人們相互模仿彼此的行為是人類社會中相當普遍的現象。本文說明即使理性行為者須於不可數多個行為中做選擇，這些行為者之間仍會發生羊群行為。經由觀察所有行為者的決策歷史，行為者之間將產生一種動靜機制，此機制能確保在面對性質極差的效用函數，如無處可微的效用函數時，行為者亦能從可選集合中，選出在給定歷史之下的最佳選擇，並且隨著決策歷史的增加，行為者的行為將會趨於一致。

We show that herd behavior occurs even among rational individuals, whom has no prior understanding of the continuum many actions to be chosen from. A move-or-stand-still process induced by observing the decision history of all the individuals will be served as the optimization method for nowhere differentiable utility function.

[Thesis Verification Letter i]
[Preface ii]
[Abstract in Chinese iii]
[Abstract in English iv]
[I. Introduction 2]
[II. The Move-or-Stand-Still Process 3]
[III. Concluding Remark 9]
[Reference 10]

1. Banerjee, Abhijit V. (1992), “A Simple Model of Herd Behavior,” Quarterly Journal of Economics, 107(3), pp.797-817.
2. Bikhchandani, Sushil, Hirshleifer, David and Ivo Welch (1992), “A Theory of Fashion, Custom, and Cultural Change,” Journal of Political Economy, 100(5), pp. 992-1026.
3. Shiller, Robert J. (1995), “Conversation, Information, and Herd Behavior.” The American Economic Review, 85(2), pp. 181-185.