Effects of chlordiazepoxide and cocaine on concurrent food and avoidance-of-timeout schedules.

Five rats were trained on a concurrent schedule in which responses on one lever produced a food pellet on a random-interval 30-s schedule during 10 s of food availability associated with distinctive exteroceptive stimuli. Responses on another lever postponed for 20 s the presentation of a 50-s timeout, during which all stimuli were extinguished and the schedule contingencies on the food lever were suspended. The response rates maintained by the random-interval schedule exceeded those maintained by the avoidance contingency, but both provided a stable baseline to assess the behavioral effects of different drugs. Low doses of cocaine hydrochloride (1 and 3 mg/kg) did not affect food-reinforced responding or avoidance response rates. Intermediate doses (5.6, 10, and 13 mg/kg) produced a dose-dependent decrease in food-maintained and avoidance response rates, and both types of responding were virtually eliminated after administration of the highest doses (17 and 30 mg/kg) of cocaine. Low doses of chlordiazepoxide (1 and 3 mg/kg) increased food-maintained and avoidance response rates, and both rates decreased systematically after 10 and 30 mg/kg of this drug. The effects of cocaine and chlordiazepoxide on response rates maintained by avoidance of timeout from food presentation were unlike those reported when subjects responded to avoid shock presentation. The results of this experiment thus provide evidence to suggest that the effects of drug administration on avoidance behavior may be a function of the nature of the consequent event to be avoided.     

DOES PACKAGE SIZE MATTER? A UNIT-PRICE ANALYSIS OF “DEMAND” FOR FOOD IN BABOONS

In a study examining “demand” for food, responding of 8 adult male baboons (Papio c. anubis) was maintained under a fixed-ratio schedule of food reinforcement during daily 23-hr experimental sessions. Completion of the ratio requirement resulted in the delivery of one, five, or 10 1-g food pellets. Supplemental feeding was limited to fruit and a dog biscuit daily. Responding increased as “cost” was increased across a wide range of fixed-ratio values before reaching a maximum and then decreasing. Increasing the number of food pellets per delivery decreased total responding and the number of reinforcements per day. A unit-price analysis, in which intake was converted to grams per day and fixed-ratio values were converted to responses per gram, yielded demand functions that overlapped at lower unit prices. Under one or more multiple-pellet conditions, however, intake decreased more quickly than under the one-pellet condition as the fixed-ratio value was increased in all but 1 baboon. This indicates that even when using unit-price conversions, there was variability in total intake. Although unit-price conversions yielded intake data that were more consistent across conditions, conditions differed in response topography even at the same unit prices: Under the multiple-pellet conditions there were longer pauses in responding, running response rate was slower, and the first eating bout (i.e., “meal”) of the session was smaller than under the one-pellet condition. These findings (a) support the heuristic value of a unit-price analysis for studying responding for and consumption of commodities that have similar attributes, and (b) indicate that different response topographies may result in similar intakes of a commodity.     

The effects of smoked marijuana on progressive-interval schedule performance in humans.

In three experiments, 8 human subjects participated in a study of the effects of smoked marijuana on progressive-interval schedule performance. A two-component chained progressive-interval fixed-interval schedule of point delivery was used. In the progressive-interval component, the interval length began at 20 s and increased either geometrically or arithmetically (by either 20 s, 40 s, 80 s, 100 s, or 160 s) on each subsequent interval. After this interval elapsed, a single button press produced the fixed-interval component, with a total of five reinforcers of varying magnitude ($0.05, $0.20, or $0.40) available on a fixed-interval 20-s schedule. After the five reinforcer deliveries, the schedule returned to the initial progressive-interval component. Several relationships were found among rates of responding, postreinforcement pauses and drug administration in the progressive-interval component: (a) Postreinforcement pauses increased as the temporal requirements of the progressive-interval schedule increased; (b) rates of responding during successive progressive-interval components rapidly decreased to low rates of responding after the first few progressions; (c) postreinforcement pauses decreased systematically as dose of smoked marijuana increased; and (d) rates of responding increased after smoking active marijuana but not after smoking placebo cigarettes. Results are discussed in the context of behavioral control and relevance to other studies that have investigated the effects of smoked marijuana on schedule performance.     

Evaluating skills correlated with discriminated responding in multiple schedule arrangements

One potential solution for excessively high‐rate functional communication responses (FCR) is to establish stimulus control of the FCR through a multiple schedule. However, several studies have demonstrated difficulty with establishing discriminated responding across multiple schedule components. The primary aim of the current study was to evaluate how participants’ skills related to color discrimination may be related to the emergence of discriminated responding in a multiple schedule with colors as the schedule‐correlated stimuli. Three secondary aims of the current study were to evaluate: a) varied multiple schedule arrangements, b) if topographically dissimilar stimuli facilitated the emergence of discriminated responding, and c) if employing different colored stimuli across multiple schedule arrangements reduced the likelihood that discriminated responding emerged simultaneously across varied arrangements. Nine participants’ ability to match, select, tact, and respond intraverbally to colors was assessed, and 1 of 2 evaluations of multiple schedule arrangements were conducted. Results indicated that participants’ ability to select and tact colors was strongly correlated with the efficacy of standard multiple schedule arrangements. Additionally, multiple schedule arrangements employing topographically dissimilar stimuli were observed to be equally as effective as standard arrangements and the inclusion of different colored stimuli across arrangements did not reduce the likelihood that discriminated responding emerged simultaneously across all conditions, when it was observed to emerge at all.     

A translational comparison of contingency‐based progressive delay procedures and their effects on contextually appropriate behavior

Schedule thinning is an essential step in treating problem behavior, yet little research has been conducted to determine the method associated with sustained treatment effects. A frequently used method for thinning reinforcement is contingency‐based progressive delay, which requires the individual to meet some criteria before the reinforcers are returned. The response requirement could be dependent on (a) contextually appropriate behavior (differential reinforcement of alternative behavior‐based thinning) or (b) absence of problem behavior (differential reinforcement of other behavior‐based thinning). A translational arrangement with college students was implemented to determine the effects of these 2 response requirements. Tolerance was observed regardless of thinning method and was indicated by low rates of responding to the analogue problem behavior; however, more contextually appropriate behavior occurred during differential reinforcement of alternative behavior‐based thinning. These results support the use of response requirements for behaviors that are expected of the individual when reinforcement is not immediately forthcoming.     

USING FIXED‐TIME SCHEDULES TO MAINTAIN BEHAVIOR: A PRELIMINARY INVESTIGATION

The purpose of this study was to evaluate the potential of fixed‐time (FT) schedules to maintain behavior. Two children who had been diagnosed with autism were taught a functional task. Subsequently, three different FT schedules (i.e., yoked, thin, dense) were compared to determine their capacity to maintain task responding. Results suggested that FT schedules may be used to maintain previously acquired behavior.     

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.     

Are behaviors at one alternative in concurrent schedules independent of contingencies at the other alternative?

Some have reported changing the schedule at one alternative of a concurrent schedule changed responding at the other alternative (Catania, 1969), which seems odd because no contingencies were changed there. When concurrent schedules are programmed using two schedules, one associated with each alternative that operate continuously, changing the schedule at one alternative also changes the switch schedule at the other alternative. Thus, changes in responding at the constant alternative could be due to the change in the switch schedule. To assess this possibility, six rats were exposed to a series of conditions that alternated between pairs of interval schedules at both alternatives and a pair of interval schedules at one, constant, alternative and a pair of extinction schedules at the other alternative. Comparing run lengths, visit durations and response rates at the constant alternative in the alternating conditions did not show consistent increases and decreases when a strict criterion for changes was used. Using a less stringent definition (any change in mean values) showed changes. The stay/switch analysis suggests it may be inaccurate to apply behavioral contrast to procedures that change from concurrent variable‐interval variable‐interval schedules to concurrent variable‐interval extinction schedules because the contingencies in neither alternative are constant.     

Are choices based on conditional or conjunctive probabilities in a sequential risk-taking task?

In this study, we examined participants' choice behavior in a sequential risk-taking task. We were especially interested in the extent to which participants focus on the immediate next choice or consider the entire choice sequence. To do so, we inspected whether decisions were either based on conditional probabilities (e.g., being successful on the immediate next trial) or on conjunctive probabilities (of being successful several times in a row). The results of five experiments with a simplified nine-card Columbia Card Task and a CPT-model analysis show that participants' choice behavior can be described best by a mixture of the two probability types. Specifically, for their first choice, the participants relied on conditional probabilities, whereas subsequent choices were based on conjunctive probabilities. This strategy occurred across different start conditions in which more or less cards were already presented face up. Consequently, the proportion of risky choices was substantially higher when participants started from a state with some cards facing up, compared with when they arrived at that state starting from the very beginning. The results, alternative accounts, and implications are discussed.     

Differential antagonism of cocaine self-administration and cocaine-induced disruptions of learning by haloperidol in rhesus monkeys

Six rhesus monkeys responding under a three-component multiple schedule were administered haloperidol to determine its effects on cocaine self-administration and on cocaine's disruptive effects on the repeated acquisition and performance of response chains. In the absence of haloperidol, 0.0032-0.032 mg/kg/infusion of cocaine increased response rate and the number of infusions in the self-administration component when compared to saline administration, whereas 0.1-0.32 mg/kg/infusion decreased response rate and the number of infusions. When compared to saline administration, the two lowest infusion doses of cocaine had little or no effect on responding in the acquisition and performance components; however, higher infusion doses of cocaine dose-dependently decreased response rate in these components. In addition, the higher doses of cocaine also increased the percentage of errors in the acquisition and performance components. Pretreatment with haloperidol (0.0032 or 0.01 mg/kg, i.m.) antagonized the effects of low doses of cocaine on the number of infusions in the self-administration component, whereas only the 0.01-mg/kg dose antagonized the effects of high doses of cocaine on the number of infusions. Neither dose of haloperidol antagonized the rate-decreasing effects of cocaine on responding in the acquisition and performance components significantly; the highest dose of haloperidol alone decreased rates of responding in each component. Antagonism of cocaine's error-increasing effects by haloperidol was only evident at one dose of cocaine (0.032 mg/kg/infusion), and was more complete in the performance components than in the acquisition components. Together, these data show the limited suitability of haloperidol for selectively antagonizing cocaine self-administration in the context of a multiple schedule involving transition behavior, and show the lack of uniform antagonism across operant behaviors.