Aversive schedules with independent probabilities of reinforcement for responding and not responding by rhesus monkeys: II. Without signal.

Manipulated independently the probabilities of aversive stimulus presentation given the occurrence or the nonocurrence of a leverpress response. 10 naive male rhesus monkeys (Macaca mulatta) were divided into 5 groups, each group receiving a different sequence of the 2 probabilities and thereby a different sequence of electric shock presentation schedules ranging between avoidance and punishment. The schedules provided systematic control both of the amount of response facilitation that occurred when response-produced shocks were first introduced following avoidance training and of the postfacilitation response rate decline. When the probability of shock presentation following a response was less than that for not responding, scalloped response patterns occurred; when the relative shock probabilities were reversed, bipeak response patterns were observed. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Aversive schedules with independent probabilities of reinforcement for responding and not responding by rhesus monkeys: III. Recovery of avoidance baseline.

Investigated the effect of prior response history on subsequent avoidance responding. In Exps I and II, using 12 and 10 male rhesus monkeys that had served in previous experiments by the authors (see PA, Vol 53:Issue 6), up to 5 sequences of aversive stimulus presentation schedules provided a range from no responding to complete avoidance response recovery, whether with or without signaled shock. Exp III, with 12 naive rhesus monkeys, demonstrated that the same range of avoidance response recovery could be obtained by the use of only selected schedules rather than a prolonged sequence. These findings provide further support for the power of 2 independent probability variables, governing reinforcement delivery for responding or nonresponding, for generating schedules of reinforcement. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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)     

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)     

Effects of pedunculopontine tegmental nucleus lesions on responding for intravenous heroin under different schedules of reinforcement

The pedunculopontine tegmental nucleus (PPTg) is believed to play important roles in reward and learning. We examined the effect of PPTg lesions (0.5 microl of 0.1 M NMDA injected bilaterally over 10 min) on the learning of an operant response for opiate reward. In 14 adult male Long-Evans rats, bilateral lesions of the PPTg disrupted the acquisition of responding for intravenous heroin (0.1 mg/kg infused at a rate of 0.25 ml/28 sec) on a fixed ratio-1 (FR-1) schedule of reinforcement. The 12 remaining lesioned animals increased their heroin intake over the acquisition sessions but did not reach the response levels of sham-lesioned animals on the 15th and final session. The sham- and PPTg-lesioned animals that learned the FR-1 task exhibited similar patterns of responding during extinction and reacquisition sessions. When tested on a progressive ratio (PR) schedule of reinforcement, however, PPTg-lesioned animals had lower break points than sham-lesioned animals. Asymmetric lesions, which destroyed the majority of the nucleus in one hemisphere only, did not produce any behavioral deficits. Rats that were lesioned after training also did not show deficits in responding under either FR or PR schedules. These findings suggest that PPTg lesions reduce the rewarding effect of opiates but do not disrupt the ability either to learn an operant response or the response requirements of a PR schedule.     

Sucrose, ethanol, and sucrose/ethanol reinforced responding under variable-interval schedules of reinforcement

Adding sweeteners to ethanol solutions is a common method of inducing rats to consume ethanol. However, it has usually been assumed that it is the sweet taste and/or the calories contained in the sweet solution that controls consumption. The present experiment examined the role of ethanol in controlling responding reinforced by ethanol or an ethanol/sucrose mixture compared with sucrose solutions of various concentrations. After initiation to self-administer 10% (v/v) ethanol using the sucrose-substitution method, rats were trained to respond under a concurrent VI 5" VI 5" schedule. During one condition, responding on one lever was reinforced by the presentation of 10% ethanol, and responding on a second lever was reinforced by water or one of the following sucrose solutions: 1% (w/v), 1.5%, 2%, 2.5%, 3%, and 5%. During a subsequent condition, responding reinforced by a 10% ethanol/2% sucrose mixture was compared under the concurrent schedule with responding reinforced by water, 2%, 2.5%, 3%, 5%, or 10% sucrose (w/v). The results indicated that the ethanol or ethanol/sucrose mixture maintained more responding than did sucrose solutions that were sweeter. Data support the conclusion that, after initiation, the taste and/or pharmacological effects of ethanol had become an important component of the reinforcing stimulus independent of the sweetener.     

Delay discounting of cocaine by rhesus monkeys.

The present, subjective value of a reinforcer typically decreases as a function of the delay to its receipt, a phenomenon termed delay discounting. Delay discounting, which is assumed to reflect impulsivity, is hypothesized to play an important role in drug abuse. The present study examined delay discounting of cocaine injections by rhesus monkeys. Subjects were studied on a discrete-trials task in which they chose between 2 doses of cocaine: a smaller, immediate dose and a larger, delayed dose. The immediate dose varied between 0.012 and 0.4 mg/kg/injection, whereas the delayed dose was always 0.2 mg/kg/injection and was delivered after a delay that varied between 0 and 300 s in different conditions. At each delay, the point at which a monkey chose the immediate and delayed doses equally often (i.e., the ED50) provided a measure of the present, subjective value of the delayed dose. Dose-response functions for the immediate dose shifted to the left as delay increased. The amount of the immediate dose predicted to be equal in subjective value to the delayed dose decreased as a function of the delay, and hyperbolic discounting functions provided good fits to the data (median R2 = .86). The current approach may provide the basis for an animal model of the effect of delay on the subjective value of drugs of abuse. (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)     

Consort bonding and operant behavior by female rhesus monkeys.

An operant conditioning situation was used to relate the leverpressing performance of female rhesus monkeys to different measures of social, sexual, and agonistic behavior that underlie the formation and dissolution of consort bonds. Nine females were trained to press a lever 250 times to gain access to a male partner. After access, a standard 60-min behavioral test took place (1,440 tests). Data were analyzed independently of the stage of the menstrual cycle. Eight females were tested with 2 males, and every female gained access faster with 1 male (i.e, preferred partner). For all 8 females, the preferred male was the one that spent more time grooming the female. For 5 females, the preferred partner was also the one that ejaculated more frequently. For 4 females, where agonistic interactions with males could be evaluated, the preferred male was the one that elicited fewer submissive behavioral patterns. These results indicate that the operant behavior of female rhesus monkeys is positively reinforced by social and sexual factors and negatively reinforced by agonistic interactions and may thus provide a measure of the strength of consort bonds. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Abstract-concept learning and list-memory processing by capuchin and rhesus monkeys.

Three capuchin monkeys (Cebus apella) touched the lower of 2 pictures (same) or a white rectangle (different), increased same/different abstract-concept learning (52% to 87%) with set-size increases (8 to 128 pictures), and were better than 3 rhesus monkeys (Macaca mulatta). Three other rhesus that touched the top picture before choices learned similar to capuchins but were better at list-memory learning. Both species' serial position functions were similar in shape and changes with retention delays. Other species showed qualitatively similar shape changes but quantitatively different time-course changes. In abstract-concept learning, qualitative similarity was shown by complete concept learning, whereas a quantitative difference would have been a set-size slope difference. Qualitative similarity is discussed in relation to general-process versus modular cognitive accounts. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Serial learning by rhesus monkeys: II. Learning four-item lists by trial and error.

Three rhesus macaque monkeys were trained to produce novel 4-item lists (A → B → C → D) on which all items were displayed from the start of training. Subjects were previously trained to produce 4-item lists by adding one item at a time (A, A → B, A → B → C, and A → B → C → D; lists K. B. Swartz et al., 1991). Those lists could be mastered by responding to each new item last. To learn lists on which all items were displayed from the start of training, subjects had to recall the consequences of errors and correct responses to each item. Errors ended the trial; correct responses to A, B, or C allowed the trial to continue. A correct response to D produced food reward. Although the probability of executing a 4-item list correctly by chance was .04, each subject mastered 4 novel 4-item lists by trial and error. The ability of monkeys to use a trial-and-error strategy to learn novel lists provides a basis for studying the development of serial expertise in animals. (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)     

Effects of phentermine on responding maintained under multiple fixed-ratio schedules of food and cocaine presentation in the rhesus monkey

Drugs that decrease drug-maintained responding at doses that do not decrease other behaviors in animals may be suitable candidates for development as medications to treat drug abuse in humans. The present study examined whether this effect could be obtained with phentermine, a drug that has been reported to decrease cocaine intake in humans. Rhesus monkeys were trained under multiple fixed-ratio 30-response schedules of food and i.v. cocaine delivery. Phentermine was always given as a slow, i.v. infusion. Acute treatment with phentermine (0.3-10 mg/kg) decreased cocaine-maintained responding at doses that did not decrease, or decreased less, food-maintained responding for each of three unit doses of cocaine (10-100 microg/kg/injection). Subacute treatment with phentermine (3 or 5.6 mg/kg, daily) also decreased cocaine-maintained responding more than food-maintained responding. After subacute treatment was terminated, rates of cocaine-maintained responding generally recovered to levels comparable to those seen during untreated control sessions. Phentermine (0.3-3 mg/kg) did not generally increase responding associated with a very low (1 microg/kg/injection) unit dose of cocaine, suggesting that the decrease in cocaine-maintained responding at higher unit doses was not the result of a leftward shift in the cocaine unit dose-effect function. Phentermine (0.1-3 mg/kg) decreased responding maintained by 1-[2-[bis(4-fluorophenyl) methoxy]ethyl]-4-[3-phenylpropyl] piperazine (GBR 12909) (30 microg/kg/injection) at doses similar to those that decreased food-maintained responding. These results show that phentermine is effective in decreasing cocaine self-administration and suggest that it may be an effective medication for cocaine abuse.     

Attenuation and enhancement of instrumental responding by signals for reinforcement on a variable interval schedule.

In three experiments we used pigeons responding on a variable interval schedule to examine the effects of signaling reinforcement on instrumental performance. Using a four-component multiple schedule, we found in Experiment 1 that when reinforcement was delayed by 0.5 s for two of the components, response rates were attenuated by signaling reinforcement relative to performance in the unsignaled delay condition. A delay of 3 s in the remaining two components resulted in an enhancement of responding when the delay was signaled. An enhancement of responding occurred when we used a scheduled 0.5-s delay when the procedure ensured that responding was prevented during the delay interval by extinguishing the keylight (Experiment 2) or by resetting the delay timer when responses were emitted during the delay (Experiment 3). These results are discussed with reference to the theories of signaling reinforcement during instrumental responding. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of medial prefrontal or anterior cingulate cortex lesions on responding for cocaine under fixed-ratio and second-order schedules of reinforcement in rats

Four experiments examined the effects of excitotoxic, axon-sparing lesions of the medial prefrontal cortex or anterior cingulate cortex in rats on responding under different schedules of intravenous cocaine self-administration and on the locomotor stimulant effects of cocaine. Experiment 1 tested the acquisition and maintenance of cocaine self-administration under a fixed ratio schedule. Rats with medial prefrontal cortex lesions showed facilitated acquisition and enhanced responding for low doses of the drug when lesions were induced before self-administration behaviour was established. Lesions of the anterior cingulate cortex did not affect cocaine self-administration. In experiment 2, rats were trained to respond under a second-order schedule of cocaine reinforcement, where responding during the fixed interval was reinforced by presentation of a cocaine-associated visual stimulus under fixed-ratio contingencies. In control rats, these schedule conditions were found to maintain high rates of responding and a scalloped pattern of responding over time. Omission of conditioned stimulus presentation during the fixed interval significantly disrupted response patterns, confirming that the stimulus served to maintain responding during the fixed interval. By contrast, rats with medial prefrontal cortex lesions showed higher rates and disrupted patterns of responding that were unchanged by stimulus omission. Rats with lesions of the anterior cingulate cortex responded at high rates throughout the fixed interval under all test conditions, indicating that the cocaine-associated stimulus did not serve to maintain temporal patterns of responding in these rats. Experiment 3 demonstrated the lack of effect of either lesion on the acquisition of responding for a non-drug reinforcer, sucrose. In experiment 4, measures of spontaneous and cocaine-induced locomotor activity revealed that rats in both lesion groups were significantly more active than controls regardless of test conditions. These data indicate that facilitated acquisition of cocaine self-administration and disrupted response patterns under second-order schedule contingencies may result from deficits in behavioural inhibition induced by medial prefrontal cortical lesions that contrast with deficits following damage to other limbic cortical regions, such as the basolateral amygdala or anterior cingulate cortex.     

Dissociated learning and state-dependent retention induced by pentobarbital in rhesus monkeys.

Demonstrated that 8 rhesus monkeys were subject to drug-dissociated learning and state-dependent retention in training situations involving color choices when alternate pharmacological states were produced by intraperitoneal injections of sodium pentobarbital or saline. Learning of a position discrimination was only moderately dissociated between states. Overtraining of color discrimination problems reduced dissociation between states and made subsequent cue reversal learning more difficult. A simple motor response did not dissociate between states. (24 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Oral cocaine self-administration in rhesus monkeys: Strategies for engendering reinforcing effects.

Orally delivered cocaine was established as a reinforcer for 8 rhesus monkeys (Macaca mulatta). Initially, each monkey was given a choice between the water vehicle and a 0.2 mg/ml cocaine concentration. The 0.2 mg/ml solution was not consumed in preference to water. One or more acquisition procedures were used with each monkey to establish orally delivered cocaine as a reinforcer. A common feature of all but one procedure was environmental situations that lead to the elective drinking of the cocaine solution. Evidence confirming the establishment of cocaine's reinforcing effects was obtained by testing each monkey across a broad range of cocaine concentrations under conditions of concurrent access to the cocaine solution and vehicle. Over a range of concentrations, the monkeys obtained greater cocaine than vehicle deliveries. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual observing by rhesus monkeys: influence of potentially threatening stimuli

7 rhesus monkeys were afforded the opportunity to observe a series of projected color slides of other monkeys exhibiting five content categories of social-communicative behavior (submission, intense threat, mild threat, grooming, and neutral behavior) combined with two levels of familiarity (familiar vs unfamiliar) with reference to the animals depicted in the slides. Mean duration of observing was significantly influenced by the social-communicative content categories, while mean frequency of observing was significantly affected by the familiarity dimension. The data were discussed in terms of the threat potential or fear-arousing capacity of social stimuli in relation to visual obsrving.     

Adrenal responses to reinforcement and extinction: Role of expectancy versus instrumental responding.

Measured plasma corticosterone levels during operant conditioning to determine the effect of reinforced and nonreinforced responding (extinction) on adrenal activation; Ss were 44 male Long-Evans rats. The influence of instrumental responding was assessed by comparing trained Ss with yoked Ss that received a matched reward schedule in the absence of an operant task. Reinforcement sessions resulted in a significant decrease in adrenal secretion at 20 min but not at 5 min, whereas extinction caused a rapid increase in corticosterone levels at 5 min and an even greater elevation at 20 min. Comparison of the operant and yoked Ss showed that this effect of reinforcement and extinction was not dependent on instrumental responding, but rather on the receipt or withdrawal of the expected reward. (21 ref) (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)