Identity Discrimination Research Articles

Right lateral fusiform gyrus dysfunction during facial information processing in schizophrenia

Background Patients with schizophrenia exhibit facial information processing deficits that likely contribute to their social dysfunction. Whether the deficits involve facial affect and/or identity processing or result from other cognitive abnormalities in schizophrenia remains controversial, and a brain dysfunction specifically related to them has never been reported. If such dysfunction existed, it should be consistently observed across groups of patients and during performance of different facial information processing tasks, independently of whether such tasks demand working memory (WM), semantic, or other cognitive processes. We hypothesized that the right lateral fusiform gyrus (rLFG), one of several human brain areas involved in facial information processing, would consistently show activation abnormalities during both facial affect and identity discrimination in schizophrenia. Methods We used functional magnetic resonance imaging to measure brain activation in two groups of six chronic, stable schizophrenic outpatients and two of six age- and gender-matched healthy controls. One group of patients and one of controls performed facial affect—with or without semantic processing—and identity discrimination tasks, and the other two groups WM tasks with facial expression cues and varying attentional demands. Results Patients from either group failed to activate the rLFG when compared to controls in any task. Other activation abnormalities were task-specific (i.e., seen only during performance of one set of tasks) and not consistently observed in both groups of patients, and thus could not be directly and solely linked to facial information discrimination. Conclusions These results indicate a specific rLFG dysfunction during early facial information—identity or affect—processing, independent from other cognitive deficits, in schizophrenia.

Salience of caller identity in rhesus monkey (Macaca mulatta) coos and screams: perceptual experiments with human (Homo sapiens) listeners.

Recent evidence from acoustic analysis and playback experiments indicates that adult female rhesus monkey (Macaca mulatta) coos are individually distinctive but their screams are not. In this study, the authors compared discrimination of individual identity in these sounds by naive human listeners who judged whether 2 sounds had been produced by the same monkey or 2 monkeys. Each of 3 experiments using this same-different design showed significantly better discrimination of vocalizer identity from coos than from screams. Experiment 1 demonstrated the basic finding. Experiment 2 also tested the effect of non-identity-related scream variation, and Experiment 3 added a comparison with human vowel sounds. Outcomes suggest that acoustic structural differences in coos and screams influence salience of caller-identity cues, with significant implications for understanding the functions of these calls.

Functional asymmetry in sheep temporal cortex.

Sheep, like humans, show a bias in favour of the left visual field when discriminating familiar faces. This, in humans, is thought to be caused by a right hemisphere dominance for processing faces involving the temporal cortex. We have directly investigated inter-hemispheric differences in face-processing in sheep by recording the frequencies and response profiles of single cells in the temporal cortex which respond selectively to faces. While there was no evidence for increased frequencies of face-sensitive neurones within the right temporal cortex, or their relative selectivity for individual faces, there was a pronounced response latency difference between the two hemispheres. The cells in the left hemisphere responding selectively to particular faces did so up to 400 ms later than those in the right and with a greater degree of temporal variability between cells. No hemispheric latency differences were found, however, in other cells responding to general visual stimuli or to many faces. The data suggest that, while specialised face-sensitive neural circuits in the right hemisphere may play a key role in the rapid (< 200 ms) identification and discrimination of facial identity, those on the left may be involved more with slower processes associated with integrating the emotional or mnemonic consequences of recognition.

The Effect of Conflict and Power Differentials on Social Identity and Intergroup Discrimination

Social identity theory posits that situational factors increase category salience that, in turn, brings intergroup bias, such as prejudice, stereotype, and discrimination. This study investigates the effects of two situational factors, conflict and power differentials, on social identity and intergroup discrimination. We hypothesize that high-conflict or high power differentials raise the strength of social identity and therefore result in greater intergroup discrimination. Result showed that intergroup power differentials had a direct effect on intergroup discrimination, not mediated by social identity strength. Additionally, different response patterns were found between male and female subjects, with females showing stronger gender identity and less intergroup discrimination than males. Male's gender identity was stable across conditions, while female showed greater variability of gender identity across conditions. Some implications on managing diversity were suggested.

Ethnic Identity Achievement, Self-Esteem, and Discrimination among Surinamese Adolescents in the Netherlands

This study examines ethnic identity achievement among Surinamese adolescents in the Netherlands as it relates to self-esteem, perceived discrimination, and Dutch national identification. Using a sample of 94 ethnic Surinamese and 281 ethnic Dutch students between the ages of 14 and 17, participants completed a survey questionnaire. Ethnic identity achievement and self-esteem were positively correlated for the Surinamese but not for the Dutch. Furthermore, regression analysis showed that ethnic identity evaluation mediated the relationship between ethnic identity achievement and self-esteem. In addition, discrimination was positively correlated with ethnic identity achievement for Surinamese males but not Surinamese females. Discrimination was also correlated with Dutch national identification. For the Surinamese, more discrimination was negatively correlated with national identification, whereas for the Dutch, more discrimination was positively correlated with national identification. Furthermore, for Surinamese males, the negative relationship between discrimination and national identification was stronger with increased ethnic identity achievement. The pattern of results is quite similar to studies in the United States, making a contribution to our understanding of the psychological processes involved in ethnic and racial identity.

Enhanced target detection and identification via optimised radar transmission pulse shape

The optimisation of the transmission radar pulse shape to maximise either target detection or identity discrimination between the T-72 and M1 main battle tanks is investigated. Significant performance improvements in target detection and identification are obtained using such matched illumination transmission waveforms over that of standard chirped pulses.

Perception of discrimination and ethnocultural variables in a diverse group of adolescents

Despite current interest in the multi-dimensionality of culture and ethnicity there are few studies that have explored the role of discrimination with ethnocultural variables. In this study social identity theory was used as a framework to test the relation between discrimination and components of ethnic identity, and attitudes towards out-groups. A school-based survey in a large south-west metropolitan area in 1994 was undertaken with students (n=3071) of African–American, European–American, Mexican–American, and Vietnamese–American descent using multiple measures of ethnicity. Hierarchical multiple regression results indicated that two components of ethnic identity played different roles in the relation between discrimination and attitudes towards others. Consistent with social identity theory, results indicated that perception of more discrimination was predicted by high ethnic exploration, and having more negative attitudes towards out-groups. However, ethnic affirmation, which is a positive sense of belonging to one's ethnic group, was only indirectly related to discrimination through attitudes toward others. In fact, contrary to social identity theory, a stronger sense of belonging to one's group was associated with more positive attitudes toward out-groups. Results have important implications for race relations.

Discrimination of facial identity and of emotions in Alzheimer's Disease

Objective: To investigate processing of human faces identity and of emotional expressions in patients with Alzheimer's Disease (AD). Background: Mechanisms responsible for discriminating facial identity may be dissociated from those involved in discriminating facial expressions. Patients with prosopagnosia often have preserved capacities for processing emotional facial expressions and occasionally, patients with focal lesions may recognize human faces without being able to recognize their facial expression. Such a dissociation has not been clearly shown in groups of AD patients. Methods: Thirty-one probable AD patients and 14 control subjects were administered tasks of discrimination of faces and of emotions. Results: AD patients were significantly impaired in discriminating facial identities and in naming and pointing to named emotions, but were comparable to controls in discriminating facial expressions of emotion. The deficits of facial discrimination and of identification of emotions were, on the whole, correlated with the MMS and Raven scores. Discrimination of emotions was not correlated to either test, suggesting that this ability is based on cognitive processes different from those underlying the MMS and the PM47. Conclusions: This dissociation implies two separate systems, one dedicated to discrimination of facial identities and the other to discrimination of emotions. This is compatible with the modular organization of cognitive deficits in AD and may explain the well known experience that nonverbal communication often remains effective even in patients with severe dementia.

Discrimination of Facial Identity and Facial Affect by Temporal and Frontal Lobectomy Patients

The purpose of this study was to determine the extent to which lobectomy affects ability to discriminate facial identity or facial expression. Fifteen right temporal, 15 left temporal, 5 right frontal, and 4 left frontal lobectomy patients, pair-matched for age, sex, and education to normal control subjects, participated in this study. Tasks included a Facial Identity Matching Task and a Facial Affect Matching task. The lobectomized patients as a whole were significantly impaired on both tasks (22% decrement in performance). The patients made twice as many errors resulting from perseveration of response-set of the first condition (identity or emotion matching) into the second condition. The site of lobectomy did not influence general performance on any one task or selective performance on any subset of affective categories. It was concluded that all four brain regions play a significant and equal role in face processing, and that circuits more specifically dedicated to visual face processing, which are responsible for hemispheric dominance affects and affect/identity dissociations, are probably located more posteriorly in the brain. Finally, it was concluded that perseveration of acquired habit may, under specific conditions, characterize temporal lobe dysfunction just as much as frontal lobe dysfunction.

The role of monkey inferior parietal cortex in visual discrimination of identity and orientation of shapes

Three cynomolgus monkeys (Macaca fascicularis) were tested for their visual learning ability following bilateral lesions to the inferior parietal cortex. In discrimination learning with patterns differing from each other in form and colour their performance was normal. In discriminating monochromatic patterns their performance depended on the nature of the pattern discrimination; when the discriminanda were different shapes (e.g. x,v) they performed well, while with discriminanda which differed only in the orientation of the shape (e.g. p,d) they performed relatively badly. These results were compared to the previously reported results of normal animals and animals with inferior temporal lesions performing the same task. The ratio of errors in orientation discrimination to errors in shape discrimination was significantly higher than normal in the group with parietal lesions, and significantly lower than normal in the group with inferior temporal lesions. These results suggest that the roles of inferior temporal and inferior parietal cortex in the discrimination of shape and orientation are complementary.

Complex discrimination with two stages of solution.

A 4-display contingent identity discrimination design was combined with a 4-display contingent position discrimination design to produce a merged task whose 8 displays appeared repeatedly over a sequence of trials. Human Ss solved the contingent identity portion of the task first in nearly all cases and maintained a high level of accuracy on the solved portion while coping with the remainder. Experimental variations related to the visual distinctiveness of the two portions proved unimportant.