Reduced Jumping to Conclusion Bias after Experimentally Induced Enhancement of Subjective Body Boundaries in Psychosis.
Naomi Lyons, Detlef E Dietrich, Johannes Graser, Georg Juckel, Christian Koßmann, Harald Krauß, Bernhard Müller, Johannes Michalak
Psychopathology January 1, 2021 Peer reviewed DOI: 10.1159/000513271 via PubMed
Summary
A brief self-massage designed to enhance the sense of bodily boundaries reduced an implicit reasoning bias linked to delusions in people with psychosis. Patients who performed a 10-minute guided self-massage made more cautious decisions on a task measuring the jumping-to-conclusion bias (average 4.11 draws before deciding) compared to those who massaged a fabric ring (average 2.43 draws). No significant difference was found in explicit paranoid beliefs. The findings support the idea that a disturbed sense of bodily boundaries may contribute to psychotic symptoms.
Study at a glance
| Design | randomized controlled trial |
|---|---|
| Sample size | 73 |
| Population | patients with psychosis |
| Key finding | Enhancing the sense of bodily boundaries through self-massage reduced the jumping-to-conclusion bias, an implicit measure of delusional reasoning, but did not affect explicit paranoid beliefs. |
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.