MAINTENANCE OF THERAPEUTIC CHANGE BY MOMENTARY DRO

Differential reinforcement of other behavior (DRO) involves delivery of reinforcement at the end of an interval during which the target behavior has not occurred. Momentary DRO, however, is a procedure in which reinforcement is delivered if a response did not occur at the end of an interval. We examined the extent to which momentary DRO maintained suppression, following initial treatment with whole-interval DRO, of nine retarded students' maladaptive behavior. Results indicate that momentary DRO maintained response suppression comparable to that obtained by whole-interval DRO.     

Conjoint control of performance in conditional discriminations by successive and simultaneous stimuli.

In a conditional discrimination, reinforcement of pigeons' responses to pairs of simultaneously presented wavelength stimuli depended on the orientation of white lines superimposed on the wavelengths. Over different conditions in Experiment 1, three wavelength differences were combined with two differences between successively presented line orientations. Measures of stimulus discriminability increased with increases in the difference between both orientation and wavelength stimuli. Conditional-discrimination performance was thus conjointly determined by stimulus disparity in the successive and simultaneous discriminations. In Experiment 2, ratios of rates of reinforcement contingent upon the two categories of correct responses were varied over several conditions for difficult and easy discriminations. Ratios of responses to wavelength pairs were sensitive to variations in the reinforcement ratio to a greater extent for the more difficult orientation discrimination than for the easier orientation discrimination. Performance in the conditional discrimination was therefore determined by the interacting effects of stimulus disparity and the relative rates of reinforcement contingent upon the two correct choices. It was concluded that the effect of temporally distant reinforcement on behavior in a prevailing schedule component is attenuated to an extent that depends on similarity of stimuli that delineate the successive components.     

Effects of chlorpromazine on fixed-ratio responding: modification by fixed-interval discriminative stimuli.

Effects of chlorpromazine (1 to 100 mg/kg) were assessed on two pigeons' responding under various modifications of a multiple schedule of food delivery. During a fixed-interval component, the first response after 5 min produced food; during the subsequent, fixed-ratio component, the 30th response produced food. Modifications of the schedule entailed changes in stimulus conditions imposed during the fixed-ratio component that did not systematically alter characteristics of performance under non-drug conditions. In the first phase of the experiment, distinctive visual stimuli were correlated with each schedule component (conventional multiple schedule); chlorpromazine produced small decreases in fixed-ratio responding (20% at 30 mg/kg). When each response during the fixed-ratio component produced the stimulus correlated with the fixed-interval schedule (fixed-interval discriminative stimulus) for 1.2 s, effects of chlorpromazine were not different from those under the conventional multiple schedule. Chlorpromazine produced greater decreases in fixed-ratio responding (55% at 30 mg/kg) when either the first response of each fixed ratio changed the stimulus correlated with the fixed-ratio schedule to the fixed-interval discriminative stimulus for the remainder of the fixed-ratio component, or when the fixed-interval discriminative stimulus was presented independently of responding according to a matched temporal sequence. When the fixed-interval discriminative stimulus was present continuously during the fixed-ratio component (mixed schedule), chlorpromazine produced even more substantial decreases in fixed-ratio responding (greater than 80% at 30 mg/kg). Effects of chlorpromazine on fixed-interval responding were also modified by the schedules of fixed-interval discriminative stimulus presentation. The effects of chlorpromazine were a joint function of the stimuli prevailing during the multiple schedule and the degree to which responding influenced these stimuli.     

Human concurrent performances: The effects of experience, instructions, and schedule-correlated stimuli

In order to investigate the effects of separate exposures to single schedules, of unique schedule-correlated stimuli, and of independency-informing instructions upon choice under concurrent variable-interval schedules, 28 human subjects were divided into eight groups. Each subject was exposed to a baseline procedure, an experimental procedure, and a return to the baseline procedure. Different combinations of these three manipulations were applied to the different groups only during the experimental phase (except for the independency-informing instructions, which were given to half of the groups at the start of training). For the group of subjects exposed to the combination of all three manipulations, the logarithms of the ratios of response frequencies tended to be linearly related to the logarithms of the ratios of reinforcement frequencies during the experimental phase. These orderly effects were not obtained with subjects in the other groups. The results suggest that human choice was well described by the generalized matching law when the three manipulations were simultaneously in effect, and that unreported differences in the use of these three procedural variables might partly account for contradictions between results in previous studies of human concurrent performance.     

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.     

Responding on concurrent-chains schedules in open and closed economies.

Pigeons' key pecks were reinforced according to concurrent-chains schedules of reinforcement. The programmed average time from the onset of the initial links to a terminal link entry was held constant across conditions while the value of variable-interval schedules in the terminal links was varied. Performance was assessed under two economic conditions: (a) an open economy in which session duration was limited to 1 hr and subjects were maintained at 80% of their free-feeding body weights with postsession food when necessary; and (b) a closed economy in which sessions were 23.5 hr long and no deprivation regimen was in effect. In all cases, the relative rate of responding in the initial links matched the reduction in overall delay to primary reinforcement correlated with entry into one terminal link relative to the reduction in delay correlated with entry into the other terminal link. Although the sum of responses made in the initial links and terminal links was found to increase, then decrease, as the rate of food presentation decreased in the closed economy, there was no consistent effect of overall rate of food presentation on total responding in the open economy. The choice data suggest that relative delay reduction predicts choice accurately, regardless of economic context.     

The development of adaptive choice in a self-control paradigm

Sixteen girls (ages 4, 6, 9, and 12) performed on concurrent-chain schedules of reinforcement. The initial links were variable-interval 10-s schedules, and the terminal links offered a long delay (20, 30, 40, or 50 s) followed by two tokens or a short delay (10 s) followed by one token. Tokens were used to buy toys and sweets. The effect of increasing the delay to the large reward differed significantly across age groups. Whereas 6- and 9-year-olds maintained a strong preference for the larger, more delayed reward under all delay conditions, half of the 4-year-olds and all the 12-year-olds showed increasing preference for the small reward as the delay to the large reward increased. The results suggest a two-stage account of the development of self-control. In the first stage, behavior is increasingly controlled by reward size, as children learn how to wait for delayed rewards, and in the second phase behavior is increasingly controlled by reward rate, as children learn when it is in fact profitable to wait.     

Income maximizing in concurrent interval-ratio schedules

Three mice chose between concurrent variable-ratio variable-interval schedules to produce a warm air stream while they were housed in a cold chamber. Across conditions, the duration of the warm air stream was varied between 10 and 80 s and was equal for both schedules. Preference for the VI schedule covaried with reinforcer duration as predicted by maximizing accounts of choice.     

Changing self-reported physical activity using different types of affectively and cognitively framed health messages,in a student population

The present research focused upon the power of different messages to increase self-reported physical activity (PA). Five hundered and ninety six participants were randomised to one of five conditions that varied in the content of message: short-term affective, short-term cognitive, long-term affective, long-term cognitive and a no message control. PA was measured at baseline and follow-up (seven days later) was done using the Godin Leisure Time Exercise Questionnaire over the subsequent seven day period. The affective short-term message (ASM) was shown to be equally effective at increasing self-reported PA as a cognitive long-term message. Furthermore, when controlling for baseline activity levels, the ASM emerged as being the message that produced the highest levels of self-reported PA at follow-up. The findings point to the value of distinguishing between health messages in terms of the focus on affective and cognitive outcomes and the temporal nature of the outcomes (short-term or long-term).