Resumo de Perception Of Facial Expressions And Brain Lateralization.

Perception of facial expressions and brain lateralization.The role that each brain hemisphere plays in the processing ofemotional information has been frequently discussed in the scientificliterature. The aim of this study was to investigate the pattern ofhemispheric dominance for the Perception of the facial expressions ofhappiness, sadness, anger and fear. In two experiments thedivided-visualfield technique was used with the taquitoscopicpresentation of stimuli on a computer screen for 150 ms. The stimuliwere composed with pictures of faces of four people (2M,2F) taken fromthe series Pictures of Facial Affect. Twenty one right-handed observers(9M,12F) took part in the experiment I. In each trial two pictures offaces were presented on the computer screen, one of them placed on theleft side and the other one on the right side of the fixation point, infour different conditions: 1) face with emotion on the left and neutralface on the right, 2) neutral face on the left and face with emotion onthe right, 3)face with emotion on the right and on the left, 4) neutralface on the right and on the left. In each trial the observersdetermined the side on which the face seemed to show greater emotionalintensity. Seventeen right-handed observers (8M, 9F) took part in theexperiment II. In each stimulus presentation, a picture of a face waspresented either on the right or left side of the fixation point,placed on the center of the screen and, on the opposite side, a grayrectangle was presented. The following stimuli conditions wereelaborated: 1) face with emotion on the left and gray rectangle on theright, 2) gray rectangle on the left and face with emotion on theright, 3) neutral face on the left and gray rectangle on the right, 4)gray rectangle on the left and neutral face on the right. In each trialthe observers determined if the face presented had emotion or not. Timereactions and judgement errors were submitted to ANOVAs for repeatedmeasures. In the first experiment, emotion was generally detected morequickly in faces presented on the left 10 visual field (p<0,01). Theexpressions of sadness and anger were also perceived more quickly whenpresented on the left visual field (p<0,05). In both experiments,expressions of happiness and fear were perceived more quickly and moreaccurately than expressions of sadness and anger (p<0,001). Theexpression of sadness was detected more easily in feminine faces andthe expression of anger in masculine faces (p<0,05). In general,however, the emotion was detected more easily in feminine faces. Inboth experiments there were differences in the perception between thefaces of the four individuals that represented the facial expressions.The right hemisphere showed superior to the left hemisphere in theperception of facial expressions, especially for the perception ofexpressions of sadness and anger. The perceptive advantage of the righthemisphere is more evident for the expressions that are detected withmore difficulty. The perception of facial expressions can be affectedby the gender of the face and the singularities of the individualfacial expression.

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