials (e.g., 30 responses before reinforcer delivery, 40 responses before reinforcer delivery). Within-session changes in response requirements in this pattern constitute a progressive-ratio (PR) schedule of reinforcement. (It should be noted that increasing response requirements over successive sessions, e.g., DeLeon, Iwata, Goh, & Worsdell, 1997; Tustin, 1994; has been conceptualized as a form of PR schedule arrangement by some, e.g., Cooper, Heron, & Heward, 2007. For the purpose of the current discussion, PR schedules will be conceptualized as those schedules that increase during the course of a single session.)
DESCRIPTORS: progressive-ratio schedules