摘要:

In Experiment 1, two conditions were compared: (a) a variability schedule in which food reinforcement was delivered for the fourth peck in a sequence that differed from the precedingNfour‐peck sequences, with the value ofNcontinuously adjusted to maintain reinforcement probability approximately constant; and (b) a control condition in which the variability constraint was dropped but reinforcement probability remained constant. Pigeons responded approximately randomly under the variability schedule but showed strong stereotyped behavior under the control condition. Experiments 2 and 3 tested the idea that variability is the outcome of a type of frequency‐dependent selection, namely differential reinforcement of infrequent behavior patterns. The results showed that pigeons alternate when frequency‐dependent selection is applied to single pecks because alternation is an easy‐to‐learn stable pattern that satisfies the frequency‐dependent condition. Nevertheless, 2 of 4 pigeons showed random behavior when frequency‐dependent selection was applied to two pecks, even though double alternation is a permissible and stable stereotype under these conditions. It appears that random behavior results when pigeons are unable to acquire the stable stereotyped behavior under a given frequency‐dep

ISSN:0022-5002    

DOI:10.1901/jeab.1992.58-241

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

In the first experiment, 4 pigeons were each presented with a recurring sequence of four key colors followed by the delivery of grain (block clock). Once the rate of pecking had stabilized, three of the colors were replaced, during different series of sessions, by a darkening of the key. The rate of pecking was reduced within those segments of the interval between deliveries of food during which the key was dark; when the key was dark during the final portion of the interval, rates were reduced throughout the entire interval. In the second experiment, 3 new pigeons were exposed to a different sequence of colors, and the final stimulus was replaced in successive conditions by a novel color, a darkened key, and a restoration of the original color. The data indicated that darkening the key had a more severe, more extensive, and more persistent effect than did a mere change in color. These results suggest that it may be fruitful to conceptualize the autoshaping procedure as a special version of the block clock in which pecking is suppressed throughout the greater part of the interval by darkening the key. In the final condition, the same stimulus appeared in each of the last three portions of the interval. The rate of pecking was lower during the last two portions than when distinctive colors were presented, with the peak rate now appearing in the fifth of seven equal temporal components.

ISSN:0022-5002    

DOI:10.1901/jeab.1992.58-265

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Key pecking of 4 pigeons was maintained under a multiple variable‐interval 20‐s variable‐interval 120‐s schedule of food reinforcement. When rates of key pecking were stable, a 5‐s unsignaled, nonresetting delay to reinforcement separated the first peck after an interval elapsed from reinforcement in both components. Rates of pecking decreased substantially in both components. When rates were stable, the situation was changed such that the peck that began the 5‐s delay also changed the color of the keylight for 0.5 s (i.e., the delay was briefly signaled). Rates increased to near‐immediate reinforcement levels. In subsequent conditions, delays of 10 and 20 s, still briefly signaled, were tested. Although rates of key pecking during the component with the variable‐interval 120‐s schedule did not change appreciably across conditions, rates during the variable‐interval 20‐s component decreased greatly in 1 pigeon at the 10‐s delay and decreased in all pigeons at the 20‐s delay. In a control condition, the variable‐interval 20‐s schedule with 20‐s delays was changed to a variable‐interval 35‐s schedule with 5‐s delays, thus equating nominal rates of reinforcement. Rates of pecking increased to baseline levels. Rates of pecking, then, depended on the value of the briefly signaled delay relative to the programmed interfood times, rather than on the absolute delay value. These results are discussed in terms of similar findings in the literature on conditioned reinforcement, delayed matching

ISSN:0022-5002    

DOI:10.1901/jeab.1992.58-277

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Procedures used to study anticipatory contrast are conceptually similar to those used to study autoshaping, in that two target stimuli signal either higher or lower rates of reinforcement in the following components of the schedule. Despite this signal contingency, anticipatory contrast entails response rates that are higher to the target stimulus followed by the lower rate of reinforcement. To determine the relation between such effects and autoshaping, different variations of the procedure were used in which the signal contingency was presented in the absence of reinforcement in the target components themselves and in which the reinforcement schedules in the different following components were signaled by the same stimulus. Autoshaping effects of this signal contingency were demonstrated when no reinforcement was available during the target‐component signals themselves. Intermediate patterns of behavior occurred when reinforcement was available during the target‐component signals and when their different following schedules were correlated with the same stimulus. Attempts to isolate these signal and contrast effects functionally by using the signal‐key procedure were unsuccessful. The results demonstrate that Pavlovian stimulus contingencies are in competition with the dynamics of anticipatory contrast, thus reducing its occurrence under some circumst

ISSN:0022-5002    

DOI:10.1901/jeab.1992.58-287

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Pigeons were trained on a multiple schedule in which two target components with identical reinforcement schedules were followed by either the same‐valued schedule or by extinction. Response rate increased in both target components but was higher in the target component followed by extinction, replicating previous findings of positive anticipatory contrast. A similar design was used to study negative contrast, in that the two target components were followed either by the same‐valued schedule or by a higher valued schedule. Negative contrast occurred equally, on average, in both target components, thus failing to demonstrate negative contrast that is specifically anticipatory in nature. When the stimuli correlated with the two target components were paired in choice tests, the pattern of preference was in the opposite direction. For the positive contrast procedure, no significant preference between the two target stimuli was evident. But for the negative contrast procedure, preference favored the stimulus followed by the higher valued schedule. The results demonstrate a functional dissociation between positive and negative contrast in relation to stimulus value. More generally, the results demonstrate an inverse relation between response rate and preference and challenge existing accounts of contrast in terms of the concept of relative va

ISSN:0022-5002    

DOI:10.1901/jeab.1992.58-303

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Two pigeons had access to multiple concurrent schedules of reinforcement for 24 hours per day in their home cages. The variable‐interval schedules comprising the multiple concurrent schedules were varied across 16 conditions. In three sets of conditions, one schedule was varied while its concurrent alternative and the concurrent schedules in the other component were held constant. Behavioral contrast was observed; that is, as the rate of reinforcement arranged by the varied schedule decreased, response rates on the constant schedules typically increased. These conditions formed part of two larger sets of conditions in which the concurrent schedules in one multiple‐schedule component remained constant while the concurrent schedules in the other component were varied. Successive independence was found, in that behavior allocation during the constant component did not vary as a function of the reinforcer ratios in the varied component. Successive independence between components in multiple concurrent schedules is a robust result that occurs in closed economies and under conditions that promote behavioral contr

ISSN:0022-5002    

DOI:10.1901/jeab.1992.58-313

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Maximization and matching predictions were examined for a time‐based analogue of the concurrent variable‐interval variable‐ratio schedule. One alternative was a variable interval whose time base operated relatively independent of the schedule chosen, and the other was a discontinuous variable interval for which timing progressed only when selected. Pigeons switched between schedules by pecking a changeover key. The maximization hypothesis predicts that subjects will show a bias toward the discontinuous variable interval and undermatching; however the obtained results conformed closely to the predictions of the matching law. Finally, a quantitative comparison was made of the bias and sensitivity estimates obtained in published concurrent variable‐interval variable‐ratio analogue studies. Results indicated that only the ratio‐based analogue of the concurrent variable interval variable ratio studied by Green, Rachlin, and Hanson (1983) produced significant bias toward the variable‐ratio alternative and undermatching, as predicted by reinforcement

ISSN:0022-5002    

DOI:10.1901/jeab.1992.58-325

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Six experimentally naive pigeons were exposed to concurrent variable‐interval variable‐interval schedules in a three‐key procedure in which food reinforcement followed pecks on the side keys and pecks on the center key served as changeover responses. In Phase 1, 3 birds were exposed to 20 combinations of five variable‐interval values, with each variable‐interval value consistently associated with a different color on the side keys. Another 3 pigeons were exposed to the same 20 conditions, but with a more standard procedure that used a nondifferential discriminative stimulus on the two side keys throughout all conditions. In Phase 2, the differential and nondifferential stimulus conditions were reversed for each pigeon. Each condition lasted for one 5‐hr session and one subsequent 1‐hr session. In the last 14 conditions of each phase, the presence of differential discriminative stimuli decreased the time necessary for differential responding to develop and increased the sensitivity of behavior to reinforcement distribution in the 1st hr of training; during the last hours of training in each condition, however, the effects of the differential discriminative stimuli could not be distinguished from the effects of reinforcement distribution per se. These results show the importance of studying transitions in behavior as well as final performance. They may also be relevant to discrepancies in the results of previous experiments that have used nonhuman and h

ISSN:0022-5002    

DOI:10.1901/jeab.1992.58-335

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

This experiment attempted to bring behavior under joint control of two distinct contingencies, one that provided food and a second that extended the periods during which that food was available. Pigeons' responses on each of two keys were reinforced according to a single random‐interval schedule of food presentation except during signaled timeout periods during which the schedule was temporarily disabled. By means of a conjoint schedule, responses on the initially less preferred key not only produced food but also canceled impending timeouts. When behavior came to predominate on this conjoint alternative, the consequences of responding on the two keys were reversed. Responding in 3 of 4 pigeons proved sensitive to the conjoint scheduled consequences, as evidenced by systematic shifts in response rates favoring the conjoint key. In 2 of these 3 pigeons, sensitivity to the conjoint contingency was evident under time‐in: timeout ratios of 2:1 (time‐in / 120 s, timeout / 60 s) and 1:5 (time‐in / 30 s, timeout = 150 s), whereas for the other pigeon preference for the conjoint key was observed only under the latter sequence of conditions. There was only weak evidence of control by the conjoint scheduled consequences in the 4th subject, despite extended training and forced exposure to the conjoint alternative. The overall pattern of results in consistent with studies of timeout avoidance but also shares features in common with positively reinforced b

ISSN:0022-5002    

DOI:10.1901/jeab.1992.58-349

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

In two experiments, key pecking of pigeons was maintained by a variable‐interval 180‐s schedule of food presentation. Conjointly, a second schedule delivered response‐dependent electric shock. In the first experiment, shocks were presented according to either a variable‐interval or a nondifferential interval‐percentile schedule. The variable‐interval shock schedule differentially delivered shocks following long interresponse times. Although the nondifferential shock schedules delivered shocks less differentially with respect to interresponse times, the two shock schedules equally reduced the relative frequency of long interresponse times. The second experiment differentially shocked long or short interresponse times in different conditions, with resulting decreases in the relative frequency of the targeted interresponse times. These experiments highlight the importance of selecting the appropriate level of analysis for the interaction of behavior and environment. Orderly relations present at one level of analysis (e.g., interresponse times) may not be revealed at other levels of analysis (e.g., overall res

ISSN:0022-5002    

DOI:10.1901/jeab.1992.58-361

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY