Shaping reduced smoking in smokers without cessation plans.

Most smokers do not plan to quit in the next 6 months. The authors previously demonstrated that percentile schedules shape lower breath carbon monoxide (BCO) levels in smokers trying to quit (R. J. Lamb, A. R. Morral, K. C. Kirby, M. Y. Iguchi, & G. Galbicka, 2004). In that study, the authors set reinforcement criteria based on the 9 most recent samples. In this study, the authors examined whether a more responsive procedure using the 4 most recent samples is more effective in smokers not trying to quit. Following institution of the contingencies in both groups, BCO levels were substantially reduced, and readiness to quit and cessation self-efficacy increased. However, more individuals in the 4-sample window group achieved a BCO level below 4 ppm, indicating recent abstinence. These individuals did so more rapidly and for a greater number of visits.

Shaping smoking cessation using percentile schedules.

Behavioral interventions that provide incentives contingent upon abstinence are effective addiction treatments. Nevertheless, these treatments often fail for individuals whose recent behaviors are very different from those reinforced. These hard-to-treat individuals may require shaping to achieve abstinence. We used percentile schedules to shape smokers' delivery of breath samples indicative of recent smoking abstinence (breath carbon monoxide (BCO) <4 ppm). Percentile schedules deliver incentives to current behaviors proximal to the target. Participants (N = 102) were assigned to treatments delivering incentives for breath COs at or below the 10th, 30th, 50th, or 70th percentile of recent breath COs. Each condition effectively ensured contact with available contingencies, and resulted in BCO <4 ppm in >90% of the 30th, 50th and 70th percentile groups versus 63% in the 10th percentile. The 30th, 50th and 70th percentiles were especially effective in a sub-sample of hard-to-treat participants who did not deliver a breath CO <4 ppm during an initial abstinence test or during a nine-visit baseline period, suggesting the value of shaping for this important sub-sample.

Improving contingency management programs for addiction.

Contingency management interventions effectively reduce or eliminate some individuals' problem substance use. Typically, those who do not benefit never experience the reward or planned contingency available through the intervention because they never produce the behavior (often abstinence) on which the reward is contingent. With two analog studies, we examine whether the effectiveness contingency management interventions improves when contingencies are arranged in ways that improve the likelihood of all participants experiencing the available reward. Participants were smokers not planning to quit. In Study 1, smokers were paid 0, 1, 3, 10, or 30 dollars each day for 5 days for delivery of breath carbon monoxide (CO) levels either < or =4 ppm or below half the median of their baseline levels. Higher payment amounts and the easier target criterion resulted in a higher likelihood of participants meeting criterion. Once participants met the 4 ppm criterion, however, they often maintained this behavior even in the absence of payments for reduced breath CO levels. An ineffective contingency management system was made effective based on these results. Study 2 examined the effectiveness of percentile schedules at reducing breath CO levels. Percentile schedules shaped lower breath CO levels. The effectiveness of percentile schedules in shaping abstinence was tested in treatment seekers, and percentile schedules were found to be effective at shaping abstinence.

Effects of selected anticholinergics on acoustic startle response in rats.

The present study compared the effects of the anticholinergics aprophen hydrochloride, atropine sulfate, azaprophen hydrochloride, benactyzine hydrochloride, biperiden hydrochloride, diazepam, procyclidine hydrochloride, scopolamine hydrobromide and trihexyphenidyl hydrochloride on acoustic startle response in rats. Peak startle amplitude, latency to peak startle amplitude and prepulse inhibition following 100- and 120-dB tones were recorded 15 min following drug administration in food-restricted rats. Aprophen, atropine, azaprophen, benactyzine, biperiden and scopolamine significantly increased peak startle amplitude and decreased latency to peak startle amplitude following 100-dB pulses. In contrast, only biperiden increased peak startle amplitude following 120-dB pulses, whereas atropine and trihexyphenidyl decreased latency to peak startle amplitude following 120-dB pulses. Benactyzine decreased prepulse inhibition following both 100- and 120-dB pulses, whereas both biperiden and scopolamine decreased prepulse inhibition following 120-dB pulses. Acoustic startle response measures were effective in differentiating the effects of anticholinergic compounds. The comparison of drug effects on the acoustic startle response may be useful in selecting efficacious anticholinergic drug therapies with a minimal range of side-effects. In addition, these data may be useful in down-selecting the number of anticholinergic drugs that need to be tested in comparison studies involving more complex behavioral tests.

Effects of advanced candidate anticonvulsants under two rodent models of 'counting'.

The behavioral effects of a variety of advanced candidate anticonvulsants for organophosphate-induced seizures were evaluated under two rodent 'counting' models. Rats pressed the left of two levers a number of times (a 'run') before pressing the right lever. The targeted performance was a run of 12. The training contingency was a targeted percentile schedule, which provided food if the current run was closer to 12 than two-thirds of the most recent runs. Baseline performance was well controlled by the target, with mean run lengths slightly less than 12. Once this performance was acquired, half the subjects were switched to a procedure providing food following runs of different lengths with a probability yoked to previous percentile schedule performance. The two procedures generate comparable baseline performances, but behavioral disruptions generate reinforcement loss only under the yoked procedure. Atropine, scopolamine, azaprophen, aprophen, trihexyphenidyl, procyclidine, benactyzine, biperiden and diazepam were tested. All produced dose-related decreases in overall run length and response rate. Responding was disrupted more readily under the yoked procedure than under the percentile procedure. Only atropine affected responding at doses below those effective against soman-induced seizures. Of the present candidates, trihexyphenidyl, procyclidine, benactyzine and biperiden appear most promising for further development.

Behavioral and immunological effects of exogenous butyrylcholinesterase in rhesus monkeys.

Although conventional therapies prevent organophosphate (OP) lethality, laboratory animals exposed to such treatments typically display behavioral incapacitation. Pretreatment with purified exogenous human or equine serum butyrylcholinesterase (Eq-BuChE), conversely, has effectively prevented OP lethality in rats and rhesus monkeys, without producing the adverse side effects associated with conventional treatments. In monkeys, however, using a commercial preparation of Eq-BuChE has been reported to incapacitate responding. In the present study, repeated administration of commercially prepared Eq-BuChE had no systematic effect on behavior in rhesus monkeys as measured by a six-item serial probe recognition task, despite 7- to 18-fold increases in baseline BuChE levels in blood. Antibody production induced by the enzyme was slight after the first injection and more pronounced following the second injection. The lack of behavioral effects, the relatively long in vivo half-life, and the previously demonstrated efficacy of BuChE as a biological scavenger for highly toxic OPs make BuChE potentially more effective than current treatment regimens for OP toxicity.

Dose-response curves and time-course effects of selected anticholinergics on locomotor activity in rats.

RATIONALE: In order to facilitate direct comparisons of anticholinergic drug effects on activity, nine drugs were tested in one laboratory using a standardized procedure. OBJECTIVE: The present study compared the effects of aprophen hydrochloride, atropine sulfate, azaprophen hydrochloride, benactyzine hydrochloride, biperiden hydrochloride, diazepam, procyclidine hydrochloride, scopolamine hydrobromide, and trihexyphenidyl hydrochloride on activity levels in rats. METHODS: Both fine motor activity (reflecting smaller movements) and ambulatory activity (reflecting larger movements) were recorded for 23 h following drug administration in food-restricted rats. All drugs were administered during the light period of the photocycle. RESULTS: Atropine, azaprophen, biperiden, scopolamine, and trihexyphenidyl increased both ambulations and fine motor activity significantly during the first hour post-injection, but the increased activity levels returned to vehicle control levels within 2-6 h post-injection. Benactyzine and procyclidine only increased fine motor activity significantly above vehicle control levels and activity levels returned to vehicle control levels within 2-3 h. Finally, aprophen and diazepam generally did not increase measures of activity significantly above vehicle controls at the dose ranges examined. CONCLUSIONS: Based on potencies relative to scopolamine, the potency of the drugs could be ranked as follows: scopolamine > trihexyphenidyl > biperiden > azaprophen > procyclidine > benactyzine > atropine > aprophen. The comparison of drug effects on activity may be useful in selecting anticholinergic drug therapies with a minimal range of side effects. In addition, these data may reduce the number of anticholinergic drugs that need to be tested in comparison studies involving more complex behavioral tests.

Daily rhythms in a complex operant: targeted percentile shaping of run lengths in rats.

Daily rhythms in response output and accuracy were examined when reinforcement for a complex operant was uncoupled from accuracy of performance. Rats housed in operant conditioning chambers earned their daily ration of food under a targeted percentile procedure for responding on two levers. The targeted pattern was a series of consecutive responses on the left lever (a "run"), followed by a single response on the right lever. The targeted run length was either "O" (i.e., undefined, under the nondifferential baseline), 6, 12 or 24. Under baseline, a random third of all trials ended in pellet delivery; under the percentile conditions, trials with runs closer to the target than two-thirds of the runs from the most recent 24 trials ended in pellet delivery. This contingency shaped run lengths while ensuring that approximately one-third of all trials produced pellets. Responding tracked the target value well, with mean obtained run lengths equal to 90% of the target or better. Daily rhythms were clearly evident in measures of overall output, with subjects responding primarily 3-7 h into the dark period. The only substantial light-period responding observed in all subjects occurred during the 2 h after noon, when the chambers were serviced. No systematic variation in this pattern was observed as a function of target. Run length was much less variable across the daily cycle than was response output, with only a suggestion under the longest target that response accuracy was lower during periods removed from the period of peak activity.

Behavioral effects of enantiomers of dizocilpine under two "counting" procedures in rats.

Stereoisomers of the N-methyl-D-aspartate antagonist dizocilpine (MK-801) were studied to determine whether behavioral effects on complex operants depend on reinforcement loss accompanying behavioral disruption. Rats earned food pellets if the run of consecutive left-lever presses preceding a trial-terminating right-lever press approximated a target of 12. A percentile schedule reinforced any run closer to the target than two-thirds of the runs on the most recent 24 trials. Once the sequence was learned, half the subjects were shifted to a procedure that yoked reinforcement for each length run to the probability that length generated pellets during asymptototic percentile performance. Although these two procedures generate similar control run and reinforcement distributions, disrupting behavior reduced reinforcement probability far more under the yoked than the percentile procedure. Despite this difference in drug-induced reinforcement loss, both enantiomers produced similar dose-related decreases in run length and response rate under both procedures, with the (-) isomer approximately one log unit less potent than the (+) isomer. The absence of differential effects under these procedures diminishes the likelihood that reinforcement loss contributes to dizocilpine's effects, indirectly bolstering claims that dizocilpine directly affects learning.

Shaping in the 21st century: Moving percentile schedules into applied settings.

The present paper provides a primer on percentile reinforcement schedules, which have been used for two decades to study response differentiation and shaping in the laboratory. Arranged in applied settings, percentile procedures could be used to specify response criteria, standardizing treatment across subjects, trainers, and times to provide a more consistent training environment while maintaining the sensitivity to the individual's repertoire that is the hallmark of shaping. Percentile schedules are also valuable tools in analyzing the variables of which responding is a function, both inside and outside the laboratory. Finally, by formalizing the rules of shaping, percentile schedules provide a useful heuristic of the processes involved in shaping behavior, even for those situations that may not easily permit their implementation. As such, they may help further sensitize trainers and researchers alike to variables of critical importance in behavior change.

Response acquisition under targeted percentile schedules: a continuing quandary for molar models of operant behavior.

The number of responses rats made in a "run" of consecutive left-lever presses, prior to a trial-ending right-lever press, was differentiated using a targeted percentile procedure. Under the nondifferential baseline, reinforcement was provided with a probability of .33 at the end of a trial, irrespective of the run on that trial. Most of the 30 subjects made short runs under these conditions, with the mean for the group around three. A targeted percentile schedule was next used to differentiate run length around the target value of 12. The current run was reinforced if it was nearer the target than 67% of those runs in the last 24 trials that were on the same side of the target as the current run. Programming reinforcement in this way held overall reinforcement probability per trial constant at .33 while providing reinforcement differentially with respect to runs more closely approximating the target of 12. The mean run for the group under this procedure increased to approximately 10. Runs approaching the target length were acquired even though differentiated responding produced the same probability of reinforcement per trial, decreased the probability of reinforcement per response, did not increase overall reinforcement rate, and generally substantially reduced it (i.e., in only a few instances did response rate increase sufficiently to compensate for the increase in the number of responses per trial). Models of behavior predicated solely on molar reinforcement contingencies all predict that runs should remain short throughout this experiment, because such runs promote both the most frequent reinforcement and the greatest reinforcement per press. To the contrary, 29 of 30 subjects emitted runs in the vicinity of the target, driving down reinforcement rate while greatly increasing the number of presses per pellet. These results illustrate the powerful effects of local reinforcement contingencies in changing behavior, and in doing so underscore a need for more dynamic quantitative formulations of operant behavior to supplement or supplant the currently prevalent static ones.

Reinforcement loss and behavioral tolerance to d-amphetamine: using percentile schedules to control reinforcement density.

Two procedures were used to examine the impact of reinforcement loss on the development of behavioral tolerance to the effects of d-amphetamine on control over response number in rats. Under both procedures, trials consisted of at least one left-lever press followed by a single right-lever press. Consecutive left-lever presses on each trial comprised a "run". A targeted percentile schedule provided reinforcement if the current run length was closer to the target length (12) than two-thirds of the most recent 24 runs. This procedure differentially reinforced runs around 12 while holding reinforcement probability constant at 0.333. A second group acquired the differentiation under the percentile schedule, but was then shifted to a procedure which yoked reinforcement probability by subject and run length to that obtained under asymptotic percentile schedule performance. The two procedures generated roughly comparable, but not identical, control run lengths, response rates, reinforcement probabilities and reinforcement rates. Only under the yoked procedure, however, did drug-induced disruptions in run length produce decreases in reinforcement density. Acute administration of amphetamine produced dose-related decreases in run length and overall response rate under both procedures. Daily pre-session administration of 1.7mg/kg amphetamine persistently suppressed run length under the percentile procedure, but not under the yoked procedure. Run lengths under the latter gradually increased with repeated amphetamine to a level equal to or slightly below baseline levels. Response rate was suppressed initially, and tolerance developed inconsistently to this effect in both groups. Dose-effect curves obtained when doses of amphetamine were substituted for the chronic dose showed a larger shift to the right with the yoked than percentile group for run length, and a similar but smaller effect for overall response rate. These results indicate that reinforcement loss substantially contributes to the development of tolerance to the behavioral effects of amphetamine, even when the comparison behaviors are generated by reinforcement contingencies that under non-drug conditions control very similar rates and patterns of behavior and reinforcement. Future comparison of acute and chronic drug effects on behaviors maintained by the percentile and yoked procedures may prove very helpful in illuminating drug-behavior interactions and the dynamic interrelations typically engendered by more traditional reinforcement schedules.

Control over response number by a targeted percentile schedule: reinforcement loss and the acute effects of d-amphetamine.

Two fixed-consecutive-number-like procedures were used to examine effects of acute d-amphetamine administration on control over response number. In both procedures, rats were required to press the left lever at least once and then press the right lever to complete a trial. The consecutive left-lever presses on each trial comprised a "run." Under the targeted percentile schedule, reinforcement was provided if the current run length was closer to the target length (16) than half of the most recent 24 runs. This differentially reinforced run length while holding reinforcement probability constant at .5. A second group acquired the differentiation under the targeted percentile schedule, but were then shifted to a procedure that yoked reinforcement probability by subject and run length to that obtained under the targeted percentile schedule. The two procedures generated practically identical control run lengths, response rates, reinforcement probabilities, and reinforcement rates. Administration of d-amphetamine disrupted percentile responding to a greater degree than yoked control responding. This disruption decreased reinforcement frequency less in the former than the latter procedure. The similar baseline responding under these two procedures suggests that this difference in sensitivity was due to behavioral adjustments to drug prompted by reduction of reinforcement density in the yoked control but not the percentile schedule. These adjustments attenuate the drug's effects under the former, but not the latter, procedure.

Tolerance to behavioral effects of physostigmine under interval schedules of positive or negative reinforcement.

The present experiments examined whether the rate and type of events maintaining responding help determine physostigmine's behavioral effects. The first two experiments examined the acute and chronic effects of physostigmine, respectively, on lever pressing of rats under variable-interval schedules of food presentation. The third examined the chronic effects of physostigmine on lever pressing under random-interval schedules of shock avoidance. Three different variable intervals (18, 56, and 180 s) and two different random intervals (20 and 60 s) were studied, each associated with a distinctive stimulus. Baseline rates of responding were directly related to the scheduled rate of food delivery or shock avoidance. Acute administration of 0.154-1.233 mumol/kg (0.1-0.8 mg/kg) physostigmine sulfate produced monotonic decreases in overall response rate under all schedules of food presentation. Acute effects (per cent of control response rate) did not differ systematically under the various interval values. Large doses (i.e., 0.4 or 0.8 mg/kg) suppressed the rate of food delivery as well. When initially administered, 0.967 mumol/kg (0.4 mg/kg) physostigmine salicylate also suppressed avoidance response rates and per cent shocks avoided. Tolerance developed to the effects of this dose of physostigmine salicylate on pellet or shock-avoidance frequency more rapidly than to effects on overall response rate. Tolerance to the latter developed only very gradually and could in the case of shock-avoidance response rates be considered partial at best. Tolerance was not affected by the scheduled rate of food or shock presentation. Blood acetylcholinesterase levels showed no recovery during chronic physostigmine. Tolerance is discussed in terms of the reinforcement-loss hypothesis.

Response-reinforcer contingency and spatially defined operants: testing an invariance property of phi.

A chamber containing 72 response keys defining the circumference of a circle 1 m in diameter was used to examine the relation between differentiation of response location and a measure of response-reinforcer contingency known as the phi coefficient. A different target key was specified in each successive phase, and response location was differentiated with respect to the target. Criterional and noncriterional responses (i.e., responses "near" and "far" from the target) were defined using targeted percentile schedules to control the overall probability of each response class. By manipulating criterional (and, hence, noncriterional) response probability and the reinforcement probabilities conditional on each, a mathematical invariance property peculiar to phi in contingency analysis was examined. Specifically, diagonally interchanging cell frequencies in a 2 x 2 table relating criterional/noncriterional responses to reinforcement/nonreinforcement leaves phi unchanged. Hence, the degree of response differentiation predicted by phi remains unchanged under the four permutations implied by the various diagonal interchanges. This predicted invariance was examined under values of phi equal to .33, .58, and .82. Increasing phi generally increased the stereotypy of response location. Three of the permutations generated almost interchangeable performance at different phi values. The remaining permutation, however, generated functions relating response concentration to phi with slopes shallower than those obtained under the other permutations. This resulted from relatively higher levels of differentiation, compared to the other permutations, at low phi values. These data strongly suggest boundary conditions on the ability of phi to reflect completely the local processes that are indexed by phi at a molar level.

Parametric manipulation of interresponse-time contingency independent of reinforcement rate.

Pecking of pigeons was reinforced under a modified interval-percentile procedure that allowed independent manipulation of overall reinforcement rate and the degree to which reinforcement depended on interresponse-time duration. Increasing the contingency, as measured by the phi coefficient, between reinforcement and long interresponse times while controlling the overall rate of reinforcement systematically increased the frequency of those interresponse times and decreased response rate under both of the reinforcement rates studied. Increasing reinforcement rate also generally increased response rate, particularly under weaker interresponse-time contingencies. Random-interval schedules with comparable reinforcement rates generated response rates and interresponse-time distributions similar to those obtained with moderate-to-high interresponse-time reinforcement contingencies. These results suggest that interresponse-time reinforcement contingencies inherent in random-interval and constant-probability variable-interval schedules exercise substantial control over responding independent of overall reinforcement rate effects. The interresponse-time reinforcement contingencies inherent in these schedules may actually mask the effects of overall reinforcement rate; thus differences in response rate as a function of reinforcement rate when interresponse-time reinforcement is eliminated may be underestimated.

Interresponse-time punishment: a basis for shock-maintained behavior.

Lever pressing of squirrel monkeys postponed brief electric shock according to a free-operant shock-postponement procedure. Pressing also produced shock with a probability proportional to the duration of the current interresponse time in some conditions, or to the fifth ordinally-preceding interresponse time in others. These conditions provided equal frequencies and temporal distributions of response-produced shocks either contingent on or independent of the current interresponse-time duration, respectively. Shock delivered contingent on the current interresponse-time duration resulted in shorter mean interresponse times and higher overall response rates that shock delivered independent of the current interresponse time. In subsequent conditions, response-produced shocks were sufficient to maintain responding following suspension of the postponement procedure only when those shocks were contingent on the current interresponse time. Presenting shock independent of the current interresponse time, conversely, suppressed response rate and ultimately led to cessation of responding in the absence of a conjoint shock-postponement procedure. These results demonstrate interresponse-time punishment in the absence of any indirect avoidance contingencies based on overall shock-frequency reduction, and strongly support similar interpretation at the more local level of shock-frequency reduction correlated with particular interresponse times. Differential punishment of long interresponse times also provides both an a priori basis for predicting whether a schedule of shock presentation will maintain or suppress responding and a framework for interpreting many of the functional relations between overall response rate and parameters of consequent shock presentation. Finally, these results and others indicate the importance of response-consequence contiguity above and beyong any notion of noncontiguous contingency in the control of behavior.