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Chapter 5 Schedules of Reinforcement

Synopsis: A schedule of reinforcement describes the arrangement of discriminative stimuli, operants, and consequences. Understanding schedules of reinforcement is central to understanding behavior. Schedules of reinforcement generate consistent, steady, predictable patterns of behavior. Behavior analysts use of schedules as the primary independent variable in their studies and as baselines in examining how other variables (such as drug use or epigenetic factors) influence the steady, predictable patterns of behavior generated by a particular schedule. The basic schedules of reinforcement include: continuous reinforcement (CRF), fixed-ratio (FR), variable-ratio (VR), fixed-interval (FI), and variable-interval (VI) schedules. Research indicates that behavior is more resistant to extinction when it is reinforced (1) intermittently and (2) on a variable schedule. Postreinforcement pausing is an important characteristic of schedule-controlled behavior. In many studies, human response patterns have differed from those observed in other animals. These differences most likely relate to language as well as the extensive reinforcement histories with ratio schedules. Differences in response rates and pausing between ratio and interval schedules have been explained with both molecular and molar accounts of behavior. Behavioral researchers are exploring the area of behavioral dynamics in hopes of determining basic principles and rules to explain how behavior transitions from unstable to steady-state equilibrium.

Study Questions: 1. Identify the three elements of a schedule of reinforcement. 2. Identify three roles that the biological factors play in observed schedule effects on behavior. 3. What explanation would a behavior analyst give for behavior that is often attributed to motivation, habit, and personality traits? 4. Explain the observed response patterns when every response on a fixed-ratio schedule of reinforcement is shocked. What happens when the schedule is changed to a fixed-time schedule of reinforcement? 5. What does the Mechner notation describe? 6. Provide the Mechner symbol for the following: (a) discriminative stimulus, (b) S-delta, (c) response (operant class), (d) positive reinforcer, and (e) negative reinforcer. 7. What is a conjugate reinforcement schedule? 8. Identify two characteristics of behavior on a CRF schedule. 9. Identify and discuss two meanings for PRP. What factors determine the length of the PRP on FR schedules? 10. Identify three reasons discussed in the text for why human adults don’t typically produce the FI “scallop” pattern. © 2017 Taylor & Francis

11. Describe Nevin’s (1974) study using multiple schedules of reinforcement that explored behavior momentum. 12. How might a researcher use a progressive ratio schedule to explore the reinforcement efficacy of a particular drug? 13. What is ratio strain? How are the IRI and PRP involved in ratio strain? 14. Explain the changes in schedules of reinforcement that children experience as they move from childhood to adolescence. 15. Describe the outcome of Roll, Higgins, and Badger’s (1996) experiment on contingency management and cigarette smoking. 16. What is the primary difference between molecular and molar accounts of schedule performance? 17. Identify two problems with the interresponse time (IRT) account of rate differences on ratio and interval schedules. 18. What is a variable-interval plus linear feedback (VI+) schedule? 19. Describe the expected distribution and average for PRPs on an FI 180-s schedule. 20. What is the area of research known as behavioral dynamics?

Study Questions (Answers): 1. A schedule of reinforcement identifies the discriminative stimulus, the operant, and the consequence. 2. Three ways in which biology affects behavior are (1) through specific neurophysiological events that function as reinforcement, (2) neurophysiological events that serve as discriminative stimuli, and (3) biological variables that may also constrain or enhance environment–behavior relationships. 3. Rather than inferring dispositions as internal causes, a behavior analyst would say that these are patterns of steady-state responding, regularities of behavior that are maintained by the consistency of the schedule of reinforcement. The actual causes of predictable behavior patterns are the behavioral contingencies, not dispositional internal states. 4. When every response on a fixed-ratio schedule of reinforcement (reinforcement after a fixed number of responses) is shocked, the pause length after reinforcement increases (Azrin, 1959). Once the animal emits the first response, however, the operant rate to finish the run of responses is unaffected. In other words, the pause increases with continuous punishment, but otherwise behavior on the schedule remains the same. When behavior is reinforced after a fixed amount of time, the pattern of behavior remains the same—as when no shocks are provided—and the rate of response declines. 5. Mechner notation describes: (1) the independent variables and (2) what the experimenter (instrumentation or computer) does. This notation does not describe the behavior of organisms. 6. SD = discriminative stimulus, SΔ = S-delta, R = response (operant class), Sr+ = positive reinforcer, and Sr− = negative reinforcer 7. Conjugate reinforcement is a type of CRF schedule in which properties of reinforcement, including the rate, amplitude, and intensity of reinforcement, are tied to particular dimensions of the response.

© 2017 Taylor & Francis

8. CRF produces weak resistance to extinction and generates stereotypical response topographies. 9. The flat part of the cumulative record is often called the postreinforcement pause (PRP), to indicate where it occurs. As the upcoming requirements exert predominant control over the PRP, contemporary researchers often refer to the PRP as a preratio pause. The length of the PRP on FR schedules is influenced by (1) the moment of reinforcement, which becomes discriminative for non-reinforcement (S); (2) the upcoming ratio requirement (as the ratio requirement increases, longer and longer pauses appear in the cumulative record); and (3) the size of the upcoming reinforcer. 10. Three reasons for the non-scalloped response patterns are: (1) adult humans typically use clocks, watches, and other electronic devices to keep track of time; (2) schedule performance in humans reflects the influence of language; and (3) adult humans tend to have significant experience with ratio-type contingencies of reinforcement. 11. Nevin (1974) used a multiple schedule of reinforcement with two separate VI reinforcement components, each with a discriminative stimulus (SD) and separated by a third darkened component. Rates of responding were higher in the richer VI component. When free food was provided in the third darkened component (disruption), responding decreased less in the VI condition with the higher rate of reinforcement. Thus, behavior in the component with the rich VI schedule (high rate of reinforcement) showed increased momentum. It continued to keep going despite the disruption by free food. 12. On a progressive ratio (PR) schedule of reinforcement the ratio requirements for reinforcement are increased systematically, typically after each reinforcer. The highest ratio value completed on the PR schedule is designated the breakpoint. The breakpoint for a drug indicates how much operant behavior the drug will sustain at a given dose. 13. Ratio strain occurs when the organism pauses longer and longer after reinforcement, possibly ceasing responding altogether. One explanation for ratio strain is that the time between successive reinforcements contributes to the postreinforcement pause (PRP). The pause gets longer as the interreinforcement interval (IRI, or time between reinforcement) increases. Because the PRP makes up part of the IRI and is controlled by it, the animal eventually stops responding. Thus, there is a negative feedback loop between increasing PRP length and the time between reinforcements in the shift from CRF to the large FR schedule. 14. When a youngster reaches puberty, parents, teachers, peers, and others require more behavior and more skillful performance than they did during childhood. A young child’s reinforcement schedules are usually simple, regular, and immediate. On the other hand, a teenager is told to fix her own food and clean up the mess. Money becomes a reinforcer on a FR schedule. The amount of work required in school increases. 15. Smokers in the progressive and fixed reinforcement groups passed more than 80% of the abstinence tests, while the control group only passed about 40% of the tests. Only 22% of those on the progressive schedule resumed smoking, compared with 60% and 82% in the fixed and control groups, respectively. Around 50% of those on the progressive reinforcement schedule remained abstinent for the five days of the experiment, compared with 30% and 5% of the fixed and control participants, respectively.

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16. Molecular accounts focus on small moment-to-moment relationships between behavior and its consequences. Molar accounts are concerned with large-scale factors that occur over the length of an entire session. 17. One problem is that experiments on selective reinforcement of IRTs do not prove the IRTs are controlled in this way on interval or ratio schedules. A second problem is that there is evidence that when long IRTs are reinforced, organisms continue to emit short bursts of rapid responses. 18. A VI+ schedule is a schedule with the molar properties of a VR schedule, higher rates of response correlating with higher rates of reinforcement (linear feedback), but with the molecular properties of a VI schedule—differential reinforcement of longer IRTs. 19. The average PRP is half the IRI, which would be 90 seconds for an FI 180-s schedule. The distribution of PRPs would be normally distributed with a range from 0 to 180 seconds. 20. Behavioral dynamics is the study of behavior allocation through time. Behavioral dynamics involve feedback processes that move the system (organism) from an unstable, transitional state toward steady-state equilibrium. If performance on schedules can be reduced to a small number of fundamental principles, either laws of dynamics or equilibrium, then reasonable interpretations may be made about any particular arrangement of the environment.

Essay Questions (Student): 1. Define each of the following schedules of reinforcement and describe the typical response pattern associated with each schedule: a. Fixed ratio b. Variable ratio c. Fixed interval d. Variable interval ANS: A fixed-ratio (FR) schedule is programmed to deliver reinforcement after a fixed number of responses have been made. FR schedules produce a rapid run of responses, followed by reinforcement, and then a pause in responding. There is a steep period of responding (run of responses), followed by reinforcement (oblique line), and finally a flat portion (the pause)—a pattern known as break and run. Variable-ratio (VR) schedules are programmed to deliver reinforcement after a variable number of responses are emitted. The average number of responses defines the schedule but the number of responses required for reinforcement varies after each reinforcement (not random). VR schedules typically produce a high rate of response with fewer and smaller PRPs than on FR schedules. On fixed-interval (FI) schedules, an operant is reinforced after a fixed amount of time has passed. FI schedules produce a characteristic steady-state pattern of responding. There is a pause after reinforcement (PRP), then a few probe responses, followed by more and more rapid responding to a constant high rate as the interval times out. This pattern of response is called scalloping. © 2017 Taylor & Francis

On a variable-interval (VI) schedule, responses are reinforced after a variable amount of time has passed. The average amount of time required for reinforcement is used to define the schedule. On this schedule, rate of response is moderate and steady. The pause after reinforcement that occurs on FI does not usually appear in the VI record. 2. Describe the running and eating behavior of rats in a closed economy with contingent access to food (CON) on a progressive ratio schedule (Fonseca et al., 2014). What possible explanation is given for this pattern of responding? ANS: At first, running by the rats in the CON group closely matched their average level of wheel running (travel distance) to the PR scheduled distance. Although distance traveled matched the early PR values and rats received the six 4-g pellets, food consumed (actually eaten) showed a sharp drop (from 24 g to 18 g) for the first three days of wheel running on the PR schedule. Following this initial drop, food consumed partially recovered; however, consumption by CON rats remained suppressed relative to the NONgroup (21 g vs. 24 g). When the distance requirement increased to approximately 6000 m per day (1000 m/pellet), CON rats’ average distance traveled no longer approximated the PR value—even though rats did complete longer distances at higher ratios, exceeding 8000 m a day. Rats traveled less than required by the PR value, giving up some of the daily food ration that they could have obtained. A possible explanation is that the animals were sensitive to energy balance or homeostasis—balancing as best as possible energy expenditure by wheel running with energy intake from food consumption.

Essay Questions (Instructor): 1. What is biofeedback and how did Cohen and colleagues (2001) show that schedules of reinforcement provide a behavioral explanation for this type of behavior? ANS: Biofeedback is usually defined as the apparent willful control of physiological processes and bodily states. The procedure is said to involve conscious, intentional control of bodily functions, such as brainwaves, heart rate, blood pressure, temperature, headaches, and migraines—using instruments that provide information or feedback about the ongoing activity of these systems. An alternative view is that biofeedback involves operant responses of bodily systems regulated by behavioral consequences, producing orderly changes related to the schedule of “feedback.” Cohen and colleagues (2001) investigated five different schedules of feedback on forearm-muscle tension: FR, VR, FI, VI, and CRF and extinction. Ratio schedules (FR and VR) produced higher rates of EMG electrical responses in the forearm muscles than interval contingencies (FI or VI). Additionally, the VI and VR schedules showed the most resistance to extinction. CRF produced the most sustained EMG responding, while FR and VR schedules engendered more muscle pumping action of the exercise ball. The EMG electrical responses used in this study were sensitive to the schedule of feedback, indicating the operant function of electrical activity in the forearm muscles. © 2017 Taylor & Francis

The Cohen et al. (2001) experiment shows that responses of the somatic nervous system also are under tight operant control of the schedule of reinforcement (feedback). 2. Explain the molecular and molar accounts for the higher response rates in ratio schedules compared to interval schedules. ANS: Molecular account: Generally, ratio schedules produce shorter IRTs, and consequently higher rates of response, than interval schedules. Skinner (1938) suggested that this came about because ratio and interval schedules reinforce short and long interresponse times, respectively. Ratio schedules generate rapid sequences of responses with short interresponse times. On a ratio schedule, consider what the probability of reinforcement is following a burst of very fast responses (short IRTs) or a series of responses with long IRTs. Recall that ratio schedules are based on the number of responses that are emitted. Bursts of responses with short IRTs rapidly count down the ratio requirement and are more likely to be reinforced than sets of long IRT responses (slow responding). Thus, ratio schedules, because of the way they are constructed, differentially reinforce short IRTs. According to the molecular IRT view of schedule control, this is why the rate of response is high on ratio schedules Molar account: Molar explanations of rate differences are concerned with the overall relationship between responses and reinforcement. In molar terms, the correlation between responses and reinforcement or feedback function produces the difference in rate on interval and ratio schedules. Generally, if a high rate of response is correlated with a high rate of reinforcement in the long run, animals will respond rapidly. When an increased rate of response does not affect the rate of reinforcement, organisms do not respond faster. The rate of reinforcement and rate of response are directly correlated in ratio schedules, producing a high rate of response. For interval schedules, after some moderate value, it does not pay to increase the rate of response on interval schedules— hence low to moderate response rates are maintained on interval schedules.

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Review of the basic schedules of reinforcement https://www.youtube.com/watch?v=UOiC310cju4 Skinner discussing schedules of reinforcement https://www.youtube.com/watch?v=rst7dIQ4hL8 Applications of schedules of reinforcement to work situations https://www.youtube.com/watch?v=gkcNgE4OGDM Discussion of the use of schedules of reinforcement in video games https://www.youtube.com/watch?v=PMN_yVbMZD0 Progressive-ratio responding for palatable high-fat and high-sugar food in mice https://www.jove.com/video/3754/progressive-ratio-responding-for-palatable-high-fathigh-sugar-food

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A schedule of reinforcement describes how and when discriminative stimuli and behavioral consequences are arranged. Mechner notation is a system of notation that depicts the programmed contingencies, or relations among discriminative stimuli, responses, and consequent events as arranged in the laboratory. The notation describes the independent variable (contingency) but does not prescribe the effects of the independent variable on behavior. Intermittent schedules of reinforcement produce response patterns that are more resistant to extinction than continuous schedules. Variable schedules of reinforcement produce steadier response rates than fixed schedules —which typically have very predictable and consistent postreinforcement pauses (PRP). The molecular account of schedule performance focuses on small moment-to-moment relationships between behavior and its consequences. The molar account of schedule performance is concerned with large-scale factors that occur over the length of the entire session.

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