囚犯困境博弈中分離效應之檢驗

Examining Whether There is a Disjunction Effect in Prisoner's Dilemma Games

本研究旨在驗証「分離效應」（Disjunction Effect）（Shafir & Tversky, 1992；Tversky & Shafir, 1992）和「齊差求辨」（Equate-to-differentiate）模型（Li, 1994a）對一次性囚犯困境（Prisoner's Dilemma）問題所作的解釋和預測。「分離效應」認為，人們對決策結果的評估不是以相因而生（consequentialist）的方式進行，當參與者知道對手採取了競爭或合作策略，參與者均清楚競爭比合作更有利，故多半會採取競爭策略應付；當參與者不知對手採取了何種策略，相互合作隱約變得更有吸引力，故參與者傾向採取合作策略應付。「齊差求辨」抉擇模型則認為，囚犯困境博弈中的決策行為是權衡在“自己收益維度”上作選擇還是在“他人收益維度”上作選擇的過程。人們選擇競爭是因為最終決策只在“自己收益維度”上進行；人們選擇合作是因為最終決策只在“他人收益維度”上進行。本研究設計了7種類型的囚犯困境問題，並在3種條件下對此進行檢驗：（1）參與者已知對手採取了競爭策略；（2）參與者已知對手採取了合作策略；（3）參與者不知對手採取了何種策略。結果顯示，「齊差求辨」策略比「分離效應」能更滿意地對違背「確定事件原則」（sure thing principle）的決策行為作出解釋。本實驗所作的嘗試亦為進一步探索其它分離條件下推理困難現象提供了新的途徑。

The aim of this study was to investigate the Disjunction Effect (Shafir & Tversky, 1992; Tversky & Shafir, 1992) explanation and the Equate-to-Differentiate (Li, 1994a) prediction regarding the performance of adult subjects on 7 variants of the Prisoner's Dilemma under conditions (a) where it was known that the other player chose to compete, (b) where it was known that the other player chose to cooperate, and (c) where the subject did not know what the other player would choose. The equate-to-differentiate approach, which takes into account the relative payoffs for each player in the decision-making situation, yet allows for the individual's limited cognitive capacity to process all the relevant information available, thus provides an alternative and seemingly better account of the disjunction effect observed for decision-making on the Prisoner's Dilemma. To test the generality of this explanation for other phenomena where difficulties of thinking with disjunctions have been identified, the present exploration would provide us with a new guidance as to the route further research might take.