Neuroscience, Neurolinguistics, and Narrative
Narratives take the form of sequences of words, which makes the principles of
linguistics relevant. Words have both simple, direct meanings and connotations,
in addition to metaphoric use. Modern neurolinguistics probes into the brain
structures and organization that support narratives.17
Contagious narratives often function as metaphors. That is, they suggest some
idea, mechanism, or purpose not even mentioned in the story, and the story
becomes in effect a name for it. The human brain tends to organize around
metaphors. For example, we freely incorporate war metaphors in our speech. We
say an argument was “shot down” or is “indefensible.” The human brain notices
these words’ connection to war narratives, although the connection is not always
a conscious one. The connection enriches the speech by suggesting other
possibilities. So when we speak of a stock market “crash,” most of us are
reminded of the rich story of the 1929 stock market crash and its aftermath.
Linguist George Lakoff and philosopher Mark Johnson (2003) have argued that
such metaphors are not only colorful ways of writing and speaking; they also
mold our thoughts and affect our conclusions. Neuroscientist Oshin Vartanian
(2012) notes that analogy and metaphor “reliably activate” consistent brain
regions in fMRI images of the human brain. That is, the human brain seems
wired to respond to stories that lead to thinking in analogies.

Consilience Calls for Collaborative Research
The dazzling array of approaches to understanding the spread of narratives,
briefly summarized in this chapter, means that collaborative research between
economists and experts in other disciplines holds the promise of revolutionizing
economics. Particularly important are the ideas and insights of epidemiologists,
whose models successfully forecast the future trajectory of disease epidemics
and explain how to counteract these epidemics. As we will see in the next
chapter, economists can adapt these epidemiological models to improve their
own models and forecasts. The marriage of economics and epidemiology is our
first example of consilience in this book.

Chapter 3
Contagion, Constellations, and
Confluence
Before we embark on a study of how economic narratives go viral, it is helpful
to consider how bacteria and viruses spread by contagion. The science of
epidemiology offers valuable lessons and may help explain how the story of
Bitcoin (and many other economic narratives) went viral.
Let us consider diseases first, caused by real viruses. Consider as an example
the major Ebola epidemic that swept through West Africa—Guinea, Liberia, and
Sierra Leone—between 2013 and 2015. Ebola is a viral disease for which there
is no approved vaccine or treatment, and it kills most people who contract it.
Ebola spreads from person to person via body fluids. Its infectiousness can be
lowered through hospitalization and quarantine, and through proper handling and
burial of the dead.
In Figure 3.1 we see a typical example of an epidemic curve, for Ebola, in a
community, this from Liberia. Note that the number of newly reported Ebola
cases has a hump-shaped pattern. The epidemic first rises, then falls. The rising
period is a time when the contagion rate, the rate of increase of newly infected
people, exceeds the recovery rate plus the death rate. During the rising period,
the rise in the number of infected people due to contagion outnumbers the fall in
the number due to recovery or death. The process is reversed during the falling
period. That is, the fall in the number of infected people due to recovery or death
outweighs the rise in the number due to contagion, putting the number infected
into a steady downward path marking the termination of the epidemic.

FIGURE 3.1. Epidemic Curve Example, Number of Newly Reported Ebola Cases in Lofa County, Liberia, by
week, June 8–November 1, 2014
We will see many examples of economic narratives whose prevalence in digitized databases follows a
similar hump-shaped pattern. Source: US Centers for Disease Control and Prevention.
After the epidemic started, contagion rates of the Ebola virus eventually fell
for various reasons, notably the heroic efforts of Médecins Sans Frontières
(Doctors 
Without 
Borders), 
more 
than 
a 
hundred 
nongovernmental
organizations, and individuals who risked their lives to lower the contagion in
Africa. According to the World Health Organization, health-care workers were
twenty-one to thirty-two times more likely to catch the disease than the general
population there, and there were 815 confirmed and probable cases of health-
care worker infection as of 2015. Most of these workers died.1