Why do you act differently around your close friends than you do around your boss? What makes a clever marketing campaign so persuasive? Why do we sometimes go along with a group, even when we have a feeling they’re wrong? These are the kinds of questions that social psychology tries to answer.

It’s different from personality psychology, which focuses on individual traits, and sociology, which looks at society as a whole. Social psychology zooms in on the individual within a social context. It explores the powerful, often invisible, forces that shape our daily interactions.

A huge part of our mental energy is spent thinking about other people. This is the domain of social perception and social cognition. We’re constantly forming impressions and trying to understand why people do what they do.

To navigate this complex social world, our brains use mental shortcuts. We create categories and assumptions, known as schemas, to quickly process information. When you meet a librarian, you might automatically assume they are quiet and love books. That's a schema at work. It might be right, or it might be wrong, but it saves you the effort of starting from scratch with every new person.

We also make judgments about the causes of behavior. When someone cuts you off in traffic, do you think, “What a jerk!” or “Maybe they’re in an emergency?” The first is a personal attribution (blaming their personality), while the second is a situational attribution (blaming the circumstances). This process of explaining behavior is a central theme in social psychology.

Our social lives are built on attitudes, which are our evaluations of people, objects, and ideas. You have attitudes about everything from political candidates to pineapple on pizza. These attitudes have three components: cognitive (what you believe), affective (how you feel), and behavioral (how you act).

Marketers and politicians spend billions of dollars trying to change your attitudes. Persuasion can happen through strong, logical arguments or through more subtle cues, like using a celebrity endorsement. Understanding how attitudes form and change is key to understanding social behavior.

Perhaps the most powerful force in social psychology is social influence. We are constantly adjusting our behavior in response to the people around us. One of the most common forms of this is conformity.

Classic experiments in the 1950s by Solomon Asch showed this in a striking way. Participants were asked to judge the length of a line, a simple visual task. But they were in a room with actors who were all instructed to give the same wrong answer. A surprising number of participants went along with the group's obviously incorrect choice, just to avoid standing out.

This reveals a fundamental human tendency: our need to belong and be accepted can sometimes be stronger than our desire to be right. This is just one example of how the social world profoundly shapes who we are and what we do.