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.

Concave mask; schizophrenia; decision making