A developmental study of timing behavior in 4 1/2- and 7-year-old children

The present study investigated effects of age and instructions on temporal regulations of behavior in children. In the first experiment 4 1/2-year-old and 7-year-old subjects were trained with a DRL (differential reinforcement of low rates) 5-s and a DRL 10-s schedule. Results demonstrate that age and timing performance are related. Seven-year-olds are more efficient than the 4 1/2-year-olds. A striking decline in the 4 1/2-year-old children's capacity to space responses was observed in the DRL 10-s schedule as compared to the DRL 5-s schedule. Analysis of individual performances suggests that the evolution of DRL performance between 4 and 7 years of age depends not only on the development of the capacity to delay responding but also on the acquisition of the ability to represent the reinforcement contingencies, that is, the temporal parameters of the task to oneself. In order to test this hypothesis a second experiment was conducted where instructions to wait between operant responses were given to a group of 4 1/2-year-old subjects at the beginning of a DRL 5-s and a DRL 10-s schedule. The results show that these instructions enhance DRL performance. By directing the 4 1/2-year-old subjects' attention to the temporal requirements of the task, instructions led to efficient performance and accurate timing of responses to the DRL schedule.     

AGGRESSION AS POSITIVE REINFORCEMENT IN MICE UNDER VARIOUS RATIO‐ AND TIME‐BASED REINFORCEMENT SCHEDULES

There is evidence suggesting aggression may be a positive reinforcer in many species. However, only a few studies have examined the characteristics of aggression as a positive reinforcer in mice. Four types of reinforcement schedules were examined in the current experiment using male Swiss CFW albino mice in a resident—intruder model of aggression as a positive reinforcer. A nose poke response on an operant conditioning panel was reinforced under fixed‐ratio (FR 8), fixed‐interval (FI 5‐min), progressive ratio (PR 2), or differential reinforcement of low rate behavior reinforcement schedules (DRL 40‐s and DRL 80‐s). In the FR conditions, nose pokes were maintained by aggression and extinguished when the aggression contingency was removed. There were long postreinforcement pauses followed by bursts of responses with short interresponse times (IRTs). In the FI conditions, nose pokes were maintained by aggression, occurred more frequently as the interval elapsed, and extinguished when the contingency was removed. In the PR conditions, nose pokes were maintained by aggression, postreinforcement pauses increased as the ratio requirement increased, and responding was extinguished when the aggression contingency was removed. In the DRL conditions, the nose poke rate decreased, while the proportional distributions of IRTs and postreinforcement pauses shifted toward longer durations as the DRL interval increased. However, most responses occurred before the minimum IRT interval elapsed, suggesting weak temporal control of behavior. Overall, the findings suggest aggression can be a positive reinforcer for nose poke responses in mice on ratio‐ and time‐based reinforcement schedules.     

Differential reinforcement of low rates performance by impulsive and reflective children

Third-grade boys classified as either cognitively impulsive or reflective were reinforced for key pressing according to a DRL (differential reinforcement of low rates) 6-sec schedule of reinforcement. Half of each group received instructions about the behavioral requirements for obtaining reinforcements. Prior to DRL training, impulsive Ss showed a low probability of key press responding at long interresponse time (IRT) intervals while reflective Ss exhibited an equal probability of terminating either short or long IRTs. During training and in the absence of instructions, impulsives exhibited a less precise temporal discrimination, characterized by a greater predominance of response bursts (0–2 sec IRTs) following reinforcements, than reflective Ss. While impulsive and reflective Ss displayed similar frequencies of collateral behavior between successively reinforced responses, impulsives engaged in the reinforced response more frequently and tended (p < .08) to obtain fewer reinforcements. Instructions served to enhance the DRL performance.     

Effects of reinforcer magnitude on responding under differential-reinforcement-of-low-rate schedules of rats and pigeons

Experiment I investigated the effects of reinforcer magnitude on differential-reinforcement-of-low-rate (DRL) schedule performance in three phases. In Phase 1, two groups of rats (n = 6 and 5) responded under a DRI. 72-s schedule with reinforcer magnitudes of either 30 or 300 microl of water. After acquisition, the water amounts were reversed for each rat. In Phase 2, the effects of the same reinforcer magnitudes on DRL 18-s schedule performance were examined across conditions. In Phase 3, each rat responded unider a DR1. 18-s schedule in which the water amotnts alternated between 30 and 300 microl daily. Throughout each phase of Experiment 1, the larger reinforcer magnitude resulted in higher response rates and lower reinforcement rates. The peak of the interresponse-time distributions was at a lower value tinder the larger reinforcer magnitude. In Experiment 2, 3 pigeons responded under a DRL 20-s schedule in which reinforcer magnitude (1-s or 6-s access to grain) varied iron session to session. Higher response rates and lower reinforcement rates occurred tinder the longer hopper duration. These results demonstrate that larger reinforcer magnitudes engender less efficient DRL schedule performance in both rats and pigeons, and when reinforcer magnitude was held constant between sessions or was varied daily. The present results are consistent with previous research demonstrating a decrease in efficiency as a function of increased reinforcer magnituide tinder procedures that require a period of time without a specified response. These findings also support the claim that DRI. schedule performance is not governed solely by a timing process.     

Prenatal choline supplementation alters the timing, emotion, and memory performance (TEMP) of adult male and female rats as indexed by differential reinforcement of low-rate schedule behavior

Choline availability in the maternal diet has a lasting effect on brain and behavior of the offspring. To further delineate the impact of early nutritional status, we examined effects of prenatal-choline supplementation on timing, emotion, and memory performance of adult male and female rats. Rats that were given sufficient choline (CON: 1.1 g/kg) or supplemental choline (SUP: 5.0 g/kg) during embryonic days (ED) 12-17 were trained with a differential reinforcement of low-rate (DRL) schedule that was gradually transitioned through 5-, 10-, 18-, 36-, and 72-sec criterion times. We observed that SUP-females emitted more reinforced responses than CON-females, which were more efficient than both groups of males. In addition, SUP-males and SUP-females exhibited a reduction in burst responding (response latencies <2 sec) compared with both groups of CON rats. Furthermore, despite a reduced level of burst responding, the SUP-males made more nonreinforced responses prior to the DRL criterion as a result of maintaining the previous DRL criterion following transition to a new criterion. In summary, long-lasting effects of prenatal-choline supplementation were exhibited by reduced frustrative DRL responding in conjunction with the persistence of temporal memory in SUP-males and enhanced temporal exploration and response efficiency in SUP-females.     

A computer analysis of serial interactions in spaced responding

Serial dependencies in interresponse times were studied by means of a digital computer. In monkeys exposed to a DRL 20-sec schedule of reinforcement, serial interactions appeared at all stages of training. Early in training the serial effects consisted of trains of relatively long interresponse times interspersed among trains of relatively short ones. Later on, the serial effects appeared to be characterized by a tendency to drift up and down in long wavelength periods around the minimum interval required for reinforcement. After training to a point at which most interresponse times produced reinforcement, serial effects of a still more subtle nature appeared. These effects were made apparent by autocorrelation and power spectrum methods and consisted of both long-term and extremely short-term fluctuations in interresponse times.     

Effects of a DRL contingency added to a fixed-interval reinforcement schedule

Following 30 days of reinforcement for the bar press response of two white rats on 30-sec fixed-interval (FI), a DRL component was added so that a minimal interresponse time (IRT) for the reinforced response, in addition to the FI variable, was necessary for reinforcement. Marked control over response rate by the superimposed DRL requirement was demonstrated by an inverse hyperbolic function as the DRL component was increased from 1 to 24 sec within the constant 30-sec FI interval. Interresponse time and post-reinforcement (post-S^R) “break” distributions taken at one experimental point (DRL = 24 sec) suggested that a more precise temporal discrimination was initiated by an S^R than by a response, since the relative frequency of a sequence of two reinforced responses appeared greater than that of a sequence of a non-reinforced response followed by a reinforced one. This latter finding was confirmed with new animals in a follow-up experiment employing a conventional 24-sec DRL schedule.     

Some determinants of remote behavioral history effects in humans

Undergraduates were exposed to a series of reinforcement schedules: first, to a fixed-ratio (FR) schedule in the presence of one stimulus and to a differential-reinforcement-of-low-rate (DRL) schedule in the presence of another (multiple FR DRL training), then to a fixed-interval (FI) schedule in the presence of a third stimulus (FI baseline), next to the FI schedule under the stimuli previously correlated with the FR and DRL schedules (multiple FI FI testing), and, finally, to a single session of the multiple FR DRL schedule again (multiple FR DRL testing). Response rates during the multiple FI FI schedule were higher under the former FR stimulus than under the former DRL stimulus. This effect of remote histories was prolonged when either the number of FI-baseline sessions was small or zero, or the time interval between the multiple FR DRL training and the multiple FI FI testing was short. Response rates under these two stimuli converged with continued exposure to the multiple FI FI schedule in most cases, but quickly differentiated when the schedule returned to the multiple FR DRL.     

Exclusive preference develops less readily on concurrent ratio schedules with wheel-running than with sucrose reinforcement

Previous research suggested that allocation of responses on concurrent schedules of wheel‐running reinforcement was less sensitive to schedule differences than typically observed with more conventional reinforcers. To assess this possibility, 16 female Long Evans rats were exposed to concurrent FR FR schedules of reinforcement and the schedule value on one alternative was systematically increased. In one condition, the reinforcer on both alternatives was .1 ml of 7.5% sucrose solution; in the other, it was a 30‐s opportunity to run in a wheel. Results showed that the average ratio at which greater than 90% of responses were allocated to the unchanged alternative was higher with wheel‐running reinforcement. As the ratio requirement was initially increased, responding strongly shifted toward the unchanged alternative with sucrose, but not with wheel running. Instead, responding initially increased on both alternatives, then subsequently shifted toward the unchanged alternative. Furthermore, changeover responses as a percentage of total responses decreased with sucrose, but not wheel‐running reinforcement. Finally, for some animals, responding on the increasing ratio alternative decreased as the ratio requirement increased, but then stopped and did not decline with further increments. The implications of these results for theories of choice are discussed.     

Motivational control of impulsive behavior interacts with choice opportunities

Impulsive behavior has been investigated through choice between a smaller/immediate reinforcer and a larger/delayed reinforcer, or through performance on a differential reinforcement of low rate (DRL) schedule. In the present study, we investigated a methodological divergence between these two procedures: in the former procedure, delay is a consequence of the subject's own choice, whereas in the later procedure, subjects are explicitly reinforced for delaying a response. In Experiment 1, 7 rats maintained at 80% of their free-feeding weights showed poorer efficiency of lever-pressing responses on a DRL 30-s schedule than when they were maintained at 90% of free-feeding weight. In Experiment 2, 16 rats were subjected to a concurrent chain schedule: the initial link was concurrent fixed ratio 1 fixed ratio 1, and each of these alternatives was followed by a short-DRL requirement with a one pellet reinforcer or a long-DRL requirement with a three pellet reinforcer. In one block of trials, rats were not allowed to choose between the two terminal links (forced-choice), whereas in the other block of trials rats were allowed to choose freely between the two terminal links (free-choice). Compared with rats maintained at 95% of their free-feeding weights, rats maintained at 80% of their free-feeding weights showed poorer efficiency in the terminal links’ DRL schedule performance (just as in Experiment 1), but this difference was shown only in the forced-choice blocks. These results indicate that motivational control of DRL schedule performance interacts with type of choice-making opportunity and highlight the direct comparison of motivational control of impulsive choice and DRL schedule performance.     

Some properties of spaced responding in pigeons

Pigeons exposed to a schedule which reinforces interresponse times (IRTs) longer than a given value (DRL schedule) eventually reach a stable pattern of responding which is shown to be a function both of the DRL value and of previous experience with other DRL values. On any given DRL schedule, the stable performance of most pigeons which have been previously exposed to a variety of such schedules, shows an IRT distribution with median equal to the DRL value. For DRL values longer than about 30 sec, however, the median IRT falls short of the DRL value; this failure of adjustment to longer values appears to be a species characteristic of pigeons. The function relating reinforcement rate to 1/DRL value is also shown to be approximately linear over the same range, with variable slope (less than 45°) and a downturn in the vicinity of DRL 30.     

Temporal regulation of children with autism spectrum disorder exposed to a differential-reinforcement-of low-rates schedule

This study investigated temporal adjustment of children with autism spectrum disorder under a differential-reinforcement-of-low-rates (DRL) schedule. Sixteen participants, aged 3.2 to 7 years, were exposed to two conditions, DRL 5 s and DRL 20 s. Children participated in 7 sessions in each condition, except for 1 participant who attained the adjustment criteria in the DRL 5-s schedule. Temporal adjustment was measured with the proportion of reinforced interresponse times (IRTs) and the mean IRT. The operant response was a press on a touch screen and the reinforcers were cartoons. IQ and receptive language were measured prior to the DRL sessions. Results showed that the mean proportion of reinforced IRTs was slightly higher in the DRL 5-s schedule. The mean IRT was above the IRT requirement in both conditions. However, substantial individual variability was observed. Children with higher IQ and receptive language scores presented a greater proportion of reinforced IRTs in both conditions. Moreover, participants who adjusted their responses to the DRL 5-s schedule were more likely to adjust responding to the DRL 20-s schedule. This suggests that some children might be more sensitive to reinforcement contingencies than others. This study points at future research in the field of timing in children.     

INFLUENCES ON COCAINE TOLERANCE ASSESSED UNDER A MULTIPLE CONJUNCTIVE SCHEDULE OF REINFORCEMENT

Under multiple schedules of reinforcement, previous research has generally observed tolerance to the rate‐decreasing effects of cocaine that has been dependent on schedule‐parameter size in the context of fixed‐ratio (FR) schedules, but not under the context of fixed‐interval (FI) schedules of reinforcement. The current experiment examined the effects of cocaine on key‐pecking responses of White Carneau pigeons maintained under a three‐component multiple conjunctive FI (10 s, 30 s, & 120 s) FR (5 responses) schedule of food presentation. Dose‐effect curves representing the effects of presession cocaine on responding were assessed in the context of (1) acute administration of cocaine (2) chronic administration of cocaine and (3) daily administration of saline. Chronic administration of cocaine generally resulted in tolerance to the response‐rate decreasing effects of cocaine, and that tolerance was generally independent of relative FI value, as measured by changes in ED50 values. Daily administration of saline decreased ED50 values to those observed when cocaine was administered acutely. The results show that adding a FR requirement to FI schedules is not sufficient to produce schedule‐parameter‐specific tolerance. Tolerance to cocaine was generally independent of FI‐parameter under the present conjunctive schedules, indicating that a ratio requirement, per se, is not sufficient for tolerance to be dependent on FI parameter.     

Reinforcement of mediating behavior on a spaced-responding schedule

This paper describes a procedure for gaining experimental control over mediating behavior on a spaced-responding schedule of food reinforcement. Three rats, food-deprived, were trained on a DRL 16 sec schedule of food reinforcement. Then, a concurrent schedule of food reinforcement was introduced on a second (mediating) lever, such that the first response to occur on the mediating lever, after the DRL interval had timed out, was reinforced with food, as was the next response to occur on the DRL lever. Reinforcement via the mediating lever became a discriminative stimulus for a food-reinforcement opportunity on the DRL lever. Next, food reinforcement for the mediating behavior was replaced by a conditioned reinforcer consisting of onset of a buzzer signaling timing-out of the DRL interval. Under these conditions, chaining of behavior on the two levers was strong, and timing on the DRL lever was more accurate than under ordinary DRL conditions. As the DRL requirement was lengthened from 16 sec to 24 sec to 60 sec, mediating behavior weakened slightly. When the inter-response requirement for food reinforcement on the DRL lever was made shorter than the inter-response requirement for conditioned reinforcement on the mediating lever, the mediating behavior extinguished. Performance in the experiment was analyzed into a four-component chain, and the factors contributing to the maintenance, and later extinction, of mediating behavior are discussed.     

Choice between response units: The rate constancy model

In a conjoint schedule, reinforcement is available simultaneously on two or more schedules for the same response. The present experiments provided food for key pecking on both a random-interval and a differential-reinforcement-of-low-rate (DRL) schedule. Experiment 1 involved ordinary DRL schedules; Experiment 2 added an external stimulus to indicate when the required interresponse time had elapsed. In both experiments, the potential reinforcer frequency from each component was varied by means of a second-order fixed-ratio schedule, and the DRL time parameter was changed as well. Response rates were described by a model stating that time allocation to each component matches the relative frequency of reinforcement for that component. When spending time in a given component, the subject is assumed to respond at the rate characteristic of baseline performance. This model appeared preferable to the absolute-rate version of the matching law. The model was shown to be applicable to multiple-response concurrent schedules as well as to conjoint schedules, and it described some of the necessary conditions for response matching, undermatching, and bias. In addition, the pigeons did not optimize reinforcer frequency.     

DIFFERENTIALLY REINFORCING LOW RATES OF MISBEHAVIOR WITH NORMAL ELEMENTARY SCHOOL CHILDREN1

Effective nonpunitive procedures for reducing counterproductive classroom behaviors are of potential benefit to both students and teachers. A recent strategy for dealing with this class of problem behaviors involves the reinforcement of acceptably low levels of such behavior. The laboratory version of this procedure, called differential reinforcement of low rates of responding (or DRL), provides for a reinforcer to be delivered contingent upon a response that is separated from the last preceding response by a minimum amount of time. To make this procedure more amenable to classroom use, the present authors have modified it so that a reinforcer is delivered if fewer than a specified number of responses occur within a preset time interval (Deitz and Repp, Journal of Applied Behavior Analysis, 1973, 6 , 457–463). Previous studies using this procedure have found it effective in reducing and maintaining low rates of targeted behaviors. However, these effects have been demonstrated with groups of subjects and/or individuals from dependent populations. The present study investigated use of this modified DRL procedure with individual students in normal elementary classrooms. In the first of three studies, “talk-outs” of an 11-yr-old fifth-grade male were reduced when nonexchangeable gold stars were made contingent on two or fewer responses per session. During baseline sessions, an average of 4.45 talkouts were observed per 45-min session. Average responding subsequently fell to 1.83 when the modified DRL contingency was applied, increased to 7.60 during a reversal phase, and dropped again to an average of 1.20 when the contingency was reapplied. In the second study, out-of-seat behavior of a 12-yr-old sixth-grade female was reduced when gold stars were made contingent on two or fewer responses per 45-min class period. Baseline responding averaged 6.10 responses per session. When the contingency was applied, average responding fell to 0.16. During the reversal period, responding increased to an average of 6.00 and fell again, after the contingency was re-introduced to an average of 0.40. In the third study, a reduction in both talking-out and out-of-seat behaviors of another 11-yr-old fifth-grade male was demonstrated with a multiple-baseline design. Using different lengths of baselines, gold stars were made contingent first on a low rate of out-of-seat behavior, and then on a low rate of talk-outs. Out-of-seat responding fell from a baseline average of 7.50 to a treatment average of 1.14. Talk-outs went from a baseline average of 4.66 to a treatment average of 1.14. In all three studies, the modified DRL procedure proved effective with the children and was manageable by the classroom teacher. For the students, nonexchangeable conditioned reinforcers (stars) were sufficient to maintain lowered rates of inappropriate behavior with the modified DRL schedule; there was no need for an elaborate token economy, a process that in many cases may be only a form of behavioral “overkill”. As in other studies investigating DRL schedules, students were not informed of their accumulation of responses; the differential effects of providing or withholding this feedback need to be investigated. Overall, these studies add single-subject replication with normal children to the literature on modified DRL procedures.     

Punishment of temporally spaced responding

The responses of pigeons were maintained by a DRL schedule of food reinforcement. With this schedule, responses were reinforced only when a fixed period of time elapsed without an intervening response. Punishment of all responses reduced the frequency of these responses as a direct function of the punishment intensity. As a consequence of the increased temporal spacing of responses, more reinforcements resulted during punishment. Under progressively higher intensities of punishment, the reinforcement frequency increased to a maximum value and then decreased at the highest intensities. The increased frequency of reinforcement which resulted during punishment did not counteract the suppressive effect of punishment, nor did it lead to a low response rate after punishment was removed. Punishment did not reduce the inter-response time distribution uniformly, but rather especially reduced the number of short inter-response times. Even at the low punishment intensities, the number of short inter-response times was considerably reduced. After punishment was discontinued, performance recovered almost completely after a compensatory burst. The number as well as the temporal pattern of responses returned to normal.     

Effects of timeout on spaced responding in pigeons

Three pigeons were trained under a differential-reinforcement-of-low-rate schedule of 20 sec, and then exposed to a schedule under which responses terminating interresponse times less than 20 sec produced timeout and responses terminating interresponse times greater than 20 sec produced reinforcement. Response-produced timeouts selectively decreased the probability of short interresponse times and thereby produced a higher frequency of reinforcement. The suppressive effect of timeout was independent of timeout duration, with timeouts of 5, 10, or 20 sec. Similar effects were found when the minimum interresponse time that could be terminated by response-produced reinforcement was increased to 30 sec. The suppressive effects of timeout on responding maintained by these schedules were similar to previous reports in which responding was punished with electric shock.     

Stimulus generalization and the response-reinforcement contingency

Generalization gradients along a line-tilt continuum were obtained from groups of pigeons that had been trained to peck a key on different schedules of reinforcement. In Exp. I, gradients following training on a differential-reinforcement-of-low-rate (DRL) schedule proved to be much flatter than gradients following the usual 1-min variable interval (VI) training. In Exp. II, the value of the VI schedule itself was parametrically studied; Ss trained on long VI schedules (e.g., 4-min) produced much flatter gradients than Ss trained on short VI schedules (30-sec; 1-min). The results were interpreted mainly in terms of the relative control exerted by internal, proprioceptive cues on the different reinforcement schedules. Several implications of the results for other problems in the field of stimulus generalization are discussed.     

Electroencephalographic correlations of temporally spaced responding and avoidance behavior

This study was undertaken to determine whether any EEG changes occurred during a multiple schedule of reinforcement consisting of repeated periods of avoidance behavior, a time-out (TO) period, and a period of differential reinforcement of low rates (DRL). The two monkeys were permanently implanted with bipolar electrodes in various subcortical areas. The EEG was recorded from these electrodes for several weeks before any behavioral training was undertaken. Training was then begun in the multiple schedule, and EEG recordings were taken frequently throughout the training period. When a stable performance level was achieved, drugs (dl-amphetamine and sodium pentobarbital) were introduced which disrupted the DRL performance but had little or no effect on avoidance behavior. The EEG recordings continued throughout these drug studies.

The data indicate that the marked behavioral differences noted in each component of the schedule were not reflected in the EEG. However, the EEG did correlate with the general level of alertness of the animals during the various components. The drugs which differentially affected the behavior in the components of the schedule did not differentially affect the EEG, but they did change the brain-wave activity equally in all components. Finally, EEG changes correlated with the complex motor response of lever pressing were not observed.