What 50 Years of Research Tell Us About Pausing Under Ratio Schedules of Reinforcement Henry D
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The Behavior Analyst 2008, 31, 39–60 No. 1 (Spring) What 50 Years of Research Tell Us About Pausing Under Ratio Schedules of Reinforcement Henry D. Schlinger California State University, Los Angeles Adam Derenne University of North Dakota Alan Baron University of Wisconsin–Milwaukee Textbooks in learning and behavior commonly describe performance on fixed-ratio schedules as ‘‘break and run,’’ indicating that after reinforcement subjects typically pause and then respond quickly to the next reinforcement. Performance on variable-ratio schedules, on the other hand, is described as steady and fast, with few long pauses. Beginning with Ferster and Skinner’s magnum opus, Schedules of Reinforcement (1957), the literature on pausing under ratio schedules has identified the influences on pausing of numerous important variables, in particular ratio size and reinforcement magnitude. As a result, some previously held assumptions have been called into question. For example, research has shown that the length of the pause is controlled not only by the preceding ratio, as Ferster and Skinner and others had assumed (and as implied by the phrase postreinforcement pause), but by the upcoming ratio as well. Similarly, despite the commonly held belief that ratio pausing is unique to the fixed-ratio schedule, there is evidence that pausing also occurs under variable-ratio schedules. If such widely held beliefs are incorrect, then what about other assumptions? This article selectively examines the literature on pausing under ratio schedules over the past 50 years and concludes that although there may indeed be some common patterns, there are also inconsistencies that await future resolution. Several accounts of pausing under ratio schedules are discussed along with the implications of the literature for human performances, most notably the behaviors termed procrastination. Key words: fixed-ratio schedule, variable-ratio schedule, postreinforcement pause, preratio pause, animal models, procrastination 2007 marked the 50th anniversary ditioning (what was later to become of the publication of Charles Ferster the fixed-interval [FI] schedule) and and B. F. Skinner’s magnum opus, fixed-ratio (FR) reinforcement (he Schedules of Reinforcement (1957), hadn’t yet used the term reinforce- which reported the results of experi- ment schedule)inThe Behavior of ments carried out under contracts to Organisms (1938), it wasn’t until the the Office of Naval Research with publication of Schedules of Reinforce- Harvard University between 1949 ment that he (and Ferster, working as and 1955. Although Skinner had a research fellow under Skinner’s previously discussed periodic recon- direction) distinguished several sim- ple and complex schedules based on Correspondence concerning this article can be nonhuman (pigeons and rats) perfor- addressed to Hank Schlinger, Adam Derenne, mances. In addition, they investigat- or Alan Baron, Department of Psychology, ed the effects of many different types California State University, Los Angeles, 5151 of those schedules along with a State University Dr., Los Angeles, California 90032 (e-mail: [email protected]); Adam variety of other variables (e.g., drugs, Derenne, Department of Psychology, Box 8380, deprivation level, ablation of brain University of North Dakota, Grand Forks, tissue, added counters, etc.) that were North Dakota 58202 (e-mail: adam.derenne@ described in terms of rate of response und.nodak.edu) or Alan Baron, Department of Psychology, University of Wisconsin–Milwau- and depicted on cumulative records. kee, Milwaukee, Wisconsin 53201 (e-mail: ab@ Their research documented the power uwm.edu) of schedules of reinforcement to 39 40 HENRY D. SCHLINGER et al. control behavior and established the ratio schedules reduces overall rein- study of schedules as a focus within forcement rates. Because reinforce- the experimental analysis of behavior. ment rates under ratio schedules Ferster and Skinner’s research paint- depend strictly on response rates, ed a detailed picture of the perfor- optimal performance would be for mances of the subjects as seen on a subjects to resume responding imme- response-by-response basis. Howev- diately. Yet they pause, and the er, their wide-ranging effort did not resultant loss of reinforcement persists attempt to provide systematic infor- over extended exposure to the sched- mation about the effects of paramet- ule without diminution. The critical ric variations across conditions and question, then, is: Why would an subjects. It remained for subsequent animal pause when that very action researchers to fill in the gaps. delays reinforcement and reduces Fifty years and innumerable exper- overall reinforcement rate? One possi- iments later, it is common for text- bility is that the animal is fatigued books on learning to illustrate FR after working so hard. For example, performances with cumulative records pauses are generally shorter under FR and to describe the resulting patterns 10 than under FR 100. Because the FR as ‘‘break and run’’ (see Figure 1). As 100 involves more work, it is possible explained by Lattal (1991), ‘‘following that subjects rest longer before resum- a period of nonresponding (a break, ing work. Another possibility is that more precisely the postreinforcement food consumption creates satiation, pause) after food delivery, there is a which weakens the motivational oper- relatively quick transition to a high ation of food deprivation. However, steady rate of responding (a run) that we will see that neither of these is maintained until the next food seemingly reasonable explanations presentation when the pattern re- survive simple tests and that the peats’’ (p. 95). FR performances are picture is much more complicated. often contrasted with those under Ratio pausing within the laborato- variable-ratio (VR) schedules, in ry is also of special interest because it which the size of the ratios varies resembles the human problem of within the schedule. Under VR sched- procrastination: In both cases, an ules, performances are ‘‘characterized action is put off even though the by high response rates with little resulting delay may be disadvanta- systematic pausing either after rein- geous. Social commentators have forcement or at other times’’ (p. 95).1 noted that procrastination is a major Among the myriad response pat- contributor to behavioral inefficiency terns observed under various sched- in schools, industry, and our daily ules of reinforcement, pausing under lives in general (Steel, 2007). Identi- ratio schedules (especially FR sched- fication of the variables that control ules) has attracted special attention. the ratio pause in the laboratory may Unlike the pause that follows rein- help to reveal techniques for the forcement on interval schedules, the modification of procrastination. pause that follows reinforcement on Our primary purpose in this article is to identify the variables that govern 1 A pause is usually defined as the time from pausing under ratio schedules. Re- the delivery of a reinforcer until emission of search on pausing under ratio sched- the first response of the subsequent ratio and has been variously referred to as a postrein- ules has come a long way since forcement or preratio pause. Although there is Ferster and Skinner’s (1957) pioneer- evidence that pauses will sometimes occur ing contributions. They set us on our after the first response (Ferster & Skinner, way, but in the ensuing 50 years 1957; Griffiths & Thompson, 1973; Mazur & Hyslop, 1982), we use the terms pause and increasingly sophisticated questions pausing to refer to the postreinforcement or and experimental designs have re- preratio pause. vealed a more complex picture. A PAUSING UNDER RATIO SCHEDULES 41 Figure 1. Cumulative records showing performances under FR 90 and VR 50 schedules of reinforcement (Ferster & Skinner, 1957). Reproduced from Figure 2 (Lattal, 1991) and reprinted with permission of Elsevier Science Publishers. fundamental issue in research on ical mechanisms that govern pausing ratio schedules, then, concerns how under ratio schedules. pausing should be summarized and described. In the present article we PAUSING UNDER review the research on pausing under FR SCHEDULES ratio schedules of reinforcement in an Skinner (1938) first described the attempt to glean an understanding of performances of rats under FR and why pausing under such schedules FI reinforcement as including a pause occurs. We first take a look at that was under the stimulus control research on pausing with simple FR of the previous reinforcer: schedules, then consider research with complex (multiple and mixed) In both types of experiment the discrimination schedules with FR components, and, from the preceding reinforcement is active, finally, look at pausing under VR since one reinforcement never occurs immedi- schedules. We then discuss the real- ately after another. A reinforcement therefore D world implications of ratio pausing, acts as an S in both cases. As the result of this discrimination the rat stops responding for a in particular, the bearing of labora- short period just after receiving and ingesting tory research on the pervasive social a pellet of food. (p. 288) problem of human procrastination. Finally, we offer a set of conclusions Thus, from the very beginning of his that might shed light on the theoret- research on FR schedules, Skinner 42 HENRY D. SCHLINGER et al. assumed that the pause was a func- Building on Skinner’s (1938) and tion of the preceding reinforcer. Ferster and