見面三分情與終局效果：囚犯困境賽局之實驗

Face-to-Face and End-Game Effects in Prisoner Dilemma Games – An Experimental Study

本研究利用實驗經濟的方法來檢驗雙佔Bertrand市場中，廠商的決策行為是否會因為匿名與否以及是否事先知道賽局回合數及何時結束而有顯著的差異。本文有別於過去相關賽局文獻以合作為實驗分析重點，我們改用 ＂背叛＂－－即不合作為分析重點，並再將之細分為弱式和強式背叛進行檢定。實驗的結果顯示匿名與否會造成受試者的決策行為有顯著的差異；亦即在不匿名的情況下，即使是與對手只有一面之緣，受試者採取背叛策略的次數顯著較少，故從實驗結果確定見面三分情的效果的確顯著。此外，本文亦針對在重覆賽局中，若受試者是否因知道賽局何時結束，而在賽局結束前幾回合即提前背叛，即所謂「終局效果」來進行檢定。經無母數的檢定結果證實在匿名時，終局效果是顯著的，受試者在遭對手背叛之前會選擇先下手為強；但在不匿名的情況下，可能受到見面三分情的影響，終局效果並不顯著。

This experimental study aims to examine the end-game effects of prisoner’s dilemma games presented in a form of Bertrand competition with the face-to-face versus anonymity treatments in a repeated game. Our experimental findings are summarized as follows. First, it is found that firm's decisions to defect in the face-to-face condition are statistically different from that in the anonymous condition. Specifically, the frequencies of firm's defections in the face-to-face condition are significantly less than the ones in the anonymous condition. Second, the results also confirm the end-effects as predicted by the reputation model in which cooperation occurs in early rounds of the game and then is followed by defection in rest of rounds in a finitely repeated game under the anonymity condition. However, the end-game effects are attenuated under the face-to-face condition.