I am human and let nothing human be alien to me.

—Terence, ancient Roman playwright (195/185–159 BC)

The central question that social psychologists attempt to answer is, Why do people behave the way they do? From this very general question, we can derive more specific ones that focus on problems we would like to remedy. Why can’t people get along with each other better? Why do people care so much about what others think of them? Why do people sometimes conform but other times struggle to stand out from the crowd? Why do people so often make bad choices? How is it possible that the same species that created the Sistine Chapel, the Taj Mahal, Moby Dick, penicillin, the Underground Railroad, democracy, and the Red Cross also produced slavery, the Crusades, concentration camps, the bombing of Hiroshima, and the events of September 11, 2001?

Typically, social psychologists try to answer these broad questions by focusing on more specific inquiries into aspects of human behavior. Where do stereotypes of groups come from? How do stereotypes affect the ways people who believe them view members of the stereotyped group? What information do people use to infer the causes of another person’s behavior? How well does a person’s image of herself match the image that others have of her? Does violent content in the mass media encourage violent behavior in viewers? If so, how? Does the nature of people’s attachment to their parents play a role in their adult romantic relationships? Political scientists, sociologists, anthropologists, economists, philosophers, poets, and novelists all attempt to address some of these questions. However, each discipline approaches them from a particular perspective based on some core assumptions. Such assumptions help define a particular field and distinguish it from others. Contemporary social psychology is based on four core assumptions.

One core assumption is based on an idea proposed by Kurt Lewin (1936), who is generally considered the father of modern social psychology: Any given behavior is determined by the combined influences of individual features of the person and specific aspects of the situation.

To grasp Lewin’s idea fully, we first need to appreciate that a person’s immediate environment profoundly influences how he or she thinks, feels, and acts in social life. This idea of the power of the situation—sometimes referred to as the “great lesson of social psychology” (Jones & Nisbett, 1971)—means that certain situations elicit pretty much the same behavior from people, regardless of how those people differ from each other. Look around at the other students in your social psych class. Some of them are very extraverted and talkative, whereas others are quieter and more reserved. And yet all of them are quiet while the instructor lectures. Why? Because the situation tells them, in a classroom, this is how you behave. In fact, situations can be so powerful that they lead people to do things they normally would never do. This was vividly demonstrated in Stanley Milgram’s (1974) famous studies of obedience. As we’ll discuss in more detail in chapter 7, participants in these studies were remarkably compliant when ordered by an authoritative experimenter to administer what appeared to be potentially lethal electrical shocks to an innocent victim.

And yet, each of us is a unique individual, with a constellation of personality traits, values, attitudes, and beliefs about the world that sets us apart from every other person. Because of the unique genetic makeup that we inherit from our biological parents and even more because of the lessons we have learned from the vast array of experience we have had over the course of our lives, we develop dispositions: consistent preferences, ways of thinking, and behavioral tendencies that manifest across varying situations and over time.

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The field of personality psychology is focused largely on describing traits and documenting their influence on behavior. And the field finds, in fact, that people show a good deal of consistency in behavior across diverse situations that reflect their unique ways of adapting to the world. There is also a high level of consistency in behavior and traits across the lifespan. For example, Costa and McCrae (1994) have shown that behavior observed in the first years of life is associated with related behavioral tendencies in early, middle, and late adulthood. Dispositions powerfully guide how we think, feel, and act in social life. If we go back to your social psych class, chances are that one or two students are talking while the instructor lectures—their dispositional extraversion overrides the power of the situation. And even in the classic Milgram study, 35 percent of the participants refused to continue shocking the victim prior to the final command to do so.

Now that we’ve recognized the power of the situation and the influence of the person’s dispositions, we might be tempted to argue about which is more important than the other in determining people’s behavior. And indeed, for many years psychologists have debated the relative importance of the roles played by individual differences in personality, attitudes, and values on the one hand and situational forces on the other. But following Lewin’s lead, most social psychologists focus on understanding how personality dispositions and situational factors interact to determine our thoughts, feelings, and actions. In other words, the focus is on what types of situations lead particular types of persons to behave in specific ways. Therefore, throughout this book, we’ll consider the influence of the person’s situation, his or her unique personality, attitudes, and values, and the ways in which these factors interact.

A second assumption of social psychology is that virtually all human thoughts, feelings, and actions involve and are influenced by other people and thus are social in nature. Throughout life, we routinely encounter and interact with other people. But even when we’re completely alone, people routinely occupy and consequently help to shape our thoughts. As a result, our view of reality is shaped by our connections to others.

Imagine, for example, a student named Carly who lives alone and is startled from sleep by the piercing sound of her alarm clock. She awakens to thoughts of the Western civilization class she has in an hour and what a bore Professor Drone is. She worries a bit about an upcoming exam and whether she is smart enough to do well in the class. Gazing at the clock, Carly thinks of her younger sister Jen, who gave it to her the day she left for college. Then she wonders why she let her friend Megan talk her into taking an 8 a.m. class with her. As she gets out of bed, Carly notices the Monet painting of a bridge in a garden on the calendar hanging from her closet door. She opens Pandora on her tablet and hears an old Kanye West song. Then Carly lays out her clothes, thinking about what would be the right look for her lunch date with Dwayne. She jumps in the shower and starts singing the new Miley Cyrus single—quietly, so Nick, her neighbor in the next apartment, won’t be disturbed. So in the course of a mere half hour alone with her thoughts, Carly’s inner world has been populated by internal representations of eight other people: Professor Drone, her sister Jen, her friend Megan, Claude Monet, Kanye West, her lunch date Dwayne, Miley Cyrus, and her neighbor Nick.

These and many other people fundamentally shape the way Carly views the world and her place in it. Take, for example, her insecurity about her Western civilization class. How does she know if she is smart enough? Certainly her current grade in the class provides some information. But that grade is feedback from the instructor. In addition, on receiving a grade, most students wonder how everyone else did. In 1954, Leon Festinger pointed out that looking to others—our social comparisons—is essential to how we understand ourselves. We get a sense of the right or wrong way to act, what is good or bad, and what is true or not true by examining what other people do or say. Whether it’s Carly’s aptitude for history or her choice of appropriate attire for a lunch date, her knowledge and consequent behavior are products of the social reality in which she lives.

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If our very view of reality is shaped by our social connections with others, then the third assumption, that social cognition shapes behavior, should come as no surprise. This assumption is based on the work of another pioneering figure in social psychology, Fritz Heider (1958), who emphasized the important role people’s causal explanations of others’ actions play in determining their behavior. For example, in March 2003, President George W. Bush launched an invasion of Iraq. Some Americans believed he did this to avert a terrorist threat or to promote freedom in the Middle East. Others believed Bush wanted to gain access to Iraqi oil or seek revenge against Saddam Hussein. Each individual American’s understanding of the president’s motives for this action likely played a significant role in how each American felt about Bush and voted in the 2004 election. Because people—the president; our parents, friends, or lovers; or even the salespeople who try to sell us products—play such a major role in our daily existence, we spend a great deal of time and energy thinking about them, trying to understand them, and struggling to make sense of what they say and do. The way each individual understands other people, whether the understanding is accurate or not, has a powerful influence on that individual’s social behavior.

The final core assumption of social psychology, also inspired by Kurt Lewin, is that science is the best way to understand the causes and consequences of the thoughts, feelings, and behaviors of social life. As we noted earlier, many fields attempt to understand human affairs, including anthropology, economics, sociology, history, humanities, philosophy, and sociology. Social psychology can be distinguished most clearly from these other pursuits by greater emphasis on the scientific method, and especially the use of experiments, as a way of developing, testing, and refining theories to understand the determinants of social behavior. The field developed as a way of refining intuitive thinking, to help us get closer to the truth by providing more accurate conceptions of the way the world really is. The scientific method provides the basis for how social psychologists accumulate knowledge regarding the determinants of human thoughts, feelings, and actions. However, before we describe the specifics of the scientific method, we need a brief overview of how people intuitively come to comprehend the world around them and the people who inhabit that world. These insights are important because they help to explain why social psychologists rely so heavily on the scientific method for understanding the causes and consequences of social behavior.

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