Acquired equivalence learning with antecedent and consequent unconditioned stimuli.

The conditions under which cues with similar training histories are treated by rats as being equivalent were examined. A significant event, food, either preceded, followed, or preceded and followed each of the Stimuli A and B; Stimulus C was not food-associated. Next, B was counterconditioned with footshock until it suppressed an appetitively motivated behavior. When A and C were tested for generalized suppression, A (treated like B) evoked more suppression than C (treated differently than B). However, this equivalence effect was strong only when A and B predicted food and were treated alike. (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)     

Supernormal conditioning.

In Experiment 1, rats received an A+AX° discrimination in which food was presented after Stimulus A by itself but not after a simultaneous compound of A with Stimulus X. AX was then paired with food in a 2nd stage, followed by test trials with A alone. Responding on the test trials with A was more vigorous than during a control stimulus that had been consistently paired with food. The remaining experiments were of similar design to Experiment 1, except that the 2nd stage also contained conditioning trials with X. The results from the test trials were essentially the same as for Experiment 1. The high level of responding during the test trials with Stimulus A is regarded as evidence of supernormal conditioning. Overall, the results are more consistent with a configural than an elemental theory of conditioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The influence of predictive accuracy on serial autoshaping: Evidence of orienting responses.

In four experiments we examined the influence of the predictive accuracy of the first element of a serial compound on the rate of autoshaped keypecking. In Experiment 1 a single group of pigeons received trials on two keys. On one key, Stimulus A was followed by either 5-s conditioned stimulus (CS) or a different CS of 20-s duration. On the other key, Stimulus B was also followed by different stimuli, but both were randomly either 5- or 20-s duration. All trials ended with the delivery of food. It was found that responding was faster during A than B. Experiment 2 replicated this finding by using a between-groups design. In Experiments 3 and 4 response rates were faster to A, which was followed on some trials by a 10-s duration CS and on others by a 30-s duration CS, than to B, which was always followed by a 10-s duration CS. These results can be most readily explained by the proposal that autoshaped keypecking consists of two kinds of response—a conditioned response and an orienting response—and the strength of the latter is inversely related to the accuracy with which the immediate consequences of the CS can be predicted. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Selective attention to elements of a morphine stimulus: Idiosyncratic stimulus additivity of incidental cues.

Twelve male Sprague-Dawley rats (Rattus norvegicus) were trained to discriminate between the presence and absence of 5.6 mg/kg morphine sulfate in a lever-press operant task under a fixed-ratio 10 schedule of food delivery. Stimulus cross-generalization profiles were determined for a number of over-the counter (OTC) medications that were hypothesized to engender elements of a compound morphine cue including sedation and lethargy: dextromethorphan, doxylamine, diphenhydramine, pyrilamine, loperamide, and the B vitamins, pyridoxine, thiamine, and cyanocobalamin. On the basis of the individual rat's cross-generalization profile, each rat was retested for stimulus element additivity following the administration of various OTC binary and ternary combinations. For each rat, a test combination was formulated that engendered > 90% morphine-appropriate responding. These test combinations were idiosyncratic, exhibited high test-retest reliability, and followed rules predicted by simple effect additivity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acquired equivalence and distinctiveness of cues: II. Neural manipulations and their implications.

Neural manipulations were used to examine the mechanisms that underlie the acquired equivalence and distinctiveness of cues in rats. Control rats and those with excitotoxic lesions of either the hippocampus (BPC) or entorhinal cortex (EC) acquired the following conditional discrimination: In Contexts A and B, Stimulus X --3- food and Stimulus Y --* no food, and in Contexts C and D, Y - food and X ---> no food. Rats then received many food pellets in A but not in C. After this treatment, control rats showed more magazine activity in B than in D-an acquired equivalence- distinctiveness effect. This effect was also evident in BPC rats but not in EC rats. These results indicate that changes in stimulus distinctiveness are dissociable from the process of conditional leaming. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Combining CSs associated with the same or different USs

In three experiments, hungry rats received appetitive training with four stimuli, A, B, X, and Y. In each Experiment, A and B were paired with one unconditioned stimulus (US; e.g. food pellets) whereas X and Y were paired with a second US (e.g. sucrose). Subsequently, rats responded more vigorously to combinations of stimuli associated with different USs (A-Y & X-B) than to combinations of stimuli associated with the same US (A-B & X-Y; Experiments 1, 2, & 3). This effect was observed when the stimuli were presented simultaneously and during the second elements of serial compounds (Experiments 2 & 3). Moreover, combining CSs associated with different USs resulted in a more marked CR than combining CSs that had each been paired with both US1 and US2 (Experiment 3). These results suggest that the sensory properties of appetitive reinforcers have an important influence on performance.     

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)     

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)     

Effects of d-amphetamine on responding of squirrel monkeys maintained under second-order schedules of food presentation, electric shock presentation or stimulus-shock termination

The effects of d-amphetamine (0.01-5.6 mg/kg i.m.) were studied on lever pressing of squirrel monkeys maintained under various second-order schedules by a visual stimulus (S) that, with separate monkeys, was occasionally paired with the presentation of either food, electric shock or with the termination of a stimulus in the presence of which shocks occurred. Under one condition, the first response after 5 min produced a 3-sec stimulus change and the fourth stimulus change was followed immediately by food delivery, electric shock presentation or by the termination of a stimulus in the presence of which shocks occurred [fixed-ratio (FR); fixed-interval (FI) [FR 4 (FI 5-min:S)]. The effects of d-amphetamine were also studied under the food- and shock-presentation schedules when food or shock occurred only once, at the end of each session, after completion of 53n 3-min fixed-intervals all of which ended with a brief stimulus change [FR 10 (FI 3-min : S)]. Under a third condition, each thirtieth response produced the 3-sec brief stimulus (FR 30 : S) and the first FR 30 completed after 5 min elapsed produced the stimulus followed by food or, with separate monkeys, electric shock [FI 5-min (FR 30:S)]. Low to intermediate doses of d-amphetamine (0.03-0.3 mg/kg) generally increased and higher doses (0.56-5.6 mg/kg) decreased responding under all conditions. The effects of d-amphetamine on responding maintained by brief stimuli under different types of second-order schedules are generally similar, regardless of the type of reinforcing event or particular second-order schedule.     

Stimulus and temporal cues in classical conditioning.

In 2 experiments, separate groups of rats were given stimulus conditioning, temporal conditioning, untreated control and (in Experiment 2) learned irrelevance control procedures followed by a compound with both stimulus and temporal cues. Stimulus conditioning consisted of a random 15-s duration conditioned stimulus (CS) followed by food; temporal conditioning consisted of food–food intervals of fixed 90 s (Experiment 1) or fixed 75?+?random 15 s (Experiment 2). The stimulus group abruptly increased responding after CS onset, and the temporal group gradually increased responding over the food–food interval. When the food–food interval was fixed 90 s, the temporal cue exerted stronger control in the compound, whereas when the food–food interval was fixed 75?+?random 15 s, the stimulus cue exerted stronger control. The strength of conditioning, temporal gradients of responding, and cue competition effects appear to reflect simultaneous timing of multiple intervals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acquired equivalence and distinctivenes of cues: I. Exploring a neural network approach.

Rats were placed in 4 contexts (A, B, C, D) where they received 2 auditory stimuli (X, Y); in A and B presentations of X were paired with food and those of Y were not, and in C and D, Y was paired with food and X was not. Rats then received combinations of contexts that had provided congruent (AB, CD) or incongruent (AD, CB) information about X and Y's relationship to food. Responding was more variable during congruent than incongruent trials (Experiment 1) and was systematically increased and decreased during congruent (relative to incongruent) trials by the presentation of food or no food, respectively (Experiment 2). These results support a connectionist approach to acquired changes in stimulus distinctiveness. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential conditioning of the rabbit's nictitating membrane response to serial compound stimuli.

Conducted 3 experiments with 213 male and female albino rabbits (Orytolagus cuniculus) to determine the time course and contents of conditioned stimulus/stimuli (CS) representations through an examination of differential conditioning of the S"s nictitating membrane response to 2 serial compounds. One compound (A-X+) was always paired with the unconditioned stimulus/stimuli (UCS), and the other (B-X–) was always presented alone. All 3 experiments entailed manipulation of the interstimulus interval between the initial distinctive element of each compound (A and B) and the 2nd shared element (X). The joint results reveal that (1) conditioned response (CR) acquisition to the initial elements depended on the presence of X in the A-X+ compound; (2) differentiation between A and B appeared across interstimulus intervals up to 4,600 msec; and (c) conditional control over responding following A and B appeared at interstimulus intervals of at least 4,600 msec and perhaps up to 12,600 msec. (51 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cine analysis of visual orientation and pursuit by the Mongolian gerbil.

Six adult male gerbils were trained to run quickly to a disk baited with food reward. By using film records, the amplitude and pattern of head turns were measured during pursuit of these targets. With peripheral targets, Ss made a series of successive rapid head turns, each guided by new visual information obtained during a brief pause. When Ss were presented with moving stimuli in the frontal visual field, the orientation indicated that they could predict the pathway of the target so as to complete the turn on target. This practical use of motion-direction discrimination was associated with very short reaction times. A brief stimulus, which did not elicit orientation, facilitated responding to a 2nd presentation of the stimulus within the same part of the visual field. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acquisition of intravenous cocaine self-administration with concurrent access to food in cynomolgus monkeys.

The present study used a concurrent schedule of food and drug delivery in socially housed male cynomolgus monkeys (Macaca fascicularis; N?=?15) to study variables that influence cocaine acquisition. Each monkey was implanted with subcutaneous vascular access ports, and responding was maintained under a concurrent food, saline schedule with the lever associated with each stimulus presentation varied daily. Next, increasing cocaine doses (0.003–0.3 mg/kg/inj) were concurrently available with food for at least 5 consecutive sessions per dose. Under these conditions, an unexpected lever bias emerged in all 15 monkeys. The development of the lever bias could not be predicted on the basis of cocaine dose or total intake and was not related to social rank. These findings suggest that in monkeys, concurrent fixed-ratio schedules of food and cocaine presentation may result in persistent biased responding that overshadows cocaine preference in studies of acquisition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Judging interevent relations: from cause to effect and from effect to cause

Stimulus competition was studied in college students' correlational judgments in a medical decision-making setting. In accord with prior findings, subjects making cause-to-effect (predictive) judgments discounted a stimulus event that was moderately correlated with a target event when rival stimuli were more highly correlated with the effect. However, subjects making effect-to-cause (diagnostic) judgments were not at all disposed to discount a stimulus event which was moderately correlated with a target event when rival stimuli were more highly correlated with the cause. The theoretical implications of these results are considered in connection with associative and mentalistic models of causal attribution.     

Glucocorticoid Receptor Agonist Enhances Pavlovian Appetitive Conditioning but Disrupts Outcome-Specific Associations.

A Pavlovian-instrumental transfer design was used to investigate the impact of the glucocorticoid receptor agonist dexamethasone (dex) on Pavlovian associations involving the sensory and motivational aspects of rewards. Rats were trained with 2 lever responses, Rl and R2, for different rewards, Outcome (O)l and O2. In separate Pavlovian training sessions. Stimulus A was paired with Ol and Stimulus B with O2. Administration of dex after A-O1 sessions enhanced A-O1 associations measured in extinction, relative to B-O2 pairings that were followed by saline. In lever-press transfer tests, presentation of Stimuli A or B enhanced general responding to the same degree. However, outcome-specific transfer (selectively greater enhancement of Rl during A and R2 during B) was abolished for Stimulus A. This suggests that memory enhancement by posttraining dex is simultaneously detrimental to processing of outcome-specific sensory information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Counterconditioning of an overshadowed cue attenuates overshadowing.

In 3 Pavlovian conditioned lick-suppression experiments, rats received overshadowing treatment with a footshock unconditioned stimulus such that Conditioned Stimulus (CS) A overshadowed CS X. Subjects that subsequently received CS X paired with an established signal for saccharin (CS B) exhibited less overshadowing of the X–footshock association than subjects that did not receive the X–B pairings (Experiment 1). Experiment 2 replicated this effect and controlled for some additional alternative accounts of the phenomenon. In Experiment 3, this recovery from overshadowing produced by counterconditioning CS X was attenuated if CS B was massively extinguished prior to counterconditioning. These results are more compatible with models of cue competition that emphasize differences in the expression of associations than those that emphasize differences in associative acquisition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Associative modulation of the orienting response: Distinct effects revealed by hippocampal lesions.

The ability of auditory stimuli to modulate rats' tendency to orient to visual targets was assessed. In Experiment 1, trials where an auditory stimulus (A) signaled one visual array (X) were intermixed with unsignaled presentations of a second array (Y). Comparison of the orienting responses (ORs) to X and Y revealed that A produced a transient (unconditioned) and an emerging (conditioned) disruptive influence on the OR to X. In Experiments 2 and 3, trials where A signaled X were intermixed with others where another auditory stimulus (B) signaled Y. Stimulus A's ability to modulate the OR to X was then assessed by presenting A prior to test arrays containing both X and Y Control rats were more likely to orient to Y than X (Experiments 2 and 3) and rats with excitotoxic lesions of the hippocampus were more likely to orient to X than Y (Experiment 3). These results show that auditory stimuli exert distinct modulatory influences on the OR to visual stimuli with which they are associated. (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)