.           
1.2 The Theory of Ego Identity
Ego identity is a key concept in Erikson's theory. It refers to a psychological construct composed of components or dimensions that are dynamically integrated and gradually change with age and experience. According to Erikson, the task of identity formation, or that of gaining a clear and coherent sense of knowing oneself and what one will be in life, is regarded as a normative developmental process influenced by personal and social contextual factors.
“Ego identity has been a crucial phenomenon in the study field of developmental psychology since Erikson first proposed the concept. Empirical study concerning self identity has been largely based on Marcia's identity status model.”
IDENTITY STATUSES
                               Identity Status
Position on
Occupation
and Ideology    Identity Achievement
(Renton later)    Foreclosure
(Diane)    Identity Diffusion
(Renton’s friends)    Moratorium
(Renton at the beginning)
Crisis    Present    absent    present or absent    in crisis
Commitment    Present    present    absent    present but vague
“The identity statuses were developed as a methodological device by means of which Erikson's theoretical notions about identity might be subjected to empirical study. They seem now to have become a part of identity theory. The identity statuses are four modes of dealing with the identity issue characteristic of late adolescents:
1. Identity Achievement
2. Foreclosure
3. Identity Diffusion
4. Moratorium                                             
Those classified by these modes are defined in terms of the presence or absence of decision making period (crisis) and the extent of personal investment (commitment) in two areas: occupation and ideology. Identity Achievements are inpiduals who have experienced a decision-making period and are pursuing self-chosen occupation and ideological goals. Foreclosures are persons who are also committed to occupational and ideological positions, but these have been parentally chosen rather than self-chosen. They show little or no evidence of "crisis." Identity Diffusions are young people who have no set occupational or ideological direction, regardless of whether or not they may have experienced a decision-making period. Moratoriums are inpiduals who are currently struggling with occupational and/or ideological issues: they are in an identity crisis.” (Marcia, 1980, 111-112)

2 Three Types of Characters
According to the features of characters in the film, the figures in the film can be classified into three modes.
2.1 Renton
The first kind is Renton. In the film, Renton belongs to Moratorium at first. He is a person who is addicted to drugs and is always fooling around with his friends. However, at the same time, he feels anxiety and tries to quit drug. So he belongs to Moratorium mode, meaning that he is in an identity crisis, in the meantime he tries to make some commitment.      
2.2 Renton’s Friends
The second kind is Renton’s friends. They belong to Identity Diffusion. They do the worst things in the society. They use drugs, they get drunk, they bull around, and they do robberies. Their daily lives consist of all evil behavior. They don’t know where their future lies and they don’t want to know. They just choose not to choose. So these people belong to Identity Diffusion. They are in crisis, but they have no desire to make any commitment. 论电影《猜火车》中的青少年成长(2):http://www.751com.cn/yingyu/lunwen_2688.html