Decision criteria in the concave mask illusion in schizophrenia

ABSTRACT Objective Some studies have shown that individuals with schizophrenia do not experience the illusion of the concave mask. In this phenomenon, a mask presented on its concave side is perceived as convex. The occurrence of this illusion, according to a hypothesis, would be due to the inhibition of the top-down processes on the bottom-up processes. In this study, we investigated whether there was a statistically significant difference between individuals with schizophrenia compared to healthy individuals in distinguishing the concave side of the convex from a mask, as well as which hypothesis best explained the phenomenon, top-down inhibition or different decision criteria. Methods Adopting the theory of the detection of the signal and in two tasks of data collection, the Confidence Rating and the 2-AFC, we tried to verify the performance in the judgments of the individuals with schizophrenia compared to the healthy individuals in front of a mask that now was presented on its concave side or on its convex side. Results In this study, individuals with schizophrenia were susceptible to delusion and more liberal in their judgments before the stimulus mask. Conclusions The hypothesis of top-down inhibition on bottom-up processes does not seem to be a plausible explanation. Perhaps, decision making or decision criteria better explain the results found in this study. Further studies are needed to better elucidate the phenomenon of the concave mask illusion in individuals with schizophrenia.摘要 ## 研究目的 已有研究表明，精神分裂症患者不会出现凹面面具错觉。该错觉指当面具以凹侧朝向观察者时，会被感知为凸侧。有假说提出，该错觉的产生源于自上而下加工（top-down）对自下而上加工（bottom-up）的抑制作用。本研究旨在探究精神分裂症患者与健康个体在区分面具凹侧与凸侧时是否存在统计学意义上的显著差异，并验证哪种假说能更好地解释该现象：是自上而下加工的抑制效应，还是二者的决策标准存在差异。 ## 研究方法 本研究采用信号检测论（Signal Detection Theory），设置两项数据收集任务：信心评定任务（Confidence Rating）与二择一迫选任务（2-AFC），以对比精神分裂症患者与健康个体在观察以凹侧或凸侧呈现的面具时的判断表现。 ## 研究结果 本研究发现，精神分裂症患者更易受妄想症状影响，且在面对刺激面具时的判断更为宽松。 ## 研究结论 自上而下加工抑制自下而上加工的假说似乎并非合理的解释。决策过程或决策标准或能更好地阐释本研究所得的结果。未来仍需开展更多研究，以进一步阐明精神分裂症患者的凹面面具错觉现象。