Manifestation of oppel kundt illusion using cross type distractor stimuli among people with schizophrenia spectrum disorders

Abstract

Introduction: scientific studies have shown the differences in early visual processing, gain control and integration for patients diagnosed with schizophrenia spectrum disorders(SSD). To learn more about patients affected by SSD we havechosen to study the manifestation of Oppel Kundt(OK) illusion together with cross type distractor stimuli. During earlier studies differences were noted in comparison to the typical OK illusion. This study will allow us to get more insights in visual perception for individuals diagnosed with SSD. Aim: To investigate the manifestation of Oppel Kundt illusion with cross type distractor stimuli among people diagnosed with schizophrenia spectrum disorders Material and Methods: in the prospective study were included 22 patients, who were diagnosed with SSD and matched with a comparison group without any mental, neurological diseases or visual impairment. OK figures used in the experiments consisted of three white spots presented horizontally against the black background with horizontal two-sided line(cross) type distractor stimuli. Using computerized equipment in OK figures the subjects were asked to adjust the three dots of the stimulus to be equal in length to the filled (referential) one. ANOVA, T-test and post hoc Bonferroni correction were used for statistical analysis. Results: the manifestation of the OK illusion is measured by the means of the patient and control groups. The data collected was statistically significant, as shown by Sig.(2-tailed), except for cross150 the numbers did not exceed 0,05. The results show that the illusion was strongest in the patient group. The farther the mean is from zero the stronger the manifestation of the illusion. The illusion became stronger in both groups as the size of the distractor stimuli increased. The strength of the illusion in the patient group was the biggest near distractor stimuli cross95, after that the strength of the illusion started decreasing. In comparison the strength of the illusion in the control group was much smaller until distractor stimuli cross111, after that the strength of the illusion rose sharply. Conclusions: illusion tended to manifest stronger for patients with SSD. The illusion among patients diagnosed with SSD manifested diametrically opposite in comparison to healthy individuals.