Duration Of Reinforcement Research Articles

Experimental Study of Erosion Prevention Model by Bio-Cement Sand

Microbially induced carbonate precipitation (MICP) technology is employed to reinforce the surface soil of a dam, aiming to prevent erosion caused by water flow and damage to the dam slope. The relationship between penetration depth, calcium carbonate content, and bonding depth was investigated at eight measuring points on the sand slope surface of a mold under different reinforcement durations. It was observed that as grouting reinforcement times increased, there was a gradual increase in calcium carbonate content but a rapid rise in penetration resistance. Moreover, the bonding depth of sand on the bio-reinforced sand slope increased with higher levels of calcium carbonate content. Microbial grouting reinforcement enhanced soil particle bonding force, requiring water flow to overcome this force for activation of sand particles. Consequently, microbial grouting reinforcement significantly improved shear strength and critical starting flow velocity on sand slope surfaces. The experimental results demonstrated that after MICP surface treatment through spraying, a dense and water-stable hard shell layer composed of bonded calcium carbonate and soil particles formed continuously on sample surfaces, effectively enhancing the strength and erosion resistance of sandy soils. These findings provide reliable evidence for silt slope reinforcement and dam erosion prevention.

Comparison of synchronous reinforcement and accumulated reinforcement for increasing on-task behavior in preschoolers.

In synchronous-reinforcement schedules, the duration of behavior directly controls the duration of reinforcement on a moment-to-moment basis. We replicated and extended Diaz de Villegas et al. (2020) by comparing the effects of synchronous reinforcement with two accumulated-reinforcement schedules for increasing on-task behavior for seven preschoolers. One accumulated schedule was the same as the one used in Diaz de Villegas et al. and did not include tokens, whereas the other accumulated schedule included the delivery of tokens within session. Furthermore, we assessed preference for the three reinforcement schedules. The results showed that synchronous reinforcement was effective for increasing on-task behavior for all seven participants. Furthermore, it was most effective for increasing on-task behavior for three out of seven participants and preferred by all participants. For some participants, other schedules were also similarly effective. The results are discussed with respect to implications for application.

Social familiarity and reinforcement value: a behavioral-economic analysis of demand for social interaction with cagemate and non-cagemate female rats.

Rats were studied in social reinforcement procedures in which lever presses opened a door separating two adjacent spaces, permitting access to social interaction with a partner rat. The number of lever presses required for social interaction was systematically increased across blocks of sessions according to fixed-ratio schedules, generating demand functions at three different social reinforcement durations: 10 s, 30 s, and 60 s. The social partner rats were cagemates in one phase, and non-cagemates in a second phase. The rate at which social interactions were produced declined with the fixed-ratio price, and was well described by an exponential model that has been successfully employed with a range of social and non-social reinforcers. None of the main parameters of the model varied systematically with social interaction duration or with the social familiarity of the partner rat. On the whole, the results provide further evidence of the reinforcing value of social interaction, and its functional parallels with non-social reinforcers.

Impact of medication correction of labor weakness on obstetrical complications and newborn status

Objectives: To analyze the impact of medical correction of labor weakness with oxytocin on obstetric and newborn complications.Materials and methods. 100 cases of childbirth with weakness of labor activity and medical correction with oxytocin (main group) and 50 cases of childbirth without weakness of labor activity (control group) were analyzed. The analysis included pregnancy and childbirth histories of mothers aged 20–32 years with a gestation period of 37– 41 weeks with uncomplicated pregnancies, without significant somatic and obstetric-gynecological pathology, who gave birth in the Perinatal Center of Kyiv during the last 3 years.Depending on the method of delivery, the women of the main group were divided into 3 subgroups: Iа – natural vaginal, spontaneous delivery (n = 60), Ib – operative vaginal delivery using a vacuum extractor (n = 22), Іc – delivery by cesarean section (n = 18).The following factors were studied in each group: assessment of newborns status according to the Apgar scale at the 1st and 5th minutes, pH level of the umbilical cord blood, frequency of fetal distress based on cardiotocography (Fischer score < 6 points), duration of labor induction, color of the amniotic fluid.Results. The average duration of labor was the largest in the subgroup of spontaneous vaginal deliveries, the smallest in the subgroup of cesarean section. In subgroup Ib in 14 (63.6%) cases indications for the vacuum extractor were signs of fetal distress and only in 8 (36.4%) cases – weakness of labor activity.In subgroup Ia compared to subgroup Ic, there was a longer average duration of labor and higher percentage of deliveries with meconium-stained waters (28.3%), higher frequency of neonatal acidemia (16.7%) and the birth of children with an Apgar score at the 5th minute ≤ 6 points (8.4%). In subgroup Ic compared to subgroup Ia, there was a higher value of cases of Fischer score < 6 points (50%), the duration of labor reinforcement for more than 4 hours (44.5%), more cases of asphyxia (44.5%), and the birth of children with an Apgar score at the 1st minute ≤ 6 points (38.9%). Indications for caesarean section in subgroup Ic in 50% of cases were signs of fetal distress, in 38.9% – weakness of labor activity which was not associated with medication, in 11.1% – a clinically narrow pelvis.In all groups there was a relationship between the duration of labor induction and the condition of the newborn (the frequency of asphyxia of newborns was higher when the infusion of oxytocin lasted more than 4 hours).In subgroup Ib fetal distress was the indication for urgent delivery in 63.6% of cases, and in subgroup Iс it was 50%. This indicates signs of a mediated negative effect of exogenous oxytocin on the fetus during childbirth. The newborns condition, according to the studied criteria, was worse in the groups with labor reinforcement compared to the control group, regardless of the method of delivery.Conclusions. The use of oxytocin during childbirth can have a negative effect on the fetus, which increases the frequency of operative vaginal deliveries and cesarean sections and, as a result, is a risk factor for complications in the postpartum period. There is a correlation between duration of oxytocin injection and condition of the newborn.

A Comparison of Fixed and Incrementing Reinforcement Durations during Schedule Thinning for Individuals with Escape-Maintained Problem Behavior

A Comparison of Fixed and Incrementing Reinforcement Durations during Schedule Thinning for Individuals with Escape-Maintained Problem Behavior

An operant analog of food caching in the pigeon (Columba livia).

Although pigeons do not naturally cache and recover food items as found in members of the corvid and parid families, an operant analog of food caching and recovery in pigeons was studied in four experiments. Pigeons were trained to peck a caching key that added a fixed increment of time to the final duration of reinforcement obtained by pecking a payoff key. The same key served as the caching and payoff keys in Experiment 1, but separate caching and payoff keys were used in Experiments 2-4. In Experiments 2-3, each peck on a left red caching key added 0.5 s of reinforcement earned by pecking a right white payoff key. In Experiment 4, red or green caching keys appeared on different trials, with 0.5 s of reinforcement earned for pecking the red key and 1.0 s of reinforcement earned for pecking the green key. Pigeons showed an increased number of pecks on the caching key over ten sessions in Experiments 1-3 and more pecks on the green caching key than on the red caching key in Experiment 4.

Cobiax and post-tension slabs: A comparative study based on the construction duration time and cost

Slabs are one of the most basic components concerning the cost of the structure, because of the number of building materials utilized. It is of incentive to think about the current technologies available, meaning to make these slabs cost less or even improve its behaviour. Cobiax and post-tension slabs systems show up as an appropriate alternative. In light of this reason, this paper focuses on demonstrating the advantages and disadvantages of both Cobiax and post-tension systems. Nowadays, these systems are very popular all around the world. It is very necessary to have a wide understanding of the differences in cost and the construction duration between these two systems and have good knowledge about the advantages and disadvantages of both types. Firstly, the properties of these types of slabs have been reported and the advantages and disadvantages for both systems and then the cost and time has been compared, which are the most important factors for the owners. Finally, it has been made a comparison between the reinforcement quantities, concrete quantities, final cost and duration to finalize the construction stage. As a result, it has been found that the post-tension system is more economical than the Cobiax system according to reinforcement quantities, on the other hand, Cobiax system is more economical in concrete quantities which leads to lighter buildings and fewer reinforcement quantities in foundations. When the construction duration has been considered, it has been found that the post-tension is the quickest system in the construction field because it is increasing the strength and durability of the structure which the Cobiax system cannot provide.

Effects of Reinforcement Parameters on Preference for an Increased Duration of Reinforcement in Pigeons

Pigeons were trained in a two-key, concurrent-chains choice procedure to investigate the effects of increased relative duration of reinforcement on preference. Throughout the study, the initial- and terminal-link schedules were equal for both choices. Across conditions, the duration of reinforcement in the terminal links was either equal or unequal. Equal durations were 3 s versus 3 s. Unequal durations were 3 s versus 6 s. Pigeons accessed the relatively longer duration of reinforcement via a food hopper elevated for one 6-s reinforcement interval or two successive 3-s reinforcement intervals separated by a 0.1-s blackout. The color of the light that illuminated the relatively longer duration was either the same as or different from the color of the light that illuminated the relatively shorter duration. A significantly greater mean preference ratio was recorded in conditions in which the hopper lights were different and when the 6-s reinforcement interval was presented as two successive 3-s hopper activations. The combination of the two procedures resulted in the greatest significant increase in preference. The differential hopper lights and multiple successive intervals of grain access facilitated the discrimination of the longer duration of reinforcement and allowed the hopper to replenish with grain, respectively. The combined arrangement of increased access to grain resulted in enhanced control of preference by the relative reinforcement duration.

Duration of wheel-running reinforcement: Effects on reinforcement value and motivation in free-feeding and food-deprived rats

Ten (pair housed) female Long-Evans rats were exposed to 5s, 30s, and 90s wheel-running reinforcement durations on a response-initiated variable interval 20s schedule as food deprivation was manipulated. On free feeding, never-deprived rats showed low wheel running and lever-pressing rates with long postreinforcement pauses (PRPs) for the 5-s reinforcement duration. Subsequently, when food deprived (Deprived 1), rats showed no effect of reinforcement duration on all measures. Under a second deprived condition (Deprived 2) with the rats maintained in single cages, there was no effect of housing (single vs. paired). When data from both deprivation assessments (Deprived 1 and Deprived 2) were combined, rats showed lower wheel running and overall lever-pressing rates with longer pauses on the 90-s duration compared to 30s and 5s bouts of wheel activity. The pattern of results challenges a reinforcement value interpretation, but is consistent with shifts in the motivational basis of wheel running. On free feeding, never-deprived rats were intrinsically motivated to run on wheels and operant lever-pressing was maintained at moderate rates by the automatic reinforcement of wheel running, except at the short reinforcement duration (5s). When food deprived, motivation became food-related and rats showed high rates of lever pressing even at the shortest duration. The weak effects under initial deprivation (Deprived 1) raise questions about equivalence between wheel-running reinforcement duration and reinforcement magnitude using food reinforcement.

An individualized method for establishing and thinning multiple schedules of reinforcement following functional communication training

Using multiple schedules of reinforcement following functional communication training (FCT) can produce discriminated mands while maintaining low rates of problem behavior (Fisher et al., 1998; Hanley et al., 2001). A review of this literature (Saini et al., 2016) noted the absence of a method for systematically determining the duration of reinforcement (SD) and extinction (SΔ) components in such multiple-schedule arrangements. The same review also suggested that introducing a momentary differential-reinforcement contingency could aid in producing discriminated mands by eliminating the possibility of adventitious reinforcement. The current investigation attempted to evaluate these two recommendations by altering the durations of SD and SΔ components of a multiple schedule based on participants’ response patterns during treatment. Specifically, we (a) yoked the duration of the initial SΔ component to the rate of mands during FCT and (b) introduced a delay to the SD following instances of problem behavior. All five participants exhibited discriminated mands. In addition, mands maintained for all five participants, and problem behavior remained low for four participants when the schedule of reinforcement was systematically thinned.

Resistance to extinction of lever-pressing rates maintained by different wheel-running reinforcement durations

Previous research using resistance to extinction to assess response strength has shown slower attenuation of responding maintained by larger than smaller reinforcement magnitudes. The current study sought to generalize this reinforcement-magnitude effect to extinction of lever-pressing rates maintained by wheel-running reinforcement of different durations. Rats responded on a response-initiated variable interval 20-s schedule for the opportunity to run in a wheel for 5s, 30s, and 90s. Following training on each reinforcement duration, lever pressing for wheel running was placed on extinction. Results showed that responding maintained by 5s of wheel-running reinforcement declined slower in extinction than for the 90-s duration, while 30s of wheel-running reinforcement produced inconsistent effects on attenuation of response rates. These results suggest that shorter periods of wheel-running reinforcement have higher reinforcement value than longer durations—findings incompatible with the earlier research showing more resistance to extinction with large reinforcement magnitudes. We offer an interpretation based on response deprivation arising from restriction of the wheel-access interval and its motivational impact on wheel running as a reinforcing consequence and on responding for wheel-running reinforcement. An alternative analysis proposes that discrimination of the shift to extinction is more salient for the long wheel-running duration—accounting for the rapid attenuation of responding in extinction with the long periods of wheel-running reinforcement.

Financial incentives to promote extended smoking abstinence in opioid-maintained patients: a randomized trial.

Prior studies by our group demonstrated the efficacy of a brief but intensive behavioral intervention for producing initial smoking abstinence among opioid-dependent patients. In the present study, our aim was to promote longer-duration abstinence in this population. Following an initial 2-week incentive intervention for smoking abstinence, we examined whether a 10-week maintenance arm involving continuation of contingent reinforcement will produce greater smoking abstinence than a similar duration of noncontingent reinforcement. Randomized, 12-week, parallel-group study. Out-patient research clinic in Burlington, Vermont, USA. Opioid-maintained smokers (n = 88) who provided breath carbon monoxide and urinary cotinine specimens and received contingent reinforcement for smoking abstinence during weeks 1-2 (phase 1), with 63 randomized on day 14 to an extended contingent (EC; n = 31) or extended noncontingent (EN; n = 32) experimental condition for weeks 3-12 (phase 2). The EC condition consisted of voucher values that escalated across consecutive negative samples until they reached $30, after which they remained at $30 per negative sample. A positive or a missing sample resulted in no vouchers for that day and reset the value of the next negative same to $9. Two consecutive negatives returned the schedule to the pre-reset value. The EN control condition consisted of vouchers delivered for providing scheduled samples, but independent of smoking status. The primary outcome was percentage of biochemically abstinent samples during phase 2. Secondary measures included abstinence status at final study visit, complete abstinence, participants' longest duration of continuous abstinence, cotinine and carbon monoxide (CO) levels and self-reported cigarettes per day. EC participants achieved greater smoking abstinence during phase 2 than EN participants [46.7 versus 23.5% negative samples, respectively; odds ratio (OR)=2.98, 95% confidence interval (CI)=1.16-7.65, χ(2) 1 (=) 5.0, P=0.02]. When longest duration of continuous abstinence was compared between experimental groups, EC participants achieved twice the mean duration of continuous abstinence compared with EN participants (3.31 versus 1.68 weeks; t61 =1.83, P=0.07). An effect of experimental condition was also seen on mean cotinine levels (42.5 versus 210.6 ng/ml, respectively; F1,61 =5.9, P=0.02). Among opioid-maintained smokers receiving an initial period of daily contingent incentives, a contingent reinforcement intervention appears to be more effective at extending smoking abstinence than noncontingent reinforcement over 10 weeks.

A quantitative analysis of the behavior maintained by delayed reinforcers.

Random-interval reinforcement was arranged for a sequence of pigeon first-key pecks followed by second-key pecks. First-key pecks, separated from reinforcers by delays that included number of second-key pecks and time, decreased in rate as delays increased. Delay functions, or gradients, were obtained in one experiment with reinforced sequences consisting of M first-key pecks followed by N second-key pecks (M + N = 16), in a second where required first-key pecks were held constant (M = 8), and in a third where minimum delay between most recent first-key pecks and reinforcers varied. In each, gradients were equally well fitted by exponential, hyperbolic and logarithmic functions. Performances were insensitive to reinforcer duration and functions were consistent across varied random-interval values. In one more experiment, time and number delays were independently varied using differential reinforcement of rate of second-key pecks. Delay gradients depended primarily on time rather than on number of second-key pecks. Thus, reinforcers have effects based on earlier responses, not just the ones that produced them, with the contribution of each response weighted by the time separating it from the reinforcer rather than by intervening behavior. Situations where unwanted responses (e.g., errors) often precede reinforced corrects can maintain them unless designed to avoid such effects of delay.

Rocuronio en obesos: ¿Debe dosificarse por peso real o peso ideal?

The universal increase in prevalence of obesity has caused that anesthesiologist are frequently encountered with anesthetizing obese patients. There stills exists doubt on how to dosage drugs to these patients. Literature recommends dosing rocuronium in the obese based on ideal weight (IBW), being this suggestion based more on prudence than on evidence. Randomized control trial was designed for obese patients scheduled for bariatric surgery to study the pharmacodynamics of rocuronium in this population. Patients were randomly assigned into two groups: rocuronium dosage 0.6 mg·kg -1 for real weight (TBW) or rocuronium dosage of 0.6 mg·kg -1 for ideal weight (IBW). Ideal weight was calculated according to Lemmens formula. The reference group was the dosage based on IBW. Previous calibration, evaluating the first twitch of train-of-four (T 1 ), we registered onset time, clinical duration, recovery index, level of muscle relaxation to which the first reinfor cement was administered and clinical duration of rocuronium reinforcement. A total of 100 patients were part of the study: 54 in group TBW and 46 in group IBW. When administering rocuronium based on real weight (TBW) a prolongation in clinical duration was found: Medium (IQR*); 79.5 (67 - 105) minutes versus 44.5 (33 - 63.5 minutes) in the IBW group (p < 0.001) with a decrease in latency in the TBW group 120 (90-150 secs.) versus the IBW group 180 (120 - 270 secs.) (p < 0.001). There were no differences in the recovery index between both levels of dosing. There was a marked prolongation of both clinical duration and recovery index in both groups, as supported in some literature. Based on the evidence, we recommend to dose rocuronium in obese patients based on ideal weight, with the exception of cases were quick intubation is required. * IQR = interquartile range.

Effectiveness of 3 methods of anchorage reinforcement for maximum anchorage in adolescents: A 3-arm multicenter randomized clinical trial

The objective of this 3-arm parallel randomized clinical trial was to compare the effectiveness of temporary anchorage devices (TADs), Nance button palatal arches, and headgear for anchorage supplementation in the treatment of patients with malocclusions that required maximum anchorage. This trial was conducted between August 2008 and February 2013 in 2 orthodontic departments in the United Kingdom. The study included 78 patients (ages, 12-18 years; mean age, 14.2 years) who needed maximum anchorage. Eligibility criteria included no active caries, exemplary oral hygiene, and maximum anchorage required. The primary outcome was mesial molar movement during the period in which anchorage supplementation was required. The secondary outcomes were duration of anchorage reinforcement, number of treatment visits, number of casual and failed appointments, total treatment time, dento-occlusal change, and patients' perceptions of the method of anchorage supplementation. Treatment allocation was implemented by contacting via the Internet the randomization center at the University of Nottingham, Clinical Trials Unit. The randomization was based on a computer-generated pseudo-random code with random permuted blocks of randomly varying size. A research assistant who was blinded to the group allocation recorded all data. The patients were randomly allocated to receive anchorage supplementation with TADs, a Nance button on a palatal arch, or headgear. They were all treated with maxillary and mandibular preadjusted edgewise fixed appliances with 0.022-in slot prescription brackets. They were followed until orthodontic treatment was complete. Seventy-eight patients were randomized in a 1:1:1 ratio among the 3 groups. The baseline characteristics were similar in the groups, and they were treated for an average of 27.4 months (SD, 7.1 months); 71 completed orthodontic treatment. The data were analyzed on a per-protocol basis and showed no differences in the effectiveness of anchorage supplementation between TADs, Nance button palatal arches, and headgear. Compared with headgear, the average mesial movements of the maxillary right molar were 0.62 mm (-0.32 to 1.55 mm) with the Nance and -0.58 mm (-1.53 to 0.36 mm) with TADs; the maxillary left molar was moved -0.09 mm (-1.00 to 0.83 mm) with the Nance and -0.96 mm (-1.89 to -0.04 mm) with the TADs. Peer assessment rating scores were significantly better with the TADs than in the headgear and Nance groups. The patient questionnaires showed that comfort levels on placement of the TADs and the Nance were similar. Headgear was more troublesome and less popular with the patients. There was no difference in the effectiveness between the 3 groups in terms of anchorage support. There were more problems with the headgear and Nance buttons than with the TADs. The quality of treatment was better with TADs. As a result, TADS might be the preferred method for reinforcing orthodontic anchorage in patients who need maximum anchorage. ClinicalTrials.gov Identifier: NCT00995436. The protocol was published on the above site before the trial commencement. The British Orthodontic Society Foundation funded the study and American Orthodontics provided all the TADs and associated equipment.

The Effects of Varying Quality and Duration of Reinforcement on Mands to Work, Mands for Break, and Problem Behavior

Research on the effects of concurrent schedules of reinforcement during treatment of problem behavior has shown that response allocation can be biased in favor of adaptive responses by providing increased reinforcement for these responses. However, this research has focused on the effects of only two concurrently available response options. In applied situations, it is likely that more than two concurrently available response options exist. The purpose of this study was to evaluate the effects of varying qualities and durations of reinforcement on problem behavior, mands for breaks, and mands to work. Participants were 5 to 12 years old, had disabilities, and displayed escape-motivated problem behavior. Results showed that all participants' responding was sensitive to changes in quality and duration of reinforcement. That is, participants allocated responding to the response that produced the highest quality and longest duration of reinforcement. These results are consistent with previous literature on choice when two concurrent schedules of reinforcement were in effect. Implications for practice are discussed, as well as future research that could expand the findings.

Reinforcer probability, reinforcer magnitude, and the reinforcement context for remembering.

Traditional theories of delayed matching-to-sample performance do not predict that accuracy will improve when absolute levels of reinforcement are increased. This prediction emerges only when reinforcement context is considered (J. A. Nevin, M. Davison, A. L. Odum, & T. A. Shahan, 2007). To provide quantitative data, the authors factorially manipulated between conditions the probability and duration of reinforcement for correct choices by pigeons. In Experiment 1, increasing the value of either variable improved initial discriminability of the forgetting functions, but did not affect the rate of forgetting. In Experiment 2, initial discriminability covaried with changes in choice immediacy and trial completion rate, suggesting a relationship with response strength consistent with Nevin et al.'s behavioral momentum model. Adding reinforcement context to K. G. White and J. T. Wixted's (1999) model also generates predictions consistent with the present experiments and with the effects of manipulating extraneous reinforcement. The inclusion of reinforcement context thus improves predictions of delayed matching-to-sample performance.

A BRIEF OPPORTUNITY TO RUN DOES NOT FUNCTION AS A REINFORCER FOR MICE SELECTED FOR HIGH DAILY WHEEL‐RUNNING RATES

Mice from replicate lines, selectively bred based on high daily wheel-running rates, run more total revolutions and at higher average speeds than do mice from nonselected control lines. Based on this difference it was assumed that selected mice would find the opportunity to run in a wheel a more efficacious consequence. To assess this assumption within an operant paradigm, mice must be trained to make a response to produce the opportunity to run as a consequence. In the present study an autoshaping procedure was used to compare the acquisition of lever pressing reinforced by the opportunity to run for a brief opportunity (i.e., 90 s) between selected and control mice and then, using an operant procedure, the effect of the duration of the opportunity to run on lever pressing was assessed by varying reinforcer duration over values of 90 s, 30 min, and 90 s. The reinforcement schedule was a ratio schedule (FR 1 or VR 3). Results from the autoshaping phase showed that more control mice met a criterion of responses on 50% of trials. During the operant phase, when reinforcer duration was 90 s, almost all control, but few selected mice completed a session of 20 reinforcers; however, when reinforcer duration was increased to 30 min almost all selected and control mice completed a session of 20 reinforcers. Taken together, these results suggest that selective breeding based on wheel-running rates over 24 hr may have altered the motivational system in a way that reduces the reinforcing value of shorter running durations. The implications of this finding for these mice as a model for attention deficit hyperactivity disorder (ADHD) are discussed. It also is proposed that there may be an inherent trade-off in the motivational system for activities of short versus long duration.

Rats do not respond differently in the presence of stimuli signaling wheel-running reinforcers of different durations

Rats were exposed to a fixed interval 30 s schedule that produced opportunities to run of equal or unequal durations to assess the effect of differences in duration on responding. Each duration was signaled by a different stimulus. Wheel-running reinforcer duration pairs were 30 s 30 s, 50 s 10 s, and 55 s 5 s. An analysis of median postreinforcement pause duration and mean local lever-pressing rates broken down by previous reinforcer duration and duration of signaled upcoming reinforcer showed that postreinforcement pause duration was affected by the duration of the previous reinforcer but not by the stimulus signaling the duration of the upcoming reinforcer. Local lever-pressing rates were not affected by either previous or upcoming reinforcer duration. In general, the results are consistent with indifference between these durations obtained using a concurrent choice procedure.

Aspartame demand in rhesus monkeys: Effects of volume and concentration manipulations

Three rhesus monkeys' lever presses produced aspartame-sweetened water according to a fixed-ratio schedule. The response requirement was increased across sessions and a demand-function analysis was used to assess the reinforcing effectiveness of different magnitudes of aspartame by manipulating reinforcer duration (1 and 3s) in Phase 1 and concentration (0.3, 0.5, 0.7, and 1.0mg/ml) in Phase 2. When duration was manipulated, the number of aspartame deliveries was mainly a function of the response requirement rather than unit price (responses/duration), suggesting that changes in duration did not significantly affect the reinforcing effectiveness of aspartame. When concentration was manipulated and the lowest concentration excluded, consumption was best described by unit price (responses/concentration) in two monkeys and by the response requirement in the third. Although results from the concentration manipulation provide some evidence that consumption was modulated by unit price, the results overall suggest that scalar equivalence does not exist between the components of unit price; specifically, the response requirement exerted a larger influence than duration or concentration on total consumption. Finally, a normalized demand analysis revealed that aspartame is a more elastic commodity than food and drug reinforcers.