Introduction: Positive symptoms in schizophrenia often deal with themes of control. For the first time, the "illusion of control" bias was examined in patients with schizophrenia.
Methods: A total of 32 patients with schizophrenia and 31 nonclinical controls were administered two versions of an illusion of control paradigm. Participants were presented two sequences of green and red stimuli and could choose to press or not press a computer key to get the (desired) green stimulus (participants should press the key to test their level of control). Later, they were asked to rate their level of control over the appearance of the green sequence. The chain of events followed a fixed pseudo-random sequence (experiment A: 75% desired events; B: 25%).
Results: Both groups displayed an illusion of control bias. The subgroup with high positive symptom scores showed excessive illusion of control in experiment A relative to individuals scoring low on positive symptoms. Hallucinators scored significantly higher on illusion of control compared to both healthy individuals and non-hallucinators.
Discussion: Illusion of control was elevated in high-positive-symptom patients, particularly those with hallucinations. Future studies should elucidate whether the magnitude of the illusion of control effect is moderated by the specific contents of positive symptoms, as delusions of control can manifest as active or passive control beliefs.
- positive symptoms
- illusion of control