Effects of ratio reinforcement schedules on discrimination performance by Japanese monkeys

In Experiment 1, Japanese monkeys were trained on three conditional position-discrimination problems with colors as the conditional cues. Within each session, each problem was presented for two blocks of ten reinforcements; correct responses were reinforced under continuous-reinforcement, fixed-ratio 5, and variable-ratio 5 schedules, each assigned to one of the three problems. The assignment of schedules to problems was rotated a total of three times (15 sessions per assignment) after 30 sessions of acquisition training. Accuracy of discrimination increased to a moderate level with fewer trials under CRF than under ratio schedules. In contrast, the two ratio schedules, fixed and variable, were more effective in maintaining accurate discrimination than was CRF. With further training, as asymptotes were reached, accuracy was less affected by the schedule differences. These results demonstrated an interaction between the effects of reinforcement schedules and the level of acquisition. In Experiment 2, ratio sizes were gradually increased to 30. Discrimination accuracy was maintained until the ratio reached 20; ratio 30 strained the performance. Under FR conditions, accuracy increased as correct choice responses cumulated after reinforcement.     

The effects of reinforcement frequency and response requirements on the maintenance of behavior.

Six rats responded under fixed-interval and tandem fixed-interval fixed-ratio schedules of food reinforcement. Basic fixed-interval schedules alternated over experimental conditions with tandem fixed-interval fixed-ratio schedules with the same fixed-interval value. Fixed-interval length was varied within subjects over pairs of experimental conditions; the ratio requirement of the tandem schedules was varied across subjects. For both subjects with a ratio requirement of 10, overall response rates and running response rates typically were higher under the tandem schedules than under the corresponding basic fixed-interval schedules. For all subjects with ratio requirements of 30 or 60, overall response rates and running response rates were higher under the tandem schedules than under the corresponding basic fixed-interval schedules only with relatively short fixed intervals. At longer fixed intervals, higher overall response rates and running rates were maintained by the basic fixed-interval schedules than by the tandem schedules. These findings support Zeiler and Buchman's (1979) reinforcement-theory account of response strength as an increasing monotonic function of both the response requirement and reinforcement frequency. Small response requirements added in tandem to fixed-interval schedules have little effect on reinforcement frequency and so their net effect is to enhance responding. Larger response requirements reduce reinforcement frequency more substantially; therefore their net effect depends on the length of the fixed interval, which limits overall reinforcement frequency. At the longest fixed intervals studied in the present experiment, reinforcement frequency under the tandem schedules was sufficiently low that responding weakened or ceased altogether.     

Effects of concurrent schedules on human fixed-interval performance

Young adults performed a lever-pressing task for money on two schedules of reinforcement: concurrent fixed-interval 1 min—differential-reinforcement-of-low-rate 20-sec, and concurrent fixed-interval 1-min—fixed ratio 100 responses. All subjects were trained on both schedules. Fixed-interval performance concurrent with the differential reinforcement procedure was characterized by high constant rates with no post-reinforcement pauses. Fixed-interval performance concurrent with fixed ratio was characterized by low rates and lengthy post-reinforcement pauses. These results differ from those obtained in prior studies on the effects of conditioning history upon subsequent fixed-interval performance. The prior work, using non-concurrent procedures, had shown that fixed-interval performance following differential reinforcement of low rates was characterized by post-reinforcement pauses and low rates, while fixed-interval performance following fixed ratio exhibited high constant rates and no post-reinforcement pause. The present results suggest that alternative concurrent contingencies are another major determinant of human fixed-interval performance.     

Computer program to generate operant schedules

A computer program for programming schedules of reinforcement is described. Students can use the program to experience schedules of reinforcement that are typically used with nonhuman subjects. A cumulative recording of a student’s responding can be shown on the screen and/or printed with the computer’s printer. The program can also be used to program operant schedules for animal subjects. The program was tested with human subjects experiencing fixed ratio, variable ratio, fixed interval, and variable interval schedules. Performance for human subjects on a given schedule was similar to performance for nonhuman subjects on the same schedule.     

Rate dependent effects of imipramine: Effects of imipramine on operant behaviour in rats at various levels of water deprivation

The behavioural effects of 1.0, 3.10 and 6.0 mg/kg imipramine injections on lever pressing of rats were studied. Lever pressing was reinforced according to a continuous reinforcement schedule at 0, 24, and 48 h of water deprivation, according to fixed ratio schedules with 22 1/2 h of water deprivation, and according to differential-reinforcement-of-low-rate schedules with 22 1/2 h of water deprivation. The mean rate of responding per min increased significantly at 1.0 mg/kg on the continuous reinforcement schedule at 24 h of deprivation. Otherwise, a dose-related significant reduction in the mean response rate per min occurred on the fixed raito schedules and partly on the differential-reinforcement-of-low-rate schedules, thus lending support to the idea that rate dependent effects may be produced only on schedules of reinforcement such as the fixed ratio, the fixed interval and the variable interval. The results also indicate that depenent effects may be produced only at moderate levels of water deprivation. Some critical comments are made on concepts of rate dependency in view of the results and of previous finding.     

A comparison of ratio and interval reinforcement schedules with comparable interreinforcement times

Pigeons were trained to peck keys on fixed-ratio and fixed-interval schedules of food reinforcement. Both schedules produced a pattern of behavior characterized as pause and run, but the relation of pausing to time between reinforcers differed for the two schedules even when mean time between reinforcers was the same. Pausing in the fixed ratio occupied less of the time between reinforcers for shorter interreinforcer times. For two of three birds, the relation was reversed at longer interreinforcer times. As an interreinforcer time elapsed, there was an increasing tendency to return to responding for the fixed interval, but a roughly constant tendency to return to responding for the fixed-ratio schedule. In Experiment 1 these observations were made for both single-reinforcement schedules and multiple schedules of fixed-ratio and fixed-interval reinforcement. In Experiment 2 the observations were extended to a comparison of fixed-ratio versus variable-interval reinforcement schedules, where the distribution of interreinforcement times in the variable interval approximated that for the fixed ratio.     

EFFECTS OF A SIGNALED DELAY TO REINFORCEMENT IN THE PREVIOUS AND UPCOMING RATIOS ON BETWEEN-RATIO PAUSING IN FIXED-RATIO SCHEDULES

Domestic hens responded under multiple fixed‐ratio fixed‐ratio schedules with equal fixed ratios. One component provided immediate reinforcement and the other provided reinforcement after a delay, signaled by the offset of the key light. The components were presented quasirandomly so that all four possible transitions occurred in each session. The delay was varied over 0, 4, 8, 16, and 32 s with fixed‐ratio 5 schedules, and over 0, 8 and 32 s with fixed‐ratio 1, 15 and 40 schedules. Main effects of fixed‐ratio value and delay duration were detected on between‐ratio pauses. Pauses were longer when the multiple‐schedule stimulus correlated with a delayed‐reinforcer component was presented, with the longest pauses occurring at the transition from a component with an immediate reinforcer to one with a delayed reinforcer. Pause durations were shortest during immediate components. Overall, both the presence or absence of a delay in the upcoming component, and the presence or absence of a delay in the preceding component affected pause length, but the upcoming delay had the larger effect. Thus changes in delay had similar effects to past reports of the effects of changes in response force, response requirement, and reinforcer magnitude in multiple fixed‐ratio fixed‐ratio schedules.     

Effects of timeout on a discrimination between fixed-ratio schedules

A discrimination was established between two fixed-ratio schedules of reinforcement. In one, fixed ratio 25, the reinforcer was delivered on the twenty-fifth response; on the other, fixed ratio 50, the fiftieth response was reinforced. In the first component of a chain, either fixed ratio 25 or fixed ratio 50 was randomly programmed on the center key of a three-key pigeon box. Reinforcement of a single peck on the side key was contingent upon discriminating which schedule had just been completed on the center key. During test trials, a timeout was introduced after the first response on fixed ratio 25 and after either the first or twenty sixth response on fixed ratio 50. When the timeout followed the first response on fixed ratio 25 and fixed ratio 50, the accuracy of the discrimination was unaffected. When the timeout followed the first response on fixed ratio 25 and the twenty sixth response on fixed ratio 50, the accuracy of the discrimination decreased rapidly to chance as a function of the duration of the timeout. The loss of discrimination was primarily due to errors after fixed ratio 50 was completed. The timeout appears to weaken the control over the choice response by the response-produced stimuli which preceded the timeout. The results are consistent with the interpretation that the discrimination between fixed ratio 25 and fixed ratio 50 is maintained by chaining of response-produced stimuli within the ratio cycle.     

Preference for mixed- versus fixed-ratio schedules

Pigeons' pecks on one key produced a stimulus correlated with a mixed-ratio schedule of food reinforcement. Pecks on a second key produced a stimulus correlated with a fixed-ratio schedule. When the arithmetic mean of the mixed ratios equaled the fixed ratio, the former stimulus maintained a higher rate of pecking. When the fixed ratio was sufficiently smaller, preference shifted to it. The pigeons' relative preference for the schedules could be described by comparing the geometric mean of the reinforcement rates in the several mixed-ratio components with the reinforcement rates in the fixed-ratio components.     

Choice for aperiodic versus periodic ratio schedules: A comparison of concurrent and concurrent-chain procedures

Choice between mixed-ratio schedules, consisting of equiprobable ratios of 1 and 99 responses per reinforcement, and fixed-ratio schedules of food reinforcement was assessed by two commonly used procedures: concurrent schedules and concurrent-chains schedules. Rats were trained under concurrent fixed-ratio mixed-ratio schedules, in which both ratio schedules were simultaneously available, and under a concurrent-chains schedule, in which access to one of the mutually exclusive ratio schedules comprising the terminal links was contingent on a single “choice” response. The distribution of responses between the two ratio schedules was taken as the choice proportion under the concurrent procedure, and the distribution of “choice” responses was taken as the choice proportion under the concurrent-chains procedure. Seven of eight rats displayed systematic choice; of those, each displayed nearly exclusive choice for fixed-ratio 35 to the mixed-ratio schedule under the concurrent procedure, but each displayed nearly exclusive choice for the mixed-ratio schedule to fixed-ratio 35 under the concurrent-chains procedure. Thus, preference for a fixed or a mixed schedule of reinforcement depended on the procedure used to assess preference.     

Effects of reinforcement magnitude on interval and ratio schedules

Rats' lever pressing was studied on three schedules of reinforcement: fixed interval, response-initiated fixed interval, and fixed ratio. In testing, concentration of the milk reinforcer was varied within each session. On all schedules, duration of the postreinforcement pause was an increasing function of the concentration of the preceding reinforcer. The running rate (response rate calculated by excluding the postreinforcement pauses) increased linearly as a function of the preceding magnitude of reinforcement on fixed interval, showed slight increases for two of the three animals on response-initiated fixed interval, and did not change systematically on fixed ratio. In all cases, the overall response rate either declined or showed no effect of concentration. The major effect of increasing the reinforcement magnitude was in determining the duration of the following postreinforcement pause, and changes in the response rate reflected this main effect.     

A Comparison of Escalating Versus Fixed Reinforcement Schedules on Undergraduate Quiz Taking

Drug abstinence studies indicate that escalating reinforcement schedules maintain abstinence for longer periods than fixed reinforcement schedules. The current study evaluated whether escalating reinforcement schedules would maintain more quiz taking than fixed reinforcement schedules. During baseline and for the control group, bonus points were distributed on random days for attending class. Following baseline, students in the fixed reinforcement section received 5 bonus points for each quiz completed while students in the escalating reinforcement received 3 bonus points for the first quiz with an increase of 0 or 1 point for each consecutive quiz completed. Results indicated that the escalating reinforcement schedule maintained quiz taking significantly longer than the fixed reinforcement schedule. The control group took the fewest number of quizzes. Students with good attendance took significantly more quizzes under the escalating reinforcement schedule than students with good attendance exposed to the fixed reinforcement schedule or control condition. This study demonstrates a potential novel application for escalating reinforcement schedules. Results indicate that escalating reinforcement schedules may be successfully applied to academic settings, but more research is needed.     

Tolerance to effects of cocaine on behavior under a response-initiated fixed-interval schedule

Tolerance to effects of cocaine can be modulated by schedules of reinforcement. With multiple ratio schedules, research has shown an inverse relationship between ratio requirement and amount of tolerance that resulted from daily administration of the drug. In contrast, tolerance to the effects of cocaine on behavior under multiple interval schedules generally has developed regardless of interval value. Under interval schedules reinforcement depends on the animal making one response following a time interval. Thus, as time to respond increases, the time to reinforcement decreases. On the other hand, fixed ratio schedules require a specified number of responses to be made prior to reinforcement. Therefore, delaying the initiation of responding does not coincide with a significant decrease in the time to reinforcement. In the current experiment, 6 pigeons were trained to respond under a three-component multiple schedule, with a different tandem fixed-ratio 1 fixed-interval schedule in each component. The multiple schedule required one response, which was followed by one of three fixed-interval values (5, 15, or 60 s). Thus, the multiple schedule was interval-like because after the fixed-ratio 1, only one more response was required for reinforcement, but it was also ratio-like because the length of the pause at the beginning of each interreinforcer interval affected the time until the next reinforcer. Acute administration of cocaine generally resulted in dose-dependent decreases in responding. Chronic (i.e., daily) administration of a rate-decreasing dose resulted in tolerance patterns similar to those usually obtained with multiple ratio schedules. That is, the magnitude of tolerance was related inversely to schedule size. These results suggest that delay to reinforcement from the initial response may play a role in the development of schedule-parameter-related tolerance.     

The reductive effects of noncontingent reinforcement fixed-time versus variable-time schedules.

The effects of fixed‐time (FT) and variable‐time (VT) schedules on responding were evaluated with 2 adults with mental retardation. Multielement and reversal designs were used to compare the effects of FT and VT schedules in reducing responses previously maintained on variable‐ratio reinforcement schedules. The schedules were equally effective in reducing the target behavior.     

Cooperative responding in rats maintained by fixed‐ and variable‐ratio schedules

The present study investigated the effects of fixed‐ratio (FR) and variable‐ratio (VR) reinforcement schedules on patterns of cooperative responding in pairs of rats. Experiment 1 arranged FR 1, FR 10, and VR 10 schedules to establish cooperative responding (water delivery depended on the joint responding of two rats). Cooperative response rates and proportions were higher under intermittent schedules than under continuous reinforcement. The FR 10 schedule generated a break‐and‐run pattern, whereas the VR 10 schedule generated a relatively high and constant rate pattern. Experiment 2 evaluated the effects of parametric manipulations of FR and VR schedules on cooperative responding. Rates and proportions of cooperative responding generally increased between ratio sizes of 1 and 5 but showed no consistent trend as the ratio increased from 5 to 10. Experiment 3 contrasted cooperative responding between an FR6 schedule and a yoked control schedule. Coordinated behavior occurred at a higher rate under the former schedule. The present study showed that external consequences and the schedules under which the delivery of these consequences are based, select patterns of coordinated behavior.     

Preference for and effects of variable-as opposed to fixed-reinforcer duration

Pigeons were trained on multiple schedules in which a fixed number of pecks produced either a fixed or a variable period of access to food, the average variable-duration reinforcement equalling the fixed. Pecking rates were generally higher during the variable-duration component. Subsequent performance on concurrent schedules revealed an initial preference for variable-duration reinforcement for all subjects; for most subjects, this preference was sustained. For one subject, the average variable duration was gradually reduced to half the fixed duration: continued preference for the variable component resulted in a loss of up to 30% of available reinforcement time. A return to multiple schedules with unequal pay-off shifted the preference to the greater fixed duration, and this preference was maintained even when the variable duration was again raised to equal the fixed duration. For the remaining subjects, the initial variable-duration preference on concurrent schedules was gradually replaced by a side preference. When the range of variable durations was varied, keeping the average variable duration equal to the fixed, the occasional longer reinforcers sustained a preference for variable-reinforcer durations for three of the four subjects.     

Hypothalamic self-stimulation in rats following immunosympathectomy or central nerve growth factor antiserum injection.

In Experiment 1, immunosympathectomized rats self-stimulated at a much lower rate on high variable ratio schedules of reinforcement than injected controls. No differences were found for responding on continuous reinforcement or low variable ratio reinforcement schedules. In Experiment 2, a similar reduction in varialbe ratio response rate was found for subjects centrally injected with nerve growth factor-antiserum relative to controls. The results suggest a reduction in central catecholamine levels as a result of antiserum treatment.     

Performance in concurrent interval schedules: a systematic replication

Five pigeons were trained on a variety of concurrent interval schedules that arranged reinforcements at either fixed or variable times after the last reinforcement. Two measures were obtained: the number of responses on each schedule, and the time spent responding on each schedule. Ratios of response rates on the two schedules did not equal ratios of reinforcement rates when both schedules were variable nor when one was variable and the other fixed. Ratios of times spent responding approximately equalled ratios of reinforcement rates when both schedules were variable, but did not do so when one was fixed.     

Concurrent fixed-ratio fixed-interval performances in adult human subjects

Two undergraduate males worked for money on a button-pressing task associated with concurrent fixed-ratio fixed-interval schedules of reinforcement. Manipulations of the fixed-ratio requirement produced an interaction between the various fixed-ratio and fixed-interval performances. When the fixed ratio was small, more fixed-interval responding occurred per interval than when the fixed ratio was large. In general, the data were similar to those obtained with lower organisms except that no post-reinforcement pause or ratio strain was seen.     

Children's preference for mixed‐ versus fixed‐ratio schedules of reinforcement: A translational study of risky choice

Laboratory research has shown that when subjects are given a choice between fixed‐ratio and bi‐valued mixed‐ratio schedules of reinforcement, preference typically emerges for the mixed‐ratio schedule even with a larger ratio requirement. The current study sought to replicate and extend these findings to children's math problem completion. Using an ABCBC reversal design, four fourth‐grade students were given the choice of completing addition problems reinforced on either a fixed‐ratio 5 schedule or one of three mixed‐ratio schedules; an equivalent mixed‐ratio (1, 9) schedule, a mixed‐ratio (1, 11) schedule with a 20% larger ratio requirement, and an equally lean mixed‐ratio (5, 7) schedule without the small fixed‐ratio 1 component. This was followed by a reversal back to the preceding phase in which preference for the mixed‐ratio schedule had been observed, and a final reversal back to the mixed‐ratio (5, 7) phase. Findings were consistent with previous research in that all children preferred the mixed‐ratio (1, 9) schedule over the equivalent fixed‐ratio 5 schedule. Preference persisted for the leaner mixed‐ratio (1, 11) schedule for three of the four children. Indifference or preference for the fixed‐ratio 5 alternative was observed in phases containing the mixed‐ratio (5, 7) schedule. These results extend previous research on risky choice to children's math problem completion and highlight the importance of a small ratio component in the emergence of preference for bi‐valued mixed‐ratio schedules. Implications of these results for arranging reinforcement to increase children's academic responding are discussed.