Preference assessments provide individuals with an opportunity to make choices and thus, increase their autonomy. Furthermore, preference assessments are used to identify stimuli that can be used as reinforcers in behavior change programs. Two studies were conducted to examine the validity of vocal preference assessments used with adults with developmental disabilities. In Study 1, the concurrent validity between vocal and stimulus paired-choice assessments, with and without activity access following a participant's selection, was evaluated. Spearman's rank correlation coefficients were computed to evaluate the correspondence between assessments. Results showed that similarity in consequence (i.e., activity access) impacted the correspondence between preference assessment results; whereas, similarity in antecedent (i.e., assessment format) did not impact the correspondence between preference assessment results. In Study 2, the predictive validity of reinforcer effectiveness of the preference assessments from Study 1 were evaluated. Specifically, the reinforcing efficacy and potency of high-preference activities were evaluated using a progressive-ratio schedule of reinforcement, within a multielement design. Results showed the preference assessments that included activity access were more likely to identify reinforcers that were effective under increasing response requirements, than were assessments that did not include activity access.

It has been proposed that relapse vulnerability in previously dependent individuals results from augmentation of drug-induced reinforcement due to repeated associations between the interoceptive properties of the drug and reduction of acute withdrawal distress. To test this hypothesis, male Sprague-Dawley rats self-administered 0.05 mg/kg/inf heroin on continuous and progressive ratio (PR) schedules. During this period, they also received injections of vehicle or escalating doses of heroin. Following tests of naloxone-precipitated withdrawal (0.01 or 0.1 mg/kg, SC), as well as abstinence (4 days), and extinction training (9 sessions), they were pre-treated with vehicle or yohimbine (0.5 mg/kg, IV) and tested for resumption of heroin self-administration (0.05 mg/kg/inf) on continuous and PR schedules (Experiments 1 & 2), or tested for reinstatement in extinction conditions. Differences between vehicle- and heroin-injected rats were noted on self-administration on the continuous reinforcement schedule, but not on the PR schedule, in spite of greater signs of withdrawal precipitated by naloxone in the heroin-injected rats. More importantly, there were no group differences in resumption of heroin self-administration, and this was not altered by yohimbine. These results suggest that relapse vulnerability cannot be uniquely ascribed to the altered reinforcing action of drugs; contextual and other conditioning factors must play a role in modulating resumption of drug intake after periods abstinence.

Past research has shown that preference for a stimulus is correlated positively with reinforcer efficacy – more preferred stimuli tend to be more potent reinforcers. Researchers have recently examined the use of progressive ratio (PR) reinforcement schedules to evaluate preference. However, research on the concordance between preference and performance under a progressive ratio schedule is limited. Therefore, two experiments were conducted to extend this research. In Experiment 1 I compared the relative reinforcing efficacy of six stimuli obtained under a PR schedule to the mean preference hierarchy obtained through paired-stimulus preference assessments conducted before and after PR reinforcement sessions. In Experiment 2 I evaluated the PR schedule for quantifying the reinforcing value of three stimuli from Experiment 1 (i.e., one high, one medium, and one low preference stimulus). The results of Experiment 1 indicated that items that yielded higher breaking points and responses per minute were also more preferred. However, concordance between percent preference and breaking points and response rates for less preferred items was more variable. The results of Experiment 2 showed that high preference stimuli increased responding over baseline for all participants. However, low preference reinforcers also increased responding over baseline for some participants.

Past research has shown that preference for a stimulus is correlated positively with reinforcer efficacy – more preferred stimuli tend to be more potent reinforcers. Researchers have recently examined the use of progressive ratio (PR) reinforcement schedules to evaluate preference. However, research on the concordance between preference and performance under a progressive ratio schedule is limited. Therefore, two experiments were conducted to extend this research. In Experiment 1 I compared the relative reinforcing efficacy of six stimuli obtained under a PR schedule to the mean preference hierarchy obtained through paired-stimulus preference assessments conducted before and after PR reinforcement sessions. In Experiment 2 I evaluated the PR schedule for quantifying the reinforcing value of three stimuli from Experiment 1 (i.e., one high, one medium, and one low preference stimulus). The results of Experiment 1 indicated that items that yielded higher breaking points and responses per minute were also more preferred. However, concordance between percent preference and breaking points and response rates for less preferred items was more variable. The results of Experiment 2 showed that high preference stimuli increased responding over baseline for all participants. However, low preference reinforcers also increased responding over baseline for some participants.

We used a combined multi-element, ABCBC reversal design to examine whether qualities of various negative reinforcers can be assessed under progressive-ratio schedules. Two adults with disabilities participated in this study. We assessed five sounds three times using progressive-ratio schedules to obtain mean break points for each stimulus and ranked negative reinforcers according to their mean break points. We called the stimulus with the highest mean break point the high-quality escape (HQE) stimulus and the stimulus with the lowest break point the low-quality escape (LQE) stimulus and examined responding according to different schedules of reinforcement for each stimulus: FR2, FR4, and FR8 for Jenny and FR1 and FR11 for April. We identified preferred and nonpreferred sounds for both participants.We observed differential responding for both participants between preferred and nonpreferred sounds. We observed differential responding between HQE and LQE stimuli for April but not for Jenny; a larger range in break points was observed for April. These results demonstrate a method to identify preferred and nonpreferred sounds and provide support for the possibility of using progressive-ratio schedules to rank negative reinforcers of various qualities.

Problem gambling is a growing social concern that results in debt, lost jobs, broken families, and at times, suicide. Slot machines are the most popular and most addictive form of gambling, generating nearly 70% of annual profits for the commercial casino industry in North America. Behavioral researchers have identified variables that establish and maintain problem gambling on slot machines, and the data reveal characteristics that influence preference for specific games, and subsequently, time spent engaged with specific machines. A degree of variability has been reported in the outcomes observed across participants and studies; such variability may be influenced by generic features of the games used by researchers utilizing a “one machine suits all” approach to slot research, i.e., within most studies a single machine is used for all participants rather than chosen according to participant preference for the machine or features therein. The following set of studies aimed to investigate variables related to slot machine selection, gambler preference for structural characteristics, and the reinforcing effectiveness of the machine on gambling behavior. The first of three experiments evaluated participant preference for functional and structural characteristics of popular three-, four- and five-reel electronic Vegas-style slot machines according to (a) a Likert rating scale of attitudes toward the machines, (b) forced ranking of most-preferred machines, and (c) a paired-stimulus preference assessment. Experiment II utilized a series of multiple schedules randomized across participants to examine differences in the rate of play when participants gambled on their most- and least-preferred machines. In Experiment III, the reinforcing effectiveness of the machines was evaluated. Participants engaged in an arbitrary task to gain access to their highest- and least-preferred machines as indicated in Experiment I. Response effort during the work task was evaluated under a progressive ratio schedule of reinforcement to determine the degree to which the individual would work to gain access to the machine. Participant break points were compared across the two conditions. Results of Experiment I yielded significant differences in the degree to which participants rated the machines: three-reel machines and those displaying a win were rated significantly higher in the attitude assessment when compared to four- or five-reel machines, and when compared to those with a loss, respectively. During the forced ranking procedure, participants again selected three-reel machines significantly more frequently in their “top five” favorite machines than four- or five-reel options. Last, when subjected to the paired stimulus preference assessment, participants selected three-reel machines on a significantly higher percentage of trials than five-reel alternatives. Results of Experiment II demonstrated that rate of play on high-preference machines is on average, faster than rate of play on lower-preference machines, and results from Experiment III yielded on average, higher break points in participant responding when offered the opportunity to gamble on high-preference slot machines following a response requirement than when offered a low-preference option; however, the average rate of response on the work task that led to machine access was lower during high-preference conditions than low-preference conditions. Implications of these findings for the gambling literature and for the effective prevention and treatment of disordered slot machine gambling are discussed.

The general purpose of the current study was to evaluate the potency of different categories of reinforcers with young children diagnosed with developmental delays. The participants were two boys and one girl who were between the ages of seven and eight. In Phase 1, we evaluated the reinforcing potency of tokens, edible items, and leisure items by using a progressive ratio (PR) schedule. For two participants, we found that tokens resulted in the highest PR break points. For one participant, edibles resulted in the highest break points (tokens were found to have the lowest break points). In Phase 2, we evaluated the effects of presession access on the break points of edibles and tokens. This manipulation served as a preliminary analysis of the extent to which tokens might function as generalized conditioned reinforcers. During Phase 2, presession access altered the break points of edibles, but not tokens. The findings of the current study suggest that PR schedules may be useful as a means to better assess certain dimensions of tasks and how they affect reinforcer effectiveness (e.g., amount of effort the client is willing to exert, the duration at which the client willing to work, how many responses the client will emit, etc.), and to evaluate to what extent tokens actually function as generalized conditioned reinforcers.

Rationale: Amphetamine abuse by adolescents predicts long-term drug dependence. Heightened vulnerability to drug abuse could be due to higher sensitivity to drug’s reinforcing effects. Rodents are used to study age-related sensitivities to drugs. Objective: We compared intravenous amphetamine self-administration between adolescent and adult male rats on an operant schedule of reinforcement measuring the reinforcing efficacy of a drug. Methods: After surgery, adolescent and adult rats acquired lever-pressing behavior reinforced by amphetamine infusions. Results: Both age groups exhibited more infusions per session as dose increased. However, neither the number of infusions per session nor total amphetamine intake differed across age groups. Conclusion: Although rapid transition is reliable to test reinforcing properties of stimulants, results suggest that amphetamine is an equally efficacious reinforcer among both age groups. In regards to humans, these results suggest that other factors, like social influences, explain higher rates of drug intake by adolescent compared with adult humans.

This study examined the relationships between motivation and cognitive performance in male and female common marmosets (Callithrix jacchus). This question was driven by prior data from the Lacreuse lab showing a robust female impairment in reversal learning, as assessed by the number of trials needed to acquire a reversal following a simple discrimination between two stimuli. This thesis tested the hypothesis that the female impairment in reversal learning was mediated by deficits in motivation. Two sets of measures were used to test this hypothesis. I evaluated physical effort via testing on the progressive ratio (PR), a test that requires animals to produce an increasing number of responses to get a reward. Cognitive effort was evaluated through the number of refusals (aborted trials) produced during performance of a reversal. Because estrogen replacement was previously shown to impair reversal learning in ovariectomized females, I also examined whether PR performance was affected by estrogen levels in a subset of female subjects. Contrary to my hypothesis, reversal learning was not significantly associated with cognitive or physical effort in either males or females. Estrogen levels did not significantly affect physical effort, but there was too much variability in a small sample of females for these results to be compelling. We conclude that the sex difference in reversal learning performance is unlikely to be mediated by sex differences in motivation. Instead females may be more likely than males to engage in habitual processes implicating the dorsal striatum, likely through the action of estrogens on this brain region.

Progressive-ratio schedules are useful for studying the reinforcing effects of drugs. Earlier human laboratory studies showed that d-amphetamine significantly increased break points relative to placebo. However, the magnitude of the increase was modest, which may be attributable to rather high levels of placebo responding. We used novel response requirements in a modified progressive-ratio procedure and hypothesized that the altered range of response requirements would decrease responding for placebo and increase responding for d-amphetamine. Eight participants completed the study. The participants first sampled oral doses of d-amphetamine (0, 8, 16, and 24mg). In subsequent sessions, the participants were offered the opportunity to work for the sampled dose on a modified progressive-ratio procedure with response requirements ranging from 400 to 1800 mouse clicks. A battery of participant-rated drug-effect questionnaires, a performance measure, and cardiovascular measures were included to more fully characterize the effects of d-amphetamine. Placebo maintained low levels of responding. The intermediate dose of d-amphetamine increased responding significantly above placebo levels. d-Amphetamine produced prototypical subject-rated effects that were an orderly function of dose. These data suggest that the modified response requirements resulted in lower levels of placebo taking and a larger separation between the number of placebo and d-amphetamine capsules earned. Behavioural Pharmacology.