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（concave mask illusion）。该错觉指当以凹面朝向观察者呈现面具时，观者会将其感知为凸面。有假说提出，此错觉的产生源于自上而下（top-down）加工对自下而上（bottom-up）加工的抑制。本研究旨在探究两个核心问题：其一，相较于健康个体，精神分裂症患者在区分面具的凹面与凸面时是否存在统计学意义上的显著差异；其二，哪种假说能更好地解释该现象——是自上而下加工抑制假说，还是决策标准差异假说？
研究方法
本研究采用信号检测论（signal detection theory），通过信心评定（Confidence Rating）和二择一迫选（2-AFC）两种数据收集任务，验证精神分裂症患者与健康个体在面对凹面或凸面呈现的面具时的判断表现。
研究结果
本研究结果显示，精神分裂症患者易受妄想影响，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解释本研究所得结果。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。