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1.
In previous studies of anticipatory contrast, identical target components (A and B) preceded either a lower (extinction) or a richer schedule. Higher response rates occurred during the target preceding the lower rate of reinforcement, whereas preference was in favor of the target preceding the richer schedule. In Experiment 1, the response and preference measures were positively related when additional stimuli, with no reinforcement of their own, preceded the target components. The effect of these additional stimuli was presumed to be due to their overshadowing of the Pavlovian association between the target components and their following schedules. Experiment 2 also demonstrated a consistent relation between response rate and preference in a conditioned reinforcement procedure. In the absence of a strong Pavlovian association, anticipatory contrast, like other forms of contrast in free-operant procedures, reflects an increase in the value of the target component with an unchanged reinforcement schedule. 相似文献
2.
Ben A. Williams 《Learning & behavior》1988,16(2):206-216
Pigeons were trained on multiple schedules with component stimuli of different degrees of similarity. In Experiment 1, a two-component schedule was used in which the two stimuli were either two line orientations or a line orientation versus a diffuse color. Reinforcement rate was varied in one component to determine the effects of stimulus similarity on different aspects of behavioral contrast. Contrast in terms of average response rates (molar contrast) was larger with less similar stimuli. Local contrast effects at the beginning of the component were larger for more similar stimuli, but these effects were more variable and did not attain statistical significance. Independent of the level of molar contrast, the local pattern of schedule interaction differed for the two levels of similarity: with more similar stimuli, the maximum degree of interaction occurred at the beginning of the components and then decreased; with less similar stimuli, the degree of interaction increased throughout the components and was at its maximum near their end. In Experiment 2, the same three stimuli were used while reinforcement rate in the middle component of a three-component sequence was varied; this isolated the effects of the preceding schedule from those of the following schedule. Contrast effects were generally greater in the target component preceding the variable schedule, and these were enhanced by less similar stimuli. Contrast in the target component following the variable schedule was manifested primarily in terms of the behavior at the beginning of the component, and these effects were inconsistently related to stimulus similarity. The functional separation of the effects of stimulus similarity on the different locations of contrast suggest that “anticipatory contrast” and “local contrast” depend upon different mechanisms, thus excluding any account of contrast solely in terms of relative rate of reinforcement. 相似文献
3.
Ben A. Williams 《Learning & behavior》1991,19(4):337-344
Behavioral contrast was produced in two target components of a four-component multiple schedule by having two target stimuli followed either by a higher rate of reinforcement or by extinction. Response rate was higher in the target followed by extinction. Periodic probe trials were then presented in which the two target stimuli were presented together. Choice on these probe trials was in favor of the stimulus followed by the higher rate of reinforcement during regular training. Experiment 2 replicated this finding but with probe trials presented throughout training. Here, preference for the stimulus followed by the higher rate of reinforcement was evident early in training, substantially before the contrast effects developed. The results challenge interpretations of contrast based on the concept of relative value. 相似文献
4.
Ben A. Williams 《Learning & behavior》2002,30(1):1-20
Behavioral contrast is defined as a change in response rate during a stimulus associated with a constant reinforcement schedule,
in inverse relation to the rates of reinforcement in the surrounding stimulus conditions. Contrast has at least two functionally
separable components: local contrast, which occurs after component transition, and molar contrast. Local contrast contributes
to molar contrast under some conditions, but not generally. Molar contrast is due primarily to anticipatory contrast. However,
anticipatory contrast with respect to response rate has been shown to be inversely related to stimulus preference, which challenges
the widely held view that contrast effects reflect changes in stimulus value owing to the reinforcement context. More recent
data demonstrate that the inverse relation between response rate and preference with respect to anticipatory contrast is due
to Pavlovian contingencies embedded in anticipatory contrast procedures. When those contingencies are weakened, anticipatory
contrast and stimulus preference are positively related, thus reaffirming the view that the reinforcing effectiveness of a
constant schedule is inversely related to the value of the context of reinforcement in which it occurs. The underlying basis
of how the context of reinforcement controls reinforcement value remains uncertain, although clear parallels exist between
contrast and the effects of contingency in both Pavlovian and operant conditioning. 相似文献
5.
Behavior reduced as a consequence of extinction or intervention can relapse. According to behavioral momentum theory, the extent to which behavior persists and relapses once it has been eliminated depends on the relative training reinforcement rate among discriminative stimuli. In addition, studies of context renewal reveal that relapse depends on the similarity between the training stimulus context and the test stimulus context following disruption by extinction. In the present experiments with pigeons, we arranged different reinforcement rates in the presence of distinct discriminative stimuli across components of a multiple schedule. Following extinction, we attempted to reinstate responding in the presence of those target components with response-independent food presentations. Importantly, we arranged the reinstating food presentations either within the target components or in separate components, either paired with extinction (Experiment 1) or reinforcement (Experiment 2) during baseline. Reinstatement increased with greater training reinforcement rates when the reinstating food presentations were arranged in the target components and the separate components paired with reinforcement during training. Reinstatement was smaller and was not systematically related to training reinforcement rates in the target components when reinstating food presentation occurred in separate components paired with extinction. These findings suggest that relapse depends on the history of reinforcement associated with the discriminative stimuli in which the relapse-inducing event occurs. 相似文献
6.
Ben A. Williams 《Learning & behavior》1989,17(2):223-233
Previous research has produced conflicting results regarding the effects of component duration on interactions in multiple schedules. In Experiment 1, potential sources of this conflict were evaluated. Both the effects of absolute reinforcement rate and carry-over effects (hysteresis) from a preceding condition were isolated. When 10-sec components were used, the sensitivity of relative response rate to relative reinforcement rate was affected very little by hysteresis effects and absolute reinforcement rate, but it was systematically reduced as a function of the number of prior conditions. Sensitivity to relative reinforcement rate was also substantially higher with the 10-sec components than with 2-min components. In Experiment 2, this effect of component duration was decomposed into two separate effects. Contrast effects during presentation of a target component with a constant reinforcement rate were greater the shorter the target component was itself; but they were smaller the shorter the alternative component in which reinforcement rate was varied. The latter effect was smaller and more unreliable across subjects. The existence of these two separate effects demonstrates that the usual method of studying component duration—that is, holding all components equal in duration—systematically causes underestimation of the effects of the component duration, and obscures the different processes controlling the two effects. 相似文献
7.
Pigeons’ choice responding on 10-sec interpolated probes was studied after baseline training on multiple variable-interval variable-interval schedules of food reinforcement. Unreinforced choice following training with three different relative reinforcement rates (Experiment 1), with a 3-ply multiple schedule (Experiment 2), and with three different relative reinforcement durations (Experiment 3) was examined. Least squares lines were fit to choice relative response rate and schedule relative response rate as functions of training relative reinforcement rate; choice slope was significantly greater than schedule slope in all three experiments. This result is counter to the prediction of Herrnstein’s (1970) theory that these slopes should not differ. Luce’s (1959) theory also failed to account for the data. It was concluded that choice responding was controlled by both approach to the stimulus associated with the smaller mean interreinforcer interval or the longer duration, and avoidance of the other stimulus. 相似文献
8.
Pigeons were exposed to differentially cued autoshaping trials in which conditioned stimuli were followed by food after 6 or 14 sec. Average and momentary rates of keypecking were examined on two types of unreinforced test trials: single-stimulus probe trials and simultaneous choice trials, each 40 sec in duration. Rates averaged over the 40-sec test trials did not favor the cue associated with the shorter delay to food (the short-delay cue) on either type of test trial; however, average rates prior to the scheduled time of food delivery were reliably higher for the short-delay cue on choice trials. Momentary rates of keypecking during choice trials varied as a function of both cue and elapsed time from trial onset. At short elapsed trial times, rate of pecking was higher for the short-delay cue, with this difference reversing at longer times. A reversal of the programmed relation between key color and delay to food presentation for 5 birds confirmed the generality of these findings. Implications of these data for models of Pavlovian conditioning and for methods of assessing conditioned response strength are discussed. 相似文献
9.
Pigeons were studied on multiple variable-ratio yoked-variable-interval schedules in which components had equal rates of food reinforcement and appeared equally often on each of two keys. Interpolated between component changes on the final multiple schedule were 10-sec probes in which both schedule stimuli were present, one on each key. During multiple schedule training, variable-ratio response rates were greater than yoked-variable-interval rates; however, response rate differences in the components were not a function of the mean ratio value for the 40-to-320-ratio range studied. During the choice probes, subjects responded more to the stimulus associated with the interval schedule than to the one associated with the ratio schedule. It was concluded that pigeons prefer interval schedules over equal reinforcement rate ratio schedules, because the former generate fewer responses per reinforcement. 相似文献
10.
Pigeons were exposed to a two-component multiple fixed-ratio X fixed-ratio Y schedule of reinforcement in which X was always less than Y. Components were equal in duration and alternated at rates that varied between 2 sec and 23.5 h. Relative response rate in the FR X component: (1) increased as the duration of components increased between 2 sec and 15 min, (2) was at a maximum between 15 min and 6 h, and (3) decreased as the duration of components increased from 6 h to 23.5 h. The changes in relative response rate were attributable primarily to changes in absolute response rates during the FR Y schedule as absolute response rates during the FR X schedule were relatively invariant. These results pose complexities for several theoretical formulations. 相似文献
11.
Pigeons were trained on a multiple schedule of reinforcement in which each component was a concurrent schedule. The concurrent schedules were programmed by the changeover-key procedure. The primary purpose was to determine if the relative behavior allocated to two response alternatives is affected when absolute changes in these behaviors occur; i.e., to determine if matching is affected when positive behavioral contrast occurs. Results showed that (1) relative behavior in the unaltered component of the multiple schedule is not disrupted when positive contrast occurs in that component, (2) positive contrast occurred when the overall frequency of reinforcement in the reinforcement-correlated component(s) was high, but not when it was low, (3) changeover behavior was susceptible to positive contrast effects, and (4) changeover contrast and food-key contrast are independent phenomena. 相似文献
12.
Samuel G. Charlton 《Learning & behavior》1983,11(1):27-34
Differential conditionability is the empirical finding that not all responses are equally amenable to the same conditioning paradigm. One phenomenon associated with the conditioning of grooming behavior (a difficult-to-condition response) is a decrease in its average duration when followed by food reinforcement. The first experiment investigated this phenomenon by reinforcing golden hamsters (Mesocricetus auratus) with food for grooming or open rearing (a readily conditionable response) under three duration-dependent reinforcement schedules. The obtained data showed that different densities of food delivery had no differential effects on the average durations of grooming responses, indicating that the decreases were not the result of reinforcement-produced interruption. In the second experiment, golden hamsters were reinforced with food for grooming or for open rearing or received free food, under three interval reinforcement schedules. This experiment demonstrated that decreases in the average duration of grooming are independent of grooming behavior’s resistance to conditioning. Furthermore, although duration-dependent reinforcement schedules are largely ineffective in conditioning grooming behavior, interval schedules are shown to be quite effective in increasing rates of grooming. 相似文献
13.
McSweeney and her colleagues (e.g., McSweeney, Hatfield, & Allen, 1990) have demonstrated reliable, large magnitude rate changes in maintained operants within daily sessions under a wide variety of reinforcement schedules. The present paper examined the role of schedule of reinforcement, reinforcement rate, and total amount of food access in determining those within-session rate changes. When median rates across birds were considered, all procedures resulted in a brief period of an increasing rate, followed by a modest rate loss across the major portion of the session. However, not all individuals exhibited that pattern. When the amount of food access per session was limited by lower reinforcement rates, shorter sessions, or shorter reinforcement durations, the magnitude of the withinsession rate change was reduced from that occurring without those constraints. Additionally, under the conditions that produced strong within-session rate changes, the magnitude of the within-session rate loss was correlated with the bird’s body weight. These effects are consistent with what is typically labeledsatiation. 相似文献
14.
In a second-order schedule, fixed-interval components were reinforced according to a variable-interval schedule. A brief stimulus accompanied the completion of each fixed interval. Brief-stimulus duration was varied across conditions from 0.5 to 8 sec. Patterning was greater the longer the duration of the stimulus. Additionally, exposure to relatively long brief-stimulus durations enhanced patterning upon reexposure to shorter brief-stimulus durations. 相似文献
15.
Bruce L. Brown Nancy S. Hemmes David A. Coleman Alison Hassin Eva Goldhammer 《Learning & behavior》1982,10(3):365-376
Control of pigeons’ keypecking by a stimulus-reinforcer contingency was investigated in the context of a four-component multiple schedule. In each of three experiments, pigeons were exposed to a schedule consisting of two two-component sequences. Discriminative stimuli identifying each sequence were present only in Component 1, which was 4, 6, or 8 sec in duration, while reinforcers could be earned only in Component 2 (30 sec in duration). Control by a stimulus-reinforcer contingency was sought during Component 1 by arranging a differential relation between Component 1 cues and schedule of reinforcement in Component 2. In Experiment 1, rate of keypecking during Component 1 varied with the presence and absence of a stimulus-reinforcer contingency. When a contingency was introduced, rate of keypecking increased during the Component 1 cue associated with the availability of reinforcement in Component 2. In Experiment 2, the stimulus-reinforcer contingency was manipulated parametrically by varying the correlation between Component 1 cues and Component 2 schedules of reinforcement. Responding in Component 1 varied as a function of strength of the stimulus-reinforcer contingency. The relatively high rates of Component 1 responding observed in Experiments 1 and 2 pose difficulties for conceptions of stimulus-reinforcer control based on probability of reinforcement. In these two experiments, the stimulus-associated probabilities of reinforcement in Component 1 were invariant at zero. An alternate dimension of stimulus-reinforcer control was explored in Experiment 3, in which Component 1 cues were differentially associated with delay to reinforcement in Component 2, while probability of reinforcement was held constant across components. When the stimulus-reinforcer contingency was in force, rate of responding in Component 1 varied inversely with delay to reinforcement in Component 2. In a quantitative analysis of data from Experiments 2 and 3, relative rate of responding during Component 1 was strongly correlated with two measures of relative delay to reinforcement. 相似文献
16.
Rats were trained to run up and down an alleyway for sucrose reinforcement on a variable interval schedule. Differential aversive classical conditioning with auditory CSs was then conducted in a separate apparatus (“off the baseline”) prior to those CSs being presented while the subjects were responding for sucrose in the alleyway. Once the effects of the CSs had extinguished, shock was reintroduced following one CS but not the other (“on the baseline” differential aversive classical conditioning). Both “off the baseline” and “on the baseline” conditioning resulted in conditioned suppression to the CS followed by shock, but little effect of the CS followed by no shock was found. In the “on the baseline” phase, total suppression of baseline responding occurred at moderate US intensities, and this appeared to result from the subject avoiding the location at which he was last shocked. At lower values, both baseline response rate and relative suppression ratio were functions of US intensity. The results are discussed in relation to the effects found in similar experiments using avoidance baselines. 相似文献
17.
Two experiments examined the effects of differences in the parameters of a clocked interfood interval on the obtained distribution of responding to the stimuli in that interval. In the first experiment, a 3×3 factorial design assessed the effects of the number of components and the durations of those components. Food was presented irrespective of behavior following 5, 10, or 20 discrete stimuli across durations of 3, 6, or 12 sec each. Responding began at the approximate midpoint of the interval. More responding occurred in earlier portions of the last half of the interval as the number and the durations of individual stimuli decreased or as the overall interfood interval decreased. The second experiment, also a 3×3 factorial design, manipulated the probability and duration of food presentation following a 60-sec trial containing 10 discrete stimuli. A 2.0-, 3.5-, or 5.0-sec food presentation followed 100%, 25%, or 10% of the trials. Responding again began at the approximate midpoint of the interval. More responding occurred in earlier portions of the last half of the interval only when both food duration and the proportion of reinforced trials increased. Both experiments therefore showed that the onset of responding occurs at the approximate midpoint of clocked interfood intervals in spite of a wide variety of CS and US manipulations. 相似文献
18.
Previous experiments on behavioral momentum have shown that relative resistance to extinction of operant behavior in the presence of a stimulus depends on the rate of reinforcement associated with that stimulus, even if some of those reinforcers occur independently of the behavior. We present three experiments examining whether the rate of reinforcement in the presence of a stimulus similarly modulates the relative relapse of operant behavior produced by reinstatement, resurgence, and renewal paradigms. During baseline conditions, pigeons responded for food reinforcement on variable-interval 120-sec schedules in alternating periods of exposure to two stimuli arranged by a multiple schedule. Additional response-independent food presentations were also delivered in the presence of one of the multiple-schedule stimuli. Consistent with previous research, baseline response rates were lower in the presence of the stimulus with the added response-independent reinforcement, and relative resistance to extinction was greater in the presence of that stimulus. In addition, following extinction, the relative relapse of responding produced by reinstatement, resurgence, and renewal paradigms was greater in the presence of the stimulus associated with the higher rate of reinforcement. We suggest that a model of extinction from behavioral momentum theory may be useful for understanding these results. 相似文献
19.
Experiment 1 investigated the behavior of rats trained to leverpress on a concurrent variable ratio (VR) 30 VR-30 schedule with a brief, 500-msec, light occurring at the midpoint of the ratio on one of the levers. Higher response rates were recorded on the lever associated with this stimulus, a finding that paralleled the effect produced by inserting primary reinforcement at the midpoint (i.e., by training on a concurrent VR-30 VR-15 schedule). Similar results were found in Experiment 2 using a concurrent VR-20 VR-20 schedule with a 2-sec visual stimulus presented midway through one of the components. In addition, a brief stimulus inserted midway through the VR-20 component of a concurrent VR-20 VR-10 schedule retarded the development of a difference in response rates between the components relative to a VR-20 VR-10 group lacking the signal. In Experiment 3, multiple VR VR schedules were used. Again, the response rate was higher in the component that had the added stimulus or, for a second group of subjects, on the component with the smaller response requirement. Probe-choice trials revealed a preference for the component that generated the higher rate in both groups. Presenting a stimulus partway through a ratio appears to reduce the effect on response rate and choice of a large ratio value. 相似文献
20.
Lick suppression experiments with rats revealed that the magnitude of both second-order conditioning (Experiment 1) and sensory preconditioning (Experiment 2) was superior when that conditioning was based on backward (US→CS) relative to forward (CS→US) first-order pairings of a CS and US. The superiority of backward relative to forward first-order conditioning on suppression to the higher order cues can be understood by assuming that the magnitude of higher order conditioning was determined by a memory representation of the higher order cues that provided information about the expected temporal location of the US. The results suggest that temporal information such as order between paired CSs and USs was encoded, preserved, and integrated with memory for the higher order stimuli. The relevance of these findings to memory integration in Pavlovian learning, the temporal coding hypothesis (Barnet, Arnold, & Miller, 1991; Matzel, Held, & Miller, 1988), backward excitatory conditioning, and the associative structure that underlies second-order Pavlovian fear conditioning are discussed. 相似文献