People with schizophrenia are more likely to jump to conclusions about things than other people. In one experiment participants were asked to judge whether a jar contained more of one or another colour of beads as they were pulled out, one by one; compared to other people people with schizophrenia made early, premature and incautious decisions in 40-70% of cases. Researchers are unsure whether this is because people with schizophrenia are anxious and don't cope with uncertainty very well or because they have a lower threshold for believing things than other people - something psychologists call liberal acceptance. A team of researchers from Germany and Canada investigated this further by showing 27 people with schizophrenia and 32 without pictures of obscure paintings. The paintings were given four alternative titles, one correct and three wrong ones. The participants were asked to rate the likelihood that each title was the correct one and could - but did not have to - make a decision about which was the right one. While they were doing this either happy, anxiety-making or no music was played in the background. People with schizophrenia were more likely to make a decision about the title of the paintings even if two of the alternatives were very close to one another. They were also more likely to give higher marks to some of the more implausible titles. Overall there was no difference in people jumping to conclusions while they were being played the anxiety-making music but people currently experiencing delusions were more likely to jump to conclusions while listening to it.
Moritz, S. ... [et al] - Decision making under uncertainty and mood induction: further evidence for liberal acceptance in schizophrenia Psychological Medicine November 2009, 39(11), 1821-1829