Abstract: The debate about the function of base-rate in Bayesian reasoning has never been stopped. There are three main viewpoints: (1) people overweight the base-rate; (2) people neglect the base-rate completely; (3) people take it into account, but think poorly of its function. Considering the majority existing studies use the posterior probability and reaction time to infer the reasoning process reversely and lack support of the real-time data, the study provided eye-movement evidences for the process of Bayesian reasoning by using Eye View Monitoring Systems for the first time. The research hypothesized that the eye-movement targets induced by different levels of base-rate and cognitive styles will be significantly different. Thirty-five college students were sampled for this experiment. In order to examine the effects of two different levels of base-rate (e.g. high vs. low) and two kinds of cognitive styles (e.g. the field dependence cognitive style vs. the field independence cognitive style) on Bayesian reasoning , the study recorded the total fixation duration and numbers of fixation by using Eye View Monitoring Systems. The inference materials were about illness which were divided into four area of interests (AOI), AOI1 was about the base-rate, AOI2 was about the hit-rate, AOI3 was about the false alarm rate, and AOI4 was the area where the question located. The results were as follows: (1) when compared the total fixation duration and numbers of fixation, the main effect of base-rate and cognitive style were not significant, but the interaction between them was significant, and the simple effect analysis showed: a. when the base-rate was low, the total fixation duration and numbers of fixation of the group with the field dependence cognitive style were more than those of the group with the field independence cognitive style; b. the total fixation duration and numbers of fixation of the group with the field independence cognitive style in high base-rate level were more than those in low base-rate level; (2) when compared the total fixation duration and numbers of fixation, the main effect of AOI was significant, the order of the extent of each AOI was paid attention to was: AOI2＞AOI3＞AOI1＞AOI4. These results indicated that: (1) in the process of Bayesian reasoning, the probability information were differently followed with interest, the order was: hit-rate＞false alarm rate＞base-rate, and the base-rate was not neglected completely but was just underweighted. (2) people with different cognitive styles held different process ways, generally speaking, people with the field independence cognitive style intended to think rationally while those with the field dependence cognitive style were always influenced by the external information.

Key words: base-rate, cognitive styles, Bayesian reasoning, eye-movement

摘要： 选取35名本科生为被试，采用EyeLink II眼动仪，考察了基础比率和认知风格对贝叶斯推理的影响，探讨了基础比率作用机制的争论。实验采用2（基础比率：高、低）×2（认知风格：场依存、场独立）双因素被试间设计，要求每位被试完成一道贝叶斯推理题，问题内容为疾病情境。将推理材料划为AOI1（描述基础比率）、AOI2（描述击中率）、AOI3（描述虚报率）、AOI4（提问）4个兴趣区，分别记录被试的总注视时间、注视次数等。结果发现：（1）在总注视时间和注视次数指标上，基础比率和认知风格的主效应均不显著，两者的交互作用显著；（2）在总注视时间和回视次数指标上，各兴趣区差异显著，关注程度从高到低依次为：AOI2＞AOI3＞AOI1＞AOI4。这说明，在贝叶斯推理中，并没有完全忽视基础比率；对于不同认知风格的个体而言，基础比率所起的作用是不同的。这也给我们一点启示：或许我们不能单一地去考虑基础比率的作用机制，而应该将它与个体的某些因素结合起来综合加以讨论。

关键词: 基础比率 认知风格 贝叶斯推理 眼动