School of Psychology, University of Central Lancashire, Preston, UK.
Department of Psychology, Goldsmiths College, University of London, New Cross, UK.
Scand J Psychol. 2019 Oct;60(5):405-420. doi: 10.1111/sjop.12560. Epub 2019 Jun 26.
Probability judgment is a vital part of many aspects of everyday life. In the present paper, we present a new theory of the way in which individuals produce probability estimates for joint events: conjunctive and disjunctive. We propose that a majority of individuals produce conjunctive (disjunctive) estimates by making a quasi-random adjustment, positive or negative, from the less (more) likely component probability with the other component playing no obvious role. In two studies, we produce evidence supporting propositions that follow from our theory. First, the component probabilities do appear to play the distinct roles we propose in determining the joint event probabilities. Second, contrary to probability theory and other accounts of probability judgment, we show that the conjunctive-less likely probability difference is unrelated to the more likely disjunctive probability difference (in normative theory these quantities are identical). In conclusion, while violating the norms of probability judgment, we argue that estimates produced in the manner we propose will be close enough to the normative values especially given the changing nature of the external environment and the incomplete nature of available information.
概率判断是日常生活中许多方面的重要组成部分。在本文中，我们提出了一种关于个体如何对联合事件（合取和析取）产生概率估计的新理论。我们提出，大多数个体通过从不太可能的成分概率进行正向或负向的准随机调整来产生合取（析取）估计，而其他成分则没有明显作用。在两项研究中，我们提供了支持我们理论的命题的证据。首先，组成概率似乎确实在确定联合事件概率中发挥了我们所提出的不同作用。其次，与概率论和其他概率判断理论相反，我们表明，合取的不太可能概率差异与更可能的析取概率差异无关（在规范理论中，这两个数量是相同的）。总之，虽然我们的估计方法违反了概率判断的规范，但我们认为，特别是考虑到外部环境的变化性质和可用信息的不完整性，我们提出的这种估计方法产生的结果将足够接近规范值。
