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  • Hi, my name is Nicholas Christakis and I'm a physician and a social scientist and the

  • discipline I'm going to be speaking about to you today is sociology.  Sociology is

  • the field in which you study human behavior and human experience and how it relates to

  • the fact that individuals are embedded within larger groups and collections of individuals.

  •  When you see an individual as a member of a group or the collectivity you get a completely

  • different perspective on that person and on the groups of which they are a member and

  • in fact, in sociology we explore a fundamental tension and that tension arises because of

  • two facts.  On the one hand you yourself have your own identity and your own agency

  • and your own ability to make choices that affect your life, but on the other hand there

  • is a collective responsibility for your life as well and it turns out that collective supra-individual

  • factors can have as much to do with all kinds of aspects of your life, including whether

  • you live or die as your own genes or your own choices and it turns out that supra-individual

  • collective factors can have as much to do with what happens to you in your life and

  • even with whether you live or die as things within you, your own genes or your own choices.


  • supra-individual factors such as where you live, what kind of networks you are a part

  • of, social interactions you are a part of, what kind of institutions are nearby, for

  • instance governments or hospitals, all of these are critical in shaping your life and

  • all of our lives and these supra-individual factors can include things like inequality,

  • culture and religion as well.

Supra-individual factors like where you live or where you are

  • located in these vast face-to-face networks that we human beings assemble or what kinds

  • of formal institutions are near you like governments or hospitals for example can have as much

  • to do with what happens to you in your life as your own decisions and your own actions.

  •  Other sorts of things are important too, like inequality or culture or religion and

  • those sorts of supra-individual factors have a similar importance.

This is the difference

  • between what we want to understand as structure and agency between social constraints and

  • opportunities on the one hand and individual choices and actions on the other hand and

  • a second key idea beyond that first one-
This the difference between structure and agency,

  • between collective constraints and opportunities that constrain and permit you to do certain

  • kinds of things in your life on the one hand and your own individual choices and actions

  • that permit you to do other sorts of things on the other hand.  That is the first big

  • idea that I’d like to communicate today.  

The second big idea that sociology

  • explores and that I would like to communicate today is that collective phenomena are not

  • mere aggregations of individual phenomena.  There is something different, something

  • special about groups of people, about collectivities that does not reside within the individuals

  • themselves, something that emerges, something that transcends, something that is above and

  • not a part of solely individual kinds of things that you might think of.  

A second

  • key idea in sociology is that collective phenomena are not mere aggregations of individual phenomena.

  •  There is something special, something weird almost about groups of individuals, about

  • collectivities, something weird that you cannot see if you just study individuals, but that

  • you must study whole groups of people in order to really understand.

So how did I become interested in these crazy ideas?  Actually

  • I started my career as a physician and I went to medical school and at the time I wanted

  • to be a reconstructive surgeon and I wanted to operate on people who had cranial facial

  • abnormalities or people whose extremities had been cut off and reattach these extremities

  • and I used to cut class my first year of medical school and go operate with some of the surgeons

  • at Children’s Hospital in Boston and I did this for quite awhile and eventually as we

  • would operate on these kids they were primarily kids, one after another, day after day, I

  • came to the realization that the kind of healthcare that I wanted to practice was not the kind

  • that took care of people one at a time, but rather, the kind that tried to take care of

  • whole populations of people.  I mean I wanted to understand why do groups of people become

  • sick, not just why do individuals become sick and how can we make groups become well, not

  • just individuals become well one at a time and part of this was prompted by my realization

  • that I was running around putting my fingers in the dike.  One hole after another was

  • springing water and we were running around, all of us, trying to plug these holes and

  • I was interested in how can we make a better dike, how can make a situation in which fewer

  • people become sick to begin with, in which we spring fewer holes to begin with, in the

  • dike as it were and in fact I began to ask what I came eventually to see as sociological

  • questions about the origins of illness and disease and suffering and death in our society

  • and I wanted to understand how we could have a sociological response, a collective response

  • to these sorts of problems and in fact this dovetails to some extent with an interest

  • in public health, which can be contrasted with a kind of interest in clinical medicine

  • which takes care of patients one at

  • a time.  

  • So let’s start by taking a look at a personal testament, a very seemingly individualistic

  • statement that a human being is making about their own life, about what would seem to be

  • a quintessentially private individualistic decision, namely whether to take your own

  • life and to commit suicide.  This is Charlotte Perkin Gilman’s suicide note.  She was

  • 75 years-old when she took her life and the note says:  “The time is approaching when

  • we shall consider it abhorrent to our civilization to allow a human being to die in prolonged

  • agony which we should mercifully end in any other creature.  Believing this choice to

  • be of social service in promoting wiser views on this question, I have preferred chloroform

  • to cancer.” 

And the note said:  The time is approaching when we shall consider

  • it abhorrent to our civilization to allow a human being to die in prolonged agony which

  • we should mercifully end in any other creature.  Believing this choice to be a social service

  • in promoting wiser views on this question, I have preferred chloroform to cancer.”


So despite the fact that this woman is taking her life and despite the fact that

  • she is writing a suicide note notice that the note contains or eludes to kind of connections

  • to others even as she was ending her own life.  She bemoans the fact that society is not

  • sensitive to her pain and even while dying she is trying to make a contribution to society.

  •  She is trying to be connected to other individuals.  

Here is another note:  “Dear God,

  • please have mercy on my soul.  Please forgive me.  I can’t stand the pain anymore.”

  •  And that note was written by a 76 year-old grandmother who isolated by depression and

  • disability crawled into her basement freezer to kill herself by the cold and you might

  • ask what kind of a social system permits this to happen, permits one of its members to be

  • so alone, to feel so isolated that this is the choice that they would make and in fact

  • you might ask was this suicide truly an individual act, was it really purely an individual choice. 


  • one, Ron Berst jumped off the Golden Gate Bridge and in his will he donated $10,000

  • to AIDS research.  This is his note:  “To the San Francisco Police Department or equivalent

  • jurisdiction.  This is to state that I, Ron R. Burst did take my own life due to the fact

  • that I have the disease AIDS and it has progressed both rapidly and to the point where number,

  • I constantly feel ill and have almost no energy and number two, I very soon expect to become

  • a burden to my friends and family and I do not want to put any of them through such an

  • ordeal.  I sincerely regret any inconvenience that this may have caused anyone involved.

  •  I honestly believe that a fast end such as this while one is still able, yet ill enough

  • to justify it is easier on my close friends who have been so unbelievably supportive emotionally

  • for me and my family who have been no less so than to drag this out.  I did not give

  • up.”

So again in Mr. Berst’s note notice the social concern.  His death is

  • not an individual act at all.  First of all, it was public.  He jumped off the Golden

  • Gate Bridge.  People saw him.  Second, it was guided by a concern for others.  He is

  • worried about his friends and family and third, it is infused with the social ties that connect

  • him to his family and his friends.  

Now there is another way that suicide is social

  • as well.  It is not just the connection the individual has to others.  It is the responsibility

  • that others have to the individual.  It is about how social and structural factors constrain

  • or permit individual acts even like suicide.  For example, this is an image of the Golden

  • Gate Bridge from which Ron Berst jumped and this bridge is unusual in its design because

  • the sidewalk as you can see is directly next to the edge of the image.  He walked along

  • the sidewalk and then just jumped over that railing, stood there and jumped right over.


  • this is a picture of Kevin Hines who almost met the same fate as Mr. Berst.  In September

  • of 2000 at the age of 19 suffering from depression he went to the Golden Gate Bridge and he stood

  • there for 40 minutes crying.  No one approached him to ask what was wrong and then eventually

  • a tourist came up and asked him if he could take her photograph.  Hines interpreted this

  • as a clear sign that no one cared.  He took the picture and then when she walked away

  • he turned around and he jumped right over the railing, but instantly he says he realized

  • that he had made a mistake.  He changed his mind.  “Oh shit,” he thought, “I don’t

  • want to die.”  “What am I going to do?” he later recalled.  In midair he came up

  • with a plan to save his life as he described as follows:  “It was simply this.  “A;

  • God save me, B; throw your head back and C; hit feet first.”  And it takes four seconds

  • to drop the 220 feet from the height of the Golden Gate Bridge to the water and you eventually

  • reach a speed of 75 miles per hour and among the over 1,200 people who have jumped off

  • the bridge since 1937 only 26 are believed to have survived and interestingly a large

  • percentage of those who attempt the jump when they are interviewed afterwards say that they

  • regretted the decision as soon as they jumped.  

For example, another jumper, Kevin

  • Baldwin was 28 and also severely depressed in August of 1985 when he jumped and he later

  • said the following thing:  “I still see my hands coming off the railing.  I instantly

  • realized that everything in my life that I thought was unfixable was totally fixable

  • except for having just jumped.”

It is 220 feet from the deck of the bridge to

  • the water and it takes just four seconds to reach the bottom and by which point you are

  • traveling at 75 miles per hour.

Even allowing for the fact that we cannot know

  • what all the successful suicides would have said had we been able to interview them these

  • kinds of reports by people who jumped and survived beg the question of how to prevent

  • these kinds of supposedly purely individual acts.  What would happen to these people

  • if somehow society could have prevented them from jumping, if there somehow had been a

  • structure in place which had constrained the agency of these individuals?  One landmark

  • study conducted in 1978 of 515 people who were removed from the Golden Gate Bridge before

  • they had jumped and followed them for an average of about 26 years afterwards found that 94%

  • were still alive or had died of natural causes many years later, so suicidal behavior is

  • acute and crisis driven and if the individual is prevented from acting on their suicidal

  • impulses by those around him it might not be repeated.

There are quite a number of remarkable things about

  • such stories.  No doubt these individuals and their illnesses are central actors in

  • the experience of the individual, but I want to highlight two other observations.  One

  • is the role of the perceived indifference expressed by the person that Kevin encountered.

  •  This point points to an important theme in sociology, the rule of social connection

  • in our personal experience and the role of our embededness in the lives of others.  So

  • one thing I would like to highlight is the perceived indifference on the part of the

  • person that approached Kevin.  One thing that I would like to highlight is the perceived

  • indifference on the part of the person, the tourist that approached Kevin because this

  • highlights an important theme or an important idea in sociology, namely the idea that we

  • are all connected to each other.  The role of connection in our experience of the world

  • and the role of our embededness in others is in fact a key consideration or a key point

  • that sociologists are interested in.  

The other important thing to realize from these

  • stories is the importance of extra individual factors that help determine individual outcomes

  • as I alluded to the role of structure versus the role of agency.  Now the Golden Gate

  • Bridge has a foot path adjacent to the railing unlike most bridges and people still regularly

  • kill themselves from it and if you look at the Golden Gate Bridge you can see some ideas

  • about how we might constrain individual agency, how we might as a society respond to prevent

  • people from jumping.  For example, suicide barriers such as this one at other sites have

  • drastically reduced and often even eliminated suicides such as at the Eifel Tower, the Empire

  • State Building or the Sydney Harbor Bridge, but a barrier has not been put at the Golden

  • Gate Bridge for reasons that many, myself included find a bit silly.  Namely, that

  • it would somehow ruin the aesthetics of the bridge, but here is an artist rendering of

  • one possible solutions and it doesn’t look so bad.  This argument it turns out has been

  • around for years, but finally in February of 2010 the Golden Gate Bridge Board after

  • many years of lobbying agreed to put some suicide nets under the bridge to catch jumpers,

  • but they did not agree to assign the use of any toll revenue for this purpose, so still

  • there is nothing there to prevent suicide.

So this is a particularly specific and dramatic

  • illustration of the interplay between structure and agency, between policy decisions made

  • at the collective level and the ability of an individual even to stay alive.  Moreover,

  • this is a particularly powerful illustration not only of the issue of structure versus

  • agency, but also of more complicated ideas, namely, the issue of group level phenomena

  • or of emergence which is the second big idea I would like to talk to you about today.


  • suicide has been used as an example to illustrate this idea ever since 1897 by a very famous

  • sociologist by the name of Emile Durkheim who wrote about this topic and Durkheim had

  • a number of arguments including the following.  He said or he wroteso Durkheim had a

  • number of arguments about suicide including the following.  He wrote:  “The individual

  • is dominated by a moral reality greater than himself, namely, collective reality.  When

  • each people is seen to have its own suicide rate more constant than that of general mortality,

  • that its growth is in accordance with a coefficient of acceleration characteristic of each society,

  • when it appears that the variations through which it passes at different times reflect

  • the rhythm of social life and that marriage, divorce, the family, religious society, the

  • army, etcetera affect it in accordance with definite laws then these states and institutions

  • will no longer be regarded simply as characterless, ineffective ideological arrangements.  Rather

  • they will felt to be real, living, active forces which because of the way they determine

  • the individual prove their independence of him, which if the individual enters as an

  • element in the combination whence these forces ensue at least control him once they are formed.”


  • the individuals come and go in Durkheim’s analysis.  People come and go, but the rates

  • of suicide stay the same, so he was looking at suicide rates in different religious groups

  • in different periods in France and he found that these rates are constant across time

  • and vary across religious groups even though the individual members of those groups in

  • those particular times changed dramatically, so the Protestants in 1800 France are completely

  • different than the human beings who are the Protestants in 1850 France and yet the suicide

  • rate let’s say is the same.  Hence this constancy of rates and this variation across

  • societies is indicative of something else going on beyond individual choice or brain

  • biology.  It is as if the society determines thisit is as if the society determines

  • this seemingly purely individual act, suicide.  Hence this constancy of rates and this variation

  • across societies is indicative of something else going on beyond individual choice or

  • individual biology.  It is as if society determines this seemingly purely individual

  • act, this seemingly purely individual choice.  So you see groups can have properties of

  • their own and the individuals within them are affected by those properties.

  • Sociologist have been studying social networks beginning with the pioneering work of Georg

  • Simmel in the 1890s and they have been doing this, studying networks for well over 100

  • years and social networks are one particular kind of supra-individual factor that can affect

  • individual choices, that can shape your destiny and shape what happens to you in your life.

  •  Now by social networks I don’t mean Facebook or MySpace of the kinds of recent networks

  • that many of you might be thinking about.  I actually mean the kind of face-to-face

  • networks that human beings have been making for tens of thousands of years.  In fact,

  • ever since we lived on the African Savannah. 

Now each of us forms or inherits certain kinds

  • of connections to friends, to coworkers, to our relatives, to our neighbors and each of

  • those individuals in turn also has friends and coworkers and relatives and neighbors

  • and as a result of this we form this incredibly ornate, almost baroque structure known as

  • social networks and we precede to live out our lives embedded within these networks.


  • what is the difference between a group and a network?  Here is a picture of a group

  • and a group maybe of 100 people.  Each dot represents a person, but a network in addition

  • to the 100 people also has ties, the ties that connect the people to each other and

  • it has specific ties at that and there are two kinds of networks, artificial networks

  • and natural networks.  So for example, here is an example of one of the simplest type

  • of artificial networks you can imagine, a bucket brigade.  It is

  • a simple linear network.  It has 100 people to which we have added 99 ties.  


  • is connected to the guy on the right and to the guy on the left and assembling the people