Ethnocentrism and stimulus generalization.

"This study is an attempt to demonstrate that ethnocentrism is related to an 'over-generalization process' as has been postulated by various authors. The performance of a group of student nurses on a stimulus-generalization task was correlated with their scores on the California E scale yielding a significant μ = .44. Some possible theoretical implications are discussed and mention is made of further research which is in progress." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ethnocentrism and stimulus generalization: A replication and further study.

Data were previously reported giving "support to the hypothesis that ethnocentrism represents an 'overgeneralization phenomena.' " In a study of 60 female student nurses, aged 18 through 22, who were given the MMPI, the CVS Intelligence Scale, and the California Ethnocentrism Scale as well as two stimulus generalization (SG) tasks, significant correlations were not found between E Scale scores and total error scores on each stimulus generalization task. Previous positive finding "must therefore probably be attributed to chance. While present results do not preclude the possibility that ethnocentrism is related to overgeneralization in thinking, the functions involved in performance on the tasks investigated do not appear to be on the same psychological continuum." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mediated stimulus generalization and words connoting mood.

90 words connoting mood were scaled for degree of elation or depression. 70 of the words were selected as the stimuli in a study of mediated stimulus generalization. For 2 groups of men and 2 groups of women the training stimuli were extremely elated words, and for 2 different groups of men and women, the training stimuli were extremely depressed words. In each of the 2 groups for both sexes, one group was reinforced for whispering and the other for shouting. After training all groups received a generalization series consisting of words varying in degree of elation or depression. Ss trained to shout elated and whisper depressed stimuli produced steeper mediated stimulus generalization gradients than Ss trained to whisper elated and shout depressed stimuli. The Shout-Depressed group produced partially inverted gradients. The results were consistent with an asymmetrical Matching Principle: with connotative stimuli there is a strong tendency to make an intense response to an intense stimulus and a moderate tendency to make a weak response to a weak stimulus. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Relationship of manifest anxiety to stimulus generalization.

This study examined the relationship between anxiety and stimulus generalization in psychiatric patients. The results suggested that "there is no relationship between MAS [Manifest Anxiety Scale] and stimulus generalization in psychiatric Ss. Moreover, situational factors do not seem important in limiting the generality of such an interpretation. Since the relationships between anxiety and learning phenomena are generally well recognized, these negative results presumably reflect the inadequacy of the Taylor scale as a relevant index of anxiety levels in psychiatric subjects." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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)     

Effects of varying stimulus size on object recognition in pigeons.

The authors investigated the pigeon's ability to generalize object discrimination performance to smaller and larger versions of trained objects. In Experiment 1, they taught pigeons with line drawings of multipart objects and later tested the birds with both larger and smaller drawings. The pigeons exhibited significant generalization to new sizes, although they did show systematic performance decrements as the new size deviated from the original. In Experiment 2, the authors tested both linear and exponential size changes of computer-rendered basic shapes to determine which size transformation produced equivalent performance for size increases and decreases. Performance was more consistent with logarithmic than with linear scaling of size. This finding was supported in Experiment 3. Overall, the experiments suggest that the pigeon encodes size as a feature of objects and that the representation of size is most likely logarithmic. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contextual modulation of stimulus generalization in rats.

One connectionist analysis of the acquired equivalence/distinctiveness of cues assumes that when similar compounds (e.g., AX and BX) are paired with the same outcome (e.g., food, +; or no food, ?), their components come to activate the same configural unit (ABX). When these compounds are paired with different outcomes, their components will come to address different units. Here, rats received appetitive training with eight compounds (e.g., AX+, BX+, CX?, DX?, AY+, BY?, CY?, DY+) that should generate the following configural units: ABX, CDX, ADY, and BCY. In Experiment 1, rats then received aversive conditioning to A, which should activate and revalue representations ABX and ADY. Subsequently, compounds that provided dual activation (i.e., BX and DY) of one of the revalued configural units (ABX and ADY) were shown to elicit greater fear than those compounds that provided a single source of activation to each unit (i.e., DX and BY). Experiment 2 confirmed and extended these findings. These results provide support for the connectionist analysis outlined above and are consistent with the application of this approach to the acquired equivalence/distinctiveness of cues. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Invariance of perceptual spaces and perceptual separability of stimulus dimensions

This article reports an extension of a paradigm for studying processing of perceptual dimensions. The paradigm is the complete identification task with a feature-complete factorial design (FCFD) of stimuli providing data for multidimensional signal detection analyses. The extension uses blocks of trials with subsets of the FCFD stimulus set, allowing estimation of various d's for inferring perceptual separability (PS) of dimensions and for disambiguating stimulus configurations when PS fails. Results of 4 experiments found the following: PS of arc curvature and line orientation in a discrimination task (Experiment 1), increasing PS failure in detection of horizontal and vertical lines (Experiment 2a), 45 degrees and 135 degrees (Experiment 2b), and 50 degrees and 60 degrees oblique lines (Experiment 2c). In each experiment, corresponding d's remained equivalent across blocks with different stimulus subsets.     

Differences in gradients of stimulus generalization as a function of psychiatric disorder.

On the basis of the "Dollard and Miller… principle that 'increasing the strength of the drive raises the entire gradient of generalization… ' [and that]… such emotional states as fear, anxiety, and guilt can acquire the properties of a drive… . The present research investigates the hypotheses that there are differences in the shape of the SG gradients among psychotic, neurotic, and control Ss… . The results indicate that (a) the psychotics showed more generalization than the nonpsychotics; (b) the neurotics showed less… than the psychotics, but did not differ from the controls; and (c) the brain-damaged Ss showed more generalization than the nonpsychotics, but they did not differ from the psychotics." (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)     

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)     

Distortions in the gradient of stimulus generalization related to cortical brain damage and schizophrenia.

Measurement of the gradient of stimulus generalization (GSG) of 60 schizophrenics (S group), 60 medical control patients (C group), and 60 patients with cortical brain damage (O group), by means of an apparatus consisting of a panel of 11 lamps placed in an arc around the subject, showed: "(1) The GSG for both the C and S groups is considerably more elevated than that of the control group (O group). (2) The differences between the S and C groups, while in the main in the predicted direction, are not conclusive. (3) Damage to the cortex of the dominant hemisphere results in considerably more diminution of the elevation of the GSG than damage to the cortex of the non-dominant hemisphere. (4) The number of EST's received by patients in the S group was found to vary inversely with the degree of SG responsivity; but in view of the limitations of the data, no conclusions were drawn." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Exemplar and prototype models revisited: Response strategies, selective attention, and stimulus generalization.

J. D. Smith and colleagues (J. P. Minda & J. D. Smith, 2001; J. D. Smith & J. P. Minda, 1998, 2000; J. D. Smith, M. J. Murray, & J. P. Minda, 1997) presented evidence that they claimed challenged the predictions of exemplar models and that supported prototype models. In the authors' view, this evidence confounded the issue of the nature of the category representation with the type of response rule (probabilistic vs deterministic) that was used. Also, their designs did not test whether the prototype models correctly predicted generalization performance. The present work demonstrates that an exemplar model that includes a response-scaling mechanism provides a natural account of all of Smith et al's experimental results. Furthermore, the exemplar model predicts classification performance better than the prototype models when novel transfer stimuli are included in the experimental designs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Color coding and visual separability in information displays.

12 experimental Ss performed both visual search and class counting tasks, viewing displays containing 20, 60, or 100 items. Each item consisted of a vector, letter, and 3-digit number grouped together, and was presented as white-on-black in some displays, or in 1 of 5 colors. The color code was redundant with the 5 class-designator letters that were used. Average search and counting time, and counting errors, increased with increasing display density (number of items). None of these measures varied significantly among the 5 different target classes (colors). Addition of the redundant color code resulted in an average time reduction of 65% in the visual search task and 69% in the counting task, with a reduction of 76% in errors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus generalization as a function of clinical anxiety and direction of generalization.

"This experiment studied stimulus generalization in psychiatric patients as a function of direction of generalization and clinical anxiety. It was found that direction of generalization along the height continuum did not significantly affect the gradient of stimulus generalization. Level of clinical anxiety, as measured by the Taylor Manifest Anxiety Scale, also did not significantly affect the gradient of stimulus generalization. The validity of the Taylor scale with psychiatric patients was discussed briefly." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Semantic generalization in French and English bilinguals.

In order to examine between-language generalization (BLG), eight two-syllable French and English words were presented, with half of the words in each language paired with shock. After this conditioning procedure shock was withheld and one translated equivalent of each word was presented. GSRs, digital and cephalic vasomotor activity were recorded. Responses to the translations of the words paired with shock were greater than to the translations of the neutral words. The results were accepted as an illustration of BLG and were discussed in relation to the dynamics of semantic systems and bilingual typing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Familiarity-based stimulus generalization of conditioned suppression in rats is dependent on the perirhinal cortex.

We report that bilateral, excitoxic lesions of the perirhinal cortex attenuate rats' familiarity-based stimulus generalization. After surgery, rats were preexposed either to 2 auditory stimuli (A and B) or to only 1 auditory stimulus (B). Following preexposure, all rats received pairings of A and a footshock before assessment of generalized responding (conditioned suppression) to B. Sham rats' generalization was greater when preexposure was to both A and B than when preexposure was to B only. That pattern was abolished in lesioned rats, though no general deficiency was found in other measures of auditory processing. Our findings suggest that the perirhinal cortex is required for rats to encode familiarity as part of stimulus representations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

What-where-when memory in pigeons.

The authors report a novel approach to testing episodic-like memory for single events. Pigeons were trained in separate sessions to match the identity of a sample on a touch screen, to match its location, and to report on the length of the retention interval. When these 3 tasks were mixed randomly within sessions, birds were more than 80% correct on each task. However, performance on 2 different tests in succession after each sample was not consistent with an integrated memory for sample location, time, and identity. Experiment 2 tested binding of location and identity memories in 2 different ways. The results were again consistent with independent feature memories. Implications for tests of episodic-like memory are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A comparative analysis of the categorization of multidimensional stimuli: II. Strategic information search in humans (Homo sapiens) but not in pigeons (Columba livia).

Pigeons and undergraduates learned conditional discriminations involving multiple spatially separated stimulus dimensions. Under some conditions, the dimensions were made available sequentially. In 3 experiments, the dimensions were all perfectly valid predictors of the response that would be reinforced and mutually redundant; in 2 others, they varied in validity. In tests with stimuli in which 1 of the 3 dimensions took an anomalous value, most but not all individuals of both species categorized them in terms of single dimensions. When information was delivered as a function of the passage of time, some students, but no pigeons, waited for the most useful information, especially when the cues differed in objective validity. When the subjects could control information delivery, both species obtained information selectively. When cue validities varied, almost all students tended to choose the most valid cues, and when all cues were valid, some chose the cues by which they classified test stimuli. Only a few pigeons chose the most useful information in either situation. Despite their tendency to unidimensional categorization, the pigeons showed no evidence of rule-governed behavior, but students followed a simple “take-the-best” rule. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial peak shift and generalization in pigeons.

How pigeons generalize across spatial locations was examined in the 4 experiments reported in this article. During training, a square was presented at a fixed height at 1 of 2 horizontal locations on a monitor screen. One location (S+ ) signaled reward, whereas the other one (S–) signaled no reward. The birds were then tested occasionally with a range of locations. After training with S+ only, the generalization gradient peaked at S+ and was approximately Gaussian in shape. After training with equal numbers of S+ and S– trials, response rates were higher on the S+ side of the distribution. This asymmetry diminished over testing. When the S+ and S– were close together, the peak of responding was shifted on initial generalization tests. Generalization gradients along the orthogonal vertical dimension were approximately exponential in shape. This is the first demonstration of generalization and peak shift in the spatial domain. (PsycINFO Database Record (c) 2010 APA, all rights reserved)