Speed, Accuracy, and Efficiency of Judgements of Coincidence between Speech Acts and Auditory Perception during a Delayed Auditory Feedback Paradigm: A Behavioral Study in Patients with Schizophrenia

The inability to differentiate between one’s actions and their consequences from sensory inputs originating from an alien source might cause classical first-rank symptoms in schizophrenia, such as audio-verbal hallucinations (AVH). We aimed to determine whether patients with or without AVH perform differently in a task challenging the audio-verbal self-monitoring system compared to controls. Controls (n = 21) and schizophrenia patients with (AH, n = 11) and without AVH (NH, n = 9) participated. Subjects had to discern whether they heard a sound they had just uttered with or without delay. Reaction time, accuracy as well as sensitivity and response bias were compared between groups. There were no group effects in reaction time. Controls were significantly more accurate in the detection of delays compared to AH and to NH. However, the most salient observation was that these deficits were not uniformly present, but were selectively elicited by the delay, reducing patients’ response accuracy to chance level. The analysis of the data based on signal detection theory revealed a significant drop in sensitivity in both patient groups compared to the controls, and a response bias: Particularly the patients with AVH seemed to be biased not to consider a delay, rather than falsely signaling a delay. Such a deficit may blur the distinction between external events and self-initiated actions, thus eventually interfering with the patients’ sense of agency.