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PubMed1976

Stimulus generalization: some predictions from a model of Pavlovian conditioning.

Three experiments examined predictions generated by incorporating a common-elements account of stimulus generalization within the Rescorla-Wagner model of conditioning. All experiments employed rats in a conditioned suppression situation. Experiments 1 and 2 found that conditioning of a similar stimulus augmented the excitation controlled by a near-asymptotic target stimulus more than did further conditioning of the target itself. Prior discrimination training between the target and the similar stimulus enlarged this effect, compared with prior discrimination between the target and another dissimilar stimulus. Nonreinforced exposure of the similar stimulus prior to its reinforcement also increased the effect. Experiment 3 examined a related prediction for inhibition. After discrimination training, extinction of the previously reinforced stimulus revealed more inhibition to the previously nonreinforced stimulus when those two stimuli were more similar. These outcomes are consistent with deductions from the present model and encourage further testing of its expansion to the case of stimulus generalization.

Acoustic Stimulation↗
PubMed1975

Stimulus generalization and anxiety in schizophrenic and normal subjects.

Sixty schizophrenics and 60 normal subjects were compared on a test of stimulus generalization. The generalization stimuli were lines differing in length. Both schizophrenics and normals were divided into two groups (30 subjects each) and trained either on a short line or on a long line. In addition to the generalization stimuli, subjects were presented with an irrelevant stimulus (circle). Although there was a significant difference between the generalization gradients of the groups, this difference was limited to generalization stimuli away from the negative training stimulus. The concept of peak shift was invoked to interpret these data. That the groups did not respond to the irrelevant stimulus is inconsistent with interference theory and gives some support to the differentiation between conceptual overinclusion and perceptual overinclusion. The relationship between stimulus generalization and scores on the Manifest Anxiety Scale was inconsistent.

Anxiety↗
PubMed1966

A comparison of different measures of response strength in the study of stimulus generalization.

In Experiment 1, three pigeons were given variable interval training to peck at a light of 550 mmu and then were tested for stimulus generalization in extinction to several different wavelengths. A gradient was obtained for latency of the first response in each test period, for the number of test periods in which responding occurred, and for the measure of response rate. When the response rate gradient was corrected for differences in initial latency and in number of responded trials, the change was minimal, indicating that the major component of response rate as usually measured is rate of responding having once responded. In Experiment 2, three other pigeons were trained to respond to 550 mmu (for variable interval reinforcement) and not to 570 mmu (extinguished). Analysis of generalization gradients dictated the same conclusion as that reported for generalization following single stimulus training.

Animals↗
PubMed1968

The peak shift in stimulus generalization: equivalent effects of errors and noncontingent shock.

Terrace suggested that the peak shift in stimulus generalization occurs because the training stimulus not correlated with reinforcement has become aversive. This hypothesis is plausible in the light of instances where the peak shift is obtained compared with those where it fails to appear. The present experiment attempted to test implications of this hypothesis. Two groups of pigeons learned the same two-stimulus discrimination between colors by different training methods in a free-operant situation. When the discrimination was trained with many errors, a large peak shift was obtained in a subsequent generalization test of wavelength; after discrimination training with few errors, a negligible shift was observed. Half of each group then received noncontingent aversive shock during presentations of the stimulus not correlated with reinforcement in continued discrimination training. After this treatment, the errorless-shock subgroup showed a large peak shift and the error-shock subgroup tended to show a larger shift than before. Nonshocked control groups showed little change in the peak shift. It was concluded that pairing aversive shock with a stimulus not correlated with reinforcement is sufficient to produce or enhance a peak shift. In their effect on the peak shift, aversive shock and large amounts of nonreinforced responding appear to be equivalent.

Analysis of Variance↗
PubMed1975

Latent inhibition and stimulus generalization of the classically conditioned nictitating membrane response in rabbits (Oryctolagus cuniculus) following dorsal hippocampal ablation.

Rabbits received 0 to 450 exposures of a tone conditioned stimulus (CS) prior to classical defensive conditioning of the nicitating membrane response based on an infraorbital eye shock unconditioned stimulus. Tone preexposure resulted in retarded conditioning in normal rabbits. This latent inhibition effect was not present in animals with bilateral dorsal hippocampectomy produced by aspiration. Control animals with bilateral neocortical and callosal aspiration lesions demonstrated a latent inhibition effect similar to that shown by normal nonoperated animals. The failure of CS preexposure to retard conditioning in hippocampal rabbits was not due to differences in threshold of the conditioned response to the CS or to differences in response mechanisms as determined by tests of habituation and dishabituation of the unconditioned response. A subsequent experiment employed combined-cue summation tests to confirm the fact that preexposure did not endow the tone with conditioned as well as latent inhibitiory properties. Finally, tests of stimulus generalization along the auditory frequency dimension indicated flatter relative gradients for hippocampals than for nonoperated controls, with cortical controls in between. These findings were discussed in terms of Douglas' model of hippocampal function.

Acoustic Stimulation↗
PubMed1993

Cocaine-stimulus generalization to two new designer drugs: methcathinone and 4-methylaminorex.

Rats were trained to discriminate 8 mg/kg cocaine from saline vehicle for the purpose of examining the stimulus properties of two novel and structurally related drugs of abuse recently confiscated on the illicit market: (+/-)methcathinone and cis(+/-)4-methylaminorex. The stimulus properties of these controlled substance analogs were compared with those of their parent compounds (+/-)cathinone and aminorex, respectively. All agents resulted in cocaine-stimulus generalization with the following rank order of potency: aminorex (ED50 value = 0.8 microM/kg) > methcathinone (1.9 microM/kg) > cathinone (3.7 microM/kg) > 4-methylaminorex (5.2 microM/kg) > cocaine (7.6 microM/kg).

Animals↗
PubMed1975

"Stimulus generalization" between differentiated visual, auditory, and central stimuli.

Cats were trained to discriminate between two different repetition rates of flicker and of click. Both approach-approach and avoidance-avoidance discriminations were used. After substantial overtraining, transfer of frequency discrimination was initiated to stimulation of the reticular formation using bursts of electrical pulses at the same two repetition rates. Significant levels of discriminated performance were obtained in all cats very quickly, indicating good cross-modal transfer between the peripheral discriminanda and the central stimuli. The literature on stimulus generalization and cross-modal transfer is reviewed and the findings of this experiment are discussed in that context. Certain conditions are defined which, if satisfied, justify the interpretation that stimulus generalization or rapid cross-modal transfer indicate that facilitation of subsequent tasks in a training sequence can be attributed to mediation by a specific neuronal mechanism established by training on a previous task. The present experiment was designed in view of such criteria. The evidence of good cross-modal transfer is interpreted to mean that brain mechanisms storing memories about discriminations between visual or auditory stimuli with different repetition rates can be effectively activated by gross electrical stimuli at the same repetition rates. Conflict trials were then carried out in which flicker or click at either frequency was contradicted by concurrent RF stimuli at the other frequency. As the current level of RF stimuli was parametrically increased, it was found that the central stimuli achieved almost complete control over the behavioral outcome in most cases. Concurrent transfer of training, using a counterbalanced training sequence, was then carried out to stimulation of the visual cortex, lateral geniculate, medial geniculate, and the intralaminar nuclei of the thalamus. In each case, rapid transfer was displayed by at least one animal. Once performance to brain stimulation at a given repition rate was established, little change was observed when the fine structure of the stimulus was altered by changing parameters of the stimulus burst. These findings are interpreted as providing support for a statistical theory of memory, since they constitute evidence that previously learned discriminative behavior can readily be elicited by compelling large ensembles of neurons in various brain regions to discharge with particular temporal patterns. It is difficult to reconcile these results with theories which postulate that learning establishes new synaptic pathways in which discharge must occur for memories to be retrieved.

Animals↗
PubMed1984

Stimulus generalization of conditioned taste aversion in rats.

Relatively little information is available regarding the intradimensional stimulus generalization of conditioned taste aversion (CTA). Experiment 1 employed a between-groups generalization test to examine the extent to which conditioned flavor aversion to one sucrose solution generalized to other concentrations of sucrose in adult rats. Evidence of a gradient of aversion was obtained. Because generalization gradients in other tasks have been found to flatten over a retention interval, Experiment 2 investigated the effects of delayed testing (2, 7, or 21 days) upon the slope of the generalization gradient. The generalization gradient flattened at the intervals, suggesting that subjects forgot the specific attributes of the conditioning concentration and avoided generalized stimuli as if they were the original CS. Experiment 3 used a long delay between taste and toxicosis to degrade the associative contingency and found no evidence that the generalization gradients found in the first two experiments could be explained in terms of enhanced neophobia due to poisoning. These findings provide further evidence (cf. A. W. Logue, 1979, Psychological Bulletin, 86, 276-296; M. Domjan, 1980, in J. S. Rosenblatt, R. A. Hinde, C. Beer, & M. Busnel (Eds.), Advances in the study of behavior, Vol. 11, New York: Academic Press) that CTA shares a number of similarities with other learning processes. Further, they illustrate that stimulus forgetting can be detected in a paradigm considered relatively immune to retention loss.

Animals↗
PubMed1977

Subcutaneous injections of apomorphine, stimulus generalization and conditioning: serious pitfalls for the examiner using apomorphine as a tool.

This report shows that stimulus generalization occurs in rats conditioned by a single injection of apomorphine. The data suggest that apomorphine initially acts as an unconditioned stimulus (UCS) of an unconditioned response (UCR) that, in turn, produces stimuli which become conditioned stimuli (CS) of a conditioned response (CR) having a nature identical to that of the UCR. The study also shows that behaviour elicited by a subcutaneous injection of apomorphine depends on the part of the body selected for administration. The mentioned properties should be taken into account when apomorphine is used as a tool in studies on brain and behaviour.

Animals↗
PubMed1967

Interhemispheric transfer of lever pressing as stimulus generalization of the effects of spreading depression.

Rats trained to lever-press with spreading depression in one cerebral hemisphere showed weak responding when tested with depression shifted to the trained hemisphere. The rats were then divided into two groups: one group (normal) was permitted a single reinforced response with neither hemisphere depressed, the other group (depressed) was permitted a single reinforced response with the trained hemisphere depressed; both groups were then tested with the trained hemisphere depressed. Responding during this second test increased for both groups, but the magnitude of the increase tended to be greater for the depressed than for the normal group. Since memory transfer could not have occurred with the trained hemisphere depressed, the results were taken to indicate that the single reinforced response strengthened stimulus generalization between train-test conditions.

Animals↗
PubMed1969

Stimulus generalization as a function of discrimination learning with and without errors.

After discrimination learning with and without errors, three groups of pigeons were tested for generalization to the angularity (negative stimulus) dimension. For half the subjects from each group, each angle was superimposed on a light of 555-nanometer wavelength, the positive stimulus during training; for the other half, the angles were on a black background. When tested to the angularity alone, the group which had made errors (pecked at the negative stimulus) during discrimination training showed a typical incremental (inverted) gradient of responding to the negative stimulus dimension. The control group and the one learning the discrimination without errors showed no differential control by the negative stimulus dimension. When each angle was superimposed on the positive stimulus during testing, a decremental gradient with maximum response strength to the negative stimulus was evidenced by the group learning with and the one group learning without errors.

Animals↗
PubMed1993

The effects of "do", "don't" and "wait" requests training on compliance behavior and stimulus generalization.

Previous implementation of compliance training has involved the use of aversive behaviors, as consequents, which bear neither a topographical nor a functional relationship to the behaviors under training. The present study explores compliance training in which training behaviors, used as consequents, are both topographically and functionally identical to the target behaviors. This study extends the compliance literature through: (1) an analysis of the effects of compliance training in long-term institutionalized mentally retarded adults, (2) the investigation of a third response class "Wait" requests, and (3) an assessment of stimulus generalization. Findings discussed include (a) the treatment effects of compliance training, across response classes, within treatment sessions; (b) the spontaneous generalization of treatment effects outside the treatment conditions; (c) the collateral effects of training upon aggressive outbursts; (d) the heightened potential for the utilization of these techniques in long-term care institutions.

Adult↗