Dudley R E, John C H, Young A W, Over D E
Department of Psychology, University of Durham, UK.
Br J Clin Psychol. 1997 May;36(2):243-58. doi: 10.1111/j.2044-8260.1997.tb01410.x.
People who experience delusions have been found to request less information prior to making a decision than control participants on tasks that are unrelated to the theme of the delusion (Huq, Garety & Hemsley, 1988). Two studies investigated whether people with delusions have an absolute deficit in reasoning or a more specific data-gathering bias. In Expt 1, 12 people with delusions, 12 people with depression and 12 normal controls were shown the results of spinning a supposedly biased coin. The evidence provided varied in the number of heads to tails. In normal controls a high ratio of head to tails produces a high estimate that the coin is biased. In this experiment, where the evidence gathered was predetermined by the experimenter, all groups of participants were shown to reason in a similar way. Experiment 2 tested whether a difference would exist between the groups in conditions where participants were free to determine the amount of evidence seen, in contrast to when all of them viewed the same evidence. Two jars of beads in opposite but equal ratios (e.g. 85:15, 15:85) were shown to 15 people with delusions, 15 with depression and 15 normal controls. On the basis of beads being drawn one at a time, it was the participants' task to determine which jar they came from. When free to decide when they wished, people with delusions decided on the basis of less evidence than the other groups. However, as in Expt 1, the group with delusions did not differ when made to view the same amount of beads as other participants. Therefore, people with delusions have a data-gathering bias rather than a difficulty in employing the data in reasoning. This "jump to conclusions' bias generalized to a less discriminable ratio of beads (60:40), and was not a consequence of impulsiveness or memory deficit.
研究发现，与对照组参与者相比，有妄想症的人在做出决策前收集的与妄想主题无关的任务信息更少（胡克、加雷蒂和赫姆斯利，1988年）。两项研究调查了有妄想症的人是在推理方面存在绝对缺陷，还是存在更具体的数据收集偏差。在实验1中，向12名有妄想症的人、12名患有抑郁症的人以及12名正常对照组展示了抛一枚据说有偏差的硬币的结果。提供的证据中正面与反面的数量各不相同。在正常对照组中，正面与反面的比例很高会导致人们高度认为硬币有偏差。在这个由实验者预先确定收集到的证据的实验中，所有参与者组的推理方式相似。实验2测试了在参与者可以自由决定查看证据量的情况下，与他们都查看相同证据时相比，各组之间是否会存在差异。向15名有妄想症的人、15名患有抑郁症的人以及15名正常对照组展示了两罐珠子，珠子比例相反但相等（例如85:15、15:85）。参与者的任务是根据一次抽取一颗珠子来确定珠子来自哪一罐。当可以自由决定何时停止时，有妄想症的人比其他组的人基于更少的证据就做出了决定。然而，与实验1一样，当让有妄想症的组与其他参与者查看相同数量的珠子时，该组没有差异。因此，有妄想症的人存在数据收集偏差，而不是在推理中运用数据存在困难。这种“急于下结论”的偏差在珠子比例更难区分的情况下（60:40）也存在，并且不是冲动或记忆缺陷的结果。
