Effects Of Reinforcer Magnitude Research Articles

The effects of reinforcement magnitude during token gain and loss on procedural efficacy and preference.

The effects of reinforcement magnitude during token gain and loss on procedural efficacy and preference.

Rats’ Choice in a Coordination Task

We designed a free-operant choice procedure that represents a technical improvement to assess the control of mutual reinforcement contingencies over the choice of coordinated behavior. We demonstrate the advantages of the new procedure with eight rats that were trained to continuously move a steel ball from end to end of a gutter. Subjects were assigned to pairs and had to choose between two response options: one in which reinforcement was contingent upon an individual response, and another in which reinforcement depended on the coordination of intra-pair behavior. We evaluated (a) the effect of reinforcement magnitude over the distribution of responses, and (b) the role of behavioral cues on the rats’ coordinated actions via dividing the experimental chamber in two compartments with a clear/opaque partition. The coordinated actions were more likely when the larger reinforcer was initially associated with the mutual reinforcement option. The visual interaction between subjects did not impact their coordinated actions. The possibility to control organisms’ preference for social or nonsocial alternatives opens potential lines of research. For instance, identifying how the coordination of activities combines with the future value of outcomes to produce stable cooperative equilibria.

The effects of reinforcer magnitude in the preceding and upcoming ratios on between-ratio pausing in multiple, mixed, and single fixed-ratio schedules.

Hens responded under multiple fixed-ratio schedules with equal response requirements and either a 1-s or a 6-s reinforcer. Upcoming reinforcer size was indicated by key color. Components were presented in a quasirandom series so that all four component transitions occurred. Postreinforcement pauses were affected by the upcoming and preceding reinforcer size, with longer pauses after large reinforcers followed by small reinforcers than when followed by large ones, and longer pauses after small reinforcers that were followed by small reinforcers rather than large ones. Pauses increased with fixed-ratio size and the effects of reinforcer size were larger the larger the ratio. When reinforcer size was not signaled-mixed fixed-ratio schedules-pauses were shorter after small than after large reinforcers. Signalling the upcoming reinforcer attenuated the effect of the previous reinforcer size on pause duration when small was followed by small and when either small or large by large, but enhanced the effect when large was followed by small. There was no effect of reinforcer size on pause duration when single fixed-ratio schedules were arranged. The effects of reinforcer size on pauses depends on the size and range of the fixed ratios as well as the exact procedures used in the study.

Effects of reinforcer magnitude and distribution on preference for work schedules.

When the overall magnitude of reinforcement is matched between 2 alternative work schedules, some students prefer to complete all of their work for continuous access to a reinforcer (continuous work) rather than distributed access to a reinforcer while they work (discontinuous work). We evaluated a student's preference for continuous work by manipulating the overall magnitude of reinforcement associated with continuous work. Preference for continuous work persisted despite a 20% decrease in reinforcer magnitude; however, a 40% decrease in reinforcer magnitude produced a shift in preference to discontinuous work.

Effects of reinforcer magnitude on response acquisition with unsignaled delayed reinforcement

Sixteen rats received eight 1-h sessions of a tandem fixed-ratio 1 differential-reinforcement-of-other-behavior 30-s schedule with reinforcer magnitude at one or six food pellet(s) across groups of eight rats. The larger reinforcer magnitude established the lever press more effectively. First, mean schedule completions differed across groups, in terms of both their overall difference and in their increase across sessions. Second, whereas the larger reinforcer magnitude established reliable response acquisition in all eight rats by the end of the experiment, the smaller reinforcer magnitude only established reliable response acquisition in four of eight rats. The present results systematically replicate earlier findings obtaining more reliable response acquisition with unsignaled delayed reinforcement with greater food deprivation. Taken together, this work demonstrates the influence of motivational variables on response acquisition with unsignaled delayed reinforcement.

WHY PIGEONS SAY WHAT THEY DO: REINFORCER MAGNITUDE AND RESPONSE REQUIREMENT EFFECTS ON SAY RESPONDING IN SAY—DO CORRESPONDENCE

The effects of reinforcer magnitude and response requirement on pigeons' say choices in an experimental homologue of human say-do correspondence were assessed in two experiments. The procedure was similar to a conditional discrimination procedure except the pigeons chose both a sample stimulus (the say component) and a comparison stimulus that corresponded to it (the do component). Correspondence was trained on red, green, and white key colors before the duration of food presentations following correspondence on each key color (Experiment 1) and the number of key pecks required as the say response on each key color (Experiment 2) were manipulated in an attempt to influence the initial say response. The frequency of say responses on each key color coincided with programmed changes in the duration of food presentations and the key-peck requirements assigned to each key color. Correspondence accuracy remained stable in all conditions, even those in which the say responding occurred primarily on two of the three key colors. Implications for human behavior are discussed.

Effects of reinforcer magnitude and alternative reinforcer delay on preference for alcohol during a multiple-choice procedure

The Multiple-Choice Procedure [MCP; Griffiths, R.R., Troisi II, J.R., Silverman, K., Mumford, G.K., 1993. Multiple-choice procedure: an efficient approach for investigating drug reinforcement in humans. Behav. Pharmacol. 4, 3–13; Griffiths, R.R., Rush, C.R., Puhala, K.A., 1996. Validation of the multiple-choice procedure for investigating drug reinforcement in humans. Behav. Pharmacol. 4, 3–13] was developed to investigate the relationship between drug preferences and alternative reinforcers. The current study was designed to better characterize the relationships among reinforcer magnitude, delay associated with an alternative reinforcer, and preference for alcohol among a sample of undergraduate drinkers. Participants were 27 male undergraduates, over the age of 21, who reported engaging in at least three occasions of binge drinking over the previous month. All participants took part in a single laboratory session, during which six versions of the MCP questionnaire were administered. Across the versions, participants made a total of 180 discrete choices between three amounts of alcohol (12, 24, or 36 ounces of beer; deception was used to mask the fact that 36 ounces of beer would not actually be provided during the sessions) and escalating amounts of money ($0 to $20) delivered immediately or after a one-week delay. Response on the MCP varied as a function of the amount of alcohol available and the delay associated with the alternative monetary reinforcer, with the effect of the delay diminishing as the dose of alcohol increased. Results of the current study are consistent with previous laboratory studies of choice behavior and with behavioral economic theories of substance use.

The effects of reinforcer magnitude on timing in rats.

The relation between reinforcer magnitude and timing behavior was studied using a peak procedure. Four rats received multiple consecutive sessions with both low and high levels of brain stimulation reward (BSR). Rats paused longer and had later start times during sessions when their responses were reinforced with low-magnitude BSR. When estimated by a symmetric Gaussian function, peak times also were earlier; when estimated by a better-fitting asymmetric Gaussian function or by analyzing individual trials, however, these peak-time changes were determined to reflect a mixture of large effects of BSR on start times and no effect on stop times. These results pose a significant dilemma for three major theories of timing (SET, MTS, and BeT), which all predict no effects for chronic manipulations of reinforcer magnitude. We conclude that increased reinforcer magnitude influences timing in two ways: through larger immediate after-effects that delay responding and through anticipatory effects that elicit earlier responding.

Fluvoxamine and desipramine on fixed-ratio responding: effects of reinforcement magnitude

Fluvoxamine, a serotonin reuptake blocker, was previously shown to decrease ethanol-maintained behavior at doses lower than those needed to decrease food-maintained behavior. While these effects could have been due to different response rates and histories of the two groups being compared, a subsequent study found differential effects using a within-subjects design, in which rates of responding were well equated. Another explanation for such differential effects is that food and ethanol reinforcement differ in a quantitative fashion. This is difficult to resolve when comparing between behaviors maintained by different events. To examine how such quantitative differences in reinforcement magnitude might influence the effects of fluvoxamine, we used a multiple schedule of fixed-ratio 30 responding in the pigeon. In each of the three fixed-ratio 30 components, behavior was maintained by a different duration of grain presentation (2, 4, and 8 s). The effects of fluvoxamine and also desipramine were examined. Both dose-dependently decreased fixed-ratio responding. Their effects were independent of the duration of grain presentation maintaining responding. These results do not support the idea that the differential effects of fluvoxamine on ethanol-maintained behavior, as compared with food-maintained behavior, are a result of quantitative differences in reinforcement magnitude.

Effects of reinforcer magnitude on an animal model of impulsive behavior.

The effects of altering sucrose solution concentration on discounting of delayed rewards in rats were examined. Five different delays were used (0, 1, 2, 4, and 8s) and three different sucrose solution concentrations (3, 10, and 30%). It was hypothesized that high value sucrose solution concentrations would be discounted less than low value sucrose solution concentrations. The results indicated that the rats discounted the 30% sucrose solution concentration at a higher rate than the 3 or 10% sucrose solution concentration, a finding that apparently contradicted the hypothesis that higher value sucrose solution concentrations would be discounted less than lower value sucrose solution concentrations. However, a follow up experiment indicated that the 3 and 10% sucrose solution concentrations were preferred over the 30% concentration. Thus the results of Experiment 1 can be interpreted as supporting the hypothesis that high valued sucrose solution concentrations are discounted less than lower valued sucrose solution concentrations.

Effects of reinforcer magnitude on data-entry productivity in chronically unemployed drug abusers participating in a therapeutic workplace.

The Therapeutic Workplace is a substance abuse treatment wherein patients are hired and paid to work in a job contingent on daily drug-free urine samples. The present study examined data-entry productivity of 6 unemployed methadone patients who demonstrated relatively variable and low data-entry response rates. A within-subject reversal design was used to determine whether increasing reinforcement magnitude tenfold could increase response rates. Four of the 6 participants showed the highest rates of responding in the high magnitude reinforcement condition. Two participants, who had the lowest overall response rates, showed less robust changes to the magnitude manipulation. The results suggest that reinforcement magnitude can be used to improve productivity in Therapeutic Workplace participants. Chronic unemployment is a common problem among individuals with long histories of drug abuse. Unemployment rates among methadone maintenance patients have been estimated to be 50% to 80% (French, Dennis, McDougal, Karuntzos, & Hubbard, 1992). It is not surprising that unemployment among drug abusers has been shown to be associated with continued drug use, poor treatment outcome, and criminal activity (Platt, 1995).

A tuned-trace theory of interval-timing dynamics.

Animals on interval schedules of reinforcement can rapidly adjust a temporal dependent variable, such as wait time, to changes in the prevailing interreinforcement interval. We describe data on the effects of impulse, step, sine-cyclic, and variable-interval schedules and show that they can be explained by a tuned-trace timing model with a one-back threshold-setting rule. The model can also explain steady-state timing properties such as proportional and Weber law timing and the effects of reinforcement magnitude. The model assumes that food reinforcers and other time markers have a decaying effect (trace) with properties that can be derived from the rate-sensitive property of habituation (the multiple-time-scale model). In timing experiments, response threshold is determined by the trace value at the time of the most recent reinforcement. The model provides a partial account for the learning of multiple intervals, but does not account for scalloping and other postpause features of responding on interval schedules and has some problems with square-wave schedules.

Voucher-based reinforcement of opiate plus cocaine abstinence in treatment-resistant methadone patients: Effects of reinforcer magnitude.

The study tested a voucher-based abstinence reinforcement procedure for reducing opiate and cocaine use in a population of treatment-resistant opiate- and cocaine-abusing methadone patients. Vouchers exchangeable for goods and services were contingent on abstinence from both opiates and cocaine. In two conditions, participants could earn up to $374 or $3,369 in vouchers for providing opiate- and cocaine-free urine samples. Participants received a daily 60-mg dose of methadone. The dose was increased in a second phase, and the voucher conditions were replicated. Analyses of both phases revealed trends toward greater abstinence under the high voucher condition and suggested that higher doses may enhance the efficacy of voucher reinforcement. The results show that reinforcement for abstinence from 2 drugs simultaneously can be effective even in a treatment-resistant population.

Effects of reinforcement magnitude and ratio values on behaviour maintained by a cyclic ratio schedule of reinforcement.

In Experiments 1 and 2, lever pressing by rats was reinforced on a cyclic ratio schedule of food reinforcement, comprising a repeated sequence of fixed-ratio component schedules. Reinforcement magnitude was varied, on occasional sessions in Experiment 1 and across blocks of sessions in Experiment 2, from one to two or three 45-mg food pellets. In the one-pellet condition, post-reinforcement pauses increased with component schedule value. At higher magnitudes, post-reinforcement pauses increased, and overall response rates declined. Response rate on component schedules was a decreasing linear function of the obtained rate of reinforcement in all conditions. Plotted against component schedule value, response rate increased exponentially to an asymptote that decreased when reinforcement magnitude increased. These findings are consistent with regulatory accounts of food-reinforced behaviour. In Experiment 3, rats were trained under a cyclic ratio schedule comprising fixed-ratio components including higher values, and some inverted U-shaped response functions were obtained. Those rats that did not show this relationship were trained on cyclic ratios with even higher values, and all showed inverted U-shaped response functions. This suggests that behaviour on cyclic ratio schedules can reflect activating of reinforcement as well as the satiating effects seen in Experiments 1 and 2.

Effects of reinforcement magnitude and ratio values on behaviour maintained by a cyclic ratio schedule of reinforcement

In Experiments 1 and 2, lever pressing by rats was reinforced on a cyclic ratio schedule of food reinforcement, comprising a repeated sequence of fixed-ratio component schedules. Reinforcement magnitude was varied, on occasional sessions in Experiment 1 and across blocks of sessions in Experiment 2, from one to two or three 45-mg food pellets. In the one-pellet condition, post-reinforcement pauses increased with component schedule value. At higher magnitudes, post-reinforcement pauses increased, and overall response rates declined. Response rate on component schedules was a decreasing linear function of the obtained rate of reinforcement in all conditions. Plotted against component schedule value, response rate increased exponentially to an asymptote that decreased when reinforcement magnitude increased. These findings are consistent with regulatory accounts of food reinforced behaviour. In Experiment 3, rats were trained under a cyclic ratio schedule comprising fixed-ratio components including higher values, and some inverted U-shaped response functions were obtained. Those rats that did not showthis relationship were trained on cyclic ratios with even higher values, and all showed inverted U-shaped response functions. This suggests that behaviour on cyclic ratio schedules can reflect activating of reinforcement as well as the satiating effects seen in Experiments 1 and 2.

Visual Reinforcement Signals Interfere with the Effects of Reinforcer Magnitude Manipulations

Three experiments examined the effect of reinforcement magnitude on free-operant response rates. In Experiment 1, rats that received four food pellets responded faster than rats that received one pellet on a variable ratio 30 schedule. However, when the food hopper was illuminated during reinforcer delivery, there was no difference between the rates of response produced by the two magnitudes of reward. In Experiment 2, there was no difference in response rates emitted by rats receiving either one or four pellets of food as reward on a random interval (RI) 60-s schedule. In Experiment 3, rats responding on an RI 30-s schedule did so at a lower rate with four pellets as reinforcement than with one pellet. This effect was abolished by the illumination of the food hopper during reinforcement delivery. These results indicate that the influence of magnitude is obscured by manipulations which signal the delivery of reinforcement.

Sequences of Fixed-Ratio Schedules: The Relative Effects of Reinforcer Magnitude and Ratio Size in the Second Fixed Ratio

Four pigeons were given a choice between two sequences of fixed-ratio schedules. The second fixed ratio was a fixed-ratio 5 followed by 2-s access to grain in one sequence and a fixed-ratio 45 followed by 8-s access to grain in the alternative. In Phase 1, the initial fixed-ratio schedules of each sequence, which were always equal, varied from fixed-ratio 1 to fixed-ratio 50. At each initial fixed-ratio value, 3-s access to grain and a 0.25-s hopper flash were programmed. When the initial fixed ratio was small, the sequence with the 2-s reinforcer was preferred. Preference switched to the sequence with the 8-s reinforcer when the initial fixed ratio increased. In Phase 2, the effects of a 3-s hopper flash were compared with those of a 0.25-s hopper flash. The results showed that preference for the sequence with the 8-s reinforcer increased with hopper-flash duration. Together, Phase 1 and Phase 2 results show that reinforcer magnitude and ratio size of the second fixed ratio can affect choice, but their relative effects depend on initial fixed-ratio size and reinforcer duration.

DETERMINANTS OF PAUSING UNDER VARIABLE‐RATIO SCHEDULES: REINFORCER MAGNITUDE, RATIO SIZE, AND SCHEDULE CONFIGURATION

Pigeons pecked a key under two-component multiple variable-ratio schedules that offered 8-s or 2-s access to grain. Phase 1 assessed the effects of differences in reinforcer magnitude on postreinforcement pausing, as a function of ratio size. In Phase 2, postreinforcement pausing and the first five interresponse times in each ratio were measured as a function of differences in reinforcer magnitude under equal variable-ratio schedules consisting of different configurations of individual ratios. Rates were also calculated exclusive of postreinforcement pause times in both phases. The results from Phase 1 showed that as ratio size increased, the differences in pausing educed by unequal reinforcer magnitudes also increased. The results of Phase 2 showed that the effects of reinforcer magnitude on pausing and IRT durations were a function of schedule configuration. Under one configuration, in which the smallest ratio was a fixed-ratio 1, pauses were unaffected by magnitude but the first five interresponse times were affected. Under the other configuration, in which the smallest ratio was a fixed-ratio 7, pauses were affected by reinforcer magnitude but the first five interresponse times were not. The effect of each configuration seemed to be determined by the value of the smallest individual ratio. Rates calculated exclusive of postreinforcement pause times were, in general, directly related to reinforcer magnitude, and the relation was shown to be a function of schedule configuration.

EFFECTS OF MAGNITUDE OF FOOD REINFORCEMENT ON FREE‐OPERANT RESPONSE RATES

In Experiment 1 rats were trained to press a lever on a variable-ratio schedule of food presentation and were then exposed to progressively increasing magnitudes of food reinforcement. Response running rates (rates exclusive of the postreinforcement pause) were found to increase as a function of increasing reinforcement magnitudes. The effect of reinforcement magnitude on response rates inclusive of the postreinforcement pause, however, was less pronounced. Increases in the magnitude of reinforcement were also found to increase the length of the postreinforcement pause. Rats in Experiment 2 were trained to respond on a chained differential-reinforcement-of-low-rate variable-ratio schedule, and were exposed to increasing magnitudes of reinforcement as in Experiment 1. Response running rates increased in the variable-ratio component but decreased in the other component of the schedule. The results are discussed with reference to incentive accounts of reinforcement and the action of reinforcement on the response units generated by the operative contingencies.

Elucidating the effects of reinforcement magnitude.

Elucidating the effects of reinforcement magnitude.