Course Overviewand Introduction

Networked LifeCSE 112

Spring 2005Prof. Michael Kearns

What do the following questions…

• How does Google find what you want?• How do tolerant populations become segregated?• How many friends between you and Kevin Bacon?• How should you split $20 with a stranger?• What can the Internet learn from Paris subway?• How is file downloading like a competition?• How might we combat spam economically?

…have in common?

An Emerging Science• Examining apparent similarities between many

human and technological systems & organizations• Importance of network effects in such systems• How things are connected matters greatly• Structure, asymmetry and heterogeneity• Details of interaction matter greatly• The metaphor of viral spread• Dynamics of economic and strategic interaction• Qualitative and quantitative; can be very subtle• A revolution of

– measurement– theory– breadth of vision

Who’s Doing All This?

• Computer Scientists– Understand and design complex, distributed networks– View “competitive” decentralized systems as economies

• Social Scientists, Behavioral Psychologists, Economists– Understand human behavior in “simple” settings– Revised views of economic rationality in humans– Theories and measurement of social networks

• Physicists and Mathematicians– Interest and methods in complex systems– Theories of macroscopic behavior (phase transitions)

• All parties are interacting and collaborating

Course Vision and Mission

• A network-centric examination of a wide range of social, technological, biological, financial and political systems

• Examined via the tools and metaphors of:– computer science– economics– psychology and sociology– mathematics– physics

• Emphasize the common themes• Develop a new way of examining the world

A Communal Experiment

• No similar undergraduate course• No formal technical prerequisites

– greatly aided by recent books– publications in Science, Nature, etc.

• Extensive web visualizations and demos• Extensive participatory in-class social experiments• Exercises in data analysis• Note: Networked Life is now approved to fulfill the

College’s Quantitative Data Analysis Requirement

Course Outline

The Networked Nature of Society(2 lectures)

• Networks as a collection of pairwise relations• Examples of (un)familiar and important networks

– social networks– content networks– technological networks– biological networks– economic networks

• The distinction between structure and dynamics• Models of network formation

A network-centric overview of modern society.

Contagion, Tipping and Networks(2 lectures)

• Epidemic as metaphor• The three laws of Gladwell:

– Law of the Few (connectors in a network)– Stickiness (power of the message)– Power of Context

• The importance of psychology• Perceptions of others• Interdependence and tipping• Paul Revere, Sesame Street, Broken Windows, the

Appeal of Smoking, and Suicide Epidemics

Informal case studies from social behavior and pop culture.

Introduction to Graph Theory(1 lecture)

• Networks of vertices and edges• Graph properties:

– cliques, independent sets, connected components, cuts, spanning trees,…

– social interpretations and significance • Special graphs:

– bipartite, planar, weighted, directed, regular,…• Computational issues at a high level

Beginning to quantify our ideas about networks.

Social Network Theory(3 lectures)

• Metrics of social importance in a network:– degree, closeness, between-ness, clustering…

• Local and long-distance connections• SNT “universals”

– small diameter– clustering– heavy-tailed distributions

• Models of network formation– random graph models– preferential attachment– affiliation networks

• Examples from society, technology and fantasy

A statistical application of graph theory to human organization.

The Web as Network(2 lectures)

• Empirical web structure and components• Web and blog communities• Web search:

– hubs and authorities– the PageRank algorithm

The algorithmic implications of network structure.

Emergence of Global from Local(2 lectures)

• Beyond the dynamics of transmission • Context, motivation and influence• The madness of crowds:

– thresholds and cascades– mathematical models of tipping– the market for lemons– private preferences and global segregation

Begin to connect to classical issues of human and societal behavior.

An Introduction to Game Theory(2 lectures)

• Models of economic and strategic interaction• Notions of equilibrium

– Nash– correlated– cooperative– market– bargaining

• Multi-player games• Evolutionary game theory

– mimicking vs. optimizing• Network effects• Social choice theory

Powerful mathematical models of what happensover links in competitive and cooperative settings.

Interdependent Security and Networks

(1 lecture)

• Security investment and Tragedies of the Commons

• Catastrophic events: you can only die once• Fire detectors, airline security, Arthur Anderson,…

Blending network, behavior and dynamics.

Network Economics(2 lectures)

• Buying and selling on a network• Modeling constraints on trading partners• Local imbalances of supply and demand• Preferential attachment, price variation, and the distribution of

wealth

The effects of network structure on economic outcomes.

Behavioral Economics(2 lectures)

• What’s broken with economics and game theory?• How should you split 20 dollars?• Beauty contests and ultimatums• Cultural and sociological effects• The return of context• Guilt, envy and altruism: improving the theory

Controlled social psychology experimentsexamining how “rational” we really are(n’t).

Internet Basics(1 lecture)

• IP addresses• Routers• Domain Name Servers• ISPs• Congestion control, load balancing• The Web and URLs• Security issues, network vulnerability

Under the hood of the quintessentialmodern technological network.

Internet Economics(2 lectures)

• Selfish routing• The Price of Anarchy• Peer-to-peer as competitive economy• Paris Metro Pricing for QoS• Economic views of network security

The collision of network, economics, algorithms, content, and society.

Modern Financial Markets(2 lectures)

• Stock market networks– correlation of returns

• Market microstructure– limit and market orders– order books and electronic crossing networks– network, connectivity and data issues

• Quantitative trading– VWAP trading, market making– limit order power laws

• Herd behavior in trading• Economic theory and financial markets• Behavioral economics and finance• Impacts of the Internet on financial markets

A study of the network that runs the world.

Course Mechanics• Will make heavy use of course web page:

– www.cis.upenn.edu/~mkearns/teaching/NetworkedLife– You will need good Internet access!

• No technical prerequisites• Lectures:

– slides provided; emphasis on concepts– frequent demos, visualizations, and in-class experiments– please be on time to lectures! (12PM)

• No recitations this term• Readings: mixture of general audience writings and articles

from the scientific literature• Three required texts:

– “The Tipping Point”, Gladwell– “Six Degrees”, Watts– “Micromotives and Macrobehavior”, Schelling

• Assignments (1/4 of grade)– data analysis: network construction project– computer/web exercises, short essays, quantitative problems– collaboration is not permitted

• Participatory social experiments (1/4 of grade)– course social network– behavioral economics experiments

• Midterm (1/4 of grade)• Final exam (1/4 of grade)

First Assignment

• Due next lecture (Th 1/13)– Simple background questionnaire– Last-names exercise