ScAm - 09.2019

58 Scientific American, September 2019 Graphic by Jen Christiansen

SOURCES: THE WISDOM AND/OR MADNESS OF CROWDS, BY NICKY CASE

https://ncase.me/crowds;

THE MISINFORMATION AGE: HOW FALSE BELIEFS SPREAD,

BY CAILIN O’CONNOR AND JAMES OWEN WEATHERALL. YALE UNIVERSITY P

RESS, 2019

Each circular or square node is a person who

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D`››DåDUy ̈Ÿy†DU¹ùïĀ›yï›yàaction A (blue)

or action B (orangeËŸåUyïïyàÎ5›yŸàUy ̈Ÿy†

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Dé‹Í`›D ́`yï›Dïaction BŸåUyïïyàï›D ́

action AΆï›yÿD ̈ùyŸå‘àyDïyàï›D ́‹ĈÍjï›y ́

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ùåïàŸ‘›ïi

myDåÈàyDmå

÷ĈÍ

ññÍ

‹ĈÍ

÷‹Í ŽĈÍ

êêÍ

5Ÿ®y®y 5Ÿ®y®y

How to Read the Network

Epistemology Framework Plots

Action A

is better

Action B

is better

‹ĈÍ

ÀĈĈÍ

ĈÍ

÷‹Í`›D ́`yï›Dï

D` ́

ŸåUyïïyà

é‹Í`›D ́`yï›Dï

D` ́

ŸåUyïïyà

How to Read the Contagion Plots

Each circular node is a person who is

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UyïĀyy ́Ÿ ́mŸÿŸmùD ̈åÎ

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ï›yÈyà`y ́﹆ï›DïÈyàå¹ ́Ýå`¹ ́ ́y` ́å

Ā›¹›¹ ̈mDÈDàïŸ`ù ̈DàUy ̈Ÿy†Î ́ï›y

å`y ́DàŸ¹åUy ̈¹Ājï›yï›ày囹 ̈m†¹àD ́

Ÿ ́mŸÿŸmùD ̈ï¹ïD§y¹ ́ï›yUy ̈Ÿy†¹†ï›yŸà

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ĈÍ

2 ‹Í^1 ĈĈ

Í

THE CONTAGION MODEL

Contagion models treat ideas or beliefs like viruses

that spread between individuals in a social network.

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Ā¹à§Î ́å¹®y®¹my ̈åjyÿyàĂ¹ ́yĀŸ ̈ ̈UyŸ ́†y`ïym

UĂD ́Ÿ ́†y`ïym ́yŸ‘›U¹àÎ ́¹ï›yàåjŸmyDååÈàyDm

whenever some percentage of an individual’s

neighbors become infected. Here we illustrate

ï›yåyÚ`¹®È ̈yā`¹ ́ïD‘Ÿ¹ ́åÛĀŸï›yāD®È ̈yåĀ›yày

individuals take on a new belief if at least 25 percent

of their neighbors hold it. In these models, the

åïàù`ïùày¹†ï›y ́yïĀ¹à§D‡y`ï囹ĀŸmyDååÈàyDmÎ

How Network Science Maps

the Spread of  Misinformation

We use network science î ̧Uxîîxßø³lxßäîD³lš ̧ÿä ̧`žD§` ̧³³x`îž ̧³äž³‹øx³`xîšx

beliefs and behaviors of individuals in a social network—and especially how false beliefs

can spread from person to person. Here we look at two kinds of network models that

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sents an individual. Each edge, or connection between the nodes, represents a social tie.

NETWORK EPISTEMOLOGY

FRAMEWORK

Network epistemology models represent

situations in which people form beliefs by

gathering and sharing evidence. This sort

ofmodel applies to many cases in science.

Beliefs do not simply spread from individual

toindividual. Instead, each individual has some

degree of certainty about an idea. This prompts

them to gather evidence in support of it, and

that evidence changes their beliefs. Each

individual shares their evidence with network

́yŸ‘›U¹àåjĀ›Ÿ`›D ̈幟 ́Œùy ́`yåï›yŸàUy ̈Ÿy†åÎ

BONDING AND BRIDGING:In less connected groups, ideas cannot reach all members. Sometimes too many

connections can also stop the spread of an idea. Some networks have tight-knit cliques, where even if an idea

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