Chinese Journal of Psychology 2004, Vol. 46, No. 1, 57-74
個人在做判斷時， 一些對判斷沒有幫助的非診斷性訊息會沖淡診斷性訊息對判斷的影響， 而使得所做出的判斷比只根據相同的診斷性訊息所做的判斷來得保守， 此即所謂的"稀釋效果"。
實驗二中我們探計不同思考目的對稀釋效果的影響。本實驗採 6 (思考目的：價值相關涉入、反向思考、 解釋的責任、印象相關涉入、不偏誤判斷，及無特定思考目的） X 2 (訊息型態： 未稀釋組或稀釋組）的二因子受試者間設計。實驗結果顯示，只有在反向思考的目的下，方能有效消除稀釋效果。我們認為，這是因為反向思考提供了一個相反的定錨點為參考，使判斷可據此相反的定錨點加以對照修正，所以可以降低稀釋效果。
The Effects of Information Type and Thinking Purpose on Dilution Effect
Chien-Ru Sun (Department of Psychology, Chung Yuan University) , and Yi-Ru Lee (Department of Psychology, Chung Yuan University)
The dilution effect refers to the phenomenon that when diagnostic information is diluted with nondiagnostic information, our judgment or inference will become less extreme. The present study examined the effects of information type and thinking purpose on the dilution effect.
Experiment 1 aimed at exploring the possible impact of different nondiagnostic information types on the dilution effect. We manipulated typicality and typical diagnosticity of the nondiagnostic information independently. Seventy-eight subjects were randomly assigned to one of the following conditions: (1) the undiluted condition: receiving diagnostic information only, (2) the dilution condition: receiving diagnostic information and nondiagnostic information which is typical and low in typical diagnosticity, (3) the dilution condition: receiving diagnostic information and nondiagnostic information which is atypical and low in typical diagnosticity, (4) the dilution condition: receiving diagnostic information and nondiagnostic information which is typical and high in typical diagnosticity, (5) the dilution condition: receiving diagnostic information and nondiagnostic information which is atypical and high in typical diagnosticity. The results indicated that when the typical diagnosticity of the information is high, then regardless of the typicality, the dilutuion effect occurred. On the other hand, we also found that if the information is typical, then no matter the typical diagnosticity is high or low, the dilution effect also appeared. In other words, the nondiagnostic information, only when it is atypical and low in typical diagnosticity, would have no impact on our judgment.
Experiment 2 was focused on the effects of thinking purpose on the dilution effect. Subjects were randomly assigned to a 6 (thinking purpose: value-relevant involvement vs. consider-the-opposite vs. explaining to others vs. impression-relevant involvement vs. being unbiased vs. none) X 2 (information condition: undiluted vs. diluted) factorial design. The result showed that only the consider-the-opposite strategy could eliminate the dilution effect, and other thinking purposes didn't have the same impact. Further implications were also discussed.
Keywords: dilution effect, typical diagnosticity, typicality, consider the-opposite, involvement, accountability.