Listen for the verb in the stem. Contagion says behavior spreads. Convergence says similarly disposed people gather. Emergent norm theory says participants construct a rule. A crowded setting can support any of the three, so the evidence must identify the mechanism.

Early contagion accounts pictured anonymity in a crowd as weakening ordinary restraint while excitement spread from person to person. A few frightened riders rush toward one door, nearby riders copy them, and urgency moves through the car. The useful question is whether visible emotion or action spreads through mutual stimulation.

Contagion has limits. It can make a crowd sound like one suggestible mind and can ignore people who remain calm, resist a cue, or interpret it differently. Evidence of simultaneous movement is not enough. Researchers need a sequence showing that exposure to others’ emotion or conduct increased adoption.

Convergence theory begins before the gathering. People who already share a grievance, taste, fear, or readiness for direct action may select the same event. A protest crowd looks united because people with similar commitments arrived there. Prior attitudes, recruitment paths, and self-selection provide the key evidence.

Convergence should not be used merely because participants end up agreeing. If riders entered the train with mixed views and formed a new evacuation rule only after the lights failed, prior similarity cannot carry the explanation. Interviews or surveys taken before an event help show whether the relevant disposition was already present.

Emergent norm theory focuses on interaction inside an unsettled situation. People watch a few visible actors, test possible responses, and notice approval or correction. A temporary standard forms. On the stalled train, riders may begin repeating every message through the car because the first attempts receive thanks and make coordination easier.

Evidence for an emergent norm should identify a rule that was unclear at the start, the actors who modeled it, the responses that supported or challenged it, and the point at which others treated it as expected. Video, timestamped messages, and participant accounts can reconstruct that sequence.

One event can contain all three processes. People already committed to helping may converge near the nurse. Calm can spread as riders copy her tone. A new rule then forms around keeping one side of the aisle open. Theories separate mechanisms, so a researcher can use more than one if the evidence supports distinct parts of the event.

A falsification comparison asks what each account would struggle to explain. Imagine a concert audience that begins moving away from one entrance. If people who could not see or hear early movers change at the same rate, direct interpersonal transmission loses support. If pre-event surveys show no difference between those who moved and those who stayed, selection on a prior tendency becomes less plausible. If no participant can identify a new expectation, model, correction, or moment when conduct became appropriate, an emergent-rule claim is weakened.

Researchers can improve the comparison by combining three records. Entrance surveys measure relevant prior intentions. Time-stamped video reconstructs exposure and adoption. Brief interviews ask what participants thought others expected. A contagion account predicts adoption following exposure even after prior intention is held constant. A convergence account predicts that preexisting intention sorts people into the action. An emergent norm account predicts that approval, correction, or a visible model changes what participants treat as proper in the setting. None of these patterns follows from a final head count alone.

The dependent variable must also be precise. Prior willingness may explain who approached the front, while a newly formed rule explains why those people sat down at a particular signal. Emotional transmission may explain the speed of a later exit. One event can therefore support several mechanisms at different stages. The researcher assigns each claim to a distinct outcome and time window, then asks which expected evidence is absent as well as which evidence is present.

The three theories above focus on the immediate source of shared conduct. Two broader approaches ask how a whole episode becomes possible and how people assemble in the first place.

Neil Smelser’s value-added theory describes six conditions that build toward collective action. Structural conduciveness means the setting permits people to recognize a problem and communicate. Structural strain is tension created when an arrangement fails to meet needs or expectations. A generalized belief supplies a shared account of what is wrong and who or what is responsible. A precipitating factor is the event that brings the concern to a head. Mobilization for action occurs when participants gather people and resources. The response of authorities or other agents of social control can interrupt, redirect, or intensify the episode.

The phrase value-added does not mean that each stage is morally valuable. It means that each condition adds something needed for the later action. A city may have an open public square, a long dispute over unsafe housing, and a widely accepted explanation of landlord neglect. Those conditions do not identify the spark. A building collapse can become the precipitating event, while tenant networks and a scheduled march show mobilization. Police restrictions or a new inspection agreement then show the operation of social control.

Use the model when a question gives several conditions in sequence. Structural strain alone does not establish the full theory, and a dramatic trigger without a shared belief may produce scattered reactions rather than coordinated action. The order can overlap in real life, so researchers reconstruct dates, messages, meetings, and official responses instead of forcing every case into six perfectly separate boxes.

The assembling perspective, associated with Clark McPhail, starts with purposeful individuals rather than an irrational crowd mind. It follows how people learn about a gathering, travel to it, orient toward one another, coordinate activity, and disperse. A rally can look like one body from a distant camera even though participants arrived through different networks, followed several leaders, and left at different times. Arrival records, routes, conversations, and small-group coordination reveal that assembling process.

Quick review: Emotional transmission points to contagion. Prior dispositions and selection point to convergence. A new situational rule points to emergent norm theory. Value-added theory follows the conditions that build toward an episode, while the assembling perspective follows purposeful people as they gather and coordinate.

Watch the lesson connection

How Societies Change gives you a second explanation of the ideas surrounding this lesson. As you watch, pause when the lesson concept appears and explain how the example fits.

Try the idea yourself

Write one original example, one close nonexample, and one observation that would help you tell them apart. That small exercise turns a definition into a sociological tool you can use in daily life.