0:00“If all your friends jumped off a bridge, would you jump too?" It’s the lament of many an exasperated parent, but it’s also a kind of profound sociological question.

Because, when you're talking to your parents, the answer's always no. But, with the right group of friends, you might be quite happy to take a dive in the water.

The thing is, you're a different person when you're a part of a group, and you're a different person in different groups. A family, a group of friends out for a swim, a business meeting, and a choir are different kinds of groups. And the same person can be a member of all of them.

So if we want to understand how these groups are different, and even how they're similar, we need to talk about what social groups are, and why they matter, both to the people who are a part of them, and to the people who aren't. 0:38[Theme Music] The choir, the meeting, the friends, and the family are all examples of social groups. A social group is simply a collection of people who have something in common and who believe that what they have in common is significant. In other words, a group is partly defined by the fact that its members feel like they're part of a group.

This is obviously a pretty broad definition. But it does have its limits, and you can see these limits if you compare social groups to aggregates and categories. An aggregate is a set of individuals who happen to be in the same place at the same time.

All the people passing through Grand Central Station at 1:00 on a Friday afternoon are an aggregate, but they aren't a group, because they don't share a sense of belonging. Categories, meanwhile, consist of one particular kind of person across time and space. They’re sets of people who share similar characteristics.

Racial categories are a simple example. So the sense of feeling like you belong to a group is a defining feature of a group. But it also helps you differentiate kinds of groups, specifically between primary and secondary groups.

Primary groups are small and tightly knit, bound by a very strong sense of belonging. Family and friendship groups are primary groups. They’re mutually supportive places where members can turn for emotional, social, and financial help.

And as far as group members are concerned, the group is an end-in-itself. It exists to be a group, not for any other purpose. Secondary groups, however, are the reverse.

These are large and impersonal groups, whose members are bound primarily by a shared goal or activity, rather than by strong emotional ties. A company is a good example of a secondary group: Employees are often loosely or formally connected to one another through their jobs, and they tend to know little about each other. So there’s a sense of belonging there, but it's much more limited.

That's not to say that coworkers never have emotional relationships. In fact, secondary groups can become primary groups over time, as a set of coworkers spends time together and becomes a primary group of friends. And while a gang of friends and a company clearly have a lot of differences, they also have at least one major similarity: They're both voluntary – if you belong to that group, it’s because you choose to join.

But there are also plenty of involuntary groups, in which membership is assigned. Prisoners in a prison are members of an involuntary group, as are conscripted soldiers. Now that we understand a little bit about what groups are, we can start to study how they work – beginning with group dynamics, or the way that individuals affect groups, and groups affect individuals.

If we want to think about how individuals affect groups, a good place to start is with leadership. Not all groups have formally assigned leaders, but even groups that don't, often have de facto leaders, like parents in a family. A leader is just someone who influences other people in the group.

And there are generally two types of leadership: an instrumental leader is focused on a group's goals, giving orders and making plans in order to achieve those goals. An expressive leader, by contrast, is looking to increase harmony and minimize conflict within the group. They aren't focused on any particular goal, they’re just trying to promote the well-being of the group’s members.

And just as leaders may differ in what they’re trying to do, so too can they go about doing it in different ways. I’m talking here about leadership styles, of which we have three. Authoritarian leaders lead by giving orders and setting down rules which they expect the group to follow.

Such a leader earns respect, and can be effective in a crisis, but at the expense of affection from group members. Democratic leaders on the other hand, lead by trying to reach a consensus. Instead of issuing orders, they consider all viewpoints to try and reach a decision.

Such leaders are less effective during a crisis, but, because of the variety of different viewpoints they consider, they often find more creative solutions to problems. And they’re more likely to receive affection from their group’s members. Finally, laissez-faire leaders do the least leading.

They’re extremely permissive, and mostly leave the group to function on its own. This means lots of freedom, but it’s the least effective style at promoting group solidarity and least effective in times of crisis. So, leadership is one way that individuals affect groups, but groups also affect individuals.

You can see this especially clearly in group conformity, where members of a group hew to the group’s norms and standards. Basically, group conformity is the reason that you do jump off the bridge with your friends. And this has been demonstrated in some fascinating experimental results.

Let’s go to the Thought Bubble to learn about perhaps the most famous – or infamous – experiment on conformity. The Milgram Experiment was run by American psychologist Stanley Milgram in 1974, and it was presented as an experiment in punishment and learning, with two participants. One participant was the teacher, who read aloud a series of word pairs and then asked the other participant, the student, seated in another room, to recall them.

The student was strapped to a chair and wired up with electrodes. For each wrong answer, the experimenter, who was standing beside the teacher, instructed the teacher to deliver a painful electric shock to the student. With each wrong answer, the intensity increased, from an unpleasant few volts up to 450 volts, a potentially deadly shock.

But the experiment was not about punishment or learning. The student was actually an actor, a confederate of the experimenter, and the shocks were not real. The experiment was designed to test how far the teacher would go in conforming to authority.

At some point in the experiment, the confederate would feign extreme pain and beg the teacher to stop. Then he fell silent. If at any point the teacher refused to issue the shock, the experimenter would insist that he continue.

In the end, 65% of participants went all the way, administering the presumably deadly 450 volt shock. And this is usually given as proof that people tend to follow orders, but there’s a lot more to it than that. If the experimenter gave direct orders to the teacher, like “You must continue, you have no other choice,” that resulted in non-compliance.

That’s when the teacher was more likely to refuse. The prods that did produce compliance were the ones that appealed, instead, to the value of the experiment – the ones that said administering the shocks was necessary for the experiment to be successful and worthwhile. So in this instance, the value of the experiment, of science, was a strongly held group value, and it helped convince the subjects to continue, even though they might not have wanted to.

Thanks, Thought Bubble. This idea of group values points us to another important concept in understanding conformity: the idea of groupthink. Groupthink is the narrowing of thought in a group, by which its members come to believe that there is only one possible correct answer.

Moreover, in a groupthink mentality, to even suggest alternatives is a sign of disloyalty to the group. Another way of understanding group conformity is to think about reference groups. Reference groups are groups we use as standards to judge ourselves and others.

What’s "normal" for you is determined partly by your reference groups. In-groups are reference groups that you feel loyalty to, and that you identify with. But you can compare yourself to out-groups, too, which are groups that you feel antagonism toward, and which you don't identify with.

And another aspect of a social group that can affect its impacts and dynamics is its size. And here, the general rule is: the larger the group, the more stable, but less intimate, it is. A group of two people is obviously the smallest and most intimate kind of group, but it’s also the least stable.

Because, if one person leaves, there’s no group anymore. Larger groups are more stable, and if there are disagreements among members, other members are around who can mediate between them. But big groups also are prone to coalitions forming within them, which can result with one faction aligning against another.

The size of a group matters in other ways, too, for instance in terms of social diversity. Larger homogeneous groups tend to turn inward, concentrating relationships within the group instead of relying on intergroup contacts. By contrast, heterogeneous groups, or groups that have more diversity within them, turn outward, with its members more likely to interact with outsiders.

Finally, it’s worth pointing out that social groups aren’t just separate clumps of people. There's another way to understand groups, in terms of social networks. This perspective sees people as nodes that are all socially interconnected.

You can imagine a "circle of friends" who are all connected to each other in different ways, some with strong connections in a clique or subgroup, while some are connected by much weaker ties. And you can follow the ties between all of the nodes outward, to friends-of-friends and acquaintances who exist on the periphery of the network. Networks are important, because even their weak ties can be useful.

Think of the last time you were networking, following every connection you had to, say, land a job interview. Regardless of whether you think about groups as networks and ties, or as bounded sets, it's clear that they have important impacts on people, both inside and outside. If you just looked at society as a bunch of individuals, you’d miss all the ways that groups impact our lives – by acting as reference groups, by influencing our decisions through group conformity, and much more.

And groups are important for how society itself is organized. So next time, we're gonna talk about one big part of that: formal organizations and bureaucracy. For now, we’ve learned about social groups.

We talked about what social groups are and the different kinds of groups. Then we discussed group dynamics: how individuals affect groups and how groups affect individuals. We learned about leadership, group conformity, reference groups, and the impacts of group size.  And finally, we talked about groups as networks and why networks matter.

Crash Course Sociology is filmed in the Dr. Cheryl C. Kinney Studio in Missoula, MT, and it’s made with the help of all of these nice people. Our animation team is Thought Cafe and Crash Course is made with Adobe Creative Cloud. If you'd like to keep Crash Course free for everyone, forever, you can support the series at Patreon, a crowdfunding platform that allows you to support the content you love.

Thank you to all of our patrons for making Crash Course possible with their continued support.