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ABSTRACT: In a simultaneous discrimination involving a positive (S+) and a negative (S−) stimulus, positive value appears to transfer from the S+ to the S−. However, negative value does not appear to transfer from the S− to the S+. Instead, when sufficient experience with the contingencies associated with responding to the S− is provided, it appears that the presence of the S− enhances the value of the S+ (i.e., a contrast effect is found). The purpose of the present experiments was to further examine
the influence of the S+ on the S− in a simultaneous discrimination (between subjects in Experiment 1 and within subjects in Experiment 2). In both experiments,
we found that under typical training conditions, given little direct experience with the value of the S−, value transfers from the S+ to the S−. If sufficient experience with the value of the S− is provided, however, contrast between the S+ and the S− can be demonstrated. Thus, in a simultaneous discrimination, value transfer from the S+ to the S− depends on the animal’s having responded relatively little to the S−.
Learning & Behavior 04/2012; 28(2):195-200. · 2.00 Impact Factor
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ABSTRACT: Stimuli associated with less effort or with shorter delays to reinforcement are generally preferred over those associated
with greater effort or longer delays to reinforcement. However, the opposite appears to be true of stimuli thatfollow greater effort or longer delays. In training, a simple simultaneous discrimination followed a single peck to an initial stimulus
(S+FR1 S−FR1) and a different simple simultaneous discrimination followed 20 pecks to the initial stimulus (S+FR20 S−FR20). On test trials, pigeons preferred S+FR20 over S+FR1 and S−FR20 over S−FR1. These data support the view that the state of the animal immediately prior to presentation of the discrimination affects
the value of the reinforcement that follows it. This contrast effect is analogous to effects that when they occur in humans
have been attributed to more complex cognitive and social factors.
Psychonomic Bulletin & Review 04/2012; 7(1):100-106. · 2.61 Impact Factor
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ABSTRACT: There is evidence that how humans perceive time is affected by the activity in which they are engaged when they are judging time. In humans, typically, the more demanding the task, the faster time seems to pass. We asked whether a similar effect could be found in pigeons. Pigeons were trained to discriminate between a short- (2-sec) and a long- (10-sec) duration stimulus. Depending on the color of the stimulus (white or blue), the pigeons were required to peck (at least once per second or the trial was aborted) or to refrain from pecking (pecks aborted the trial). Once these tasks had been acquired to a high degree, probe trials involving white and blue stimuli were presented at durations between 2 and 10 sec. On trials in which the pigeons were required to peck, the point of subjective equality (i.e., the point at which pigeons are equally likely to choose the stimulus associated with long stimuli as the stimulus associated with short stimuli) was almost 1 sec longer than on trials in which th epigeons were required to refrain from pecking. In other words, on trials that required pecking, more time passed before the pigeons indicated that the probe duration was at the subjective midpoint between 2 and 10 sec than on trials that did not require pecking. This result suggests that like humans, the pigeons underestimated the passage of time when they were active or when attention to time-related cues had to be shared with attention to satisfying the response rate requirement.
Psychonomic Bulletin & Review 01/2007; 13(6):1038-42. · 2.61 Impact Factor
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ABSTRACT: Clement, Feltus, Kaiser, and Zentall (2000) found that when pigeons have to work to obtain a discriminative stimulus that is followed by reinforcement, they prefer a discriminative stimulus that requires greater effort over one that requires less effort. The authors suggested that such a preference results from the greater change in hedonic value that occurs between the more aversive event and the onset of the stimulus that signals reinforcement, a contrast effect. It was hypothesized that any stimulus that follows a relatively more aversive event would be preferred over a stimulus that follows a relatively less aversive event. In the present experiment, the authors tested the counterintuitive prediction of that theory, that pigeons should prefer a discriminative stimulus that follows the absence of reinforcement over a discriminative stimulus that follows reinforcement. Results supported the theory.
Learning & Behavior 09/2005; 33(3):337-42. · 2.00 Impact Factor
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ABSTRACT: Research suggests that animals are capable of forming functional equivalence relations or stimulus classes of the kind usually demonstrated by humans (e.g., the class defined by an object and the word for that object). In pigeons, such functional equivalences are typically established using many-to-one matching-to-sample in which two samples are associated with one comparison stimulus and two different samples are associated with the other. Evidence for the establishment of functional equivalences between samples associated with the same comparison comes from transfer tests. In Experiment 1, we found that pigeons can form a single class consisting of four members (many-to-one matching) when the alternative class has only one member (one-to-one matching). In Experiment 2, we ruled out the possibility that the pigeons acquired the hybrid one-to-one/many-to-one task by developing a single-code/default coding strategy as earlier research suggested that it might. Thus, pigeons can develop a functional class consisting of as many as four members, with the alternative class consisting of a single member.
Behavioural Processes 12/2004; 67(3):395-403. · 1.65 Impact Factor
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ABSTRACT: In the present research, we asked whether pigeons tended to judge time intervals not only in terms of their absolute value but also relative to a duration from which they must be discriminated (i.e., longer or shorter). Pigeons were trained on two independent temporal discriminations. In one discrimination, sample durations of 2 and 8 sec were associated with, for example, red and green hue comparisons, respectively, and in the other discrimination, sample durations of 4 and 16 sec were associated with vertical and horizontal line comparisons, respectively. If pigeons are trained on a temporal discrimination and tested with intermediate durations, the subjective midpoint typically occurs close to the geometric mean of the two trained values. The 4- and 8-sec values were selected to be the geometric mean of the two values in the other discrimination. When a 4-sec test sample was presented with the comparisons from the 2- and 8-sec discrimination, the pigeons preferred the comparison associated with the shorter sample. Similarly, when an 8-sec test sample was presented with the comparisons from the 4- and 16-sec discrimination, the pigeons preferred the comparison associated with the longer sample. Thus, a relative grouping effect was found. That is, durations that should have produced indifferent choice were influenced by their relative durations (shorter than or longer than the alternative) during training.
Psychonomic Bulletin & Review 03/2004; 11(1):113-7. · 2.61 Impact Factor
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ABSTRACT: When humans acquire a conditional discrimination and are given a novel-sample-comparison choice, they often reject a comparison known to be associated with a different sample and choose the alternative comparison by default (or by exclusion). In Experiment 1, we found that if, following matching training, we replaced both of the samples, acquisition took five times longer than if we replaced only one of the samples. Apparently, the opportunity to reject one of the comparisons facilitated the association of the other sample with the remaining comparison. In Experiment 2, we first trained pigeons to treat two samples differently (to associate Sample A with Comparison 1 and Sample B with Comparison 2) and then trained them to associate one of those samples with a new comparison (e.g., Sample A with Comparison 3) and to associate a novel sample (Sample C) with a different, new comparison (Comparison 4). When Sample B then replaced Sample C, the pigeons showed a significant tendency to choose Comparison 4 over Comparison 3. Thus, when given the opportunity, pigeons will choose by exclusion.
Psychonomic Bulletin & Review 01/2004; 10(4):959-64. · 2.61 Impact Factor
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ABSTRACT: Functional stimulus equivalence has been demonstrated using a transfer of training design with matching-to-sample training in which two sample stimuli are associated with the same comparison stimulus (A-B, C-B; many-to-one matching). Equivalence is shown by training a new association (A-D) and demonstrating the presence of an emergent relation (C-D). In the present experiment, we show that symmetry training, in which a bidirectional association is trained between two stimuli (A-B, B-A, using successive stimulus presentations followed by reinforcement), can also produce functional equivalence using a transfer of training design (i.e., train B-C, test A-C). The results suggest that training pigeons in the substitutability of two stimuli may be sufficient to produce functional stimulus equivalence between them. The results also have implications for the development of an emergent transitive relation, because training on A-B and B-C relations results in the emergence of an untrained A-C relation, if B-A training also is provided.
Psychonomic Bulletin & Review 07/2003; 10(2):387-91. · 2.61 Impact Factor
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ABSTRACT: In delayed matching to sample, once acquired, pigeons presumably choose comparisons according to their memory for (the strength of) the sample. When memory for the sample is sufficiently weak, comparison choice should depend on the history of reinforcement associated with each of the comparison stimuli. In the present research, pigeons acquired two matching tasks in which Sample S1 was associated with one comparison from each task, C1 and C3, whereas Sample S2 was associated with Comparison C2, and Sample S3 was associated with Comparison C4. As the retention interval increased, the pigeons showed a bias to choose the comparison (C1 or C3) associated with the more frequently occurring sample (S1). Thus, pigeons were sensitive also to the (irrelevant) likelihood that each of the samples was presented. The results suggest that pigeons may allow their reference memory for the overall sample frequency to influence comparison choice, independent of the comparison stimuli present.
Journal of Experimental Psychology Animal Behavior Processes 02/2002; 28(1):111-5. · 2.05 Impact Factor
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ABSTRACT: Pigeons prefer signals for reinforcement that require greater effort (or time) to obtain over those that require less effort to obtain (T. S. Clement, J. Feltus, D. H. Kaiser, & T. R. Zentall, 2000). Preference was attributed to contrast (or to the relatively greater improvement in conditions) produced by the appearance of the signal when it was preceded by greater effort. In Experiment 1, the authors of the present study demonstrated that the expectation of greater effort was sufficient to produce such a preference (a second-order contrast effect). In Experiments 2 and 3, low versus high probability of reinforcement was substituted for high versus low effort, respectively, with similar results. In Experiment 3, the authors found that the stimulus preference could be attributed to positive contrast (when the discriminative stimuli represented an improvement in the probability of reinforcement) and perhaps also negative contrast (when the discriminative stimuli represented reduction in the probability of reinforcement).
Journal of Experimental Psychology Animal Behavior Processes 02/2002; 28(1):64-74. · 2.05 Impact Factor
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ABSTRACT: 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.
Learning & Behavior 04/1999; 27(4):494-496. · 2.00 Impact Factor
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ABSTRACT: In earlier research using constant-delay matching with pigeons, there is evidence that delay of reinforcement of sample-orienting behavior may contribute to the decline in matching accuracy with increasing delay between sample and comparison stimuli. In the present research using this procedure, we found that a significant decline in matching accuracy between the first and second session can occur when delays are relatively long. This effect cannot be accounted for in terms of either additional memory loss or surprise (generalization decrement) associated with the increase in delay. Furthermore, the decline in matching accuracy occurred regardless of whether the delay was inserted between samples and comparisons (where it would be expected to affect the use of sample memory in making the comparison choice response) or between comparisons and reinforcement (where it would not be expected to affect the use of sample memory in making the comparison choice response). Thus, the decrease in matching accuracy between Session 1 and 2 following an increase in delay appears to be unrelated to sample memory at the time of choice. Instead, the results suggest that delay of reinforcement of sample-orienting behavior may play an important role in the negative slope of the retention functions obtained when constant- or mixed-delay matching procedures are used to assess animal memory.
Behavioural Processes.
