Young H F, Bentall R P
Department of Psychology, Reaside Clinic, Rubery, Birmingham.
Psychol Med. 1997 Mar;27(2):455-65. doi: 10.1017/s0033291796004540.
Research indicates that deluded patients 'jump to conclusions' on probabilistic reasoning tasks. Two experiments were carried out with patients suffering from persecutory delusions and depressed and normal controls in order to determine whether this response bias is affected by task difficulty and the meaningfulness of the materials.
Tasks were variants of those employed by Huq et al. (1988) and Garety et al. (1991). In Experiment 1, subjects judged which of two bags a sequence of coloured beads had been taken from. Difficulty was manipulated by varying the ratios of coloured beads in the bags. In experiment 2, a neutral condition required judgements about coloured beads drawn whereas, in meaningful conditions, subjects had to judge whether personality characteristics described one of two individuals.
In Experiment 1, estimates of certainty varied with task difficulty, and there was no evidence of 'jumping to conclusions' in the deluded group. In Experiment 2, all groups reached an initial level of certainty and reduced their estimates of certainty following disconfirmatory evidence more quickly in the meaningful conditions. Both clinical groups expressed higher certainty levels in early trials, and a greater magnitude of reduction in certainty following disconfirmatory information. These group differences were more evident in the meaningful conditions than in the neutral conditions.
Probabilistic reasoning is affected by task difficulty and meaningfulness of materials in both deluded and depressed subjects. Observed reasoning abnormalities were not specific to the deluded group.
研究表明，患有妄想症的患者在概率推理任务上“急于下结论”。进行了两项实验，对象为患有被害妄想症的患者、抑郁症患者以及正常对照组，目的是确定这种反应偏差是否受任务难度和材料意义性的影响。
任务是胡克等人（1988年）和加雷蒂等人（1991年）所采用任务的变体。在实验1中，受试者判断一系列彩色珠子是从两个袋子中的哪一个取出的。通过改变袋子中彩色珠子的比例来操纵难度。在实验2中，中性条件下要求对抽取的彩色珠子进行判断，而在有意义的条件下，受试者必须判断所描述的性格特征是否适用于两个人中的一个。
在实验1中，确定性估计随任务难度而变化，妄想组没有“急于下结论”的证据。在实验2中，所有组在有意义的条件下，在获得反证后，最初都达到了一定的确定性水平，并更快地降低了对确定性的估计。两个临床组在早期试验中表达的确定性水平更高，在获得反证信息后确定性降低的幅度更大。这些组间差异在有意义的条件下比在中性条件下更明显。
概率推理受任务难度和材料意义性的影响，在妄想症患者和抑郁症患者中均如此。观察到的推理异常并非妄想组所特有。
