Hello! Welcome to the eleventh module of our course. We've spent considerable time exploring the strategic interactions within a vee using game theory and the static structure of relationship networks. Now, we'll dive into the dynamic processes that unfold on these networks. Specifically, this module focuses on how information, influence, emotions, and new behaviors spread from person to person.
In this first lesson, we will tackle a fundamental distinction that governs these diffusion processes: the difference between simple contagion and complex contagion. Understanding this concept is crucial because it explains why a simple piece of news spreads differently than a controversial idea or a new relationship norm. This distinction will determine which network structures facilitate or inhibit the spread of different phenomena within a vee relationship, a concept that will be central to all the lessons that follow in this module.
Let's begin with a short video that introduces the general idea of diffusion on networks.
This video from the Systems Innovation Network, titled "Network Diffusion & Contagion," provides an excellent overview of the key factors that influence how things spread through a network.
Please watch the first five minutes, from the beginning to the end of the section on strategic diffusion. Pay attention to the four main factors mentioned: infectiousness, resistance, network topology, and strategic vs. random diffusion. These provide a great framework for our discussion.
Simple Contagion: The Power of a Single Contact
As the video hinted, the most basic model of diffusion is simple contagion. The defining characteristic of a simple contagion is that an individual can become "infected" or adopt a new state after a single exposure from one source. Think of it like catching a cold or hearing a piece of news.
- Mechanism: The core mechanism is transmission. Once you're exposed, you've got it. The number of non-exposed contacts you have is largely irrelevant.
- Examples: The spread of a virus, a stock tip, the score of a game, or a simple fact like "Partner A is running late for dinner."
In the context of a polyamorous network, if the hinge partner learns their flight is delayed and tells one of their partners, that information has been successfully transmitted. That partner doesn't need to hear it from anyone else to believe it and act on it.
Your background in stochastic processes might bring to mind classic epidemiological models like the SIR (Susceptible-Infected-Recovered) model. These are fundamentally models of simple contagion, where the primary concern is the probability of transmission upon contact.
To formalize this, let's turn to a foundational paper on this topic.
Complex Contagions and the Weakness of Long Ties
This paper by Damon Centola and Michael Macy first drew the sharp distinction between simple and complex contagions. It clearly defines the concepts.
Please read the section titled "FROM SIMPLE TO COMPLEX CONTAGIONS." Focus on the definition of simple contagions. The authors distinguish between needing multiple exposures from one source versus needing exposure to multiple sources, which is a critical point we will return to.
Complex Contagion: The Need for Social Reinforcement
Now, let's consider a different kind of diffusion. What does it take to convince someone to adopt a risky new technology, participate in a protest, or embrace a significant change in relationship norms? Often, hearing about it from a single person isn't enough. You need social reinforcement from multiple sources. This is the hallmark of a complex contagion.
A contagion is complex if adoption requires exposure to multiple "activated" neighbors. This isn't about the probability of transmission; it's about a threshold. An individual may need to see two, three, or more of their contacts adopt a behavior before they are willing to do so themselves.
But why is this reinforcement necessary? The resistance to adoption for complex contagions typically stems from four sources. As you read about them, think about how they might manifest in a vee relationship.
This book chapter, also by Centola, provides a clear and accessible explanation of the mechanisms behind complex contagions, using compelling real-world examples.
In the introduction, please read from the paragraph beginning "There are four key sources of resistance" through the end of the section. The chapter then provides a powerful example about the spread of support for same-sex marriage on Facebook. Read the section titled "A Surprising Example" to see how these principles play out in a real social movement.
As the reading highlights, the four key barriers to adoption that make a contagion complex are:
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Social Coordination (or Strategic Complementarity): The behavior or technology is only valuable if others adopt it too.
- Vee Application: Imagine the hinge proposes using a complex shared financial planning app to manage household expenses among all three partners. One non-hinge partner might be hesitant to invest the time to learn it unless they are sure the other non-hinge partner is also on board. Its utility depends on collective adoption.
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Legitimacy: The behavior is novel or violates an existing norm. Adopters need to see that the behavior is socially acceptable before they risk the social cost of adopting it.
- Vee Application: Consider the decision for the vee to be openly "out" to their families. One partner might feel it's the right thing to do, but they may not act until the other two partners also signal their readiness. The reinforcement from the other partners legitimizes the decision and mitigates the perceived social risk.
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Credibility: The claim or innovation is unverified, and its benefits are uncertain. Multiple sources serve as social proof that it's worthwhile.
- Vee Application: Suppose Partner A tells the hinge that a new, unconventional approach to conflict resolution is "amazing." The hinge might be skeptical and wait to try it until they hear positive experiences from Partner B or other trusted friends in their polyamorous community. The repetition builds credibility.
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Emotional Excitement: Some collective behaviors, like protests or celebrations, require a shared emotional energy that is amplified by group participation.
- Vee Application: The feeling of compersion (finding joy in a partner's happiness with another) can be a complex emotional contagion. It's not a simple piece of information to be transmitted. For a partner struggling with jealousy, feeling the genuine joy and excitement from the other two members of the vee can provide the emotional reinforcement needed to help cultivate that state themselves.
How Structure Shapes the Spread: Weak Ties vs. Wide Bridges
This distinction between simple and complex contagion fundamentally changes how we think about the role of network structure.
You may be familiar with Mark Granovetter's famous theory of "the strength of weak ties." He argued that weak ties—our acquaintances—are incredibly valuable because they act as bridges between distant, dense clusters of strong ties (like families or close friend groups). For a simple contagion like job information, these weak-tie bridges are essential for rapid, widespread diffusion.
However, for a complex contagion, these single-tie bridges are structurally weak. An innovation or norm that needs reinforcement can't cross a "narrow bridge" of a single acquaintance. It needs a "wide bridge"—multiple, redundant connections between groups—to provide the necessary social proof. These wide bridges are the natural byproduct of the strong, clustered ties found within close-knit communities.
Let's see how the original paper articulates this crucial idea of bridge width.
Complex Contagions and the Weakness of Long Ties
This section of the paper explains why the logic of weak ties breaks down for complex contagions and introduces the vital concept of bridge width.
Please read the section just before "DISCUSSION," focusing on the paragraphs that define and contrast bridge length and width. This is the core structural insight that distinguishes the two diffusion types.
What does this mean for a vee relationship? The three individuals in a vee form a very dense, strong-tie cluster. This structure is a natural environment for complex contagions.
- Adopting a new rule (e.g., about overnight guests) is a complex contagion that can spread effectively within the vee because the multiple pathways for reinforcement already exist. The hinge can act as a conduit, but the non-hinge partners' awareness of each other's buy-in is critical.
- Simple information (e.g., a news article one partner found interesting) can easily leave the vee through each partner's respective weak ties to their coworkers, hobby groups, etc.
Here is a table summarizing the key distinctions:
| Feature | Simple Contagion | Complex Contagion |
|---|---|---|
| Adoption Requirement | Single exposure from one source | Multiple exposures from several sources (threshold) |
| Core Mechanism | Transmission | Social Reinforcement & Confirmation |
| Key Barrier | Lack of contact | Lack of coordination, credibility, legitimacy |
| Favorable Network Feature | "Weak ties" creating long, narrow bridges | "Strong ties" creating short, wide bridges |
| Vee Example | Announcing a change in weekend plans | Deciding to move in together as a triad |
Conclusion
In this lesson, we have established a critical distinction between two modes of diffusion.
Key Takeaways:
- Simple contagions are like viruses; they spread through single contact, and their diffusion is facilitated by weak ties that bridge disparate parts of a network.
- Complex contagions involve behaviors that are costly, risky, or require coordination. They require social reinforcement from multiple sources to overcome resistance.
- The spread of complex contagions depends not on long, weak-tie bridges but on wide bridges—the redundant, reinforcing pathways typically found in dense clusters of strong ties.
This framework is not just an academic exercise. It helps us predict what will spread easily within and beyond your relationship structures and why. Simple information may flow freely, but significant changes in norms, rules, and shared emotional states will depend heavily on the reinforcing structure of your immediate relationship network.
In our next lesson, we will put these ideas into practice. We will begin by building a model to simulate the diffusion of simple information through a vee network, examining how network position affects who knows what, and when.