Jumping to conclusions in delusional and non-delusional schizophrenic patients
Article first published online: 24 DEC 2010
2005 The British Psychological Society
British Journal of Clinical Psychology
Volume 44, Issue 2, pages 193–207, June 2005
How to Cite
Moritz, S. and Woodward, T. S. (2005), Jumping to conclusions in delusional and non-delusional schizophrenic patients. British Journal of Clinical Psychology, 44: 193–207. doi: 10.1348/014466505X35678
- Issue published online: 24 DEC 2010
- Article first published online: 24 DEC 2010
- Received 13 June 2003; revised version received 18 January 2004
Objective. Several studies have provided evidence for the claim that a subgroup of (schizophrenic) patients with current delusions share a jumping to conclusions (JTC) bias. The primary aim of the present study was to investigate whether currently deluded and non-deluded schizophrenic patients perform differently on three tasks tapping probabilistic reasoning.
Method. Probabilistic reasoning was assessed in 31 schizophrenic patients, 28 psychiatric controls, and 17 healthy controls. In addition to the traditional draws to decision procedure, we employed two tasks for which participants had to judge, at each stage, the likelihood that beads come from either container (graded estimates procedure). Reaction times were recorded for the graded estimates procedure.
Results. A JTC bias was displayed by 42% of the schizophrenic patients in the draws to decision condition, while 7% of the psychiatric patients and none of the healthy controls reached a decision after only one bead. A similar pattern of results was observed for the graded estimates procedure. This bias was more pronounced in deluded schizophrenic patients, although currently non-deluded patients also showed evidence for earlier decisions. A bias to over-adjust when confronted with potentially disconfirmatory evidence was confined to deluded schizophrenic participants. There was also evidence for an increase in JTC in the deluded group over the course of the tasks. No substantial group differences occurred with respect to reaction time parameters indicating that results are not attributable to impulsivity.
Discussion. The findings provide further evidence for state and trait characteristics of abnormal reasoning in paranoid schizophrenia. Results are discussed in light of several competing explanations for JTC in schizophrenia.