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1.
Pigeons were trained to depress a treadle in the presence of a discriminative stimulus, either a tone or illumination of red houselights, in order to obtain access to grain or avoid electric shock. In avoidance training, the auditory discriminative stimulus yielded faster acquisition than did the visual one. In appetitive training, the visual discriminative stimulus yielded faster acquisition than the auditory one. Experiments 2 and 3 used these stimuli in Kamin’s (1969) blocking design. In Experiment 2, when the pigeons were trained to depress a treadle in the presence of tone to obtain grain and then red light was added as the redundant stimulus, the light acquired stimulus control over treadlepressing; blocking was not observed. In Experiment 3, when the pigeons were trained to depress a treadle in the presence of red light to avoid electric shock and then tone was added as the redundant stimulus, the tone acquired stimulus control over treadle-pressing. Again, blocking was not observed. The implications of these results for several models of stimulus control are discussed.  相似文献   

2.
The ability of visual CSs previously paired with flavored substances to substitute for those substances as conditional discriminative cues was examined in two Pavlovian appetitive conditioning experiments using rat subjects. In Experiment 1, a visual stimulus was first paired with the delivery of a sucrose solution. Then the rats were trained in conditional discrimination tasks in which sucrose delivery alone served as a conditional cue signaling whether or not a subsequent tone would be reinforced with food pellets. Subjects rapidly acquired discriminative performance to the tones, especially in a feature-negative condition in which sucrose delivery signaled when the tone would not be reinforced. In a subsequent test in which neither food nor sucrose was delivered, presentation of the visual CS also controlled discriminative performance to subsequently presented tones. Experiment 2 showed the ability of a visual CS to substitute for a flavored substance as a conditional cue to be highly stimulus specific. Experiment 2 also showed that a flavored substance was less effective as a conditional cue when it was made to be expected by preceding it with a previously associated visual signal than when it was made to be surprising by preceding it with a visual stimulus signaling another flavored liquid. These results indicate that CS-evoked representations of events can substitute for those events themselves in the control of previously established conditional discrimination performance.  相似文献   

3.
An attempt was madeto manipulate the strength of internal stimulus representations by exposing pigeons to brief delays between sample offset and comparison onset in a delayed conditional discrimination. In Experiment 1, pigeons were first trained on delayed conditional discrimination with either short (0.5-sec) delays or no delays. When delays were increased by 2.0 sec, birds trained with a delay performed at a higher level than did birds trained with no delays. In Experiment 2, subjects were first trained on a delayed simple discrimination. Following a circle stimulus, responses to a white key were reinforced; however, following a dot stimulus, responses to the white key were not reinforced. The pigeons were then trained on a delayed conditional discrimination involving hue samples and line-orientation comparisons with differential outcomes. Choice of vertical following red yielded food; choice of horizontal following green yielded no food. Mixed delays were then introduced to birds in Group Delay, whereas birds in the control group received overtraining. When tested on a delayed simple discrimination with hue stimuli (red and green initial stimuli followed by white response stimulus), pigeons in Group Delay tended to perform at a higher level than did birds in the control group (i.e., although the birds in both groups responded more following red than following green, birds in Group Delay did this to a greater extent than did birds in the control group). Thus, experience with delays appears to strengthen stimulus representations established during training.  相似文献   

4.
In Experiment I, one group of goldfish (TD) was trained to discriminate blue and green while a second group (PD) was exposed to the same colors in a “pseudodiscrimination,” after which both groups were reinforced for response to a tone. The TD group subsequently showed a sharper auditory discrimination gradient than the PD group and performed better in a differentially reinforced tone discrimination. The former PD animals then were given true discrimination training and the former TD animals pseudodiscrimination training with the colors, after which the first group showed better tone discrimination than the second. These results are analogous to those found in pigeons and rats. In Experiment II, goldfish which were trained in an easy color discrimination and shifted to a more difficult tone discrimination performed better than a control group trained from the outset with the tones. This result suggests that the dimensional specificity of the processes responsible for “transfer along a continuum” cannot safely be assumed in the absence of appropriate controls.  相似文献   

5.
In Experiment 1, three (experimental) groups of pigeons (n=8) acquired a successive wavelength discrimination in Phase 1 and a reversal in Phase 2; then, after a 24-h delay, they received a wavelength generalization test in extinction (Phase 3). For one group (“Context Same”), the same context was present throughout; for both others, a different context was used for Phase 1 and Phase 2. One group received the generalization test in the presence of Context 1, the other in Context 2. The Context Same and Context 2 experimental groups showed “recency,” with all gradients peaking at the reversal S+ value. The Context 1 group yielded several different response patterns but never showed recency, thus revealing context-generated proactive interference. In Experiment 2, eight subjects learned the original discrimination and its reversal in different contexts, and each bird was tested alternately (within a session) in both contexts. Under this condition, the test contexts were effective retrieval cues. In every case, the gradients obtained in each context peaked sharply at the appropriate S+ value. These experiments indicate that conflicting memories may be stored along with their associated contexts such that they can be retrieved by an appropriate manipulation of contextual cues at the time of retention testing.  相似文献   

6.
Pigeons were trained on a successive discrete-trial conditional discrimination, in which either of two colors appeared on the center key and either of two forms appeared on the two side keys. Some combinations of color and form (S+ trials) were followed by food; other combinations (S-trials) were followed by no food. The colors on the center key appeared throughout the intertrial interval (ITI) preceding the trial period in which both the color and the form compound were presented or the color appeared only during the trial period in compound with the forms. Presentation of the colors during the ITI substantially degraded acquisition of two separate types of conditional discrimination. The results show that the temporal correlation of the eolors-with food, independent of their association with the form cues, played a substantial role in determining their availability for acquisition of the conditional discrimination.  相似文献   

7.
We investigated whether pigeons are able to discriminate color photographs of male and female pigeons, using a categorical discrimination procedure. In Experiments 1 and 2B, 10 out of 14 pigeons learned the discrimination. Of these, 5 pigeons showed transfer to novel stimuli, demonstrating the categorical nature of the trained discrimination. Experiment 3 showed that the discriminative behavior was based primarily on the body, as opposed to the head and the neck region. In 1 out of 3 pigeons, the discriminative behavior was maintained by the black-and-white photographs. The results suggest that some pigeons have the ability to discriminate the sex of conspecifics without behavioral cues.  相似文献   

8.
Using trial-and-error training, eight pigeons did not learn to discriminate between 45° and 135° lines, but did learn to discriminate between red and green colors. Control by line tilt was induced by stimulus fading that did not include reinforcement while fading out the colors. After establishing the red–green discrimination, low-intensity lines were superimposed on colors and were gradually faded in. All of this was done using reinforcement. At the end of the line fade-in, the lines had not acquired control of responding. Finally, color intensity was gradually faded out in the absence of reinforcement, and the lines acquired discriminative control by six of the eight pigeons. Thus, reinforcement during the color fade-out was not necessary for the acquisition of discriminative control by the lines during fading. Acquisition of control by lines was attributed to overshadowing, the reduction of stimulus blocking by generalization, and the evocation of correct responding by the colors while the participants were attending to the lines. This last process was also responsible for the induction of discriminative control during sensory preconditioning, higher order conditioning, and response transfer in equivalence classes. Errors, however, were not correlated with discrimination learning during stimulus fading. Finally, transfer of control occurred very quickly with or without errors.  相似文献   

9.
Pigeons were trained on a conditional discrimination involving form and color elements in an autoshaping procedure. When the colors were also illuminated during 50% of the ITIs (Experiment 1), or were presented alone on additional extinction trials (Experiment 2), the discrimination was not acquired, indicating a loss of salience for stimuli not temporally predictive of reinforcement. But when the colors and the forms were both similarly illuminated, the discrimination was acquired, indicating that relative stimulus validity, not the absolute temporal predictiveness per se, was the controlling variable.  相似文献   

10.
Pigeons were trained to discriminate the proportion of red to green color in paired stimulus displays. Initially, the stimuli were horizontal bars composed of continuous blocks of color that varied from being all red versus all green to .5 proportions of these two colors. Discrimination accuracy decreased as a function of the disparity in the proportions of the two colors. This relationship was maintained when the stimulus configurations were altered in various ways. Tests with horizontal bars indicated that the pigeons could utilize differences in the lengths (or areas) of one of the colors when choosing between stimuli. They did not rely only on this type of cue to assess proportion disparities but rather on multiple stimulus parameters. Also, the form of the discrimination function suggests that the pigeons distinguished ratio differences, so that Weber’s law applies to this type of discrimination.  相似文献   

11.
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   

12.
Rats trained in one context to use stimuli arising from food deprivation as discriminative signals for shock were tested in other contexts to assess the basis of conditioned responding (i.e., freezing or behavioral immobility). In Experiment 1, discriminative control by 24-h food-deprivation cues failed to promote transfer responding in a test context that had no association with shock. This indicated that food deprivation cues had little direct excitatory power. However, transfer of behavioral control by 24-h food-deprivation cues was obtained in a context paired with shock only when the rats were 19 h water deprived. This finding agrees with the idea that food-deprivation cues become conditioned modulators of the capacity of external stimuli to activate their association with an unconditioned stimulus. In Experiment 2, rats trained to use 24-h food-deprivation cues as signals for shock exhibited significantly greater transfer performance when the transfer context had undergone partial extinction relative to when the transfer context had undergone only simple excitatory training. This finding with deprivation cues and transfer contexts (1) paralleled earlier results obtained with discrete (auditory and visual) conditioned modulators and transfer targets, and (2) posed difficulties for associative summation and generalization interpretations of transfer performance.  相似文献   

13.
Compared with their performance with localized (on-key) visual stimuli, pigeons are notoriously poor at performing go/no-go discriminations when keypecking for food in the presence of auditory discriminative stimuli. The difference might reflect the fact that an aversive visual onkey stimulus signaling nonreward can be escaped by looking away and not pecking, which contributes to the measure of good discriminative performance, while an auditory stimulus cannot be escaped. In Experiment 1, discriminative performance was significantly improved by providing pigeons with a response incompatible with keypecking by which they could escape a tone S+ and a tone S?. However, the pattern, frequency, and duration of escape responses were found to be insufficient to explain the improvement. In Experiment 2, it was found that the capacity to escape only S+ or only S? enhanced discriminative performance as much as the capacity to escape both. It is theorized that the Pavlovian relationship between the absence of the discriminative stimuli and the nonoccurrence of food might transfer to the instrumental relationships learned in a go/no-go discrimination. The possibility that intermittent stimuli command more attention than continuous stimuli is also considered.  相似文献   

14.
In Experiment 1, 12 pigeons were given eight sessions of VI single stimulus training with a color in a particular context followed by eight sessions of similar training with a line angle in another context. On the next day, half of the subjects were tested for wavelength and angularity generalization in each of the two contexts, a procedure that was thus consistent with training for one dimension and inconsistent for the other. The subjects made significantly more responses to each training stimulus under the consistent context condition, but there was no difference in absolute or relative generalization slopes. In Experiment 2, 12 pigeons were trained as in Experiment 1, but during generalization testing they were exposed to both contexts sequentially. Under the consistent context condition, the subjects responded more to the two training stimuli and yielded sharper absolute and relative wavelength generalization gradients: Under the inconsistent context condition, responding to the training wavelength was substantially disrupted. Thus, under appropriate testing conditions, contextual control over both the amount and the selectivity of responding can be demonstrated.  相似文献   

15.
Two experiments were run in order to investigate the influence of external contextual cues on the interaction between two conflicting memories. Rats were trained, in the same apparatus, on a passive-avoidance task and, 10 min later, on an active-avoidance task, then submitted to a 24-h delayed test (without reinforcement). When contextual cues remained unchanged throughout these three phases, the animals exhibited proactive interference, as shown by longer response latencies than those of control animals that had learned only the active-avoidance task (Experiment 1). When training contexts were made slightly different from one task to the other (by the presence of a continuous tone during either the first or the second task), the animals behaved at subsequent testing in accordance with the response contingencies present in the context exactly similar to the test context; this control of behavior by testing context was demonstrated both when the tone was absent (Experiments 1 and 2) and present (Experiment 2) at testing. A cuing procedure—a 90-sec exposure to the tone in the experimental room 5 min prior to testing—led the animals to behave in accordance with the response previously acquired in the presence of the tone (Experiments 1 and 2), exactly in the same way as animals tested in the presence of the tone (Experiment 2). The same cuing treatment was ineffective when administered 1 h before testing (Experiment 2). These results are interpreted in terms of a dual function of contextual cues at the time of retrieval: the general contextual information present during testing or during pretest cuing is assumed to induce concurrent reactivation of both memories. Consequently, the experimentally manipulated contextual cue (the tone) would have a discriminative function, leading the animals to choose between the two equally available representations.  相似文献   

16.
In three experiments, pigeons were trained to discriminate between uniform arrays of two elements that differed in color, form, or size. They were then tested with arrays that contained different proportions of the two elements on these dimensions. In all cases, orderly discrimination gradients reflected these proportions. The discrimination readily transferred to new arrays with similar stimuli, but with different total numbers of elements. In Experiment 4, the pigeons were taught to discriminate between two groups of categorical stimuli: pictures of birds and pictures of flowers. A test with different proportions of each again produced a gradient based on relative numerosity. Experiment 5 demonstrated transfer of stimulus control on the numerosity dimension when pigeons were trained with one set of instances from two categories, and then were tested with new instances from the same categories.  相似文献   

17.
In three experiments, we assessed the role of signals for changes in the consequences of cues as a potential account of the renewal effect. Experiment 1 showed recovery of responding following extinction when acquisition, extinction, and test phases occurred in different contexts. In addition, extinction treatment in multiple contexts attenuated context-induced response recovery. In Experiment 2, we used presentations of an extraneous stimulus (ES), instead of context shifts, and found that responding recovered from extinction only when the ES was presented both between acquisition and extinction and between extinction and test. In Experiment 3, we used a reversal learning design in which, during training, two cues were first paired with different outcomes, then paired with the alternative outcomes, and finally paired again with the original outcomes. In this experiment, presentation, just prior to testing, of an ES that had previously been presented between the different phases produced an expectation of reversal in the meaning of the cues.  相似文献   

18.
We trained 7 pigeons to discriminate visual displays of 16same items from displays of 16different items. The specific stimulus features of the items and the relations among the items could serve as discriminative stimuli. Unlike in most studies of same-different discrimination behavior, we gave a small number of probe tests during each session of acquisition to measure the time-course of control by the learning of specific stimulus features and relational cues. Both the specific stimulus features and relational cues exerted reliable stimulus control, with the specific stimulus features exerting more control during the final three fourths of same-different learning. These findings replicate research suggesting that pigeons encode both the specific stimulus features and relational cues, and for the first time document the time-course of control by each kind of cue.  相似文献   

19.
Goldfish, trained in the shuttlebox apparatus to avoid shock, acquired a color discrimination between two colors (red/green) and were tested in transfer with a new set of colors (yellow/blue). Transfer color shock-pairing was either consistent with (red=yellow, blue=green) or opposite to (red≠ yellow, green≠blue) categorical color coding seen in pigeons. Groups with transfer shock-pairing consistent with categorical color coding showed positive transfer, and groups with transfer shock-pairing opposite to categorical color coding showed negative transfer, similar to an attenuated reversal learning effect. These results indicate that goldfish, like pigeons, code different colors as behavioral equivalents even though they can easily learn to discriminate between them. As with pigeons, the finding of the categorical color coding phenomenon changes the conclusions drawn from earlier goldfish conditional-discrimination transfer studies using only signal color changes between acquisition and transfer testing, from evidence of concept learning to evidence for categorical color coding, on the grounds of parsimony. It is important to note that this finding affects only the explanation of conditional-discrimination transfer effects, and the fact remains that both pigeons and goldfish can learn to conditionally discriminate—pigeons for positive reinforcement, and goldfish to avoid shock.  相似文献   

20.
In two experiments, we examined the discrimination of photographs of individual pigeons by pigeons, using go/no-go discrimination procedures. In Experiments 1A and 1B, the pigeons were trained to discriminate 4 photographs of one pigeon from those of a number of pigeons. The subjects learned the discrimination, but their discriminative behavior did not transfer to new photographs taken from novel perspectives. When the pigeons were trained to discriminate between 20 photographs of five pigeons taken from four perspectives as the S+ and 20 photographs of five different pigeons as the S-, the subjects learned the discrimination, and this discriminative behavior partially transferred to new photographs taken from novel perspectives (Experiments 2A-2C). The results suggest that pigeons are able to discriminate among conspecific individuals, using stationary visual cues. This strengthens the assumption in evolutionary theory that animals can discriminate among individuals and encourages further investigation as to how this ability is used in various behaviors of animals.  相似文献   

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