Response Form, Force, And Number: Effects On Concurrent-schedule Performance

Response effort and resurgence

This study provides an initial translational examination of response effort and resurgence. Eleven typically developing adults and five adolescents with autism served as participants across two experiments. Participants received points for touching moving stimuli on a computer screen. The resurgence evaluation consisted of three phases: establishment wherein R1 was reinforced, elimination wherein R1 was placed on extinction while R2 was reinforced, and extinction wherein R1 and R2 no longer resulted in reinforcement. Rate of R1 during extinction was compared across three conditions: intermediate, easy, and difficult. Disparity in effort was created by manipulations of the size and speed of objects that moved about on a computer screen. In Experiment 2, control stimuli were added to the experimental arrangement. Across the two experiments, the magnitude of resurgence was greater when R1 was easy. In Experiment 2, both R1 and control responding were greater in the extinction phase than in the elimination phase in all conditions with all participants. The present study supports the hypothesis that response effort affects resurgence and that less effortful responses are likely to recur with greater magnitude under conditions that produce resurgence than are their more effortful counterparts.

A review of the behavioral effects of response force: Perspectives on measurement and functions

Response force is a fundamental dimension of behavior. Yet, little is known about its functional significance for learning. The present review examines the behavioral effects of force across several domains. Along the way, advantages of different measurement strategies that have been used to study force are evaluated. The behavioral functions of force are also considered in light of two commonly expressed notions about behavior. First, the Law of Least Effort predicts that animals and humans will act in ways that minimize the costs of behaving. Second, it is widely held that work requirements and effortful responding are aversive. A review of the literature, especially regarding behavioral adaptations to force, is consistent with the Law of Least Effort on many points. Empirical data are less clear on the aversive properties of force requirements. For much of the literature, there is little in coherent findings. Many disagreements and inconsistencies pertain to measurement strategies that fail to record the full range of response variants. Consistent support for aversive functions of force requirements have been obtained only when studied as a negative reinforcer.

Choice in the bluegill (Lepomis macrochirus)

To study matching in a species distantly related to mammals and birds, seven bluegill were trained to break a photobeam using a nose-poke response for access to pelleted food in their home aquaria during one-h sessions. Reinforcer ratios available from the two response alternatives varied among the following: 16:1, 8:1, 4:1, 1:1, 1:4, 1:8, and 1:16. The overall reinforcement rate was held at 0.8/min. All experiments were conducted in a closed economy, i.e., the fish's daily food ration was available only during experimental sessions. Matching functions are reported for each fish using all combinations of scheduled and obtained reinforcer ratios as the independent variables and response and time ratios as the dependent variables. All matching functions had slopes less than 1.0 and r(2) values above 0.70. Overall response rates were unrelated to the reinforcer ratios but, as with other species studied, changeover rates were highest for the 1:1 condition and lowest for the 16:1 conditions. These results are consistent with data obtained from more traditionally studied taxa (e.g., birds, mammals, and primates), and similar previous studies with fish, suggesting that matching has been conserved since fish, birds, and mammals evolved from a common ancestor over 400 million years ago.

Why pigeons say what they do: reinforcer magnitude and response requirement effects on say responding in say-do correspondence

The effects of reinforcer magnitude and response requirement on pigeons' say choices in an experimental homologue of human say-do correspondence were assessed in two experiments. The procedure was similar to a conditional discrimination procedure except the pigeons chose both a sample stimulus (the say component) and a comparison stimulus that corresponded to it (the do component). Correspondence was trained on red, green, and white key colors before the duration of food presentations following correspondence on each key color (Experiment 1) and the number of key pecks required as the say response on each key color (Experiment 2) were manipulated in an attempt to influence the initial say response. The frequency of say responses on each key color coincided with programmed changes in the duration of food presentations and the key-peck requirements assigned to each key color. Correspondence accuracy remained stable in all conditions, even those in which the say responding occurred primarily on two of the three key colors. Implications for human behavior are discussed.

Barycentric extension of generalized matching

In most studies of choice under concurrent schedules of reinforcement, two physically identical operanda are provided. In the "real world," however, more than two choice alternatives are often available and biases are common. This paper describes a method for studying choices among an indefinite number of alternatives when large biases are present. Twenty rats were rewarded for choosing among five operanda with reinforcers scheduled probabilistically and concurrently. Large biases were generated by differences among the operanda: two were levers and three were pigeon keys. The results showed that when reinforcer frequencies were systematically varied, an extension of Baum's (1974) Generalized Matching Model, referred to as the Barycentric Matching Model, provided an excellent description of the data, including individual bias values for each of the operanda and a single exponent indicating sensitivity to reinforcer ratios.

Effect of required response force on rats’ performance on a VI+ schedule of reinforcement

Three experiments were performed to examine the effect of response force on rats' performance on various schedules of reinforcement. Response force was manipulated by changing the weight of the lever in the operant chamber--a heavy lever for high response force and a light lever for low response force. Using a within-subjects design, Experiment 1 replicated previous findings that rats respond more quickly on variable ratio (VR) than on equivalent variable-interval-plus-linear-feedback (VI+) schedules. Experiment 2 replicated this finding but also showed that the use of a smaller response force abolished the response rate difference between the VR and VI+ schedules. Experiment 3 used a between-subjects design and showed a response rate difference between the VR and VI+ schedules with a high response force but no response rate difference with a low response force. This suggests that under conditions of low force, when the rats' responding can continue at prolonged high rates, these subjects show little difference in their response rates between VR and VI + schedules. These data are similar to those found for human subjects.

Demarcated response sequences and generalised matching

The generalised matching law was applied for the first time to sequences of responses. Pigeons responded on dependently arranged two-operandum concurrent schedules in which all four possible two-response sequences on these operanda were demarcated and reinforced. Reinforcer rates for the sequences were varied over a wide range, including extinction. Sequences of responses, rather than individual responses, followed the generalised matching law. We compared single-sensitivity and multiple-sensitivity versions of the generalised matching law. The multiple sensitivities were not significantly different from each other, so the single-sensitivity model provided the more efficient fit. As in previous research, responding was biased against the emission of sequences that required changeovers.

Concurrent second-order schedules: some effects of variations in response number and duration

To examine the effects on concurrent performance of independent manipulations of response-unit duration and number, 6 hens were exposed to concurrent second-order schedules of reinforcement. Each first-order operant unit required completion of a fixed-ratio schedule within the time specified by a fixed-interval schedule, with one further response completing the fixed-interval schedule. The fixed-ratio and fixed-interval requirements comprising the first-order operant units were systematically and independently varied under three pairs of concurrent variable-interval schedules to produce differences in the first-order response and duration requirements (response and duration differentials). These manipulations produced consistent changes in response, time, and operant-unit biases. A 1:4 response differential biased the time and operant-unit measures towards the smaller fixed ratio, but to a degree less than the imposed response differential. The response-based biases favored the larger fixed ratio. Duration differentials of 4:1 and 8:1 biased the response and operant-unit measures towards the shorter fixed interval, again less than the imposed duration differential, but the time biases remained close to zero. Both sorts of differentials acted to bias operant-unit completions more systematically than the other measures, but undermatching to the differentials occurred. The undermatching appears to have arisen from a pattern of fix and sample (in which visits to the less preferred alternative involved only a single completed operant unit) under combinations of unequal operant-unit requirements and reinforcer rates. The response and time bias measures appeared to arise as by-products of the changes in operant-unit completions.

Effects of past and upcoming response-force requirements on fixed-ratio pausing

Four rats obtained food by pressing a lever 30 times in each component of a two-component multiple schedule. Across conditions, the force required to press the lever was increased in one component and held constant in the other. Pausing at the outset of each component was controlled by both the past and upcoming force requirements: Pauses were longer when the upcoming requirement was high and this effect was intensified when the past requirement was low. In concert with previous research, the results support the general proposition that behavior is disrupted by abrupt, discriminable transitions from favorable to unfavorable schedule conditions, across a range of subjects and operational definitions of favorability.

Contingency discriminability, matching, and bias in the concurrent-schedule responding of possums (Trichosurus vulpecula)

Six possums (Trichosuruus vulpecula) responded under dependent concurrent variable-interval variable-interval schedules of reinforcement. Over 15 conditions, barley-carob was one reinforcer with the other reinforcer consisting of Coco Pops, coconut, or a barley-carob mixture with 0%, 2%, 4%, or 6% salt added to the barley. The schedules were both variable-interval 40 s. As has been found with other species, behavior on the concurrent schedules was biased by the type of feed, with the 6% salt and the coconut giving the greatest biases towards the barley-carob mixture. The schedules were varied over 17 conditions using the barley-carob mixture alone or the barley-carob mixture versus the mixture with 4% or 6% salt. Both the contingency-discriminability model (Davison & Jenkins, 1985) and the generalized matching law described the data from the three sets of conditions equally well. Both gave similar measures of bias; however, some of the parameter values found with the contingency discriminability model were uninterpretable. Thus, any argument for this model based on the interpretability of the parameter values becomes weak. It is worth retaining the generalized matching law as a descriptor of such data.

The general matching law describes choice on concurrent variable-interval schedules of wheel-running reinforcement

Six male Wistar rats were exposed to concurrent variable-interval schedules of wheel-running reinforcement. The reinforcer associated with each alternative was the opportunity to run for 15 s, and the duration of the changeover delay was 1 s. Results suggested that time allocation was more sensitive to relative reinforcement rate than was response allocation. For time allocation, the mean slopes and intercepts were 0.82 and 0.008, respectively. In contrast, for response allocation, mean slopes and intercepts were 0.60 and 0.03, respectively. Correction for low response rates and high rates of changing over, however, increased slopes for response allocation to about equal those for time allocation. The results of the present study suggest that the two-operant form of the matching law can be extended to wheel-running reinforcement. 'I'he effects of a low overall response rate, a short Changeover delay, and long postreinforcement pausing on the assessment of matching in the present study are discussed.