Presenter: Just before my first year of college, I was excited and nervous about meeting other new students on campus. As soon as dorm assignments were announced, we all began friending each other on Facebook and following each other on Twitter. This is how I found out that my roommate was an obsessive soccer fan and had seen all of Quentin Tarantino's movies.

The school also sponsored online forums, allowing me to learn about different student groups and to find like-minded people across campus. For example, I connected immediately with other students who share my interest in animal rescue and adoption. These online connections in groups helped my college friendships develop quickly and meaningfully and gave me a sense of belonging on campus before I even arrived.

Today I'd like to share with you how social media is being used not only to help students connect, but also as a powerful tool to advance social causes and motivate us to act on their behalf. We'll start by looking at a compelling theory of why social media is so uniquely suited to forging these connections. Next, I'll review some data on social media's meteoric rise. Finally, we'll see how today's activists are harnessing social media to support an array of social causes to make life better for us all.

Let's begin our conversation on these intriguing developments in communication by considering the underlying reasons why we want to use social media in the first place. What is it that drives us to connect through social media with like-minded people and groups? Social identity theory offers a compelling answer to this question.

First, let me define the concept of social identity. Social identity refers to how you understand yourself in relation to your group memberships. Michael Hogg, a professor of social psychology at Claremont University, focuses on social identity research.

In his 2006 book on contemporary social psychological theories, Hogg explains that group affiliations provide us with an important source of social identity, and we therefore want our groups to be valued positively in relation to other groups. By affiliations, I simply mean the groups that we join and perhaps link to online.

Social psychologist Henri Tajfel, one of the founders of social identity theory, spent years considering how we form our social identities. Tajfel believes that the groups to which we attach ourselves, both online and off, help answer the very important question, who am I? According to Tajfel's 1979 book, The Social Psychology of Intergroup Relations, we associate with certain groups to help resolve the anxiety brought about by this fundamental question of identity. By selecting certain groups and not others, we define who we are and develop a sense of belonging in the social world.

Social media sites such as Facebook provide a platform for this type of social identity formation by offering its participants certain tools, such as the ability to friend people, groups, and even brands and to like certain posts. The simple act of friending, for example, promotes affiliation between two individuals. And our Facebook friends are collectively a source of our social identity. Because we are proclaiming something important to our groups, announcing that we're in a serious relationship takes on great social significance. As we all know, it's not official unless it's Facebook official.

As you can see, social identity theory gives us insight into the reasons behind the popularity of social media sites. They let us proclaim to ourselves and to the world, this is who I am. Even so, the near miraculous rate of growth of these sites over the past decade is surprising.

According to Marcia Clemmitt's 2010 CQ Researcher article on social networking, Facebook had over 1 million users in 2005, just one year after its initial launch. This growth from zero to a million in one year was quite an impressive feat. Today, according to a May 2013 article on the number of active Facebook users published by the Associated Press, Facebook harbors over 1.16 billion members. That's almost four times the population of the United States.

Like Facebook, Twitter's growth has also been astronomical. Shea Bennett, editor of the Mediabistro-sponsored blog AllTwitter, reports in an October 2013 article that Twitter had 218 million active users at the end of June 2013. Like Facebook, Twitter's success can be largely attributed to the demand for virtual communities that enable us to connect with one another.

As the data clearly show, people around the world are defining themselves socially and answering the question who am I through the use of social media sites. And social movement organizations have taken note. Organizations of all kinds are using social media to get their messages across and spur their members into action.

Social movements, defined by Princeton.edu as a group of people with a common ideology who try together to achieve certain general goals, range across the political and social spectrum. Consider Occupy Wall Street and the Tea Party. Both of these organizations use social media to communicate their messages and build support. For example, they use Facebook to announce events and link to petitions.

In fact, a nonprofit organization called Social Movement Technologies created a Facebook page to help individual social movement organizations help get their messages out. But social media is not just being used as a platform for informing the public of a group's mission and activities, or even merely to get people to sign a petition. Increasingly activists are deploying social media to motivate like-minded people to get into the fight.

To get a sense of what this means, consider the recent efforts of a 17-year-old skateboarder from St. Cloud, Minnesota. For three years, Austin Lee found himself struggling to get support for a local skate park. But when he decided to use Facebook for his cause, things changed nearly overnight.

Lee's posting attracted 1,085 members and even drew some of those members to city council meetings on behalf of his cause. David Unze of USA Today reported that Lee won the approval and $500,000 for his state park. And it all happened within one day of Lee's original posting on Facebook.

So as you can see, if you can use social media to convince people to identify with what you want to accomplish, success is possible. Lee's accomplishment shows us that we not only identify and affiliate with groups, but also are willing to actively work towards accomplishing their goals.

Today I hope I've shown that the skyrocketing use of social media over the past decade is no accident. The human desire to develop a positive sense of social identity through group affiliations is one reason for this phenomenon. Capitalizing on this universal psychological drive, social movement organizations are harnessing these technologies to accomplish their goals.

Social media sites allow us to communicate, express, and identify with one another in ways that enable affiliation as well as action. Whether it's a major political movement or a teenager's desire for a local state park, social media technologies are powerful. So as you tweet about new groups or see the next Facebook official status update, think about what groups you like, whom you have friended, and what those affiliations may be able to do for you.