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1.
Aust and Huber (2001) demonstrated that in apeople-present/people-absentdiscrimination task, pigeons actually attended to properties of the target (i.e., the human figure). The aim of the present effort was to specify what sort of information contained in the target was used for classification, as well as to investigate whether and in what way the target-defining features interacted. Six pigeons were trained in a go/no-go procedure to discriminate between color photographs characterized by the presence or absence of people. They were then presented with various types of test stimuli that contained some category-relevant features but lacked others. The results showed that properties related to target size and internal structure played an important role and that human silhouettes were insufficient for eliciting a people-present response. Furthermore, some properties of the human figure (e.g., hands/arms) made good predictors of the people-present category, whereas others (e.g., feet/legs or skin color) did not. Responses to test stimuli that belonged to the people-absent category but nevertheless contained some features normally typical for humans (e.g., nonhuman primates) provided evidence that various category-relevant features contributed to classification in an additive way. Taken together, the results suggest that the pigeons made use of a polymorphous class rule involving collections of differently weighted target features. 相似文献
2.
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
3.
In the present experiment, we investigated whether pigeons rely exclusively on elemental information or whether they are also able to exploit configural information in apeople-present/people-absent discrimination task. Six pigeons were trained in a go/no-go procedure to discriminate between 800 color photographs characterized by the presence or absence of people. Thepeople-present stimuli were designated as positive, and thepeople-absent stimuli were designated as negative. After training and a subsequent generalization test, the pigeons were presented with both familiar and novel people-present stimuli containing human figures that were distorted in one of seven different ways. All the pigeons learned the initial discrimination and also showed generalization to novel stimuli. In the subsequent test, performance on all types of distorted stimuli was diminished in comparison with that on the intact original pictures from which they had been derived. At the same time, however, peck rates clearly exceeded the level of responding found for regular people-absent stimuli. This result strongly suggests that responding was controlled by both the constituting target components and their spatial relations and, therefore, points to the dual importance of elemental and configural information. 相似文献
4.
In two experiments, pigeons were trained on many-to-one delayed matching in which samples of food and one hue were each associated with one shape comparison, and samples of no food and a different hue were each associated with a second shape comparison. When later tested with delays between sample and comparison stimuli, pigeons showed nonparallel delay functions, typically found with food and no-food samples (i.e., steeply declining food-sample delay functions, and relatively flat no-food-sample delay functions). Furthermore, the slopes of the hue-sample delay functions were similar to those on the food/no-food-sample trials. In Experiment 2, following many-toone delayed matching, when the hue samples were associated with new comparisons and then food and no-food samples replaced the hues, evidence was found for transfer of training indicative of the common coding of samples associated with the same comparison in original training. The transfer results suggest that the asymmetrical hue-sample functions resulted from the common coding of samples associated with the same comparison. 相似文献
5.
We trained 4 pigeons in a numerical bisection task to discriminate between pairs of keylight flashes with a ratio of 1∶3 (2
vs. 6, 4 vs. 12, and 8 vs. 24) that were presented in a sample phase. Responses to the blue key were reinforced after a sequence
of a larger number of flashes, and responses to the white key were reinforced after a sequence of a smaller number of flashes.
The intervals between flashes in the sample phase were randomized to attenuate the covariation of temporal cues with flash
number. Pigeons responded accurately in each of the discriminations, with typically 85%–90% correct responses. Transfer tests
showed that the proportion of large responses increased with number and performance generalized to larger values outside the training ranges. Psychometric functions
superposed when plotted on a relative scale, and estimates of Weber fractions were approximately constant, suggesting that
variability was scalar. However, contrary to previous research in nonhumans, bisection points were located at the arithmetic,
not geometric, mean. Hierarchical logistic regressions confirmed significant control over responding by number beyond that
attributable to temporal cues. These results show that pigeons are able to respond accurately in a relative numerosity discrimination
with successively presented visual stimuli, although the nature of the numerical representation and response rule remains
unclear. 相似文献
6.
Sequence learning in pigeons was studied in asimultaneous chaining paradigm: all stimuli and the opportunity to respond to each stimulus were available simultaneously. In contrast to the traditionalsuccessive chaining paradigm, a simultaneous chaining paradigm provides no differential feedback following each response (except the last). Subjects were first trained to perform on sequences of two (AB), then three (ABC), and then four colors (ABCD). Performance greatly exceeded that predicted by models of random choice. Generalization to novel arrays of three and four colors was complete. After training with a four-color sequence, the subjects were tested with subsequences consisting of all possible combinations of two and three of the four training colors (e.g., BD, AD, BC, ACD, BCD, etc.). The successful completion of these subsequences showed that the organization of the original sequence did not entail overt pecks to successive elements of that sequence. That subjects can respond accurately on nonadjacent subsets is not readily explained by a chaining theory, or by any theory that assumes that responding to element n provides a cue for responding to element n+1. 相似文献
7.
Pigeons were trained in a forced choice task with four alternatives to categorize arrays consisting of 1, 3, 5, or 8 dots.
Before the pigeons chose a comparison stimulus, they were required to peck each dot sequentially. A single peck to a dot,
which was defined as an indicating response, changed the color of the dot so that it was differentiated from those that remained to be counted. The pigeons
successfully learned to categorize the numerical arrays and then displayed transfer to novel arrays consisting of two, four,
six, or seven dots, in a manner according to the order of 1 < 2 < 3 < 4 < 5 < 6 < 7 < 8. Subsequent tests revealed that the
pigeons discriminated the stimuli by relying on the number of indicating responses. They also utilized multiple information
(surface area, time, and other confounded events), but this was of minor significance, and after training, the pigeons were
able to disregard these cues. 相似文献
8.
Thomas R. Zentall 《Learning & behavior》1998,26(4):363-377
When two initially unrelated stimuli are associated with the same event (e.g., many-to-one conditional discriminations), an emergent relation can develop between those stimuli, allowing them to be interchangeable in other contexts. The source of the emergent relation appears to be a common representation of the two stimuli, and the nature of the representation may be retrospective, involving one of the initial stimuli (probably the stimulus that first enters into association). These emergent relations have been implicated in the establishment of stimulus equivalent relations. However, the failure to find strong evidence for other emergent relations thought to be involved in stimulus equivalence (Sidman, 1990; e.g., bidirectional associations, transitive relations, and functional equivalence associated with one-to-many conditional discriminations) suggests that the mechanisms underlying the emergent relations found using transfer designs following many-to-one training are different from those presumed to underlie stimulus equivalence. On the other hand, evidence for the common representation of stimuli associated with the same arbitrary event extends the nature of those representations beyond those well-established effects found when the common events are biologically important (e.g., the differential outcomes effect). 相似文献
9.
Pigeons learned to respond at one spatial position when a pair of stimuli matched and at a different spatial position when they mismatched. All birds were then transferred to novel stimuli on an orthogonal dimension. For the positive-transfer group, the correct positions for matching and mismatching stimuli remained as they were during training. For the negative-transfer group, the correct positions were reversed. In Experiment 1, the birds were trained with shape stimuli and transferred to hue stimuli. Significant group differences were found, in spite of considerable stimulus-specific learning. In Experiment 2, when the same birds (counterbalanced for Experiment 1 transfer group) were transferred to steady-intermittent stimuli, even larger group differences were found. The data indicate that pigeons have some capacity for representing the concepts “same” and “different” with arbitrary stimuli (i.e., symbols). The data further suggest that distinctions that have been made between matching/oddity transfer tasks and same/different tasks may be procedural rather than conceptual. 相似文献
10.
When Pavlovian stimuli activate representations of food, do these representations resemble memories of food consumed in the recent past or expectancies of food that is imminent? In Experiments 1A and 1B, this question was addressed by training pigeons on a symbolic matching-to-sample task involving different grains as memory cues or as expectancy cues for correct choices. Autoshaping trials involving these same grains were interspersed among matching-to-sample trials, as were test trials involving the substitution of autoshaping stimuli for cues in the matching-to-sample task. Control over choices transferred to autoshaping stimuli in both experiments, suggesting that associatively activated representations of food resemble both memories and expectancies. In Experiment 2, pigeons were trained on a symbolic matching-to-sample task in which food and no-food memory cues (i.e., the samples) were juxtaposed with no-food and food expectancy cues. Subsequently, autoshaping stimuli, which activated representations of food and no food, were substituted for the samples. Choices by the pigeons indicated that associatively activated representations of food-related events resemble expectancies more closely than they do memories. 相似文献
11.
Herrnstein and Loveland (1964, pp. 549–551) successfully trained pigeons to discriminate pictures showing humans from pictures that did not. In the present study, a go/no-go procedure was employed to replicate and extend their findings, the primary focus of concern being to reevaluate the role of item- and category-specific information. The pigeons readily acquired the discrimination and were also able to generalize to novel instances of the two classes (Experiment 1). Classification of scrambled versions of the stimuli was based on small and local features, rather than on configural and global features (Experiment 2). The presentation of gray-scale stimuli indicated that color was important for classifying novel stimuli and recognizing familiar ones (Experiments 1 and 2). Finally, the control that could possibly be exerted by irrelevant background features was investigated by presenting the pigeons with images of persons contained in former person-absent pictures (Experiment 3). Classification was found to be controlled by both item- and category- specific features, but only in pigeons that were reinforced on person-present pictures was the latter type of information given precedence over the former. 相似文献
12.
We report the first successful demonstration of a simultaneous, two-itemsame-different (S/D) discrimination by 6 pigeons, in which nonpictorial color and shape stimuli were used. This study was conducted because
the majority of recently successful demonstrations of S/D discrimination in pigeons have employed displays with more than
two items. Two pairs of stimulus items were simultaneously presented on a touch screen equipped computer monitor. Pigeons
were reinforced for consistently pecking at either thesame (i.e., identical) or thedifferent (i.e., nonidentical) pair of items. These pairs were created from combinations of simple colored shapes drawn from a pool
of six colors and six shapes. After acquiring the discrimination with item pairs that differed redundantly in both the shape
and the color dimensions, the pigeons were tested for transfer to items that varied in only one of these dimensions. Although
both dimensions contributed to the discrimination, greater control was exhibited by the color dimension. Most important, the
discrimination transferred in tests with novel colored, shaped, and sized items, suggesting that the mechanisms involved were
not stimulus specific but were more generalized in nature. These results suggest that the capacity to judge S/D relations
is present in pigeons even when only two stimuli are used to implement this contrast. 相似文献
13.
This study presents evidence that adaptation to colored light alters the apparent hue of subsequently presented stimuli in pigeons. During training, right and left keypecks were reinforced following responses to colored and nominally achromatic slides, respectively. During test sessions, subjects continued to observe and report on the two classes of slides while 6-min components alternated, such that the experimental chamber was illuminated with either a green flood lamp or a nominally white bulb. The proportion of right keypecks following achromatic slides was much higher during green components than during white components, indicating that the achromatic slides appeared more like the chromatic slides. 相似文献
14.
We explored response rate as a possible mediator of learned stimulus equivalence. Five pigeons were trained to discriminate
four clip art pictures presented during a 10-sec discrete-trial fixed interval (FI) schedule: two paired with a one-pellet
reinforcer, which supported a low rate of responding, and two paired with a nine-pellet reinforcer, which supported a high
rate of responding. After subjects associated one stimulus from each of these pairs with a discriminative choice response,
researchers presented two new clip art stimuli during a 10-sec FI: one trained with a differential reinforcement of low rate
schedule (DRL) after the FI and the other trained with a differential reinforcement of high rate schedule (DRH) after the
FI. Each of the stimuli that were withheld during choice training was later shown to see if the choice responses would transfer
to these stimuli. The results suggest that response rate alone does not mediate learned stimulus equivalence. 相似文献
15.
We call for a shift from a content-oriented approach to a process-oriented approach to the study of categorization in infancy. Although gains have been made in our understanding of infant categorization by evaluating the categories to which infants respond, further understanding of infant categorization, and how categorization changes with development, requires that we more directly assess infants' category formation. We argue that two directions for future research will continue to enhance our understanding of categorization in infancy (and beyond). First, contextual variations (e.g., the effects of task, stimuli, and other factors) on infants' categorization must be better understood. Second, we must more directly evaluate the kinds of information infants use when forming categories, as well as how their use of such information changes with age, task, and so forth. We argue that these two foci will provide clearer understanding of the origins and early development of categorization. 相似文献
16.
Pigeons were trained to learn an instrumental oddity-from-sample discrimination involving visual forms. One group, the “few examples” group, dealt with 5 patterns in 40 different combinations. Another group, the “many examples” group, dealt with 20 patterns in 160 different combinations. After both groups had reached asymptotic performance and had learned to operate under partial reinforcement conditions, they were tested for transfer under extinction conditions with two different groups of 5 novel patterns, each in 40 combinations. All animals showed significant above chance transfer to both of these novel stimulus sets. Transfer performance with test stimuli of similar geometric design to training stimuli was better than performance with stimuli of markedly different design. The transfer performance of the “many examples” group was marginally better than that of the “few examples” group, even though the latter’s performance on the training stimuli was better throughout. It is concluded that pigeons can learn to employ an oddity concept and that this may be promoted by the use of many training exemplars. Furthermore, it is inferred that pigeons may normally use a mixture of strategies to solve oddity and identity problems. 相似文献
17.
Eight rhesus monkeys were trained on a successive discrimination problem with light gray and dark gray stimuli. Following training, generalization tests were given with variable stimuli ranging from white to black. Responses and response latencies were recorded. Responses were faster to the training stimulus values than to middle grays or to the extreme values on the lightness continuum. The theoretical implications of this as compared to other possible findings are developed. 相似文献
18.
In three experiments, we examined pigeons’ recognition of video images of human faces. In Experiment 1, pigeons were trained
to discriminate between frontal views of human faces in a go/no-go discrimination procedure. They then showed substantial
generalization to novel views, even though human faces change radically as viewpoint changes. In Experiment 2, the pigeons
tested in Experiment 1 failed to transfer to the faces dynamically rotating in depth. In Experiment 3, the pigeons trained
to discriminate the dynamic stimuli showed excellent transfer to the corresponding static views, but responses to the positive
faces decreased at novel viewpoints outside the range spanned by the dynamic stimuli. These results suggest that pigeons are
insensitive to the three-dimensional properties of video images. Consideration is given to the nature of the task, relating
to the identification of three-dimensional objects and to perceptual classifications based on similarity judgments. 相似文献
19.
The relationship between the duration of stimuli and their conditioned reinforcing effect was investigated using a learning-tests procedure. In Experiment 1, stimuli were the same duration on training (stimulus → reward) and test (choice response → stimulus). Ten- and 30-sec stimuli provided effective differential conditioned reinforcement but 3-sec stimuli did not. In Experiment 2, different pigeons had each combination of the 3- and 30-sec stimuli on training and test trials. Evidence of conditioned reinforcement was obtained only for the birds with 30-sec stimuli on both training and test. The results were interpreted as indicating that stimuli become effective conditioned reinforcers on test trials only when their duration exceeds the duration of differential short-term memory cues resulting from a difference in the events that precede them on training and test trials. 相似文献
20.
Results of directed-forgetting research with pigeons are difficult to interpret because of alternative nonmemorial accounts of performance decrements and important procedural differences from comparable research with humans. Prior research has noted the absence of directed forgetting when artifacts have been removed (e.g., nonreward following forget cues and differences in response patterns on remember and forget trials in training). In this article, it is argued that, in human directed-forgetting research, presentation of a forget cue allows for the reallocation of memory maintenance to items to be remembered. In the present experiment, true directed forgetting is found when nonmemorial performance decrements are eliminated and forget cues allow for the reallocation of sample memory to test-relevant cues. 相似文献