人們每天作無數的決策，而作決策的目的經常是為了讓自己感受愉悅與滿足最大。早期的經濟學以擁有或消費商品數量多寡作為滿足感衡量的標準，即消費數量作為效用大小的函數，並從效用高低做出行為決策。但現今我們發現某些行為決策並非是以數量多寡或價格高低為其決策動機，而是以心理層面的認同與否來提升或降低自我效用。消費名貴的轎車與時尚品牌包皆是以社會地位的認同所產生的購買動機。因此，本研究引用Akerlof & Kranton(2000)的認同效用函數，分析他人對我或我對他人的認同行為是如何影響彼此間的效用，最後再以賽局理論的方式，探討三個人或三群人間在認同交互影響下，是如何作出最適行為決策。本研究以認同的效用函數建立一個賽局的模型，並應用在二種案例中。二種案例分別為品牌認同的決策賽局與中間選民的決策賽局。對消費者而言，由於品牌認同的緣故，產品價格對消費者而言已不重要，重要的是品牌帶給消費者背後的象徵意義與別人見到我消費此品牌是如何看待我之感受，而這將是消費者做出行為決策的重要依據。後者則是探討中間選民在選舉時，在不同政黨與候選人之間，是如何受到認同與不認同的影響，而作出投票的行為決策。最後我們發現，不論是消費者或選民，透過認同的影響，最後都能選出一種對自己最有利且效用最適的行為決策。

There are many decisions people make every day. The general purpose of making decisions is to achieve self happiness and maximum satisfaction. Traditional economics was commonly used the amount of consumption to measure the utility as standard, which means that consumption refers to the size of utility function and in order to make behavioral decision from the degree of utility. However, nowadays we find out that some behavioral decision making is not determine by high or low price, but produce self utility form the psychology of identity as policy motivation. The urchasing motive in consuming valuable cars and fashionable handbags products are produced by the identity of social status. The purpose of this research is to cites the identity utility function by Akerlof & Kranton (2000) to analyze how the identity effect the behavior of others identity. Next, the theory of game was used to discuss the interaction among three individual people to three groups of people and how it affectsfinal result to make the best behavior decision making. Procedures based on recognition utility function to create a game theory model and two cases are applied in it. The first case is the decision making game of brand identity. The second case is the decision making game of the median voter. As for the former, the price of product is no longer importance for the consumers due to thebrand identity. It is of great concern that the hidden symbol which the brand brings to the consumers and how do others look at me with the brand and how do they feel about me. It is indispensable for consumers to making a decision. As for the latter, that is, the behavior of median voters. We detected that median voters are affected by identity between political parties and they will vote only one candidate because of the higher identity utility. To sum up, we found out that whether consumers or voters, both of them will make the most benefic and optimal behavioral decision on account of the influence of identity.