Some people think that people with delusions are more likely to jump to conclusions than other people; something that helps them to maintain their delusional beliefs even when there is very little evidence. Psychologists measure this with the 'beads-in-a-jar' test. They pull different-coloured beads at random from a jar and ask people to make decisions about the proportion of different-coloured beads e.g 50:50 black and white, 90:10 red and green etc. Some people with delusions have been known to make a decision after just one bead! Researchers at Manchester University studied 39 students, 17 of whom were judged to be 'delusion-prone.' The delusion-prone students were found to be much quicker at jumping to conclusions than the other participants. The students were also asked to rate how rushed they felt when carrying out the task. Those who felt more rushed were quicker to jump to conclusions suggesting that a feeling of being rushed could be one of the factors leading people with delusions to make hasty judgements.
White, Lars O. and Mansell, Warren - Failing to ponder? Delusion-prone individuals rush to conclusions Clinical Psychology and Psychotherapy March 2009, 16(2), 111-124