Effects of stimulus similarity in discrimination training upon wavelength generalization in pigeons.

Administered variable-interval training to 30 naive adult pigeons to peck a 550-nm light and then tested them for wavelength generalization. Ss were later assigned to 1 of 3 groups, matched for both relative generalization slope and response rate. One group then received successive discrimination training between the 555-nm stimulus (S+) and a vertical white line on a 555-nm background (S-); another group experienced the same S+ but a vertical white line on a black background as S-. A 3rd group received a comparable amount of single stimulus training with the 555-nm value. On a 2nd wavelength generalization test, the 1st group yielded greater sharpening of generalization than the 2nd group, whereas the 3rd group showed no change from Test 1. Results indicate that the sharpening of generalization gradients by discrimination training was directly related to the similarity of the discrimination training stimuli. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A model for stimulus generalization in Pavlovian conditioning.

Presents a review of experiments that demonstrate the effects of generalization decrement in Pavlovian conditioning and argues that an adequate theoretical explanation for them is currently not available. A theoretical account for the processes of generalization and generalization decrement in Pavlovian conditioning is developed. This model assumes that animals represent their environment by a stimulus array in a buffer and that this array in its entirety constitutes the conditioned stimulus/stimuli (CS). Generalization occurs when some stimuli represented in the array on a test trial are the same as some of those represented in the array during training; the magnitude of generalization is determined by the proportion of the array occupied by these common stimuli during training compared with the proportion of the array they occupy during testing. It is proposed that this model can explain all the results that were difficult for its predecessors to account for. (52 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Schizophrenic patterns of arousal and stimulus barrier functioning.

Investigated the psychophysiological arousal and psychological stimulus barrier functioning in 20 male chronically hospitalized schizophrenics, 20 male outpatient schizophrenics with minimal institutionalization, and 20 male controls. Each S completed the Beck Depression Inventory (Short Form), the Structured Clinical Interview, and the Taylor Manifest Anxiety Scale. Also, each S was administered a stimulus barrier assessment interview, and skin conductance characteristics were measured in response to a standardized sequence of 15 1,000-Hz, 75-db tones. After 6 wks, the procedure was repeated. All schizophrenics exhibited either of 2 abnormal patterns of arousal that were never shown by the normal controls. Overresponders were slow to habituate and exhibited a high number of orienting responses, a high baseline skin conductance level, and a high incidence of spontaneous fluctuations. Underresponders exhibited low baseline skin conductance levels, few spontaneous fluctuations, and either an absence of orienting activity or only an isolated initial orienting response. The stimulus barrier ratings were highly correlated with these psychophysiological patterns. Certain schizophrenics alternated between these response patterns. Change status and response pattern were related to a number of psychological variables. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Autonomic functioning in process and reactive schizophrenia.

Compared the autonomic functioning of male process schizophrenics, reactive schizophrenics, and normal ss (n = 30) under rest and arousal conditions. Ss were exposed to 6 arousal conditions: (a) white noise, (b) electric shock, (c) paired associate learning, (d) word activity test, (e) finger dexterity task, and (f) pursuit rotor task. Rest periods preceded each arousal condition. Heart rate, skin resistance, respiration rate, diastolic and systolic blood pressures were recorded under all 6 conditions. Results show that under stress the levels of physiological functioning for normal ss and reactive schizophrenics were similar on skin resistance and blood pressure, with process schizophrenics showing a higher level of arousal on skin resistance and a lower level on blood pressure. Reactive schizophrenics had the fastest heart rate, with process schizophrenics next, and normals the lowest. Respiration did not reliably differentiate among the groups. Reactive schizophrenics and normals generally showed greater increments to the arousal conditions (compared with prestress base lines) than the process schizophrenics in all measures except heart rate and skin resistance. In those 2 measures, reactive and process schizophrenics were similar in their reactions to the stress conditons, and both groups showed less reactivity in general than normals. (french summary) (31 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Verbal paired-associates learning in chronic schizophrenics as a function of positive and negative evaluation.

Seventy-two chronic schizophrenics (36 regressed and 36 partially remitted) and 36 normals were given paired associates of 2 levels of association strength and 2 levels of intralist response competition to learn under positive, negative, and nonevaluation conditions. Regressed schizophrenics showed maximum decrement on low-association word pairs following positive evaluation. This was especially true for those Ss with low self-esteem. These findings suggest that heightened arousal resulting from dissonance between a negative self-image and positive evaluation of performance can lead to behavioral decrement in a difficult task requiring novel associations, such decrement being congruent with the Hull-Spence behavior theory and the Yerkes-Dodson hypothesis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A prediction of patterns of schizophrenic error resulting from semantic generalization.

Conducted a study with 2 groups of 26 male schizophrenics and normal psychiatric aides (mean age = 45 yr) to test predictions derived from a theory of disordered thought by L. J. Chapman, J. P. Chapman, and G. A. Miller (see PA, Vol. 39:10059) concerning the conditions under which schizophrenic Ss exhibit excessive generalization errors. The theory assumes that both the schizophrenic and normal are biased toward responding to words in terms of the words' strongest aspects of meaning, but that schizophrenics are more strongly biased toward this than are normals. Ss were instructed to indicate by pressing buttons marked "yes" and "no" whether or not test words presented in serial fashion on a memory drum had appeared on a previous training list. "Yes" responses to test words not appearing on a previous training list were the measures of generalization errors. The predictions were supported by the finding that schizophrenics made significantly more errors to words on the test list that shared strong meaning responses (p     

The effects of social and nonsocial censure on stimulus generalization in neurotics and schizophrenics.

36 schizophrenic and 36 neurotic depressive Ss were given a visual-spatial generalization task under either social or nonsocial (impersonal) censure conditions. The following hypotheses derived from previous investigations were tested: (1) schizophrenics would show higher gradients of generalization than neurotic depressives, and (2) generalization gradients would be higher under conditions of social as opposed to nonsocial censure, especially in schizophrenics. The data supported Hypothesis 1 but not Hypothesis 2. There was no evidence for differential responding between these 2 groups with respect to either stimulus generalization or response to censure. It was suggested that hypotheses concerning the schizophrenic's performance in these 2 situations have been biased and oversimplified by use of normal, rather than patient, control groups in previous investigations. (22 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus generalization among schizophrenics and normal subjects.

Compared schizophrenic and normal groups on a stimulus generalization (SG) task and attempted to explore whether differences in SG among schizophrenics were related to the type of reinforcement applied during acquisition or to diagnostic subtype. 48 chronic poor premorbid schizophrenics and 48 normal controls reached criterion on a size discrimination task under either praise or censure conditions and then were administered an SG task. Schizophrenics showed significantly greater SG than normals, but no differences were found between the praised and censured groups or between paranoid and nonparanoid schizophrenics. (19 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Memory retrieval deficits based upon altered contextual cues: A paradox.

It has long been recognized that memory retrieval depends on the similarity of the stimulus context at testing to the context present at encoding. This contextual-cues model appears to draw support from a variety of studies in animal and human research indicating that performance is disrupted by manipulations that reduce the correspondence in background stimuli between acquisition and testing. Although this approach has much in common with a stimulus generalization decrement interpretation of performance change, little attention has been paid to data from stimulus control research showing that generalization gradients typically flatten over time. A literature review indicates that loss of stimulus control with delayed testing occurs for background contexts as well as for conditioned or discriminative stimuli and supports the interpretation that stimulus attributes are forgotten. These findings pose a paradox: The functionally increased interchangeability of stimuli after a retention interval makes it unlikely that disruption of memory can be attributed to subtle shifts in context under the nominally identical conditions of a retention test. (82 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus generalization and overinclusion in normal and schizophrenic subjects.

Compared 38 male and 12 female schizophrenics and a matched group of normals on a test of stimulus generalization, Epstein's Inclusion Test, and the Vocabulary subtest of the WAIS. Schizophrenics generalized significantly more than normal Ss (p     

Psychophysiological correlates of responsiveness in schizophrenia.

Measured responsiveness under stress through music preferences for 11 male and 9 female schizophrenics receiving no antipsychotic medication. These Ss were compared with a control group of 7 male and 13 female hospital staff or volunteers. Results indicate that higher schizophrenic responsiveness was related to lower skin conductance, fewer body movements, greater diastolic blood pressure decrease, better word recall, and shorter periods of institutionalization. Normal controls did not differ significantly in music preferences but were lower in all physiological measures. The finding that sweat gland activity, muscle tension, and diastolic blood pressure changes were related to stress in these acute schizophrenics paralleled the findings of A. F. Ax, et al (1969) with chronic schizophrenics. The interpretation that responsiveness is related to ability to cope with stress in schizophrenia is supported by results of the current study. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus control of avoidance behavior in rats following differential or nondifferential Pavlovian training along dimensions of the conditioned stimulus.

Assigned 36 male albino Holtzman rats, following 2-way avoidance training with an auditory CS, to 1 of 6 Pavlovian manipulations: discrimination or equivalence training along frequency or intensity dimensions, nominal single stimulus training, or unsignalled shocks only. Subsequently, Ss received separate generalization tests when frequency and/or intensity were varied. Intradimensional discrimination training tended to steepen generalization gradient and resulted in a peak shift away from the negative CS (safety signal) within the frequency continuum. Pseudodiscrimination equivalence training typically reduced stimulus control, even when training and test stimuli were not along the same dimension. These modifications of avoidance generalization gradients through interpolated noncontingent training provide additional evidence of the transfer of Pavlovian control to instrumental behavior. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Task specificity in nonspecific transfer and in extradimensional stimulus generalization in pigeons.

Determined whether discrimination training per se is sufficient to produce positive nonspecific transfer and whether it sharpens extradimensional stimulus-generalization gradients, using domestic pigeons. In Exp I, 8 groups of Ss received true-discrimination (TD) or pseudodiscrimination training between 2 line orientations in either (a) a successive-conditional (SC) discrimination prior to transfer to a true SC or (b) a go/no go (GN) discrimination between 2 colors. Discriminative performance in transfer was facilitated only when the original and transfer discriminations were of the same type. Exp II showed that positive nonspecific transfer was primarily mediated by the transfer of task-specific learning rather than by the transfer of attentiveness. In Exp III, 4 groups were trained as in Stage 1 of Exps I and II and given single-stimulus training with a chromatic stimulus, followed by a wavelength stimulus generalization test. Only TD-GN discrimination training produced sharp gradients, an effect leading to the conclusion that GN discrimination training and stimulus generalization are closely related by task requirements rather than by attention. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The differential effect of induced muscular tension (drive) on discrimination in schizophrenics and normals.

In a discrimination task where the performance of schizophrenics and normals did not differ, an increase in muscular tension led to greater decrement in schizophrenics than in normals. The difference in decrements was interpreted as being due to the activating or energizing effects of increased drive. The results were compatible with an account utilizing a response strength ceiling, with schizophrenics considered as having greater reactivity to drive conditions or lower response strength ceilings than normals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Relationships of intermittent noise, intersignal interval, and skin conductance to vigilance behavior.

Army enlisted men individually monitored a CRT screen for 3 hr. in isolation. 1 of 3 signal schedules dittering in degree of intersignal interval (ISI) variability was paired with presence or absence of intermittent noise to provide 6 monitoring conditions. 6 Ss performed under each condition. Reaction time to signals and skin conductance were recorded during the vigil. Results indicated that (a) noise impaired performance when the schedule with minimum ISI was monitored. (b) detection time was inversely related to length of ISI for schedules with minimum and intermediate degrees of ISI variability, (c) conductance was negatively correlated with reaction time for Ss exhibiting an extreme decrement under the schedule with maximum degree of ISI variability. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Changes in responses of medial pontomedullary reticular neurons during repetitive cutaneous, vestibular, cortical, and tectal stimulation

1. In cats anesthetized with chloralose, responses of medial pontomedullary reticular neurons to stimulation of the body surface, vestibular nerves, superior colliculi, pericruciate cortices, cerebral peduncles, and spinal cord were studied at different stimulus rates. Raising the rate from 1/10 s to between 1/4 s and 2/s caused a significant decrement or increment in the response of most neurons tested. Response decrement typically began near the beginning of the higher frequency stimulus sequence and increased throughout the sequence. Response increment usually began somewhat later, rose to a peak, and then declined. Recovery from response decrement or increment usually occurred within 30-60 s at a 1/10 s stimulus rate.2. Measurements of response latency and of changes occurring in the initial and longer latency portions of responses indicated that all components of a response typically decreased or increased in parallel. Background spontaneous activity did not change during response decrements, but sometimes increased during response increment.3. Where changes could be detected, response decrement usually developed more rapidly when a sequence of repetitive stimulation was repeated.4. Response decrement was most pronounced at the highest stimulation rates and lowest stimulus intensities. Response increment was usually maximal at a stimulus rate of 1/s: at lower rates less increment occurred; at higher rates responses began to exhibit decrement.5. Response changes varied with the type of stimulus applied. Response decrements predominated when the body surface, vestibular nerves, or ipsilateral superior colliculus were stimulated. Approximately equal amounts of response increment and decrement were produced by repetitive stimulation of the cerebral peduncles and contralateral superior colliculus. Stimulation of the surface of the pericruciate cortex or of the spinal cord usually produced a long-lasting response increment.6. Generalization of response decrement and increment was observed in cases where trains of stimuli at a rate of 2/s applied to one point produced changes in the response to stimulation of another point which was tested once per 10 s and where single-shock stimulation of the first point was without effect on the test response. Generalization of response decrement occurred most often when two nearby points were stimulated. Generalization of response increment appeared to spread widely between distant cutaneous points and stimuli of different kinds.7. The response decrement and increment observed in medial pontomedullary reticular neurons displayed most of the parametric features of behavioral habituation and sensitization (8, 33) and therefore appear to represent neural analogs of these latter phenomena. The properties of response decrement suggest that it may occur to a large extent within afferent pathways leading to medial reticular neurons...     

Autonomic reactivity to sensory stimulation in psychopathic, neurotic, and normal juvenile delinquents.

To test the hypothesis that lowered reactivity and/or more rapid adaptation to sensory inputs is a primary characteristic in psychopaths, 19 psychopathic, 21 neurotic, and 26 normal juvenile delinquents were identified by a behavior checklist and were presented with 21 successive tone stimuli while skin conductance and heart rate (HR) were being monitored. Results indicate that psychopaths gave significantly lower GSRs to the initial stimulus and lower, though not significantly lower, HR changes and prestimulus to poststimulus basal skin conductance increases. Skin conductance levels during rest and stimulation periods were not significantly different. It is concluded that the psychopathic autonomic characteristic resides in lower initial reactivity and not in more rapid adaptation, at least in response to a simple auditory stimulus. (18 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

One-Trial Learning and Superior Resistance to Extinction of Autonomic Responses Conditioned to Potentially Phobic Stimuli.

Human subjects were exposed to pictures of potentially phobic (snakes) and supposedly neutral (houses) objects as conditioned stimuli (CSs) in a Pavlovian conditioning experiment with shock as unconditioned stimulus (US), and skin conductance and finger pulse volume as dependent variables. The skin conductance responses conditioned to phobic stimuli were acquired after one CS-US pairing, and showed practically no extinction, whereas the responses to neutral stimuli showed very little resistance to extinction after both 1 and 5 reinforcements. The superior resistance to extinction of the phobic condition was interpreted to be a specific associative effect. In general, the skin conductance acquisition data showed tendencies similar to those during extinction. For finger pulse volume responses, however, there were very weak conditioning effects, and no effect of stimulus. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Physiological effects of relaxation training and hypnotic suggestion.

Evaluated the comparative effects of hypnotic suggestion and brief relaxation training with regard to reduction of subjective tension and distress(anxiety differential) and physiological arousal (heart rate, respiratory rate, tonic muscle tension, skin conductance). 3 groups (N = 20 each) of undergraduate females participated individually for 2 sessions, 1 wk. apart, receiving: (1) abbreviated progressive relaxation training as used in systematic desensitization therapy; (2) a hypnotic induction emphasizing direct suggestions of relaxation, heaviness, warmth, drowsiness, and sleep; or (3) a self-relaxation control procedure, included to evaluate the effects of merely resting quietly for an equal period of time with instructions to relax. Both relaxation training and hypnotic suggestion produced significantly greater effects than controls, and relaxation training resulted in significantly greater effects than hypnotic suggestion. The superiority of relaxation training was most pronounced in response systems not under direct voluntary control. (37 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Associative interference in the verbal learning performance of schizophrenics and normals.

Groups of recently admitted VA schizophrenics and VA nonpsychiatric patients (17 per group) were given 1 of 2 paired-associate lists. The experimental list consisted of pairs in which each stimulus had a minimal assocative connection with its response but was highly associated with another response on the list, as judged by word association norms. Comparisons of performance on this list with that on a parallel control list indicated that the presence of the cross-associates resulted in significant performance decrement (p