Schizophrenia patients, particularly those with current delusions, show a cognitive bias known as jumping to conclusions, defined as a decision made quickly on the basis of little evidence. The aim of this work was to examine the underlying mechanisms of this cognitive bias by means of the Picture To Decision Task, which allows one to analyse the effect of the context on decisions made. We compared the performance of this task by 42 psychotic patients, 21 siblings of these patients and 77 controls. The results of the current study suggest that, relative to siblings and controls, patients display a general tendency to jump to conclusions, characterised by overestimating the conviction in their choices at the beginning of the decision process and by a lowered threshold for making decisions in ambiguous contexts, where a greater amount of information is required. These results are interpreted in terms of faulty appraisal, which would be the first mechanism responsible for the Jumping To Conclusions bias. Theoretical and clinical implications are discussed.
Several studies have demonstrated that patients with schizophrenia show a reasoning bias known as jumping to conclusions (JTC), defined as a decision made quickly on the basis of little evidence. Schizophrenia patients, particularly those with current delusions, may overestimate and use less information to arrive at a decision in tasks that require them to integrate information to make a response (Huq et al., 1988, Moritz and Woodward, 2005, Moritz et al., 2007 and Speechley et al., 2010). Similarly, JTC bias has been reported in close relatives of schizophrenia patients (van Dael et al., 2006) and individuals at a high clinical risk of psychosis (Broome et al., 2007), and it may be associated with higher levels of conviction in paranoid thoughts within the general population (Freeman et al., 2008 and Lincoln et al., 2010).
Although there is no unified explanation of the origin of this cognitive bias, two specific formal hypotheses might be considered (Averbeck et al., 2011). The first hypothesis is that patients overestimate the conviction in their choices at the beginning of the decision-making process (Huq et al., 1988, Lincoln et al., 2010 and Speechley et al., 2010). The second hypothesis is that they may have a lowered threshold for making decisions, and thus use less information in arriving at a decision, which is consistent with the so-called liberal acceptance account (Moritz et al., 2009 and Veckenstedt et al., 2011).
The principal aim of this work is to contrast the two hypotheses cited above by means of a new version of the drawing to decision task. This task has been used previously in the study of another cognitive bias related to JTC called “bias against disconfirmatory evidence” (Moritz and Woodward, 2006) and comprises the metacognitive training program for schizophrenia patients (Moritz et al., 2011). Like the beads task (Huq et al., 1988), which is the task most used in the study of JTC, the principal dependent measures are the plausibility rating of each stimulus presented and the amount of information needed to reach a final decision about the identity of the depiction. These two measures are analysed in two kinds of trial (“cued” and “uncued”; that is, with and without interpretative cues). This is a specific characteristic of the task, allowing us to analyse the effect of the context in which the decisions are made.
Exploration of both hypotheses through the same task can contribute to extending the previous results about JTC bias in two ways. Firstly, they provide a unified explanation of the many proposed causes at the origin of this bias. Secondly, an analysis of the context will allow us to discover if this bias is only present when subjects have been instructed to derive their own interpretations about reality, or when the context of a decision has been previously defined by interpretative cues. Moreover, the results from all three groups (schizophrenic patients, their siblings and controls) can be compared to reflect the hypothesised order of liability to psychosis according to the studies cited above.
A second aim of this work is to explore associations between the Jumping To Conclusions parameters of our task, psychotic symptoms, executive functioning and theory of mind. Jumping To Conclusions and theory of mind are typically found to be associated with positive symptoms, and executive functions with negative symptoms. However, empirical evidence for these associations is often not well founded. Recently, Woodward et al. (2009) applied a multivariate approach to assess this pattern of associations. Their results suggest that the JTC bias is related to executive functioning and may be independent of theory of mind deficit and positive symptoms. In short, this is an open question towards which our study may provide new insights.
