Reduced Jumping to Conclusion Bias after Experimentally Induced Enhancement of Subjective Body Boundaries in Psychosis.

A disturbed sense of self, particularly feeling disconnected from one's own body (disembodiment), may contribute to delusions in psychosis. In a randomized experiment, 73 patients with psychosis either performed a 10-minute guided self-massage to enhance bodily boundary awareness or massaged a fabric ring. Those who did the self-massage showed a reduced tendency to jump to conclusions (an average of 4.11 pieces of evidence before deciding versus 2.43 in the control group, a moderate effect). However, there was no significant difference in explicit paranoid beliefs. The findings suggest that improving the sense of bodily boundaries can reduce an implicit bias linked to delusional thinking, supporting the idea that disembodiment plays a role in psychotic symptoms.

Study at a glance

Abstract

A disturbed sense of self is frequently discussed as an etiological factor for delusion symptoms in psychosis. Phenomenological approaches to psychopathology posit that lacking the sense that the self is localized within one's bodily boundaries (disembodiment) is one of the core features of the disturbed self in psychosis. The present study examines this idea by experimentally manipulating the sense of bodily boundaries. Seventy-three patients with psychosis were randomly assigned to either a 10-min, guided self-massage in the experimental group (EG) to enhance the sense of bodily boundaries or a control group (CG), which massaged a fabric ring. Effects on an implicit measure (jumping to conclusion bias; JTC) and an explicit measure (Brief State Paranoia Checklist; BSPC) of delusion processes were assessed. The JTC measures the tendency to make a decision with little evidence available, and the BSPC explicitly measures the approval of paranoid beliefs. Patients in the EG showed a lower JTC (M = 4.11 draws before decision) than the CG (M = 2.43; Cohen's d = 0.64). No significant difference in the BSPC was observed. Our results indicate that enhancing the sense of body boundaries through a self-massage can reduce an implicit bias associated with delusional ideation and correspondingly support the idea that disembodiment might be a relevant factor in the formation of psychotic symptoms.