Recency, repeatability, and reinforcer retrenchment: an experimental analysis of resurgence

Four experiments were conducted with pigeons to assess the experimental conditions necessary for the occurrence of resurgence. The general procedure consisted of the following conditions: Condition 1--reinforcement of key pecking; Condition 2--reinforcement of treadle pressing and concurrent extinction of key pecking; and Condition 3--the resurgence condition wherein resurgence was defined as the recovery of key pecking. In Experiments 1 and 2, the resurgence condition was conventional extinction. The effect of recency on resurgence magnitude was examined in Experiment 1 by manipulating the number of sessions of Condition 2, above. Resurgence was not a function of recency with the parameters used. Repeating the three conditions revealed resurgence to be a repeatable effect in Experiment 2. In Experiment 3, a variable-time schedule was in effect for the resurgence condition. Resurgence was not produced by response-independent food delivery. In Experiment 4, the resurgence condition was a variable-interval schedule for treadle pressing that arranged a lower reinforcement rate than in Condition 2 (92% reduction in reinforcers per minute). Resurgence was lower in magnitude relative to conventional extinction, although resurgence was obtained with 2 out of 3 pigeons. The results are discussed in terms of the variables controlling resurgence and the relations between behavioral history, resurgence, and other forms of response recovery.     

Reinforcement contingencies as discriminative stimuli: II. Effects of changes in stimulus probability.

Three pigeons were trained on a matching procedure involving a sample component and a choice component. Responding in the sample component, according to either a differential-reinforcement-of-low-rate schedule on some trials or a differential-reinforcement-of-other-behavior schedule on other trials, produced access to the choice component in which each of two keys was illuminated with a unique color. The correct choice response was defined by the contingency that was met to produce the choice. The food hopper operated for 1.5 seconds following an appropriate sample response and for 3 seconds following a correct choice response. A signal-detection analysis showed that variations in the probability of presentation of the different contingencies systematically affected response bias but not sensitivity to the contingencies as stimuli. Substitution of a blackout for food at the end of the sample component did not differentially affect performance, but elimination of the delay between sample and choice components generally increased the sensitivity measure. The findings suggest a role for reinforcement contingency discrimination in schedule-controlled responding.     

Behavioral contrast and the automaintained key peck

In two experiments behavioral contrast was demonstrated during discrimination training in a positive automaintenance procedure. During the baseline condition in each experiment, a key was transilluminated for eight seconds by one of two colors (CS) following a variable intertrial interval signaled by a dark key. Keylight transillumination terminated with a response-independent food presentation. In the first experiment, food was eliminated during one CS for up to fifty sessions. After reinstatement of food following each CS, the discrimination was reversed. Six of the eight subjects showed positive behavioral contrast, i.e., response rates increased during the CS associated with food as they decreased during the CS associated with no food. The effect was replicated in Experiment II, but it did not occur when both the food and its associated CS were eliminated. These results were comparable to those obtained with operant discrimination training procedures (behavioral contrast) and with Pavlovian discrimination training. The results suggest that additivity theories of behavioral contrast may be insufficient to account for these data.     

Acquisition of a spatially defined operant with delayed reinforcement.

Two experiments investigated the role of an immediate, response-produced auditory stimulus during acquisition, via delayed reinforcement, of a response selected to control for possible unprogrammed, operandum-related sources of response feedback. Experimentally naive rats were exposed to a delayed-food reinforcement condition, specifically a tandem fixed-ratio 1 differential-reinforcement-of-other-behavior 30-s schedule. The response was defined as breaking a photocell beam located near the ceiling at the rear of the operant conditioning chamber. In Experiment 1, rates of photobeam breaking by each rat increased from near zero, regardless of the presence or absence of a tone that immediately followed the response initiating the delay interval. Though not essential, the tone facilitated response acquisition and resulted in more efficient response patterns at stability. Experiment 2 demonstrated that photobeam-breaking response rates under the delayed reinforcement contingency exceeded those in a preceding baseline condition in which no food was delivered. In addition, upon introduction of the delayed reinforcement procedure, correspondence between response patterns and the requirements of the reinforcement schedule increased over baseline levels in the absence of a food contingency. Together with a previous report of Lattal and Gleeson (1990), the present results suggest that response acquisition with delayed reinforcement is a robust phenomenon that may not depend on a mechanically defined response or an immediate external stimulus change to mediate the temporal gap between response and reinforcer.     

Signal functions in delayed reinforcement

Three experiments were conducted with pigeons to examine the role of the signal in delay-of-reinforcement procedures. In the first, a blackout accompanying a period of nonreinforcement increased key-peck response rates maintained by immediate reinforcement. The effects of dissociating the blackout from the delay interval were examined in the second experiment. In three conditions, blackouts and unsignaled delays were negatively correlated or occurred randomly with respect to one another. A signaled delay and an unsignaled delay that omitted the blackouts were studied in two other conditions. All delay-of-reinforcement conditions generally produced response rates lower than those produced by immediate reinforcement. Signaled delays maintained higher response rates than did any of the various unsignaled-delay conditions, with or without dissociated blackouts. The effects of these latter conditions did not differ systematically from one another. The final experiment showed that response rates varied as a function of the frequency with which a blackout accompanied delay intervals. By eliminating a number of methodological difficulties present in previous delay-of-reinforcement experiments, these results suggest the importance of the signal in maintaining responding during delay-of-reinforcement procedures and, conversely, the importance of the delay interval in decreasing responding.     

Early extinction effects following intermittent reinforcement: Little evidence of extinction bursts

The occurrence of extinction bursts—transient increases in response rate in excess of those observed in baseline during the period immediately following discontinuation of reinforcement of a response—was examined. In Experiment 1, key pecking of pigeons was reinforced according to a multiple schedule in which a variable-ratio schedule alternated with an interval schedule in which the reinforcers were yoked to the preceding variable-ratio component. In Experiments 2 and 3, rats were screened such that the lever-press response rates of different rats maintained by variable-interval schedules were either relatively high or relatively low. Following these baseline conditions, in Experiments 1 and 2 responding was extinguished by eliminating the food reinforcer and in Experiment 3 by removing the response–reinforcer dependency. Responses immediately following extinction implementation were examined. Response increases relative to baseline during the first 20 min of a 324.75-min extinction session (Experiment 1) or during the first 30-min extinction session (Experiments 2 and 3) were rare and unsystematic. The results (a) reinforce earlier meta-analyses concluding that extinction bursts may be a less ubiquitous early effect of extinction than has been suggested and (b) invite further experimentation to establish their generality as a function of preceding reinforcement conditions.     

The human side of animal behavior

An important element of behavioral research with nonhuman animals is that insights are drawn from it about human behavior, what is called here the human side of animal behavior. This article examines the origins of comparing human behavior to that of other animals, the ways in which such comparisons are described, and considerations that arise in evaluating the validity of those comparisons. The rationale for such an approach originated in the reductionism of experimental physiology and the understanding of the commonalities of all life forms promulgated by Darwinian evolutionary biology. Added more recently were such observations as the relative simplicity of animal behavior, tempered by the constraints placed on resulting comparisons by the absence of verbal behavior in animals. The construction of comparisons of human behavior to that of animals may be framed on the basis of Skinner's (1957) distinction between the metaphorical and generic forms of the extended tact. Both ordinary and systematic comparisons of animal and human behavior are congruent with Skinner's extended tact framework. The most general consideration in evaluating comparisons of animal and human behavior is that a functional basis for the claimed similarity be established. Systematic analysis and convergent evidence also may contribute to acceptability of these comparisons. In the final analysis, however, conclusions about the human side of animal behavior are nondeductively derived and often are assessed based on their heuristic and pragmatic value. Such conclusions represent a valuable contribution to understanding the human animal and in developing practical solutions to problems of human behavior to which much of psychology is dedicated.     

Contingency tracking during unsignaled delayed reinforcement

Three experiments were conducted with rats in which responses on one lever (labeled the functional lever) produced reinforcers after an unsignaled delay period that reset with each response during the delay. Responses on a second, nonfunctional, lever did not initiate delays, but, in the first and third experiments, such responses during the last 10 s of a delay did postpone food delivery another 10 s. In the first experiment, the location of the two levers was reversed several times. Responding generally was higher on the functional lever, though the magnitude of the difference diminished with successive reversals. In the second experiment, once a delay was initiated by a response on the functional lever, in different conditions responses on the nonfunctional lever either had no effect or postponed food delivery by 30 s. The latter contingency typically lowered response rates on the nonfunctional lever. In the first two experiments, both the functional and nonfunctional levers were identical except for their location; in the third experiment, initially, a vertically mounted, pole-push lever defined the functional response and a horizontally mounted lever defined the nonfunctional response. Higher response rates occurred on the functional lever. These results taken together suggest that responding generally tracked the response-reinforcer contingency. The results further show how nonfunctional-operanda responses are controlled by a prior history of direct reinforcement of such responses, by the temporal delay between such responses and food delivery, and as simple generalization between the two operanda.     

Early-extinction effects on a force response of humans

Humans were used to investigate changes in response force occurring soon after reinforcement was eliminated. In Experiment 1, in a 300-s baseline phase, 10 participants received a point for holding down a pressure sensor set to operate at a force equal to 85% of the maximum force the participants exerted during a pretest. Following this, during a 600-s extinction phase, criterion responses had no consequence. In Experiment 2, 6 participants worked on the same task, but (a) points were exchangeable for money and (b) after extinction, the reinforcement baseline phase was reinstated. In Experiment 3, 6 participants completed the same task as in Experiment 2, but the required minimum force was 60% of the maximum force exerted during the pretest. In each experiment, increases in response force relative to the mean and peak force exerted during the last 100 s of baseline were observed in most participants when force responses were aggregated into short sample intervals, but less so with longer ones. The increases, however, were not systematic across or within participants, questioning the generality of and the criteria for demonstrating an extinction burst.