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Dora Fix Ventura - One of the best experts on this subject based on the ideXlab platform.
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Long-Term Occupational Exposure to Organic Solvents Affects Color Vision, Contrast Sensitivity and Visual
2016Co-Authors: Thiago Leiros Costa, Daniela Maria, Oliveira Bonci, Luiz Carlos, Lima Silveira, Mirella Telles, Salgueiro Barboni, Ana Laura, Mirella Gualtieri, Dora Fix VenturaAbstract:The purpose of this study was to evaluate the visual outcome of chronic occupational exposure to a mixture of organic solvents by measuring Color Discrimination, achromatic contrast sensitivity and visual fields in a group of gas station workers. We tested 25 workers (20 males) and 25 controls with no history of chronic exposure to solvents (10 males). All participants had normal ophthalmologic exams. Subjects had worked in gas stations on an average of 9.666.2 years. Color vision was evaluated with the Lanthony D15d and Cambridge Colour Test (CCT). Visual field assessment consisted of white-on-white 24–2 automatic perimetry (Humphrey II-750i). Contrast sensitivity was measured for sinusoidal gratings of 0.2, 0.5, 1.0, 2.0, 5.0, 10.0 and 20.0 cycles per degree (cpd). Results from both groups were compared using the Mann–Whitney U test. The number of errors in the D15d was higher for workers relative to controls (p,0.01). Their CCT Color Discrimination thresholds were elevated compared to the control group along the protan, deutan and tritan confusion axes (p,0.01), and their ellipse area and ellipticity were higher (p,0.01). Genetic analysis of subjects with very elevated Color Discrimination thresholds excluded congenital causes for the visual losses. Automated perimetry thresholds showed elevation in the 9u, 15u and 21u of eccentricity (p,0.01) and in MD and PSD indexes (p,0.01). Contrast sensitivity losses were found for all spatial frequencies measured (p,0.01) except for 0.5 cpd. Significant correlation was found between previous working years and deutan axis thresholds (rho = 0.59; p,0.05), indexes of the Lanthony D15d (rho = 0.52; p,0.05), perimetry results in th
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Color Discrimination in the Tufted Capuchin Monkey, Sapajus spp
2016Co-Authors: Paulo Roney, Daniela Maria, Oliveira Bonci, Olavo De Faria Galvão, Luiz Carlos, Lima Silveira, Dora Fix VenturaAbstract:The present study evaluated the efficacy of an adapted version of the Mollon-Reffin test for the behavioral investigation of Color vision in capuchin monkeys. Ten tufted capuchin monkeys (Sapajus spp., formerly referred to as Cebus apella) had their DNA analyzed and were characterized as the following: one trichromat female, seven deuteranope dichromats (six males and one female), and two protanope males, one of which was identified as an ‘‘ML protanope.’ ’ For their behavioral characterization, all of the subjects were tested at three regions of the Commission International de l’Eclairage (CIE) 1976 u9v9 diagram, with each test consisting of 20 chromatic variation vectors that were radially distributed around the chromaticity point set as the test background. The phenotypes inferred from the behavioral data were in complete agreement with those predicted from the genetic analysis, with the threshold distribution clearly differentiating between trichromats and dichromats and the estimated confusion lines characteristically converging for deuteranopes and the ‘‘classic’ ’ protanope. The Discrimination pattern of the ML protanope was intermediate between protan and deutan, with confusion lines horizontally oriented and parallel to each other. The observed phenotypic differentiation confirmed the efficacy of the Mollon-Reffin test paradigm as a useful tool for evaluating Color Discrimination in nonhuman primates. Especially noteworthy was the demonstration of behavioral segregation between the ‘‘classic’ ’ and ‘‘ML’ ’ protanopes, suggesting identifiable behavioral consequences of even slight variations in the spectral sensitivity of M/L photopigments i
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transcranial direct current stimulation modulates human Color Discrimination in a pathway specific manner
Frontiers in Psychiatry, 2012Co-Authors: Thiago Leiros Costa, Balazs Nagy, Mirella Telles Salgueiro Barboni, Paulo S Boggio, Dora Fix VenturaAbstract:Previous research showed that Transcranial Direct Current Stimulation (tDCS) can modulate visual cortex excitability. However, there is no experiment on the effects of tDCS on Color perception to date. The present study aimed to investigate the effects of tDCS on Color Discrimination tasks. 15 healthy subjects (mean age of 25.6 ± 4.4 years) were tested with Cambridge Color Test 2.0 (Trivector and Ellipses protocols) and a Forced-choice Spatial Color Contrast Sensitivity task (vertical red-green sinusoidal grating) while receiving tDCS. Anodal, cathodal and sham tDCS were delivered at Oz for 22 minutes using two square electrodes (25cm2 with a current of 1.5mA) in sessions separated by 7 days. Anodal tDCS significantly increased tritan sensitivity (p<0.01) and had no significant effect on protan, deutan or red-green grating Discrimination. The effects on the tritan Discrimination returned to baseline after 15 minutes (p<0.01). Cathodal tDCS reduced the sensitivity in the deutan axis and increased sensitivity in the tritan axis (p<0.05). The lack of anodal tDCS effects in the protan, deutan and red-green grating sensitivities could be explained by a “ceiling effect” since adults in this age range tend to have optimal Color Discrimination performance for these hues. The differential effects of cathodal tDCS on tritan and deutan sensitivities and the absence of the proposed ceiling effects for the tritan axes might be explained by Parvocellular (P) and Koniocellular (K) systems with regard to their functional, physiological and anatomical differences. The results also support the existence of a systematic segregation of P and K Color-coding cells in V1. Future research and possible clinical implications are discussed.
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Color vision impairment in type 2 diabetes assessed by the d 15d test and the cambridge colour test
Ophthalmic and Physiological Optics, 2010Co-Authors: Claudia Feitosasantana, Marcelo Fernandes Da Costa, Galina V. Paramei, Mirella Gualtieri, Mauro Nishi, Dora Fix VenturaAbstract:Color vision impairment emerges at early stages of diabetes mellitus type 2 (DM2) and may precede diabetic retinopathy or the appearance of vascular alterations in the retina. The aim of the present study was to compare the evaluation of the Color vision with two different tests – the Lanthony desaturated D-15d test (a traditional Color arrangement test), and the Cambridge Colour Test (CCT) (a computerized Color Discrimination test) – in patients diagnosed with DM2 without clinical signs of diabetic retinopathy (DR), and in sex- and age-matched control groups. Both Color tests revealed statistically significant differences between the controls and the worst eyes of the DM2 patients. In addition, the degree of Color vision impairment diagnosed by both tests correlated with the disease duration. The D-15d outcomes indicated solely tritan losses. In comparison, CCT outcomes revealed diffuse losses in Color Discrimination: 13.3% for best eyes and 29% for worst eyes. In addition, elevation of tritan thresholds in the DM2 patients, as detected by the Trivector subtest of the CCT, was found to correlate with the level of glycated hemoglobin. Outcomes of both tests confirm that subclinical losses of Color vision are present in DM2 patients at an early stage of the disease, prior to signs of retinopathy. Considering the advantages of the CCT test compared to the D-15d test, further studies should attempt to verify and/or improve the efficiency of the CCT test.
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a computer controlled Color vision test for children based on the cambridge colour test
Visual Neuroscience, 2008Co-Authors: Paulo Roney Kilpp Goulart, Marcio L Bandeira, Daniela Tsubota, Nestor Norio Oiwa, Marcelo Fernandes Da Costa, Dora Fix VenturaAbstract:The present study aimed at providing conditions for the assessment of Color Discrimination in children using a modified version of the Cambridge Colour Test (CCT, Cambridge Research Systems Ltd., Rochester, UK). Since the task of indicating the gap of the Landolt C used in that test proved counterintuitive and/or difficult for young children to understand, we changed the target stimulus to a patch of Color approximately the size of the Landolt C gap (about 7 degrees of visual angle at 50 cm from the monitor). The modifications were performed for the CCT Trivector test which measures Color Discrimination for the protan, deutan and tritan confusion lines. Experiment 1 sought to evaluate the correspondence between the CCT and the child-friendly adaptation with adult subjects (n = 29) with normal Color vision. Results showed good agreement between the two test versions. Experiment 2 tested the child-friendly software with children 2 to 7 years old (n = 25) using operant training techniques for establishing and maintaining the subjects' performance. Color Discrimination thresholds were progressively lower as age increased within the age range tested (2 to 30 years old), and the data--including those obtained for children--fell within the range of thresholds previously obtained for adults with the CCT. The protan and deutan thresholds were consistently lower than tritan thresholds, a pattern repeatedly observed in adults tested with the CCT. The results demonstrate that the test is fit for assessment of Color Discrimination in young children and may be a useful tool for the establishment of Color vision thresholds during development.
Marcelo Fernandes Da Costa - One of the best experts on this subject based on the ideXlab platform.
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Color vision impairment in type 2 diabetes assessed by the d 15d test and the cambridge colour test
Ophthalmic and Physiological Optics, 2010Co-Authors: Claudia Feitosasantana, Marcelo Fernandes Da Costa, Galina V. Paramei, Mirella Gualtieri, Mauro Nishi, Dora Fix VenturaAbstract:Color vision impairment emerges at early stages of diabetes mellitus type 2 (DM2) and may precede diabetic retinopathy or the appearance of vascular alterations in the retina. The aim of the present study was to compare the evaluation of the Color vision with two different tests – the Lanthony desaturated D-15d test (a traditional Color arrangement test), and the Cambridge Colour Test (CCT) (a computerized Color Discrimination test) – in patients diagnosed with DM2 without clinical signs of diabetic retinopathy (DR), and in sex- and age-matched control groups. Both Color tests revealed statistically significant differences between the controls and the worst eyes of the DM2 patients. In addition, the degree of Color vision impairment diagnosed by both tests correlated with the disease duration. The D-15d outcomes indicated solely tritan losses. In comparison, CCT outcomes revealed diffuse losses in Color Discrimination: 13.3% for best eyes and 29% for worst eyes. In addition, elevation of tritan thresholds in the DM2 patients, as detected by the Trivector subtest of the CCT, was found to correlate with the level of glycated hemoglobin. Outcomes of both tests confirm that subclinical losses of Color vision are present in DM2 patients at an early stage of the disease, prior to signs of retinopathy. Considering the advantages of the CCT test compared to the D-15d test, further studies should attempt to verify and/or improve the efficiency of the CCT test.
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a computer controlled Color vision test for children based on the cambridge colour test
Visual Neuroscience, 2008Co-Authors: Paulo Roney Kilpp Goulart, Marcio L Bandeira, Daniela Tsubota, Nestor Norio Oiwa, Marcelo Fernandes Da Costa, Dora Fix VenturaAbstract:The present study aimed at providing conditions for the assessment of Color Discrimination in children using a modified version of the Cambridge Colour Test (CCT, Cambridge Research Systems Ltd., Rochester, UK). Since the task of indicating the gap of the Landolt C used in that test proved counterintuitive and/or difficult for young children to understand, we changed the target stimulus to a patch of Color approximately the size of the Landolt C gap (about 7 degrees of visual angle at 50 cm from the monitor). The modifications were performed for the CCT Trivector test which measures Color Discrimination for the protan, deutan and tritan confusion lines. Experiment 1 sought to evaluate the correspondence between the CCT and the child-friendly adaptation with adult subjects (n = 29) with normal Color vision. Results showed good agreement between the two test versions. Experiment 2 tested the child-friendly software with children 2 to 7 years old (n = 25) using operant training techniques for establishing and maintaining the subjects' performance. Color Discrimination thresholds were progressively lower as age increased within the age range tested (2 to 30 years old), and the data--including those obtained for children--fell within the range of thresholds previously obtained for adults with the CCT. The protan and deutan thresholds were consistently lower than tritan thresholds, a pattern repeatedly observed in adults tested with the CCT. The results demonstrate that the test is fit for assessment of Color Discrimination in young children and may be a useful tool for the establishment of Color vision thresholds during development.
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irreversible Color vision losses in patients with chronic mercury vapor intoxication
Visual Neuroscience, 2008Co-Authors: Claudia Feitosasantana, Nestor Norio Oiwa, Marcelo Fernandes Da Costa, Galina V. Paramei, Luiz Carlos L Silveira, Mirella Telles Salgueiro Barboni, Ana Luisa A C Simoes, Dora Fix VenturaAbstract:This longitudinal study addresses the reversibility of Color vision losses in subjects who had been occupationally exposed to mercury vapor. Color Discrimination was assessed in 20 Hg-exposed patients ~mean age 42.4 6 6.5 years; 6 females and 14 males! with exposure to Hg vapor during 10.5 6 5.3 years and away from the work place ~relative to 2002! for 6.8 6 4.2 years. During the Hg exposure or up to one year after ceasing it, mean urinary Hg concentration was 47 6 35.4 mg0g creatinine. There was no information on Hg urinary concentration at the time of the first tests, in 2002 ~Ventura et al., 2005!, but at the time of the follow-up tests, in 2005, this value was 1.4 6 1.4 mg0g creatinine for patients compared with 0.5 6 0.5 mg0g creatinine for controls ~different group from the one in Ventura et al. ~2005!!. Color vision was monocularly assessed using the Cambridge Colour Test ~CCT!. Hg-exposed patients had significantly worse Color Discrimination ~p 0.02! than controls, as evaluated by the size of MacAdam’s Color Discrimination ellipses and Color Discrimination thresholds along protan, deutan, and tritan confusion axes. There were no significant differences between the results of the study in Ventura et al. ~2005! and in the present follow-up measurements, in 2005, except for worsening of the tritan thresholds in the best eye in 2005. Both chromatic systems, blue-yellow and red-green, were affected in the first evaluation ~Ventura et al., 2005! and remained impaired in the follow-up testing, in 2005. These findings indicate that following a long-term occupational exposure to Hg vapor, even several years away from the source of intoxication, Color vision impairment remains irreversible.
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absence of binocular summation eye dominance and learning effects in Color Discrimination
Visual Neuroscience, 2006Co-Authors: Marcelo Fernandes Da Costa, Dora Fix Ventura, Felipe Perazzolo, Mauricio Murakoshi, Luiz Carlos L SilveiraAbstract:We evaluated binocular summation, eye dominance, and learning in the Trivector and Ellipses procedures of the Cambridge Colour Test (CCT). Subjects (n = 36, 18-30 years old) were recruited among students and staff from the University of Sao Paulo. Inclusion criteria were absence of ophthalmological complaints and best-corrected Snellen VA 20/20 or better. The subjects were tested in three randomly selected eye conditions: binocular, monocular dominant eye, and nondominant eye. Results obtained in the binocular and monocular conditions did not differ statistically for thresholds measured along the protan, deutan, and tritan confusion axes (ANOVA, P > 0.05). No statistical difference was detected among Discrimination ellipses obtained in binocular or monocular conditions (ANOVA, P > 0.05), suggesting absence of binocular summation or of an effect of eye dominance. Possible effects of learning were examined by comparing successive thresholds obtained in the three testing conditions. There was no evidence of improvement as a function of testing order (ANCOVA, P > 0.05). We conclude that CCT thresholds are not affected by binocularity, eye dominance, or learning. Our results differ from those found by Verriest et al. (1982) using the Farnsworth-Munsell 100 Hue test and Hovis et al. (2004) using the Farnsworth-Munsell panel D-15 test.
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multifocal and full field electroretinogram changes associated with Color vision loss in mercury vapor exposure
Visual Neuroscience, 2004Co-Authors: Dora Fix Ventura, Marcelo Fernandes Da Costa, Marcelo Vieira Costa, Adriana Berezovsky, Solange Rios Salomao, Ana Luiza Simoes, M Lago, Luiz Miguel Pereira, Marcilia De Araujo Medrado Faria, John Manuel De SouzaAbstract:We evaluated the Color vision of mercury-contaminated patients and investigated possible retinal origins of losses using electroretinography. Participants were retired workers from a fluorescent lamp industry diagnosed with mercury contamination (n 5 43) and age-matched controls ~n 5 21). Color Discrimination was assessed with the Cambridge Colour Test (CCT). Retinal function was evaluated by using the ISCEV protocol for full-field electroretinography (full-field ERG), as well as by means of multifocal electroretinography (mfERG). Color-vision losses assessed by the CCT consisted of higher Color-Discrimination thresholds along the protan, deutan, and tritan axes and significantly larger Discrimination ellipses in mercury-exposed patients compared to controls. Full-field ERG amplitudes from patients were smaller than those of the controls for the scotopic response b-wave, maximum response, sum of oscillatory potentials (OPs), 30-Hz flicker response, and light-adapted cone response. OP amplitudes measured in patients were smaller than those of controls for O2 and O3. Multifocal ERGs recorded from ten randomly selected patients showed smaller N1‐P1 amplitudes and longer latencies throughout the 25-deg central field. Full-field ERGs showed that scotopic, photopic, peripheral, and midperipheral retinal functions were affected, and the mfERGs indicated that central retinal function was also significantly depressed. To our knowledge, this is the first demonstration of retinal involvement in visual losses caused by mercury toxicity.
Adrian G Dyer - One of the best experts on this subject based on the ideXlab platform.
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does fine Color Discrimination learning in free flying honeybees change mushroom body calyx neuroarchitecture
PLOS ONE, 2016Co-Authors: Frank M J Sommerlandt, Johannes Spaethe, Wolfgang Rossler, Adrian G DyerAbstract:Honeybees learn Color information of rewarding flowers and recall these memories in future decisions. For fine Color Discrimination, bees require differential conditioning with a concurrent presentation of target and distractor stimuli to form a long-term memory. Here we investigated whether the long-term storage of Color information shapes the neural network of microglomeruli in the mushroom body calyces and if this depends on the type of conditioning. Free-flying honeybees were individually trained to a pair of perceptually similar Colors in either absolute conditioning towards one of the Colors or in differential conditioning with both Colors. Subsequently, bees of either conditioning groups were tested in non-rewarded Discrimination tests with the two Colors. Only bees trained with differential conditioning preferred the previously learned Color, whereas bees of the absolute conditioning group, and a stimuli-naive group, chose randomly among Color stimuli. All bees were then kept individually for three days in the dark to allow for complete long-term memory formation. Whole-mount immunostaining was subsequently used to quantify variation of microglomeruli number and density in the mushroom-body lip and collar. We found no significant differences among groups in neuropil volumes and total microglomeruli numbers, but learning performance was negatively correlated with microglomeruli density in the absolute conditioning group. Based on these findings we aim to promote future research approaches combining behaviorally relevant Color learning tests in honeybees under free-flight conditions with neuroimaging analysis; we also discuss possible limitations of this approach.
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aversive reinforcement improves visual Discrimination learning in free flying honeybees
PLOS ONE, 2010Co-Authors: Martin Giurfa, Aurore Avarguesweber, Maria Gabriela De Brito Sanchez, Adrian G DyerAbstract:Background: Learning and perception of visual stimuli by free-flying honeybees has been shown to vary dramatically depending on the way insects are trained. Fine Color Discrimination is achieved when both a target and a distractor are present during training (differential conditioning), whilst if the same target is learnt in isolation (absolute conditioning), Discrimination is coarse and limited to perceptually dissimilar alternatives. Another way to potentially enhance Discrimination is to increase the penalty associated with the distractor. Here we studied whether coupling the distractor with a highly concentrated quinine solution improves Color Discrimination of both similar and dissimilar Colors by free-flying honeybees. As we assumed that quinine acts as an aversive stimulus, we analyzed whether aversion, if any, is based on an aversive sensory input at the gustatory level or on a post-ingestional malaise following quinine feeding. Methodology/Principal Findings: We show that the presence of a highly concentrated quinine solution (60 mM) acts as an aversive reinforcer promoting rejection of the target associated with it, and improving Discrimination of perceptually similar stimuli but not of dissimilar stimuli. Free-flying bees did not use remote cues to detect the presence of quinine solution; the aversive effect exerted by this substance was mediated via a gustatory input, i.e. via a distasteful sensory experience, rather than via a post-ingestional malaise. Conclusion: The present study supports the hypothesis that aversion conditioning is important for understanding how and what animals perceive and learn. By using this form of conditioning coupled with appetitive conditioning in the framework of a differential conditioning procedure, it is possible to uncover Discrimination capabilities that may remain otherwise unsuspected. We show, therefore, that visual Discrimination is not an absolute phenomenon but can be modulated by experience.
Martin Giurfa - One of the best experts on this subject based on the ideXlab platform.
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aversive reinforcement improves visual Discrimination learning in free flying honeybees
PLOS ONE, 2010Co-Authors: Martin Giurfa, Aurore Avarguesweber, Maria Gabriela De Brito Sanchez, Adrian G DyerAbstract:Background: Learning and perception of visual stimuli by free-flying honeybees has been shown to vary dramatically depending on the way insects are trained. Fine Color Discrimination is achieved when both a target and a distractor are present during training (differential conditioning), whilst if the same target is learnt in isolation (absolute conditioning), Discrimination is coarse and limited to perceptually dissimilar alternatives. Another way to potentially enhance Discrimination is to increase the penalty associated with the distractor. Here we studied whether coupling the distractor with a highly concentrated quinine solution improves Color Discrimination of both similar and dissimilar Colors by free-flying honeybees. As we assumed that quinine acts as an aversive stimulus, we analyzed whether aversion, if any, is based on an aversive sensory input at the gustatory level or on a post-ingestional malaise following quinine feeding. Methodology/Principal Findings: We show that the presence of a highly concentrated quinine solution (60 mM) acts as an aversive reinforcer promoting rejection of the target associated with it, and improving Discrimination of perceptually similar stimuli but not of dissimilar stimuli. Free-flying bees did not use remote cues to detect the presence of quinine solution; the aversive effect exerted by this substance was mediated via a gustatory input, i.e. via a distasteful sensory experience, rather than via a post-ingestional malaise. Conclusion: The present study supports the hypothesis that aversion conditioning is important for understanding how and what animals perceive and learn. By using this form of conditioning coupled with appetitive conditioning in the framework of a differential conditioning procedure, it is possible to uncover Discrimination capabilities that may remain otherwise unsuspected. We show, therefore, that visual Discrimination is not an absolute phenomenon but can be modulated by experience.
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conditioning procedure and Color Discrimination in the honeybee apis mellifera
Naturwissenschaften, 2004Co-Authors: Martin GiurfaAbstract:We studied the influence of the conditioning procedure on Color Discrimination by free-flying honeybees. We asked whether absolute and differential conditioning result in different Discrimination capabilities for the same pairs of Colored targets. In absolute conditioning, bees were rewarded on a single Color; in differential conditioning, bees were rewarded on the same Color but an alternative, non-rewarding, similar Color was also visible. In both conditioning procedures, bees learned their respective task and could also discriminate the training stimulus from a novel stimulus that was perceptually different from the trained one. Discrimination between perceptually closer stimuli was possible after differential conditioning but not after absolute conditioning. Differences in attention inculcated by these training procedures may underlie the different Discrimination performances of the bees.
Mitchell A Seligson - One of the best experts on this subject based on the ideXlab platform.
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determinants of perceived skin Color Discrimination in latin america
The Journal of Politics, 2014Co-Authors: Damarys Canache, Matthew Hayes, Jeffery J Mondak, Mitchell A SeligsonAbstract:Discrimination on the basis of skin Color persists as a serious social and political problem in many of the world’s nations. Although numerous consequences of such Discrimination have been enumerated, considerably less is known regarding the bases of perceived Discrimination. In this study, individuals’ perceptions that they have been the targets of skin-Color Discrimination are examined. Using 2010 AmericasBarometer data from six nations, a multifaceted account of the possible bases of perceived Discrimination is devised and tested. Three classes of predictors are considered: (1) variables related to a person’s skin Color, race, and ethnicity; (2) extraneous demographic and psychological factors; and (3) aspects of the individual’s regional social and political context. Results reveal that both skin Color and racial and ethnic self-categorization strongly correspond with perceived Discrimination, with additional, more modest, effects identified for socioeconomic status (wealth), personality (agreeableness), and the composition of a person’s regional context.
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determinants of perceived skin Color Discrimination in latin america
The Journal of Politics, 2014Co-Authors: Damarys Canache, Matthew Hayes, Jeffery J Mondak, Mitchell A SeligsonAbstract:Discrimination on the basis of skin Color persists as a serious social and political problem in many of the world’s nations. Although numerous consequences of such Discrimination have been enumerated, considerably less is known regarding the bases of perceived Discrimination. In this study, individuals’ perceptions that they have been the targets of skin-Color Discrimination are examined. Using 2010 AmericasBarometer data from six nations, a multifaceted account of the possible bases of perceived Discrimination is devised and tested. Three classes of predictors are considered: (1) variables related to a person’s skin Color, race, and ethnicity; (2) extraneous demographic and psychological factors; and (3) aspects of the individual’s regional social and political context. Results reveal that both skin Color and racial and ethnic self-categorization strongly correspond with perceived Discrimination, with additional, more modest, effects identified for socioeconomic status (wealth), personality (agreeablenes...