Mathematician Thomas Woolley and coauthors claim that mathematical modeling can help us understand the movement of zombies, and thus how best to avoid encounters with them.  Naturally, we here at Economics of the Undead applaud the application of theoretical models to zombies.  But Woolley’s model provides an excellent example of why theory has to be tested against data – in this case, the observed behavior of zombies in film and fiction.

According to Woolley et al., zombie movement can be described as a “random walk,” a notion that has been employed in theoretical models in both physics and economics.  Basically, the idea is that each step of a zombie is a random draw:  he could move one step in any direction, and then another step in any direction from there, and so on.  Over time, Woolley and his coauthors argue, this should lead to diffusion of zombies over the available domain.

But this is inconsistent with how zombies actually behave, if existing zombie narratives can be taken as any guide.  Rather the diffusing over the landscape, zombies tend to appear in clusters and mobs, even long after the initial invasion.  In a conflict between observation and theory, it pays to look for a better theory.  And fortunately, there is one available.  In Chapter 7 of Economics of the Undead, “Order, Coordination, and Collective Action among the Undead,” Jean-Baptiste Fleury and Alain Marciano suggest that zombies do not simply wander about randomly attacking people, but in fact display a range of behaviors that allow them to coordinate their behavior for mutual advantage (with other zombies, not with humans).  Among other things, zombies tend to flock together for strength in numbers — the best-known example being the famous “zombie ant-pile” seen in the movie World War Z.

“Actually, the very fact that zombies gather in large and stable flocks, as most accounts will confirm, is evidence of an ordered society,” Fleury and Marciano argue.  “If zombies were not ordered, they would wander chaotically and scatter into the wilderness, like particles of smoke into the air.”  That description sounds a lot like Woolley’s prediction.  “But such chaotic behavior would seriously undermine zombies’ ability to hunt and eat human flesh,” they add, supporting their claim with evidence from various zombie narratives:

Due to limited agility and cognitive abilities, a zombie is not much of a threat when hunting alone. Many action sequences in The Walking Dead TV series illustrate this point: Rick and his friends are generally pretty effective when it comes to fighting with roaming individuals as well as small groups of zombies. But when attacked by hordes of “walkers,” as in the last episode of the second season, Rick and his friends are quickly overwhelmed and eventually escape only at great cost. As confirmed in many accounts, such as Romero’s Night of the Living Dead, flocks of zombies are most dangerous to humans: they can exert tremendous collective pressure so as to break down manmade barriers and barricades. Thus, zombies tend to gather in stable groups, which help them maximize their chance of success in case of confrontation with humans.

But what could be the source of such cooperative tendencies?  Fleury and Marciano suggest three possibilities.  First, zombies may retain some basic tendencies written into their human DNA, including the basic desire to congregate with others of their kind.  Second, they may retain some rudimentary memories of their prior human existence and cultural background.  (In Romero’s Dawn of the Dead, one character famously explains the convergence of zombies on a shopping mall as resulting from “a kind of instinct, a memory [of] what they used to do” because “this was an important place in their lives.”)  Third, the zombie virus itself may endow its hosts with any number of tendencies beyond the obvious craving for human flesh.  It is well-known that parasites can affect the behavior of hosts – the most famous example being toxoplasma gondii – so it shouldn’t be surprising to find the zombie virus does so as well.

Whatever the cause, Fleury and Marciano’s claim is borne out in countless zombie narratives.  Despite their shambling gait, zombies do not appear to follow a random walk.  By all indications, zombies are guided instead by a tendency to flock with other zombies in a manner that increases their efficacy in confronting their much-smarter human prey.

First of three guest posts by Enrique Guerra-Pujol

Freakonomics Radio recently broadcast a highly-entertaining program on Economics of the Undead on 30 October 2014 (“What can vampires teach us about economics?”). Among the topics discussed on that podcast was the possibility of legal markets in blood, a topic near and dear to me — see my essay “Buy or Bite?” in chapter 12 Economics of the Undead.

In addition, the discussion of blood markets on Freakonomics Radio generated a number of original and insightful comments. Many commentators objected to the possibility of blood markets, offering several thoughtful objections specific to vampires and their way of life. I have thus decided to write this post to respond to these various objections.

Let me first restate these objections in the words of the Freakonomics commentators themselves:

1. “Y’all know that … vampires aren’t real, right?” [Comment by Truth & Beauty.] Let’s call this the “hypothetical entities” argument.

2. “would you accept to work extra hours [with your boss] … if your boss is one of them?” [Comment by carlosmx37.] Call this the “fear factor” argument.

3. “most vampires consider themselves to be superior beings to humans … and as such have compunction about ‘stealing’ blood to feed them[selves].” [Comment by Owen.] Call this the “vampire superiority complex” argument.

4. “taking blood by force may be so culturally ingrained among vampires that … there is cultural barrier against [trade].” [Comment by Cuylar Conly.] The “cultural path dependence” argument.

5. “Vampires ‘procreate’ via their bite” and “Vampirism is contagious” [Comments by scott fowler and Cuylar Conly, respectively.] The “peak blood” argument.

Before proceeding, notice how these various anti-choice arguments build on each other. 1. Vampires do not exist, so the idea of markets in blood is ipso facto preposterous. 2. Even if vampires were real, most people fear such cunning creatures and would thus be reluctant to engage in any sort of voluntary trade with them. 3-4. Even if we could overcome our fear of the undead, vampires prefer raiding to trading. 5. And even if we could incentivize vampires to buy our blood on a consensual basis – instead of taking it by force – vampires would overuse or oversuck their human resources and turn us all into vampires.

I will focus on the first two objections in this blog post and then address the remaining objections in a future post.

Hypothetical entities

The crux of this objection is that vampires are not worthy of academic study because vampires are not real — they are hypothetical entities.

But is this objection correct? Or, in the words of one commentator (James), “how do [we] know there are no real vampires?”

In any case, even if vampires are imaginary creatures, thought experiments about them are still useful because they help clarify our thinking by revealing anomalies and logical inconsistencies. In the words of the historian of science Thomas Kuhn (The Essential Tension, 1977, p. 252), a thought experiment, or the careful analysis of an “imagined situation,” is useful because it confronts its audience with unanticipated consequences of our ordinary way of thinking, and thus thought experiments, especially outrageous and far-fetched ones, are often capable of producing the new insights.

But why is my particular thought experiment about blood markets any good? Because this particular example illustrates a larger problem, the problem of “legal failure” or legal barriers that prevent trade and stifle markets. We call such legal barriers to trade “legal failure” because such barriers not only make us worse off; they often lead to violence and exploitation.

Vampires and humans are rarely depicted in cooperative terms. We rarely, if ever, see vampires bargaining with humans to buy and sell blood. Instead, vampires are usually depicted as cunning and stealthy predators, and conflict between humans and most vampires is the norm. My thought experiment, by contrast, presents an alternate vampire world, one in which blood markets are legal, and poses a new hypothetical question: what would happen to the level of vampire violence in a world in which the purchase and sale of blood was legally enforceable? Would vampire violence go up, go down, or stay the same? However one answers this hypothetical question, my simple thought experiment requires one to explain and defend one’s reasoning. Therein lies the value of thought experiments generally.

In short, just because vampires are fictional or imaginary creatures doesn’t mean we should ignore them. Even if vampires are make-believe, the vampire world is still worth studying because it invites us to think about the nature and sources of violence.

What about the “fear factor,” however? That is, why should anyone trust a vampire?

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