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PubMed1962

Instructions and stimulus categorizing in a measure of stimulus generalization.

In Experiment I, three groups of 20 Ss each were exposed to a light of 550 mmu (yellowish-green) for 60 sec and then viewed a random sequence of wavelengths with instructions to respond only to the original color. The instructions given the three groups were worded differently in an attempt to vary the strength of a set-to-discriminate assumed to be created by this procedure. The three groups produced similar gradients, each with a peak of responding at 540 mmu, in agreement with Kalish's (1958) published gradient for the 550 mmu standard stimulus value. It was suggested that the nature of the task is such that a strong discriminatory set is produced regardless of the wording of the instructions.A temporal analysis of the gradient as it develops during the testing revealed that initially the peak of responding occurs at 550 mmu; but as testing progresses, it shifts gradually in the direction of the shorter wavelengths (purer greens). Experiment II was performed to test the generality of the phenomenon of regression to the primary color. Two groups of 20 Ss each were tested for generalization following exposure to 510 mmu (bluish-green) and 525 mmu (pure green), respectively. We predicted that the 510 mmu gradient would reveal a progressive shift toward the longer wavelengths (purer greens), whereas the 525 mmu gradient would show no tendency to shift. The results were strikingly in accord with these predictions. We concluded that although a physiological process could not be ruled out, the verbal labeling of the standard stimulus value may well be responsible for the regression of the gradient toward the primary color.

Color↗
PubMed1973

Stimulus generalization and delay of reinforcement during one component of a multiple schedule.

The key pecking of six pigeons was reinforced according to a variable-interval 1-min schedule during each of two successively presented stimuli. When the key was illuminated by a black line on a white background, reinforcement was delayed for 10 sec. When the key was illuminated by a plain white light, reinforcement was not delayed. All subjects responded at a lower rate during the presentation of the black line. A subsequent generalization test along the line-orientation dimension produced a U-shaped gradient, with the nadir located at or near the training stimulus, for each subject. These gradients suggested that the lower rate of response during the stimulus associated with delayed reinforcement may have been due to an inhibition of responding.

Journal Article↗
PubMed1982

Discriminative stimulus effects of pentobarbital in rhesus monkeys: tests of stimulus generalization and duration of action.

Rhesus monkeys were trained to emit 20 or 30 consecutive responses on one lever following an IM injection of pentobarbital (10 or 18 mg/kg) and the same number of consecutive responses on another lever following an injection of saline. The required number of correct consecutive responses in both cases resulted in food delivery. When responding was reliably under the control of the presession injection, the ability of a variety of other compounds to produce pentobarbital-appropriate responding was examined. Diazepam, clobazam, methohexital, pentobarbital, and phenobarbital, given 10 or 20 min before the session, produced dose-related pentobarbital-appropriate responding in each monkey. Ethylketazocine and dextromethorphan produced responding primarily on the saline-appropriate lever, whereas codeine, cyclazocine, dextrorphan, and ketamine resulted in responding that was, on the average, intermediate between that appropriate for pentobarbital and that appropriate for saline. When tested at various times after their injection, methohexital (3.2 mg/kg) and pentobarbital (10 mg/kg) produced pentobarbital-appropriate responding within 10 min. Barbital (56 mg/kg) resulted in pentobarbital-appropriate responding only if at least 1 h intervened between the injection and the experimental session. The discriminative effects of methohexital, pentobarbital, and barbital lasted approximately 20-60, 120-240, and 480-720 min, respectively. The time-course of the discriminative stimulus effects of barbiturates in the rhesus monkey appears to parallel closely other pharmacological actions of these compounds.

Animals↗
PubMed2002

Stimulus generalization by fenfluramine in a quipazine-ketanserin drug discrimination is not dependent on indirect serotonin release.

The purpose of this study was to determine if animals trained to discriminate a serotonin2A (5-HT2A) receptor agonist from a 5-HT2A receptor antagonist would also be sensitive to alterations in serotonin neurotransmission brought about by 5-HT reuptake inhibitors and releasers. Previous work from our laboratory has shown that the quipazine-ketanserin discrimination is mediated solely by the 5-HT2A receptor, thus providing a behavioral continuum of 5-HT2A receptor function. Rats were trained to discriminate quipazine (0.35 mg/kg) from ketanserin (1.0 mg/kg) on a variable interval-30 schedule of reinforcement. Following acquisition, substitution tests were conducted with the training drug, quipazine, and agents that have been shown to alter the synaptic levels of 5-HT, including fenfluramine, norfenfluramine, 5-methoxy-6-methyl-2-aminoindan (MMAI) and fluoxetine. All compounds substituted, except fluoxetine. Antagonist tests with mianserin and MDL 100,907 indicated that fenfluramine's and MMAI's substitution for quipazine was mediated by the 5-HT2A receptor. Animals were pretreated with PCPA to determine whether 5-HT release or direct agonism mediated the discriminative stimulus effects of fenfluramine and MMAI. PCPA blocked the substitution of MMAI but not of fenfluramine for quipazine. Analysis of 3H-IP formation in cells showed that norfenfluramine dose-dependently stimulated phosphoinositide hydrolysis to levels similar to that of serotonin and quipazine. These results indicate that fenfluramine's substitution for quipazine in rats trained on a quipazine-ketanserin discrimination are due to direct agonism at the 5-HT2A receptor likely mediated by norfenfluramine, an active metabolite.

Animals↗
PubMed1999

Stimulus generalization, context change, and forgetting.

Forgetting is often attributed to retrieval failure caused by background contextual cues changing over time. However, generalization between stimuli may increase over time and make them increasingly interchangeable. If this effect occurs with contextual cues, it might cancel any effect of a changing context. The authors review the evidence and suggest a resolution of this paradox. Although generalization gradients can change over time, the effect is not always strong. Increased responding to nontarget stimuli is not often shown, and few studies have demonstrated such changes with contextual cues in a way that rules out other interpretations. Even this example of forgetting may be caused by retrieval failure. The physical contexts manipulated in learning and memory experiments themselves occur within a superordinate temporal context and can thus be forgotten with no inherent challenge to a context-change account of forgetting.

Animals↗
PubMed1993

Incomplete stimulus generalization from a mixture of d-amphetamine and morphine to different doses of the component drugs.

Pigeons were trained to discriminate a mixture of 1.8mg/kg morphine plus 1.0mg/kg d-amphetamine from saline, and then tested for generalization to various doses of d-amphetamine and morphine, alone and in combination. The birds discriminated the drug mixture from saline with more than 90% responding on the drug key. The training doses of morphine (1.8mg/kg) and d-amphetamine (1.0mg/kg), as well as lower doses of these drugs, did not reliably generate responding on the drug key when given in combination with saline. Higher doses of morphine and d-amphetamine did generate responding on the drug key, but not as reliably as the training dose combination. Combination of the training dose of morphine with doses of d-amphetamine higher than those in the training dose combination resulted in somewhat less responding on the drug key than that seen with the training dose combination in one bird. These data and those from other experiments where animals were trained to discriminate drug mixtures can be characterized as the net effect of stimuli produced by the component drugs and interactions between the component drugs.

Journal Article↗
PubMed1979

Sharing in preschool children: Facilitation, stimulus generalization, response generalization, and maintenance.

Three approaches to facilitating verbal and physical sharing and of the generalizability and durability of the behaviors that were trained were investigated. During a free play period, groups of preschool children were taught to share verbally, to share physically, or to share verbally and physically; another group was not trained. Immediately following free play, the children were observed in a different setting. Follow-up was conducted 4 weeks after training ended. Physical sharing that was durable and generalizable resulted only when children were taught to share verbally. Increases in physical sharing produced by training children to share only physically were not durable and did not generalize. Training both verbal and physical sharing produced results with a magnitude slightly greater than teaching just verbal sharing. Despite a lack of special programming, some of the treatment effects generalized to another setting and were maintained during the Follow-up. There was response generalization of the effects of training verbal sharing to physical sharing but not vice versa. Problems with the concept of response class, a methodological suggestion for studying response generalization, and possibilities concerning why generalization and maintenance occurred without specific programming are discussed.

Journal Article↗
PubMed1969

Stimulus generalization as a function of the delay between training and testing procedures: a reevaluation.

Three groups of 12 pigeons each were trained to discriminate between lights of 550 mmu (S(D)), correlated with 1-min variable-interval reinforcement and 570 mmu (S(Delta)), correlated with extinction. Group A was tested for wavelength generalization in extinction 1 min after meeting the discrimination criterion; Group B was tested 24 hr later; Group C was tested 24 hr later after a 3-min (reinforced) warm-up with the S(D). The post-discrimination gradient of Group B was significantly flatter and showed significantly greater area shift than that of Groups A and C. The gradient of Group C was similar to that of Group A, indicating that the warm-up eliminated the effect of the delay period.

Journal Article↗
PubMed1973

Maintaining responding during stimulus generalization testing in extinction.

Resistance to extinction and generalization gradients were studied following training with a long-adjusting-interval schedule. One large reinforcer occurred at the end of each daily training session. Sessions varied in length from 20 sec to 42.66 min, but were usually the latter. Repeated generalization tests were subsequently conducted for these subjects and subjects trained with a more conventional short-random-interval schedule. The long-adjusting-interval schedule produced generalization gradients that were not qualitatively different from those produced by the conventional procedure. However, the advantages of the long-adjusting-interval schedule are: (1) greater resistance to extinction both within and across generalization tests and (2) more stable gradient slopes within and across tests.

Journal Article↗
PubMed1979

Stimulus generalization along a dimension based on a verbal concept.

The present study examined generalization along a dimension based on a verbal concept of occupational status. The status dimension was scaled by students who placed occupation names into five status categories, Category 1 representing highest status and Category 5 the lowest status. In two experiments, key presses by students were occasionally reinforced when a slide showing an occupation name from Status Category 3 was present. For half the subjects, key presses were not reinforced during a name from Category 1; for the other half, presses were not reinforced during a name from Category 5. Occupation names from all status categories were later singly presented. In this generalization test, subjects typically divided the dimension into two parts, responding alike to all names within each part. The results suggest that generalization along a dimension in humans is mediated by a subject's verbal classifications of stimuli.

Journal Article↗
PubMed2003

Stimulus generalization of behavioral history.

Undergraduates responded under a variable-ratio 30 schedule in the presence of a 25-mm long line and on a differential-reinforcement-of-low-rate 6-s schedule when a 13-mm long line was present. Following this, a line-length continuum generalization test was administered under a fixed-interval 6-s schedule (Experiment 1) or extinction (Experiment 2). In both experiments, obtained generalization gradients conformed to typical postdiscrimination gradients. Responses were frequent under stimuli physically similar to the 25-mm line and infrequent under stimuli physically similar to the 13-mm line. The generalization gradients were generally asymmetric with peak response rates occurring at line lengths greater than 25 mm.

Adult↗
PubMed1992

Stimulus generalization from cocaine to analogs with high in vitro affinity for dopamine uptake sites.

Previous research has shown that phenyltropane derivatives of cocaine are very potent ligands for dopamine transporters in in vitro binding and uptake, and in in vivo binding assays. In the present study, these analogs were tested for their ability to substitute for cocaine in rats trained to discriminate cocaine from saline. Results indicate that these compounds are from 6-13 times more potent than cocaine in producing cocaine-appropriate responding. This provides further evidence in support of the importance of dopamine uptake inhibition for the behavioral effects of cocaine, and suggests utility of these compounds in understanding cocaine abuse.

Journal Article↗