Prototype effects in categorization by pigeons.

In 4 experiments involving a total of 78 pigeons, Ss received a categorization task involving 6 simultaneous compounds in which the elements A, B, and C were more frequently paired with food than were the elements D, E, and F. Food was delivered after compounds ABF, AEC, and DBC but not after DEC, DBF, and AEF. Subsequent testing revealed a higher rate of responding during ABC than during any of the compounds that had signaled food and a lower rate of responding during DEF than during any of the compounds that had not signaled food. Exps 2, 3, and 4 further demonstrated that the rate of responding during test trials with ABC was faster than during a compound composed of 3 elements that had individually been paired with food. Results are more consistent with a configural than an elemental analysis of discrimination and categorization. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Configural analysis of summation in autoshaping.

In 4 experiments, pigeons received autoshaping with various combinations of three stimuli, A, B, and C, before test trials in which responding during all three stimuli, ABC, was compared with that during a three-element control compound, DEF, which had been consistently paired with food. Pairing A, B, and C individually with food resulted in similar rates of responding during ABC and DEF (Experiments 1 and 2). Responding was faster, however, during ABC than during DEF after training in which food was signaled by the pairs of stimuli (AB, AC, and BC; Experiment 1). Responding was also faster during ABC than during DEF after training involving reinforced (+) and nonreinforced (°) trials of the form ABC+ A° BC°, followed by A+ BC+ (Experiment 2), or AB+ BC+ B° (Experiments 3 and 4). The results are consistent with those of a configural analysis of summation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Failure of inhibition by B over C after A+, AB–, ABC+ training.

In 3 autoshaping experiments, pigeons were trained with an A+, AB–, ABC+ task in which Stimulus A signaled food, Stimulus Compound AB signaled no food, and Stimulus Compound ABC signaled food. Contrary to the prediction from elemental theories of conditioning, responding on a Stimulus Compound BC trial was not less than responding on a Stimulus C trial in testing. However, Stimulus B attenuated responding to another excitor (Experiment 2), and a separately trained inhibitor could attenuate responding to Stimulus C (Experiment 3). These results were consistent with a configural theory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acquired relational equivalence between contexts and features.

In 2 experiments, rats received a biconditional discrimination wherein separate presentations of A and B signaled 1 pair of associations (X?→?food and Y?→?no food) and presentations of C and D signaled a different pair of associations (X?→?no food and Y?→?food). In Exp 1, A, B, C, and D were diffuse contextual stimuli in which the associations were embedded. In Exp 2, A and C were contextual stimuli whereas B and D were features that immediately preceded the associations. To assess the associative structures acquired during training, all rats then received a revaluation procedure in which A was paired with shock and C was not. In both experiments, greater generalized suppression of behavior was observed in the presence of B than in the presence of D. These results indicate that contextual stimuli share with features the capacity to evoke the associations that they have signaled. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Feature-positive discrimination learning.

In Experiments 1, 2, and 3, pigeons were trained with an ABC+ BCo discrimination, in which three stimuli, A, B, and C, were presented together and paired with food, and the compound BC was followed by nothing; they were also trained with a DEF+ Eo Fo discrimination in which stimuli E and F were presented separately and followed by nothing, whereas the compound DEF was paired with food. On completion of discrimination training, test trials with the feature A consistently revealed a higher rate of responding than with D. In Experiment 4, reinforced presentations of D were intermixed with the DEF+ Eo Fo discrimination. Test trials revealed that E enhanced responding when it was paired with F, but it had the opposite effect when paired with D. The results are seen as being more consistent with a configural than an elemental model of conditioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Inhibition and facilitation by B over C after A+, AB–, and ABC+ training with multimodality stimulus combinations.

Previous research with keylight conditioned stimuli has revealed that pigeons failed to show inhibition by Stimulus B over Stimulus C in BC versus C testing after A+, AB–, ABC+ training where Stimulus A and Stimulus Compound ABC had signaled food, and Stimulus Compound AB had signaled no food. Indeed, B slightly facilitated responding to C on the BC trials. The present research addressed the same issue with multimodality stimulus arrangements in autoshaping with pigeons, conditioned suppression with rats, and instrumental discrimination learning with rats. Stimulus B facilitated responding to C if A and B were of the same modality and C was of a different modality. However, B inhibited responding to C if A and C were of the same modality and B was of a different modality, or if B and C were of the same modality and A was of a different modality. These results are correctly predictable by Pearce's configural model with a minor modification. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The influence of an irrelevant stimulus on two discriminations.

In 3 experiments, the effect of adding an irrelevant stimulus to a discrimination was examined. In Exp 1, a group of pigeons received autoshaping with an A+Bo discrimination in which 1 stimulus signaled food, A+, and a simultaneous compound of A with another stimulus, B, signaled the absence of food, ABo. A 2nd group received similiar training, except that a 3rd stimulus, C, was present in both types of trials, AC+BCo. The A+Bo discrimination was acquired more readily than the AC+BCo discrimination. Exps 2 and 3 used a negative-patterning design, A+Bo+. In both experiments, this problem was mastered more readily than when an irrelevant stimulus was used to create an AC+BCoC+ discrimination. The results fail to confirm predictions derived from elemental theories of conditioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acquired relational equivalence: Implications for the nature of associative structures.

In 2 experiments, rats received discrimination training in which separate presentations of A and B signaled a common pair of relationships or associations (X?→?food and Y?→?no food), whereas presentations of C and D signaled a different pair of relationships (X?→?no food and Y?→?food). To assess the nature of the associative structures acquired during this training, rats then received 2 types of revaluation procedure: In Experiment 1, A was paired with shock and C was not. In Experiment 2, the relationships that A and B had previously signaled (X?→?food and Y?→?no food) were paired with shock, whereas those that C and D had signaled (Y?→?food and X?→?no food) were not. After both types of revaluation treatment, rats showed greater generalized conditioned suppression in the presence of B than D. These results indicate that A, B, C, and D come to evoke memories of the relationships or associations that they have signaled. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Overshadowing and associability change.

Three appetitive Pavlovian conditioning experiments with rats examined the associability of stimuli A and B that had a history of compound conditioning (AB+), relative to stimuli X and Y that had a history of conditioning in isolation (X+, Y+). Following this training, Experiment 1 revealed that conditioned responding was higher to X and Y than to A and B (overshadowing). In a subsequent AY+, AX?, BY? test discrimination, the AY/BY discrimination was solved more readily than the AY/AX discrimination. In Experiment 2, following AB+, X+, Y+ training, A and Y were presented as a compound and signaled the availability of reinforcement upon the performance of an instrumental response. Test trials in which A and Y were presented alone, and in extinction, revealed that A acquired greater control of instrumental responding than Y. Experiment 3 revealed that following AB+, X+, Y+ training, A and B served as more effective discriminative stimuli for instrumental responding than X and Y. Overall, these results imply that the associability of stimuli conditioned in compound is higher than stimuli conditioned in isolation. These results are discussed in terms of attentional theories of associative learning. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Acquired equivalence between cues trained with a common antecedent.

In Exp 1, rats experienced 2 stimuli (A and N) each preceded by the same event (food) or by different events (food preceded 1 but not the other). N was then paired with shock, and the generalization of conditioned suppression to A was assessed. Generalization was more marked when A and N had been experienced along with a common antecedent. In Exp 2, 3 stimuli (A, B, and N) were presented in initial training. For 1 group, A and N were preceded by food and B was not; for a 2nd group A alone was preceded by food. In each group, suppression generalized more readily from N to the stimulus that had received the same initial training as had been given to N. Exp 3 found that generalization was not enhanced between stimuli when 1 had preceded food in initial training and 1 had followed it. These results demonstrate that stimuli that have shared a common antecedent will come to be treated as equivalent. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus–response overshadowing: Effects of signaled reward on instrumental responding as measured by response rate and resistance to change.

If every food reinforcer delivered on a VI schedule is preceded by a brief flash of light, rats leverpress for food more slowly than if light flashes are given independent of the food and their responding. This retardation in rate has been attributed to the overshadowing of the response–food association by the light–food association. Such an explanation assumes that response rate is positively correlated to the response association strength. Exps I and II investigated this account by using prefeeding and extinction procedures to test the strength of responding in 44 Long-Evans rats that had received food-correlated or random-light signals. Acquisition response rate was lower in the signaled condition (consistent with previous studies), but responding was more resistant to both extinction and satiation, regardless of whether the light cues were presented during the extinction/prefeeding phase. Exp III, with 27 Ss, revealed no difference between the signaled and random conditions either in terms of acquisition response rates or resistance to satiation when a VR schedule of reinforcement was used. Results are inconsistent with an overshadowing account of the acquisition rate difference. Instead, the signal seems to enhance the rat's sensitivity to the contingencies present on VI schedules. (44 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Unblocking in Pavlovian appetitive conditioning.

Two experiments, with 280 Sprague-Dawley rats, demonstrated unblocking in an appetitive conditioning preparation. One stimulus, A, was first paired with either a low-value reinforcer (1 food pellet) or a high-value reinforcer (1 food pellet followed by 2 more food pellets). A 2nd stimulus, X, was then added to A, and the compound was reinforced with either the high- or low-value reinforcer. Conditioning to X was blocked if the same reinforcer was used in both phases of the experiment, but there was substantial conditioning to X when the reinforcer value was shifted either up or down when X was introduced. Exp I demonstrated this unblocking phenomenon using a design that minimized the potential contribution of generalization decrement. Exp II examined the effects of a variety of posttraining manipulations on conditioned responding to the added X cue after unblocking procedures. Among Ss that received downshifts in reinforcer value when X was introduced, responding was affected by several posttraining manipulations, including changes in context value. Those manipulations had smaller effects on the responding of Ss that received upshifts in reinforcer value and no effects on responding in control conditions. Findings are considered in relation to the model of conditioning outlined by R. A. Rescorla and A. R. Wagner (1972). (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of exposure to conditioned stimulus and control of its termination in the extinction of avoidance behavior.

Describes 2 experiments in which, following signaled shuttle box avoidance training, a total of 52 female Fischer344 rats were exposed to the conditioned stimulus (CS) during no-shock treatment trials and subsequently tested during extinction trials in which shock was also absent. In Exp I, Ss that could control the termination of the CS during treatment responded significantly more often during extinction than yoked partners that received the same pattern and duration of CS exposure but could not control its termination. Exp II revealed that the probability of responding during extinction was a decreasing function of the duration of CS exposure during treatment. Thus, in the absence of shock, both lack of control over CS termination and increasing CS exposure each independently facilitated the weakening of well-established avoidance responses. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Relative aversiveness of signaled vs. unsignaled avoidable and escapable shock situations in humans.

Conducted 2 experiments dealing with signaled and unsignaled shock, using a total of 18 male college students. In Exp I 6 Ss avoided shock, and in Exp II 12 Ss escaped shock by pressing one button under an unsignaled shock condition. By pressing on a separate button, Ss could change to signaled avoidance (Exp I) or signaled escape (Exp II). All Ss changed from the unsignaled to signaled condition whether shock was avoidable or escapable. 6 Ss were also given a chance to change from signaled to unsignaled escapable shock. Changeover responding remained at or near operant levels for these Ss. Comparing results of this study with studies using the rat revealed much similarity but some differences. Differences depended upon whether an escapable or avoidable procedure was used. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of context on responding during a compound stimulus.

In 4 experiments, the authors used rats to examine the strength of responding during a clicker-tone compound in the presence of a light, after the auditory stimuli had individually been paired with food in the presence of the same light. Experiment 1 demonstrated a higher rate of responding during the compound when the duration of the light was short rather than long. In Experiments 2, 3, and 4, the long duration light was used as a signal for food in a conditional discrimination involving the tone and the clicker. Responding on test trials with the clicker-tone compound during the light was enhanced by this treatment and resulted in a level of performance that was no different from that observed when the duration of the light was short. The results are more compatible with a configural than an elemental theory of associative learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the relationship between differential outcomes and differential sample responding in matching-to-sample.

Four experiments involving 24 experimental pigeons and 24 experimentally naive pigeons examined control over choice by differential sample responding in matching-to-sample with differential outcomes. In Exp 1, Ss initially learned to match with food vs no-food outcomes. Their performances later transferred to other samples to which responding vs not responding had been explicitly reinforced with a single outcome (food). In Exp 2, Ss initially learned to produce the comparisons by pecking 1 sample but not the other. Transfer was then observed to new samples associated with food vs no food (and thus often vs seldomly pecked). Exps 3 and 4 showed that transfer of matching required differential behavior to each sample set and did not depend on explicit conditioning of that behavior prior to acquisition. Results show that differential sample behavior provides a redundant cue for choice in differential outcome matching-to-sample. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Facilitation of instrumental behavior by a Pavlovian appetitive conditioned stimulus.

In Exp I, 16 New Zealand white rabbits were trained to perform an instrumental head-raising response for sucrose reward. A jaw-movement CR was established to a 2-sec CS by pairing it with sucrose; a control stimulus was unpaired with sucrose. Instrumental responding maintained by a VI 40-sec schedule was enhanced during 10-sec presentations of the paired, but not the unpaired, CS. Responding on a VR 15 schedule was unaffected except on trials on which the pre-CS baseline response rate was low; in such cases the paired CS caused a long-lasting acceleration of responding. Noncontingent presentation of the sucrose reinforcer itself briefly suppressed responding but had no long-term effect. In Exp II (6 Ss), a CS that had been conditioned at a 10-sec duration produced the same pattern of effects as in Exp I, indicating that facilitation resulted from CS presentation rather than from the frustrative effects of nonreinforcement of the CS. In Exp III (16 Ss), an inhibitory CS blocked facilitation by the excitatory CS but did not itself affect instrumental responding. (53 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The strength of the orienting response during Pavlovian conditioning.

Exp I, with 8 male hooded-Lister rats, demonstrated that the orienting response toward a light that signaled food declined in strength during conditioning but was temporarily restored during extinction. In Exp II, using 24 male Sprague-Dawley rats, the light was paired immediately with the UCS; but in Exps III and IV (40 male Sprague-Dawley rats), it signaled a tone that in turn signaled the UCS. Exps II–IV showed that continuous reinforcement resulted in a decline in the strength of light orientation. Under conditions of partial reinforcement, orientation to the light was sustained. Exp V, with 32 male Sprague-Dawley rats, demonstrated that the decline in light orientation with a continuous reinforcement procedure was retarded either by preexposing the light for a number of trials prior to conditioning or by intermixing reinforced light trials with nonreinforced presentations of a tone. Reversing the reinforcement contingency associated with the tone restored orientation to the light. (34 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A configural analysis for feature-negative discrimination learning.

In 4 experiments, rats were initially trained with an A+ AXo discrimination in which Stimulus A by itself signaled the delivery of food, A+, whereas the simultaneous presentation of A and X was followed by nothing, AXo. In each experiment, X was then paired with food prior to a test phase in which A and X were again presented for a discrimination. The discrimination was of the form A+ AXo in Exps 1 and 2, whereas it was of the form X+ AXo for Exps 3 and 4. In all 4 experiments, the test discrimination was acquired more rapidly than a control discrimination. The results are interpreted in terms of the original A+ AXo discrimination resulting in the growth of an association between a representation of the entire AX compound and the effects of nonreinforcement. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dominance in intermale encounters and subsequent sexual success in mice.

In Exp I, when previously isolated male CD-1 mice (n?=?26) were paired and given a female, they fought before beginning to mount, and the more aggressive male ejaculated somewhat more frequently. Males housed together (n?=?26) for several days showed little aggression when jointly given a female, but those that were more aggressive in the home cage clearly ejaculated more frequently. In Exp II, with 144 Ss, males were paired for 4 days after a period of isolation. More aggressive males showed more ejaculations when subsequently tested individually with females, but not when pair members conjointly encountered females. In Exp III, 60 males were paired for several weeks before encountering females. In cases in which home cage dominance was constant, the more aggressive males ejaculated more frequently both when tested individually and when tested as pairs. Findings indicate that success in reproductive behavior in mice is contingent on dominance in intermale aggressive encounters. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)