What is the primary mechanism behind nationalism, sports-team-ism, product-ism etc.?

Question

I'm interested in doing research on the subject of nationalism, but I believe that what I'm looking for is more generic than that. I observe that nationalism looks similar to the way that people feel about their sports team or their favorite product or their religion or their race. People proselytize for these things, and people sometimes kill over them (e.g. -- soccer riots). I note also that this kind of devotion can also produce strong negative feelings towards the other teams, countries, etc.

In each case, a person exhibiting this behavior with respect to a country, sports team, or product has at least one of the following characteristics (maybe others?).

1. Person identifies personally with X.
2. Person feels a sense of belonging with others who also identify with X.
3. Person is inclined to convince others that they should also follow/admire/believe X.

Is there an underlying mechanism behind these symptoms or term that describes this behavior? What is the body of study that examines these types of behaviors (causes, definitions, and effects)? If there isn't a particular term for this as a generic subject of study, are there at least some studies that examine the common features of these behaviors?

What I have researched so far: This question helped a little bit in thinking about this issue, but I'm not sure it answers my question. Also, Maslow's hierarchy of needs points to "respect by others" and "belonging" as posibilities, but I don't know much beyond that or where to look.

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Update

I'm stuck. I'm just not sure that ingroups and outgroups really characterize the fundamental mechanism behind why people hold some beliefs with evangelistic or violent fervor. That feature of human nature is not dependent on the existence of a group. If I try to convert someone to my way of thinking, I am not doing so because of a group to which I belong. Certainly group behaviors that @PEEJWEEJ mentioned can feed such sentiments, but like I mentioned to @Ana, I'm not convinced that the group itself is the cause. Perhaps I could be persuaded otherwise, but I think there's something else going on here.

Answer 1

The terms you are looking for are ingroups and outgroups. From wikipedia:

In sociology and social psychology, an ingroup, is a social group to which a person psychologically identifies as being a member. By contrast, an outgroup is a social group to which an individual does not identify. For example, people may find it psychologically meaningful to view themselves according to their race, culture, gender or religion. It has been found that the psychological membership of social groups and categories is associated with a wide variety of phenomena.

Googling got me to this book chapter on the topic, but there's plenty more information out there.

Answer 2

In group, out group behavior would likely be the base topic for which you're looking.

I have my own thoughts and theories on the topic, but if you want to delve into some psychological reasons for why in group, out group behavior occurs, you may want to look at group think, (people tend to go along with groups even if they disagree at first) the bystander effect (when responsibility is dispersed among many people, it's less likely someone will do anything about a problem) and confirmation bias (the tendency to see evidence as confirming what you already believe).

If you want some more biological/neurological reasons for the cause, look into mirror neurons. The research suggests that when someone sees something happen to someone else, good or bad, the person seeing it feels essentially the same emotions as the person experiencing it, and the intensity of the observer's feelings seem to be correlated to the amount which that person looks and identifies with the observed person.

Answer 3

Another useful source might be research that manipulates group membership, especially to create totally new groups. If membership alone is the mechanism for these effects, then we'd expect ingroup favoritism even with novel, manipulated groups. And that's what is found. Tajfel's work, and follow-ups, show that individuals quickly and easily categorize people by group membership, and then use that membership to determine cognitions and behaviors.

https://en.wikipedia.org/wiki/Minimal_group_paradigm

Answer 4

Humans tend to evaluate things primarily based on similarity/proximity with thyself and their faiths both in terms of time, space. Their association tendency is directly proportional to the similarity and a feeling of self-worth.

Associative memory and availability heuristics are classical examples. Ref: Thinking fast and slow - Daniel Khneman

For eg: Nationalism is space associated. Most likely people identify themselves among a people of similar beliefs. In other words nationalism can be thought of as something like a religion (but based on different fundamental principles; likely to be termed as constitutions).

If some association can improve one's feeling of self-worth we humans tend to assume the association with that particular identity be it physical thing (leader, boss, celebrity) or conceptual thing (religion, 'isms, Philosophy). Association with a product is something of this kind. This is the principle behind shopping derived satisfaction.

EDIT The answer I posted has got its roots largely from "Thinking fast and slow" by Daniel Khneman.

Self-worth and the feeling of "I" is Freudian based.