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Networked and Social Systems Engineering (NETS) 112
Fall 2015
Tuesdays and Thursdays 10:30-12, Berger Auditorium, Skirkanich Hall
Prof. Michael Kearns

Jump to the course schedule.


  • What science underlies companies like Facebook and Twitter?
  • What are the economics of email spam?
  • Why do some social networking services take off, and others die?
  • What do game theory and the Paris subway have to do with Internet routing?
  • How does Google find what you're looking for... and exactly how do they make money doing so?
  • What structural properties might we expect any social network to have?
  • How might a social network influence election outcomes?
  • What problems can be solved by crowdsourcing?
  • How does your position in a social network (dis)advantage you?

    Networked Life looks at how our world is connected -- socially, strategically and technologically -- and why it matters.

    The answers to the questions above are related. They have been the subject of a fascinating intersection of disciplines, including computer science, physics, psychology, sociology, mathematics, economics and finance. Researchers from these areas all strive to quantify and explain the growing complexity and connectivity of the world around us, and they have begun to develop a rich new science along the way.

    Networked Life will explore recent scientific efforts to explain social, economic and technological structures -- and the way these structures interact -- on many different scales, from the behavior of individuals or small groups to that of complex networks such as the Internet and the global economy.

    This course covers computer science topics and other material that is mathematical, but all material will be presented in a way that is accessible to an educated audience with or without a strong technical background. The course is open to all majors and all levels, and is taught accordingly. There will be ample opportunities for those of a quantitative bent to dig deeper into the topics we examine. The majority of the course is grounded in scientific and mathematical findings of the past two decades or less (often much less).

    Fall 2015 is the twelfth offering of Networked Life. You can get a detailed sense for the course by visiting the extensive course web pages from past years:
    [Fall 2014]   [Fall 2013]   [Fall 2012]   [Fall 2011]   [Spring 2010]   [Spring 2009]   [Spring 2008]   [Spring 2007]   [Spring 2006]   [Spring 2005]   [Spring 2004]

    There is also a greatly condensed version of this class offered to the general public as part of the online education platform Coursera. While the Coursera version is not being offered online this semester, we will make the corresponding videos available in the Penn offereing.

    Networked Life is the flagship course for Penn Engineering's recently launched Networked and Social Systems Engineering (NETS) program. Throughout the course we will foreshadow material that is covered in greater depth in later NETS program courses.


    The following book is recommended but not required; it is easy and entertaining reading, and provides a high-level introduction to some course themes:

  • The Tipping Point, by Malcolm Gladwell. Paperback. Little Brown & Company, 2000.

    The following two books are required; we will read most but not all of them:

  • Six Degrees: The Science of a Connected Age, by Duncan J. Watts. Paperback. W.W. Norton, 2003.
  • Micromotives and Macrobehavior, by Thomas C. Schelling. Paperback. W.W. Norton, 1978.

    In addition to readings from these texts, there will be frequent articles from the recent scientific and popular literature that will be provided directly on this web page at the appropriate points in the syllabus.


    Prof. Michael Kearns, Course Instructor
    Levine Hall 509
    Office hours: Tuesdays 12-1 PM (right after lecture), or by appointment

    Rohan Alur, Teaching Assistant
    Office hours: Thur 3-4:30 in the public area near Levine 562 (go down the ramp near the elevators).

    Chris Lynn, Teaching Assistant
    Office hours: Weds 2-4 in the public area near Levine 562 (go down the ramp near the elevators).


    Attendance at the main lectures is considered mandatory for all enrolled students. They are held Tuesdays and Thursdays 10:30-12 in Berger Auditorium of Skirkanich Hall. There are no recitations for the course.


    Networked Life has no formal prerequisites, and is meant to be accessible to a broad range of students across SEAS, the College, and Wharton. No computer programming background is required, but students should be comfortable using computers and the Web, and accessing resources on the Internet.

    The course is open to all majors and all levels.


  • Networked Life is one of the courses satisfying the College of Arts and Sciences' Quantitative Data Analysis Requirement.
  • Networked Life can be counted as an official Engineering Elective course in CIS and SEAS.
  • Networked Life can be counted for credit in the Philosophy, Politics and Economics (PPE) and Science, Technology and Society (STSC) programs. Check with your academic advisor in these programs to confirm exactly how you can count the course.


    The main lectures for Networked Life will be in fairly traditional format, including class participation, discussion, and communal in-class experiments. PDF slides for all lectures will be provided, usually at least slightly in advance of the lecture itself.

    There will be two or three homework assignments. These will include simple quantitative exercises, as well as essay questions, computer and web exercises. Collaboration on the homeworks is not permitted.

    There will be a midterm, and a final exam. We may have a quiz or two as well.

    It is anticipated that the homeworks/quizzes, midterm and final will each count for approximately a third of the overall grade.

    Students are encouraged to bring articles, demos, web pages, news events, etc. that are relevant to course topics to the attention of Prof. Kearns. Extra credit will be given if the suggested material is used in the course (see the "Fourth Column" below).


    Except for occasional hard-copy handouts distributed in lectures, all of the material for the course will be posted in the table below. Lecture slides, reading and homework assignments, in-class and out-of-class experiments, due dates, exam information, etc. will all be provided below. The materials posted are initially those from the last offering of the class, and will be gradually updated and possibly altered as we progress through the course. New materials and topics may be added as well. Reading and working ahead are encouraged, just be aware that things may change a bit as we proceed. It is every student's responsibility to monitor this schedule closely and regularly.

    In the assigned readings below, "Watts" and "Schelling" refer to the two required texts cited above. Other readings will be directly provided as links to PDF documents. Unless specified otherwise, you should generally try to complete the assigned reading during roughly the period spanned by the dates given in the same row of the table.

    The lecture slides are all in PDF format, but they may often contain links to documents in other formats, including Postscript, JPEG, video, etc. In order to view all of the linked content you may need to be using a computer with viewers installed for these formats. Note that since slides are revised shortly in advance of each lecture date, links to future decks may not yet be active.

    In the "DATES" column of the table below, our current place in the schedule will be highlighted in red.

    "THE FOURTH COLUMN" will be used to put links to class-related materials from the popular media, the web, etc. Extra credit will be provided to those who send me such material if it is used.

    Thu Aug 27
    Course Introduction and Overview
    [PDF] [PPT]
    (Rev. 8/27)

    Here is the Coursera course overview video.

    Here is a document containing a brief background survey and our second communal social experiment. Please print them out, complete them (which should only take a few minutes), and return them at the start of the second lecture (Tue Sep 1), as we will analyze the results of the social experiment on the fly in class.

    As sample Fourth Column material, A contagion oldie but goodie.

    Tu Sep 1
    Th Sep 3
    Structural Properties of Networks: Introduction
    [PDF] [PPT]
    (Rev. 9/3)

    Link to the Erdos Number Project.

    Here are two Coursera videos that are related to this set of lectures:

    What is a Network?

    The Erdos Number Project

    We have our first cohort of freshly minted Field Agents! From F.A. Stephanie Wolf, The Wiki Game. From F.A. Daniel Sha, visualize your Linked network. From F.A. Matthew Chiaravalloti, an app for predicting personality from Facebook likes. I strongly suspect this is a by-product of this academic study.

    Tu Sep 8
    Th Sep 10
    Tu Sep 15
    Contagion in Networks
    [PDF] [PPT]
    (Rev. 9/14)
    The following three assigned papers will be discussed in lecture. At a minimum you should know what the main results are, but try to understand as much as you can.

    Can Cascades be Predicted? Cheng, Adamic, Dow, Kleinberg, Leskovec.

    Structural Diversity in Social Contagion. Ugander, Backstrom, Marlow, Kleinberg.

    The Structural Virality of Online Diffusion. Goel, Anderson, Hofman, Watts.

    Here is a link where you can download NetLogo, a very nice app with many scientific simulations and models. Throughout the term we'll be examining several of the simulations under the Networks section.

    Here is a Coursera video related to this topic:

    Contagion in Networks

    From F.A. Aaron Guo, some other numbers of interest: Morphy,   Stiglitz, and Einstein. Still, I mainly just want to lower my Ashour Number. From F.A. Natalie Borowski, the best and worst times for virality.

    Th Sep 17
    Tu Sep 22
    Navigation in Networks
    [PDF] [PPT]
    (Rev. 9/17)

    During this set of lectures, we will discuss the following five articles.

    ``An Experimental Study of the Small World Problem'', by J. Travers and S. Milgram.

    ``An Experimental Study of Search in Global Social Networks'', by P. Dodds, R. Muhamad, and D. Watts.

    Navigation in a Small World, Kleinberg.

    Identity and Search in Social Networks, Watts, Dodds, Newman.

    The Scaling Laws of Human Travel, Brockmann, Hufnagel, Geisel.

    There are two Coursera videos associated with this lecture:

    Navigation in (Social) Networks

    Navigation in Networks, Revisited

    Here is Homework 1, which is due at the start of lecture on Tuesday October 6 in hard-copy format.

    Th Sep 24
    Quiz #1

    In this lecture session we'll have our first quiz. Unlike the midterm and final exams, which will be more advanced and challenging, the quizzes will primarily test the most basic course definitions and concepts. The quiz will cover all course material to date.

    The quiz will be in multiple choice format, and is closed-book: no notes, books, materials, articles, etc. allowed, only the quiz and a pen or pencil.

    Tu Sep 29
    Th Oct 1
    Tu Oct 6
    How Do Real Networks Look?
    [PDF] [PPT]
    (Rev. 9/29)

    For these lectures and the next set, you should read Chapters 2, 3 and 4 in "Six Degrees". (I recommend simply reading the book in its entirety, but will not require it.)

    We will also be discussing the following paper:

    Four Degrees of Separation. Backstrom et al, 2012.

    Here are Coursera videos associated with this set of lectures:

    How Do Real Networks Look? I. Heavy Tails

    How Do Real Networks Look? II. Small Diameter

    How Do Real Networks Look? III. Clustering of Connectivity

    Quiz #1 has been graded and will be returned in lecture. The average was 27.125 out of 30, or about 90%; the standard deviation was 2.60, or about 9%.

    From F.A. Vijay Prabakaran, slow down the London Tube, which seems relevant to both Kleinberg's model of navigation, and to later game-theoretic topics related to commuting and routing. And closely related, from F.A. Adam Stravitz, are transit apps like Moovit (see here also).

    From F.A. Rohit Bhadange, more on Dunbar's Number and bounded degrees.

    Tu Oct 13
    Th Oct 15
    Tu Oct 20
    Models of Network Formation
    [PDF]   [PPT]
    (Rev. 10/6)

    Coursera videos associated with these lectures:

    Models of Network Formation I. The Erdos-Renyi Model

    Models of Network Formation II. Clustering Models

    Models of Network Formation III. Preferential Attachment

    The feverishly anticipated article on network analysis of squash that we discussed early in the semester has finally come out.

    Here are solutions and grading guidelines for Homework 1. The average score was 87.5, and the standard deviation was 9.3. If you have questions about solutions or grading, please first see the TA who graded the problem (indicated on the solution set).

    Here are solutions to Quiz 1.


    Th Oct 22
    MIDTERM EXAMINATION The midterm will be held in class on Thursday, October 22. It will a closed-book, closed-note exam covering all material in the course to date.

    To help you prepare for the midterm, here are past midterm examinations (some but not all with solutions) from 2014,   2013,   2012,   2011,   2010,   2009,   2008,   2007, and 2006. Please remember that course content and schedule changes from year to year, so these midterms definitely cover material we have not yet, or will not, discuss this term; and conversely, there are new topics we've introduced this term that are not represented on these past midterms.

    Tu Oct 27
    Th Oct 29
    Strategic Network Formation Experiment
    On Thursday, October 29 we will hold a required in-class experiment for course credit. Please read the accompanying description. .
    Tu Nov 3
    Th Nov 5
    Network Formation Experiment Post-Mortem;
    Incentives and Collective Behavior
    [PDF]   [PPT]
    (Rev. 11/2)

    After some discussion and analysis of last week's network formation experiment, we'll launch into our examination of "rational" dynamics in networks.

    Read Schelling, "Micromotives and Macrobehavior", Chapters 1, 3 and 4.

    Coursera video associated with this lecture:

    Towards Rational Dynamics in Networks

    From F.A. Arjun Sastry, machine learning for Where's Waldo. From R.O. Aaron Guo, an entertaining video on stuff you already know. From F.A. Angela Qu, McKinsey discovers the long tail. From R.O. Natalie Borowski, Battle of the Networks: Paul Revere vs. William Dawes. From F.A. Nicole Granet, Penn's own Dani Bassett in cartoon form.
    Th Nov 5
    Tu Nov 10
    Introduction to (Networked) Game Theory
    [PDF]   [PPT]
    (Rev. 11/10)

    Midterms have been graded and will be returned in lecture. The average was 76 and the standard deviation was 15. Here is the solution set, which also specify which TA graded each problem. If you have questions or issues with the grading of a problem, please see the respective TA first.

    Prof. Kearns will be out of town on Thursday, November 19, so we will have our second quiz on that date.

    Coursera videos associated with this lecture:

    Basics of Game Theory

    Games on Networks: Preview

    Th Nov 12
    Tu Nov 17
    Network Formation Games

    Coursera video associated with this lecture:

    Network Formation Games

    From F.A. Adel Boyarsky, game theory on the British game show Golden Balls, and another one. From F.A. Lauren Reeder, play Beauty Contest against NYT readers. From F.A. Stephanie Klein, game theory and the Seattle Seahawks and game theory and kidney exchange. From F.A. Andrew Starker, game theory and space debris. From F.A. Michael Fogel, a brief piece on the Vickrey auction. From F.A. Natalie Borowski, the psychology of randomness. From F.A. Sarah Lawson, the Parable of the Polygons. From F.A. Monica Wojciechowski, game theory and dating. And from Yours Truly, traffic routing and gaming Waze.

    Th Nov 19
    Quiz #2 Our second quiz will be similar to the first, but only covering material since the first quiz. It will be closed-book, closed-notes, in multiple choice format. .
    Tu Nov 24
    Th Dec 1
    Networked Games: Coloring, Consensus and Voting
    [PDF]   [PPT]
    (Rev. 11/17)

    Read the following articles associated with these lectures:

    Experiments in Social Computation, MK.

    Behavioral Experiments on a Network Formation Game, MK, S. Judd, Y. Vorobeychik.

    Coursera videos associated with these lectures:

    Games on Networks: Coloring and Consensus

    Games on Networks: Biased Voting

    Here is Homework 2, which is due at the start of lecture on Tuesday December 8 in hard-copy format.

    Quiz #2 was returned in lecture. The average was 23.47 out of 28, and the standard deviation was 3.19.

    Th Dec 3
    Tu Dec 8
    Internet Economics
    [PDF]   [PPT]
    (Rev. 12/1)
    Coursera videos associated with these lectures:

    Internet Games: I. Packet Routing

    Internet Games: II. Sponsored Search

    Internet Games: III. Other Economic Problems

    Tu Dec 15
    FINAL EXAMINATION, 9-11AM, Room A1 of DRLB . DRLB is the building on the corner of 33rd and Walnut, directly across 33rd St. from the Moore Building. The final will be closed-book, closed-notes, and cumulative of all class material.

    Here are some past final exams, some with solutions, to help you study. Please note that some of the questions are on topics we did not cover this year, and that we covered topics this year that are not represented on the exams.

    [2004]   [2005]   [2006]   [2007]   [2008]   [2009]   [2011]   [2012]   [2013]   [2014]