Progressive ratio schedules of reinforcement.

[Correction Notice: An erratum for this article was reported in Vol 35(2) of Journal of Experimental Psychology: Animal Behavior Processes (see record 2009-05154-003). The URL provided for the supplemental material was incomplete. The complete URL is http://dx.doi.org/10.1037/a0012497.supp] Pigeons' pecks produced grain under progressive ratio (PR) schedules, whose response requirements increased systematically within sessions. Experiment 1 compared arithmetic (AP) and geometric (GP) progressions. Response rates increased as a function of the component ratio requirement, then decreased linearly (AP) or asymptotically (GP). Experiment 2 found the linear decrease in AP rates to be relatively independent of step size. Experiment 3 showed pausing to be controlled by the prior component length, which predicted the differences between PR and regressive ratio schedules found in Experiment 4. When the longest component ratios were signaled by different key colors, rates at moderate ratios increased, demonstrating control by forthcoming context. Models for response rate and pause duration based on Bizo and Killeen (1997) described performance on AP schedules; GP schedules required an additional parameter representing the contextual reinforcement. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Responding under basic schedules of reinforcement in the crow.

Conditioned 5 crows to key-peck for food reinforcement using standard operant-conditioning apparatus and procedures. Responding under fixed-ratio, variable-interval, variable-ratio, and fixed-interval schedules of reinforcement was successfully maintained for each S with substantial schedule requirements. Terminal patterns of response under each of the schedules were similar to those displayed by other species, with the exception that crows paused longer after reinforcement, and responded more slowly under fixed-interval schedules, than pigeons usually do. Functional relationships between measures of performance and schedule requirements were quite consistent with reports on other species. (22 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Need for achievement and schedules of variable reinforcement.

In a simple stimulus discrimination experiment Ss were selected on the basis of their achievement need (n Ach) and assigned to 1 of 3 reinforcement conditions. Later 14 of the persons who had operated under a 5:1 schedule of reinforcement were paired on the basis of n Ach scores. The new persons were told it was a new type intelligence test and urged to do their best. Results indicated that the schedule of reinforced responses made for persons emitting more reinforced responses while n Ach was associated with a higher ratio of S responses over total response. The arousal made a difference in the ratio and seemingly had most effect on the low n Ach persons. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Kinetic considerations in the choice of treatment schedules for neuraxis radiotherapy

Neuraxis radiotherapy of radiosensitive tumours such as medulloblastoma is usually carried out using conventionally sized fractions and a shrinking field technique. Plowman and Doughty (Br. J. Radiol., 64 (1991) 603-607) have proposed a partial transmission block (PTB) technique which entails the use of small daily doses over a conventional time period. Radiobiological analysis suggests that, although the PTB technique may be adequate for slowly growing tumours, therapeutic efficacy is likely to be compromised where the tumour doubling time is short. Accelerated hyperfractionation (twice daily fractions) provides a possible alternative to both conventional scheduling and the PTB technique. Direct measurement of the kinetics of tumour cells in CSF, where possible, may provide useful guidance in the choice of regimes.     

Comparison of reinforcement schedules in the reduction of stereotypy with supported routines

The rates and durations of stereotypic behaviors in four adolescents with severe mental retardation were measured during two daily vocational training sessions and during contiguous periods of leisure in their special education classrooms. Vocational training was conducted in two different tasks, alternating across days. The task requirements for each participant were matched to each participant's learning and performance characteristics. The participants were exposed to a fixed ratio schedule of tokens exchangeable for food items on one task and to a variable interval schedule for the same consequences on the second task. The schedules were chosen as an initial test of a matching-law based prediction by Myerson and Hale (1984): Variable interval reinforcement for adaptive behavior will produce less allocation of responding to maladaptive behavior than will a ratio-based intervention. When work performances stabilized, the schedules of token delivery were reversed across the tasks and performances again stabilized. Results are reported for periods when work performances met stability criteria. Stereotypy occurred more during leisure than during vocational training under either schedule. The major differences in stereotypy between leisure and vocational training were differences in episode length rather than rate of onset. Onset of stereotypy in vocational training, however, occurred at higher rates under the interval schedule than under the ratio schedule in both tasks. The results are discussed in terms of Myerson and Hale's prediction and implications for further research and application.     

An investigation of responding on schedules of electrical brain-stimulation reinforcement.

In Exp I, the leverpressing responses of rats (8 male hooded Long-Evans) were maintained by reinforcement consisting of single trains of electrical stimulation of the brain (ESB) presented on random-interval (RI) schedules ranging in value from RI 3-min to RI 10-min. Both the cumulative response patterns and the relationship of response rates to reinforcement density were similar to those observed for Ss reinforced conventionally. In Exp II with 19 male hooded Long-Evans rats, leverpressing was reinforced with single trains of signalled ESB, unsignalled response-contiguous ESB, or sweetened condensed milk presented on random-ratio schedules. Most of the ESB-reinforced Ss and half of the milk-reinforced Ss stopped responding at ratio values exceeding 50:1, while the remaining Ss responded at higher ratios. Response rates were higher at lower ratio values for the ESB groups than for the milk group, but as ratio values increased, all groups showed similar decreases in rate. All Ss were observed to initiate responding faster than inexperienced controls, and priming was not required. (French summary) (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Performance of goldfish trained on multiple schedules of response-independent reinforcement.

In 3 experiments, 2 with appetitively elicited target striking and a 3rd with aversively elicited shuttling, 42 goldfish were trained on variable time schedules of response-independent reinforcement with or without a correlation between conditioned stimulus color and probability of reinforcement. Unlike pigeons in keypecking situations, Ss responded strongly even on uncorrelated schedules. In the 2nd and 3rd experiments—in which density of reinforcement and contingency were unconfounded—the level of response to a color was determined only by probability of reinforcement, independently of stimulus-reinforcer contingency. Except on the assumption that both measured responses are products entirely of adventitious response-reinforcer control, which seems particularly unlikely in the case of shuttling, the results cast doubt on the generality of the contingency interpretation of classical conditioning. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interresponse-time reinforcement and behavior under aperiodic reinforcement schedules: A case study using computer modeling.

Computer modeling was used to investigate the extent to which response rates under variable-interval and variable-ratio schedules are compatible with a simple process of interresponse time (IRT) reinforcement, as argued by Peele, Casey, and Silberberg (1984). Their computer model was duplicated, as well as its principal result of a large response rate difference between the interval and ratio schedules. After their model was run under a variety of interval and ratio schedules, it was found that the response rates produced did not exhibit patterns of sensitivity to schedule parameter variation found experimentally. Furthermore, the model predicted a large response rate difference between a variable-ratio and a "linear feedback" variable-interval schedule, contrary to the results of McDowell and Wixted (1986). We concluded that simple IRT reinforcement was probably not adequate as an explanation of schedule effects under aperiodic interval and ratio schedules, although a modification of the Peele et al. model incorporating behaviors that were not measured operants could exhibit schedule sensitivity. This suggested that realistic molecular models of schedule phenomena must involve more than simple IRT reinforcement. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ethanol preloads increase ethanol preference under concurrent random-ratio schedules in social drinkers.

Ethanol (ETOH) preference was measured following ETOH preload doses in normal social drinkers. 11 Ss participated in a 5-session, double-blind choice study. In Session 1, Ss sampled an ETOH beverage (0.8 g/kg). In Sessions 2–5, they consumed a preload beverage containing placebo or ETOH (0.25 or 0.5 g/kg). One hour later, they responded on 2 concurrent random-ratio (RR) schedules. One schedule was associated with ETOH as the reinforcer and the other with money. When the probability of earning money was low, Ss responded more on the ETOH schedule following both ETOH preloads compared with placebo. Consistent with the increased responding for ETOH, Ss reported increased desire for ETOH. These data demonstrate a priming effect of ETOH preloads in normal social drinkers. They also illustrate the use of concurrent RR schedules to quantify ETOH preference. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effectiveness of pay incentives under variable ratio and continuous reinforcement schedules.

Investigated the effectiveness of 2 variable ratio and 1 crf payment schedule(s) on the performance of 15 female undergraduates in a simulated job situation. Production for the 3 groups was compared to test hypotheses derived from instrumentality theory and the operant conditioning literature. Results fail to support instrumentality theory. Pay incentives were more effective in motivating increased production when used with a variable ratio schedule than with a crf schedule. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Benzodiazepine-GABA modulation of concurrent ethanol and sucrose reinforcement in the rat.

These experiments examined the role of the benzodiazepine (BZ)-GABA receptor complex in modulating ethanol consumption in rats. Lever presses were reinforced with concurrently available, isocaloric solutions: 10% ethanol-10% sucrose and 24% sucrose. Both reinforcers were available on independent, variable-interval 5-s schedules of reinforcement. In baseline sessions, rats earned approximately 110 sucrose reinforcers and 131 ethanol-sucrose reinforcers, equivalent to about 2 g ethanol per kilogram of body weight. Before experimental sessions, rats received injections of Ro 15-4513, Ro 15-1788, and Ro 15-4513 in combination with Ro 15-4513, chlordiazepoxide, picrotoxin, baclofen, and muscimol. Responding for the ethanol solution was significantly and selectively reduced by the BZ inverse agonist Ro 15-4513, and this effect was blocked by administration of the BZ antagonist Ro 15-1788. Conversely, responding for the ethanol solution increased following a low dose of the BZ agonist chlordiazepoxide. A low dose of baclofen significantly decreased responding for sucrose and increased consumption of ethanol. Picrotoxin and muscimol selectively reduced responding for the ethanol solution. These results are discussed in terms of the relationship between the BZ-GABA receptor complex and ethanol consumption. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of probability of reinforcement in models of choice.

A general account of choice behavior in animals, the cumulative effects model, has been proposed by D. Davis et al (see record 1993-28240-001). Its basic assumptions are that choice occurs in an all-or-none fashion for the response alternative with the highest probability of reinforcement and that the probability of reinforcement for each response alternative is calculated from the entire history of training (total number of reinforced responses/total number of reinforced and nonreinforced responses). The model's reliance on probability of reinforcement as the fundamental variable controlling choice behavior subjects the cumulative effects model to the same criticisms as have been directed toward other related models of choice, notably melioration theory. Several data sets show that the relative value of a response alternative is not predicted by the obtained probability of reinforcement associated with that alternative. Alternative approaches to choice theory are considered. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparisons of teacher reinforcement schedules for students with different social class backgrounds.

Frequencies of teacher reinforcement of lower- and middle-class students were systematically tabulated with the Teacher Reinforcement Schedule. Six observers made a total of 30 min of recordings within each of 12 1st- and 12 3rd-grade classrooms. At both grade levels, classes were equally divided into those with predominantly lower- or middle-class students. A series of repeated measures analyses of variance indicated that specific types of reinforcement were given significant more often to middle- than to lower-class children. Reliable teacher reinforcement differences between grade levels were also located, as well as significantly Pupil Socioeconomic Status-Grade Level interactions. By combining categories, it was shown that middle-class students received significantly more nonverbal reinforcements than lower-class students; however, a reliable difference in frequency of verbal reinforcement was not observed. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Primacy of interresponse-time reinforcement in accounting for rate differences under variable-ratio and variable-interval schedules.

Pigeons' keypeck rates under VR schedules are typically higher than under VI schedules when between-schedule reinforcement rates are equated. Exp I, with 4 male White Carneaux pigeons, reproduced this between-schedule rate difference in a multiple VR-VI schedule. However, when the short interresponse times (IRTs) typically reinforced under VRs were required for VI reinforcement, between-component rate differences diminished. Exp II (4 Ss) replicated Exp I except that long IRTs reinforced under VI schedules were required for VR reinforcement. This manipulation eliminated between-schedule rate differences. In Exp III (4 Ss), VR/VI and VI/VR tandems had the same correlation between response and reinforcement rates. In a simulation, C. P. Shimp's (1969) IRT response rule was used as an algorithm to mimic between-schedule rate difference. Findings show that IRT reinforcement (a molecular factor), rather than the feedback function between response rate and reinforcement rate (a molar factor), accounts for the higher response rates under VR schedules. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The choice of the optimal schedules in the vaccination procedure against influenza in elderly subjects

The paper describes a clinical case of the cerebral hyperperfusion syndrome, a rare complication of carotid endarterectomy. The syndrome appeared as the generalized convulsive syndrome in the patient in the early postoperative period. In the context of clinical observation, the results of analysis of the literature are presented and the pathogenesis, diagnosis, therapy, and prevention of the cerebral hyperperfusion syndrome considered.     

Response rate and sensitivity to the molar feedback function relating response and reinforcement rate on VI+ schedules of reinforcement.

In 5 experiments, the author examined rats' sensitivity to the molar feedback function relating response rate to reinforcement rate on schedules of reinforcement. These studies demonstrated that, at lower rates of responding, rats' performance on variable ratio (VR), variable interval (VI), and variable interval with linear feedback loop (VI+) schedules was determined largely by reinforcement of interresponse times; response rates were faster on VR than on both VI and VI+ schedules. In contrast, when procedures were adopted to maintain high rates of response, rats showed sensitivity to the molar characteristics of the schedules; they responded as fast on a VI+ schedule as on a VR schedule and faster on both of these schedules than on a yoked VI schedule. When the variance of response rate was manipulated, this factor was noted as an important element in determining sensitivity to the molar characteristics of the schedule. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influences of delay and rate of reinforcement on discrete-trial choice.

An adjusting procedure was used to measure 4 White Carneaux pigeons' preferences among alternatives that differed in the duration of a delay before reinforcement and of an intertrial interval (ITI) after reinforcement. In most conditions, a peck at a red key led to a fixed delay, followed by reinforcement, a fixed ITI, and then the beginning of the next trial. A peck at a green key led to an adjustable delay, reinforcement, and then the next trial began without an ITI. The purpose of the adjusting delay was to estimate an indifference point, or a delay that made an S approximately indifferent between the 2 alternatives. As the ITI for the red key increased from 0 to 60 sec, the green-key delay at the indifference point increased systematically, but only slightly. The fact that there was some increase showed that Ss' choices were controlled by more than simply the delay to the next reinforcer. An analysis that ignored reinforcement rate but that considered the delays between a choice response and the reinforcers on subsequent trials was able to account for most of the obtained increases in green-key delays. It is concluded that in this type of discrete-trial situation, rate of reinforcement exerts little or no control over choice behavior. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cross-modal differentiation under identical reinforcement schedules, and UCS-intensity effects in human classical eyelid conditioning.

Assesses cross-modal differentiation between light and tone CS with specially developed tests applied to selected trials of a 41-trial conditioning series which employed a delayed, 500-msec interstimulus interval, and an overall reinforcement schedule of 67%, 1-msec UCS pairings for both CS. An unpaired CS-and-UCS control group of 64 Ss indicated reliable conditioning for the 128 experimentals (Ss were undergraduates). There was some differentiation even for those 64 experimentals for whom the identity of reinforcement schedules for the CS was maintained throughout the trial series. Magnitude and frequency of CR were reliably direct functions of both between- and within-Ss variations of UCS intensity (120 or 260 V DC infraorbital shock). Emphasized was the importance of providing within-experimental differentiation tests especially for experiments where the within-Ss treatment effect fails to emerge. (French summary) (23 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Employee reaction to continuous and variable ratio reinforcement schedules involving a monetary incentive.

Examined the performance of 12 mountain beaver trappers (aged 21–40 yrs) when a monetary incentive was administered on continuous and VR-4 schedules of reinforcement. On alternate weeks (over a 12-wk period), Ss received $1 for every beaver caught. On the VR-4 schedule, each S received $4 contingent on presenting the beaver to the supervisor and correctly predicting an even or odd number on a dice roll. Consistent with operant theory, the performance of Ss was higher on the VR-4 reinforcement schedule. Ss were interviewed to determine what they viewed as differentiating the 2 schedules of reinforcement. Based on the interviews, a questionnaire was developed and administered. Results indicate that the VR-4 schedule was perceived as including job enrichment variables such as recognition, task variety, task accomplishment, and feedback, whereas this was less likely to be the case when the incentive was paid on a continuous schedule. (10 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)