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1.
Three rats were trained under a discrimination procedure in which responding was reinforced only following the repeated presentation of three bursts of white noise (S+). S? consisted of presentations of either two or four bursts of noise. All animals responded significantly more in the presence of S+ and, in two cases, showed lower response rates to both “2” and “4” stimuli. Responding by the third animal revealed differentiation between S+ and the stimulus “2,” but no reliable suppression to stimulus “4.” The present instances of discriminative control by the stimulus “3” replicate Fernandes and Church’s (1982) demonstration of control by sequential auditory stimuli in the rat. Moreover, because the present procedure involves adjacent S? values both greater as well as less than S+, these results extend our knowledge of the rat’s abilities with sequential auditory stimuli: Rats are capable of making intermediate numerical discriminations based upon something other than a simple many-versus-few dichotomy. 相似文献
2.
In two experiments, a maintained generalization procedure was employed to examine stimulus control of pigeons’ responses to a visual wavelength continuum. For both experiments, pigeons’ responses were periodically reinforced during wavelength values from one end of a continuum, while responses during other stimulus values were extinguished. In Experiment 1, the set of positive stimulus values remained constant, while the spacing of the set of negative stimuli varied. In Experiment 2, the set of negative stimulus values remained constant, while the spacing of positive stimuli varied. Positive dimensional contrast effects were obtained in both experiments. In general, the results indicated that variation in the spacing of negative stimuli had little effect on positive dimensional contrast. However, variation in the spacing of positive stimuli produced changes in the peak of the dimensional contrast gradient, without apparent change in the magnitude of the effect. 相似文献
3.
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
4.
5.
In Experiment 1, it was shown that generalization testing following successive discrimination training between two closely spaced wavelengths results in a sharp gradient with a peak of responding shifted from S+ so as to be further removed from S?. Testing after a 24-h delay resulted in a flatter gradient with greater peak (and area) shift. A 5-min pretest exposure to S+, reinforced or unreinforced, or to S? (unreinforced) reinstated immediate test performance; free reinforcement with no discriminative stimulus present had no such effect. Experiment 2 replicated the flattening of generalization gradients and enhanced peak shift in delayed testing. Free feeding in a pretest treatment with a distinctive food uniquely associated with the wavelength discrimination problem failed to reinstate immediate test performance. Experiment 3 tested the hypothesis that free feeding failed as a reactivation treatment because it did not engender keypecking. Subjects were trained to peck a vertical line stimulus before being given wavelength discrimination training. Again, the enhanced peak shift and greater flattening with delayed wavelength generalization testing was found. A pretest exposure to the vertical line stimulus elicited pecking but had no effect on subsequent wavelength generalization. Thus, only a reactivation treatment that included one of the discrimination training stimuli was effective in producing delayed test performance comparable to that obtained in an immediate test. 相似文献
6.
The effects of excitatory conditioning history on establishing inhibitory stimulus control have been investigated in classical conditioning, but not in the free-operant paradigm. The present experiments address this question within the context of discriminated free-operant avoidance in which rats’ barpressing postponed shock. When a stimulus with only a history of signaling safety was combined, on a summation test, with a stimulus that maintained avoidance, avoidance rate was reduced, on average, by 60%. In comparison, after a stimulus acquired an excitatory free-operant avoidance history, nonreinforcement alone was not adequate to make it a predictable and effective inhibitor of avoidance on a summation test. These results, consistent with the classical conditioning literature, were produced by both between-group (Experiment 1) and within-subject (Experiment 2) comparisons. These findings are discussed in terms of (1) Konorski’s distinction between “primary” and “secondary” inhibitory stimuli, (2) the Rescorla-Wagner model, (3) the potential contribution of the “reinstatement of fear” to the outcome of summation tests, and (4) their implications for assaying the effectiveness of behavior-modification treatments of phobias. 相似文献
7.
Four naive pigeons were given six generalization tests in extinction after periods of pretraining in which S+ appeared with food reinforcement and S? appeared in extinction. An analysis of sequential effects among presentations of test stimuli showed that the overall gradient was influenced differently by stimuli at the extremes of the continuum of test stimuli and by S+ and adjacent stimuli. Gradients consisting of responding in each stimulus when it was preceded by an extreme stimulus tended to peak at S+, while gradients produced when each stimulus was preceded by S+ or an adjacent stimulus tended to show a peak shift. This was true whether the overall gradient showed a peak shift or not. Two naive subjects were added and four additional tests were given after pretraining in which unequal frequencies of reinforcement accompanied both S+ and S?. Results of all 10 tests show that sequential effects occur during generalization testing in extinction and that these “local dimensional effects” are unlike local contrast. These stimulus-specific sequential effects may greatly influence overall gradient form. 相似文献
8.
Pigeons initially trained on a simultaneous discrimination of line orientation (S1) were subsequently transferred to a wavelength discrimination (S2). Three transfer procedures were employed. The abrupt-transfer Ss were “abruptly” switched from S1 to the S2 dimension. The stimulus-compounding Ss were trained on a compound stimulus consisting of S1 and S2 displayed in superimposition prior to the presentation of S2 alone. The stimulus-delay Ss were trained on a compound stimulus in which the presentation of the S1 component was delayed for successively longer intervals as a result of a correct response to the preceding trial. Stimulus-delay Ss transferred by responding to S2 prior to the presentation of S1 and the resulting formation of the compound. Ss transferred by the stimulus-compounding and the abrupt-transfer procedures displayed 5 and 10 times as many errors to the S2 dimension, respectively, as Ss receiving the stimulus-delay procedure.
相似文献9.
Rats were exposed to a procedure in which auditory stimuli signaled which of two levers was associated with a variable-interval 60-sec schedule of food presentation. Presses on the lever that was not associated with the variable-interval schedule (“errors”) postponed availability of reinforcement on the other lever by either a fixed number of responses or a fixed amount of time. Increasing the number of responses by which “errors” postponed food availability enhanced the level of stimulus control, and. alter a relatively high degree of control had been achieved, reduction of the requirement had no effect. Control experiments ruled out extended exposure to the discrimination procedure as a factor in the increase in stimulus control and suggested that the time of introduction of a changeover contingent is an important determinant of its effect. 相似文献
10.
In Experiment 1, six groups of pigeons (n=8) were tested for wavelength generalization either immediately or 24 h after learning a successive discrimination, with 550 nm reinforced and a black vertical line extinguished. The groups differed in the stimulus present during single stimulus pretraining, which was 550 nm (pretrain S+), the vertical Une (pretrain S?), or a neutral dim white light (pretrain Sn), respectively. The three immediate generalization gradients were steep and indistinguishable, reflecting only the immediately preceding discrimination training condition. The three delay gradients were flatter, with the flattening particularly marked in the pretrain S? group. This was interpreted as proactive interference (PI) resulting from the memory that both the 550-nm and the line stimuli had previously been reinforced. In Experiment 2, two (TD) groups of pigeons (n=16) were given single stimulus training with a 555-nm keylight followed by eight sessions of discrimination training with two line angles, then one session of non-differential (ND) training with the same two lines, and then a wavelength generalization test either immediately or after a 24-h delay. Two other (hold) groups (n=16) received similar training, except for the TD Une angle training sessions, in these hold groups, the wavelength gradient was flatter in a delayed test; in the TD groups it was steeper, indicating PI from the prior TD training. These two experiments suggest that the “attentional sets,” which purportedly result from TD and ND training, may fruitfully be viewed as target memories subject to the principles of interference theory. 相似文献
11.
Additive summation is observed when more responses are emitted to the simultaneous presentation (tone-plus-light) of independently conditioned stimuli (tone and light) than to either stimulus presented alone. The current experiment sought to determine if this increased rate during tone-plus-light was a function of a new modal interresponse time (IRT) or a differential mixing of pauses with a modal IRT characteristic of the responding in tone and light alone. Three rats were trained on a three-component multiple schedule where tone and light were each associated with a variable-interval 30-sec schedule while a variable-interval 100-sec operated in the simultaneous absence of these stimuli, tone-off and light-out. Baseline response rates were 2–4 times as high in tone or light as in their absence. In testing, more responses were emitted to tone-plus-light than to tone or light by all animals, but the modal IRT was in the 0.2–0.4-sec IRT bin for all test conditions. Tone-plus-light controlled fewer long IRT values and more responses in the short modal category than tone or light alone. These results support the response mixing hypothesis of stimulus control; i.e., no “new” behavior was observed during the novel combination of stimulus elements, only a mixture of previously reinforced behavior patterns in different proportions. 相似文献
12.
On the completion by pigeons of four equal fixed intervals on one key, a light on a second key signaled that one peck on that key would be followed by food. In condition A, a brief stimulus of a further color was produced on the first key by the pecks that ended the first three (but not the fourth) fixed intervals. In condition B, no brief stimuli occurred at the end of the first three fixed intervals (tandem schedule). In condition C, the unpaired brief stimulus was presented on the second key after the pecks on the first key that ended the first three fixed intervals. An ABACA reversal design was used. Postreinforcement pauses were longer in condition B (tandem) than in condition A, an effect similar to that reported in similar conventional one-key second-order schedules. Postreinforcement pauses in condition C, with the brief stimulus on the second key, were also longer than in condition A, with the brief stimulus on the first key, although similar pauses were observed after the brief stimuli in both conditions. The locus of the brief stimulus appears to affect the control it exerts over behavior in a second-order schedule. 相似文献
13.
Kelly J. Stanhope 《Learning & behavior》1989,17(3):311-321
A dissociation between the effect of reinforcer type and response strength on the force of the pigeon’s keypeck response was shown in three experiments. In Experiment 1, pigeons were trained to peck two conditioned stimuli, one paired with water and another paired with grain. The pigeons made more forceful pecks for grain than for water and also showed a tendency, albeit an unreliable one, to respond on a higher percentage of food trials than water trials. In Experiment 2, the pigeons from Experiment 1 were satiated with either food or water and were then presented with the two conditioned stimuli in an extinction test. It was found that, regardless of the drive state, the pigeons made more forceful pecks to the stimulus that predicted food than to the stimulus that predicted water. In the thirsty group, however, this difference in force was not accompanied by a difference in the percentage of trials with a response. In Experiment 3, pigeons trained with a single reinforcer pecked more often on instrumentally reinforced trials than on Pavlovian conditioning trials, but there was no difference in the force of the pecks. Taken together, these results imply that differences in response strength cannot account for the difference between the force of food- and water-reinforced pecks. Instead, stimulus-substitution theory may provide the best account of the topography of the two types of pecks. 相似文献
14.
Previous studies have shown that pigeons could learn a serial list of colors and to select each color in the proper order when presented with an array of colors. Errors of jumping forward in the required sequence (forward errors) were most probable, with jumps backward in the required sequence (backward errors) being relatively improbable. One proposed explanation for the higher probability of forward errors suggests that the pigeon pecks at the correct stimulus without activating the response switch and then pecks the next stimulus in the sequence closing the response switch. This “inadequate-peck” hypothesis suggests that forward errors are due to weak stimulus control and that increased feedback for correct pecks should therefore reduce forward error probability relative to a low-feedback condition. The present study compared responding under conditions of high and no experimenter-provided feedback for correct pecks. As the feedback did not affect the probability of forward errors, the inadequate-peck hypothesis was not supported. A short-term memory explanation is consistent with the data. 相似文献
15.
Aitken (1999) argues that, in a simultaneous discrimination, reports of the transfer of value from the positive to the negative stimulus can be more readily explained in terms of an artifact produced by the procedure in which differential inhibition accrues to the negative test stimuli during training, together with stimulus generalization (similarity between the positive and negative stimuli). We argue that (1) there is little evidence for differential inhibition, and it often occurs in the wrong direction; (2) value transfer can be demonstrated when differential value is established to the positive stimuli afterdiscrimination training, when differential inhibition is not likely to be a factor; and (3) on both logical and empirical grounds, stimulus similarity does not provide an adequate account of the transfer of value from the positive to the negative stimulus (i.e., the strongest evidence for value transfer occurs when there is least stimulus similarity). We propose that value transfer occurs whenever there is relatively little experience with the negative stimuli. However, when there is extended experience with the negative stimuli, contrast will be found. 相似文献
16.
These experiments examined one way in which the allocation of attentional resources can change performance during a visual discrimination task. Pigeons were trained to discriminate visual forms under conditions that produced dimensional contrast. In three experiments, negative training stimuli differed from positive stimuli either along a primary physical dimension alone or along both a primary dimension and an orthogonal dimension. When a negative stimulus differed from positive stimuli along two dimensions, discrimination of that negative stimulus improved. For one type of visual form, discrimination of the positive stimuli declined with orthogonal variation in a negative stimulus, whereas for other visual forms, there was no decline in performance. These results are consistent with a model of dimensional contrast that suggests that differences in the allocation of attentional resources determine discrimination performance. The results also indicate that the organization of stimulus dimensions plays a crucial role in the allocation of attentional resources in these settings. 相似文献
17.
Jacky Emmerton 《Learning & behavior》1998,26(3):243-256
Two experiments are described in which pigeons were trained in a simultaneous conditioning procedure to discriminate small arrays of dots that differed in numerosity. The birds successfully learned to choose the array of each pair that contained fewer dots when these choices were reinforced and choices of the array with more dots led to timeout. For the majority of numerosity values tested, discrimination performance for a fixed S+ value was better when the numerical difference between S+ and S-values was larger rather than smaller. This effect was seen in the first experiment when the numerical difference value was shifted between training trials and novel test trials. In the second experiment, too, performance level depended on the size of the numerosity difference when the birds were concurrently trained with two difference values that varied across trials within sessions. However, discrimination accuracy was influenced secondarily by variations in the density, or interdot spacing, of the stimulus arrays. In order to explain the latter finding, it is suggested that a tendency to “scan” a lowdensity array incompletely might alter the probability of accepting it as the smaller numerosity (S+) stimulus. This would increase error rates with S? arrays in which the dots are more widely spaced. 相似文献
18.
The capacities of three different conditioned stimulus modalities (light, noise, and airflow produced by a fan) to produce fear-potentiated startle were evaluated. Previous experiments have shown that following either light-shock or noise-shock pairings, both the light and noise conditioned stimuli acquire the ability to potentiate the acoustically elicited startle response in rats (the so-calledfear-potentiated startle effect). In Experiment 1, the ability of airflow produced by a fan to act as a conditioned stimulus was investigated. Rats were given either paired or impaired fan-shock training followed by a test for fear-potentiated startle. The fan conditioned stimulus potentiated startle only in the group given explicit fan-shock pairings. In Experiment 2, we evaluated the discriminability of the three conditioned stimulus modalities. Rats were given light, noise, or fan-shock pairings and were subsequently tested for fear-potentiated startle with the trained conditioned stimulus as well as the two remaining novel conditioned stimuli. Only the trained conditioned stimulus potentiated startle. These results show that fear-potentiated startle can be produced with three discriminable conditioned stimulus modalities, allowing the future use of fear-potentiated startle in the investigation of higher order conditioning phenomena. 相似文献
19.
Pigeons were given successive discrimination training in which pecking during a choice period when the key was white was either reinforced or not, depending upon the prior presence or absence of a discriminative stimulus, which was a two-element serial compound. The compound consisted of a keylight and food, with food presented second or first in a forward or backward pairing for different groups of pigeons. In Experiment 1, the sequence was an S+ indicating reinforced trials, while in Experiment 2, the sequence was an S? indicating nonreinforced trials. Following acquisition of discriminated operant behavior, a sequence generalization test was administered during which all possible orders of the two stimuli were presented on test trials prior to the onset of the choice period. The results showed that food overshadowed stimulus control by the color of the light on the key on the sequence-generalization test, independently of whether food was presented first or second during training and independently of whether food was associated with reinforcement or nonreinforcement. The similarity of results for the two experiments suggests that overshadowing occurs independently of whether the compound is a discriminative stimulus for reinforcement or nonreinforcement. Simultaneous presentation of elements of a compound stimulus is not necessary for overshadowing because the phenomenon was captured with sequentially presented stimuli. 相似文献
20.
Changes in affect toward a particular stimulus can take place very rapidly through Pavlovian conditioning, if presentation of the conditioned stimulus (CS+) paired with the unconditioned stimulus (US) is accompanied by presentation of a “CS?,” another value of the same dimension as the CS+ but not paired with a US. This effect has considerable generality. It has been observed in terms of both olfactory and visual CSs, in terms of appetitive as well as aversive conditioning, and for adult as well as infant rats. The CS? effect has seemed especially important for infants, which may be related to the general tendency for infants to exhibit less stimulus selection than older animals. Finally, the CS? effect has enabled the development of a simple test of short-term retention that can quite effectively assess memory for either incidental or target events. These tests so far have indicated a clear ontogenetic decrease in rate of forgetting over short intervals, corresponding to the well-known development-related decrease in forgetting over long intervals (infantile amnesia). The tests also have shown that short-term forgetting of intentional and target events is surprisingly similar, with some indication of more rapid forgetting for the incidental events. Alternative interpretations of the CS? effect and some preliminary tests of these interpretations are discussed. 相似文献