Social identity is a social theory developed by Henri Tajfel in 1979. Tajfel postulated that the groups people see themselves as belonging to are "an important source of pride and self-esteem" (Saul McLeod, "Social Identity Theory"). A social group can be considered to be anything, like a "social class, family," a sports team, a neighborhood, a country, an ethnicity, or even a gang (McLeod). Tajfel argued that making the group we belong to seem important also boosts our own self-image. For example, showing patriotism for our country will make us feel proud of ourselves, thereby increasing our level of self-esteem. Tajfel further argues that seeing ourselves in a group, we also view the world as either "us" or "them." In other words, yes, social identity affects how we view the world because we either view the people of the world as belonging to our group or groups, which is "us" or belonging to other groups outside our own, which would be "them." Such social identity is the underlying cause of prejudice and discrimination because, as McLeod states, "the in-group will discriminate against the out-group to enhance their self-image."
Tajfel also identified a three-step process to identifying an "us" group vs. a "them" group. The first step is categorization. Human beings have a natural inclination to categorize objects we see in order to understand them better and to identify them. For example, we not only categorize apples and oranges as apples and oranges, we also categorize them as types of fruit. We further create social categories, such as "black, white, Australian, Christian, Muslim, student, and bus driver," because they help us better understand our world, and each category tells us something about the people in the groups (McLeod). After we categorize, we enter the second step in the process of identifying "us" vs. "them," which is social identification. Through social identification, we categorize ourselves and identify with that group. We also adopt the identity. McLeod gives us the example that if we categorize ourselves as students, we will then start undergoing the practices that belong to students, such as studying. After social identification, we move to the third step, which is social comparison. Once we have categorized and identified ourselves as belonging to a group, we then compare our group to other groups. For example students are different from those who are in the workforce full time. It's when we start to undergo the natural step of social comparison that prejudices can arise, leading to discrimination. The reason is because, once two groups have been categorized as opposites and even "rivals," the two groups are "forced to compete in order for the members to maintain their self esteem" (McLeod). Hence, according to Tajfel, prejudice is the result of two groups competing to maintain self-esteem.
Therefore, it can be said that social identity affects how we see the world because, through the theory of social identity, we identify ourselves with groups in order to increase our self-esteem. More importantly, identifying with a group leads to human beings seeing the world through an "us" vs. "them" perspective, leading to prejudices. We undergo the process of social identity by categorizing, identifying with a category, and then comparing the categories. Comparing categories leads to rivalry between categories, which results in prejudice.
Absolutely. Social identity basically says that an individual develops notions about the world and themselves based on how he sees himself in relation to other groups.
Think about it this way. There are two groups. One is yours and then there is the other group. We can call these "us versus them." In order to establish our identity and understand our role in society, we must belong to a group. And once we do, we try to distinguish our group from others and often times, we do this by stereotyping the characteristics of the other group. We try to see ourselves as better or superior by ignoring the familiar or positive qualities of other groups and taking notice of their different and negative qualities.
Although we all have a social identity, it's not a rigid thing. Our identity can change and we can have multiple identities with one or two being more important than others. For example, I may label myself as a mother, a teacher and an American. These are all identities and the way I order them gives an idea about which identity is most important for me. It's also possible that they may be equally important. Five years from now, I may have new identities or some may become more important while others take a back seat.
So to summarize, we form a worldview, determine our place in society and interact with others based upon our social identity. It is vital for all of these.
A persons perspective on life depends entirely on their social identity. Whether it's something you choose or something you're born into, your individual identity shapes how you feel about your world and how you interact with it. For example, a rich person from New York and a poor person from Colorado will have completely different views on a law passed in America, and both will handle their veiws in a different way.