Search

We introduce to behavior analysis a way of analyzing choice behavior that exploits recent developments in nanoeconomics, financial economics, and econometrics. A response return, modeled on an economic return, is the log differenced count of responses allocated to each of two alternatives during a short time window, compared with that in the immediately preceding window. The response return is a new dependent variable which offers a novel and useful way of looking at operant behavior, especially at the molecular level of analysis. The response–return series is a near‐instantaneous measure of an organism's dynamic preferences for each of two alternatives. Analyzing such a series requires time‐analytic techniques, including Auto‐Regressive Conditional Heteroskedastic (ARCH) models. We illustrate these techniques by analyzing choices between combinations of arithmetic and exponential variable‐interval schedules with pigeon subjects. All response–return series were well‐fitted by one of three ARCH‐family models. The fitted models were differentially sensitive to transition versus steady‐state data samples. The particular insights that the ARCH analyses offer are improved understanding of the effects of the instantaneous effects of reinforcers and their absence, of how the distribution of reinforcers in time affects choice, and of the differences between choice in transition and at steady state. [ABSTRACT FROM AUTHOR]

The study and use of punishment in behavioral treatments has been constrained by ethical concerns. However, there remains a need to reduce harmful behavior unable to be reduced by differential‐reinforcement procedures. We investigated whether response‐contingent presentation of a negative discriminative stimulus previously correlated with an absence of reinforcers would punish behavior maintained by positive reinforcers. Across four conditions, pigeons were trained to discriminate between a positive discriminative stimulus (S+) signaling the presence of food, and a negative discriminative stimulus (S‐) signaling the absence of food. Once learned, every five responses on average to the S+ produced S‐ for a duration of 1.5 s. S+ response rate decreased for a majority of pigeons when responses produced S‐, compared to when they did not, or when a neutral control stimulus was presented. In Condition 5, choice between two concurrently presented S+ alternatives shifted away from the alternative producing S‐, despite a 1:1 reinforcer ratio. Therefore, presenting contingent S‐ stimuli punishes operant behavior maintained on simple schedules and in choice situations. Development of negative discriminative stimuli as punishers of operant behavior could provide an effective approach to behavioral treatments for problem behavior and subverting suboptimal choices involved in addictions. [ABSTRACT FROM AUTHOR]

Choosing the appropriate response given the circumstance is integral to all aspects of human behavior. One way of elucidating the mechanisms of choice is to relate behavior to neural correlates. Electrophysiological evidence implicates the ERP feedback-negativity (FN) and the P300 as promising neural correlates of reward processing, an integral component of learning. However, prior research has not adequately addressed how the development of a preference to select one option over another (choice preference) relates to the FN and the P300. We assessed whether variation in choice preference predicted the FN and P300 amplitude within subjects. We used a discrete-trials two-alternative choice procedure, where the reinforcer rate for each option was dependently scheduled by a concurrent variable interval. The reinforcer ratio for selecting each option was varied between sessions. Choice was quantified using both the generalized matching law sensitivity and the log odds of staying on the same versus switching to the other alternative (stay preference). The relationship between stay preference, FN, and P300 amplitudes was assessed using the innovative application of hierarchical Bayesian linear regression. The results demonstrate that stay preference was controlled by the reinforcer ratios and credibly predicted the FN amplitude but not P300 amplitude. The findings are consistent with the view that reinforcers may guide behavior by what they signal about future reinforcement, with the FN related to such a process. [ABSTRACT FROM AUTHOR]

Overall reinforcer rate appears to affect choice. The mechanism for such an effect is uncertain, but may relate to reinforcer rate changing the discrimination of the relation between stimuli and reinforcers. We assessed whether a quantitative model based on a stimulus-control approach could be used to account for the effects of overall reinforcer rate on choice under changing time-based contingencies. On a two-key concurrent schedule, the likely availability of a reinforcer reversed when a fixed time had elapsed since the last reinforcer, and the overall reinforcer rate was varied across conditions. Changes in the overall reinforcer rate produced a change in response bias, and some indication of a change in discrimination. These changes in bias and discrimination always occurred quickly, usually within the first session of a condition. The stimulus-control approach provided an excellent account of the data, suggesting that changes in overall reinforcer rate affect choice because they alter the frequency of reinforcers obtained at different times, or in different stimulus contexts, and thus change the discriminated relation between stimuli and reinforcers. These findings support the notion that temporal and spatial discriminations can be understood in terms of discrimination of reinforcers across time and space. [ABSTRACT FROM AUTHOR]

We investigated why violations to the constant-ratio rule, an assumption of the generalized matching law, occur in procedures that arrange frequent changes to reinforcer ratios. Our investigation produced steady-state data and compared them with data from equivalent, frequently changing procedures. Six pigeons responded in a four-alternative concurrent-schedule experiment with an arranged reinforcer-rate ratio of 27:9:3:1. The same four variable-interval schedules were used in every condition, for 50 sessions, and the physical location of each schedule was changed across conditions. The experiment was a steady-state version of a frequently changing procedure in which the locations of four VI schedules were changed every 10 reinforcers. We found that subjects' responding was consistent with the constant-ratio rule in the steady-state procedure. Additionally, local analyses showed that preference after reinforcement was towards the alternative that was likely to produce the next reinforcer, instead of being towards the just-reinforced alternative as in frequently changing procedures. This suggests that the effect of a reinforcer on preference is fundamentally different in rapidly changing and steady-state environments. Comparing this finding to the existing literature suggests that choice is more influenced by reinforcer-generated signals when the reinforcement contingencies often change. [ABSTRACT FROM AUTHOR]

The current experiment examined the degree to which locally varying food probabilities on two keys across time since food presentations can continue to control choice until the next food delivery. In two sets of conditions, the probability of food delivery being made available on one key relative to the other key varied sinusoidally across a 1-min period following each food delivery. In Set 1, food-probability changes were unsignaled and the number of cycles per min was varied across conditions. In Set 2, there were always two complete cycles of the sinusoid in the 1-min period, and brief key-color changes were arranged at a selection of fixed times since food delivery to signal portions of the sinusoid. In Set 1, control of choice by local probability of food on each key decreased over time since food delivery. Control by local food probabilities was greater in conditions that arranged fewer cycles per min. The onset of stimulus changes in Set 2 led to a transient reinstatement of local control by food probabilities regardless of the portion of the sinusoidal variation in food probabilities signaled by the stimuli. However, in conditions where the same colored stimuli signaled different portions of the sinusoidal variation in food-delivery probabilities, stimulus changes attenuated joint control by elapsed time and food-probability values. These results suggest that, changing relative food probabilities and stimuli can direct preference toward the likely location of the next food delivery across time since a food presentation, although the degree to which control over choice will be maintained across elapsed time depends on how experimenter-arranged contingencies are mapped onto elapsed time. [ABSTRACT FROM AUTHOR]

Four pigeons were trained on two-key concurrent variable-interval schedules with no changeover delay. In Phase 1, relative reinforcers on the two alternatives were varied over five conditions from .1 to .9. In Phases 2 and 3, we instituted a molar feedback function between relative choice in an interreinforcer interval and the probability of reinforcers on the two keys ending the next interreinforcer interval. The feedback function was linear, and was negatively sloped so that more extreme choice in an interreinforcer interval made it more likely that a reinforcer would be available on the other key at the end of the next interval. The slope of the feedback function was 21 in Phase 2 and 23 in Phase 3. We varied relative reinforcers in each of these phases by changing the intercept of the feedback function. Little effect of the feedback functions was discernible at the local (interreinforcer interval) level, but choice measured at an extended level across sessions was strongly and significantly decreased by increasing the negative slope of the feedback function. [ABSTRACT FROM AUTHOR]

Abstract: Six pigeons responded on a four-key concurrent variable-interval schedule in which a 27:9:3:1 distribution of reinforcers between the keys changed every 10 reinforcers. Their behaviour quickly came under the control of this changing four-way reinforcer ratio. However, preference between a pair of keys depended not only on the relative reinforcer rates on those keys, but also on the absolute levels of those rates. This contradicts the constant-ratio rule that underpins the matching approach to choice, but is predicted by a contingency-discriminability model that assumes that organisms may occasionally misattribute reinforcers to a response that did not produce them. Reinforcers produced strong preference pulses, or transient increases in responding on the just-reinforced key. Despite accurate tracking of the reinforcer ratio, reinforcers obtained late in components and from leaner keys still produced strong pulses, suggesting both extended and local control of behaviour. Patterns of switching between keys were graded and similarly controlled by the reinforcer rates on each key. Whether considered in terms of switching, local preference pulses, or extended preference, behaviour was controlled by a rapidly changing four-way reinforcer ratio in a graduated, continuous manner that is unlikely to be explained by a simple heuristic such as fix-and-sample. [Copyright &y& Elsevier]

Abstract: Using data from two conditions of an experiment that arranged response-contingent foods and red keylight illuminations, we compared time-indexed and response-indexed preference pulses. The interpretation of red keylight effects (relative to food effects) differed according to whether time or behaviour was used to index choice in the post-event period: preference after a red keylight was more extreme than after a food in the response pulses while preference after a food was more extreme than after a keylight in the time pulses. This was due to different response latencies following the two events in combination with a tendency for initial preference to decrease as latency increased: responding began sooner after non-foods and responding that began later, after any event, tended towards indifference. Our finding suggests that preference pulses ought to be indexed according to time since the last event delivery, particularly if the response-contingent events may result in systematically different response latencies. [Copyright &y& Elsevier]

We investigated the effects of discriminative stimuli on choice in a highly variable environment using a procedure in which multiple two-key concurrent VI VI components changed every 10 reinforcers and were signaled by differential flashes of red and yellow keylights. Across conditions, five pigeons were exposed to a number of different combinations of the following component reinforcer ratios: 27:1, 9:1, 3:1, 1:1, 1:3, 1:9, 1:27. Overall, there was clear control by the component signals in that preference, early in components and particularly before any reinforcers had been delivered, was ordinally related to the signaled reinforcer ratios. In conditions in which only two components arranged unequal reinforcer ratios (e.g., 27:1 and 1:27) with the remaining components arranging 1:1 reinforcer ratios, preference before the first reinforcer in a component showed peak shift in that the most extreme preference did not occur in the unequal reinforcer-ratio components, but in 1:1 components further towards the ends of the stimulus dimension. The contingency-discriminability model (Davison & Nevin, 1999) was fitted to the data and provided an excellent description of the interactions between stimulus and reinforcer effects in a highly variable environment. [ABSTRACT FROM AUTHOR]

We investigated the effects that sequences of reinforcers obtained from the same response key have on local preference in concurrent variable-interval schedules with pigeons as subjects. With an overall reinforcer rate of one every 27 s, on average, reinforcers were scheduled dependently, and the probability that a reinforcer would be arranged on the same alternative as the previous reinforcer was manipulated. Throughout the experiment, the overall reinforcer ratio was 1:1, but across conditions we varied the average lengths of same-key reinforcer sequences by varying this conditional probability from 0 to 1. Thus, in some conditions, reinforcer locations changed frequently, whereas in others there tended to be very long sequences of same-key reinforcers. Although there was a general tendency to stay at the just-reinforced alternative, this tendency was considerably decreased in conditions where same-key reinforcer sequences were short. Some effects of reinforcers are at least partly to be accounted for by their signaling subsequent reinforcer locations. [ABSTRACT FROM AUTHOR]

Both the response-reinforcer and stimulus-reinforcer relation are important in discrimination learning; differential responding requires a minimum of two discriminably-different stimuli and two discriminably-different associated contingencies of reinforcement. When elapsed time is a discriminative stimulus for the likely availability of a reinforcer, choice over time may be modeled by an extension of the Davison and Nevin (1999) model that assumes that local choice strictly matches the effective local reinforcer ratio. The effective local reinforcer ratio may differ from the obtained local reinforcer ratio for two reasons: Because the animal inaccurately estimates times associated with obtained reinforcers, and thus incorrectly discriminates the stimulus-reinforcer relation across time; and because of error in discriminating the response-reinforcer relation. In choice-based timing tasks, the two responses are usually highly discriminable, and so the larger contributor to differences between the effective and obtained reinforcer ratio is error in discriminating the stimulus-reinforcer relation. Such error may be modeled either by redistributing the numbers of reinforcers obtained at each time across surrounding times, or by redistributing the ratio of reinforcers obtained at each time in the same way. We assessed the extent to which these two approaches to modeling discrimination of the stimulus-reinforcer relation could account for choice in a range of temporal-discrimination procedures. The version of the model that redistributed numbers of reinforcers accounted for more variance in the data. Further, this version provides an explanation for shifts in the point of subjective equality that occur as a result of changes in the local reinforcer rate. The inclusion of a parameter reflecting error in discriminating the response-reinforcer relation enhanced the ability of each version of the model to describe data. The ability of this class of model to account for a range of data suggests that timing, like other conditional discriminations, is choice under the joint discriminative control of elapsed time and differential reinforcement. Understanding the role of differential reinforcement is therefore critical to understanding control by elapsed time. [ABSTRACT FROM AUTHOR]