So some of the smallest
most insignificant words

we use everyday, can reflect
a lot about who we are.

And I say this not
as a linguist,

or a computer scientist
but as a social psychologist.

And today I'd like
to tell you a story

that summarizes
a lot of the research

that my colleagues,
my students and I have done,

that have helped me
to come to this realization.

Now several years ago I was studying
the nature of traumatic experience

and how it is related
to physical health

and what I kept finding,
that just completely perplexed me.

Basically when people have
a major traumatic experience in their life,

they are much more likely
to get sick after that event,

if they keep the events secret,

than if they actually
talk to other people.

So, this really bugged me.
So keeping a secret it seems

is somehow toxic.

So this led me
to run some experiments

where we brought people
in the laboratory

and we asked them to write about

the most traumatic 
experiences they've had,

especially if they'd kept them secret.

And these were big traumas,
these were things like rape.

They were like
major public humiliations or failure.

And the results that we got
from this study were stunning.

We discovered that having people write
as little as fifteen minutes a day,

for 3 or 4 consecutive days,

brought about meaningful changes
in people's physical health

and even their immune function.

Translating up, saying experiences
into words makes a difference, but why?

Since then there have been 
hundreds of studies

done by labs all over the world
trying to answer this

and they haven't come up 
with a single explanation.

My own approach was to 
actually look at the essays

that these people wrote,
and try to figure out,

was there something about 
the essays that could predict

who would benefit
from writing versus who wouldn't?

I tried and I couldn't figure it out.

So I got a number of psychologists
and other experts

to read and write hundreds
of these essays,

and they couldn't see a pattern either;

I needed to try some other strategies.

So, with the help of
one of my graduate students,

Martha Francis,
we wrote a computer program.

And the idea of this computer program
was to go into any given text

and calculate the percentage
of words in that text

that were positive emotion words,
negative emotion words

or words related to topics such as

death or sex or violence 
or religion or family.

And as long as we were writing
the computer program,

I thought well let's go ahead and
throw in some parts of speech,

pronouns, prepositions. Why? 
Because it was easy, who cares?

So, I go back, start to analyze
these traumatic essays,

and quickly discover that the content
of what people were writing about

didn't matter in terms of
if they improved in their health or not.

Instead, it was these junk words,
pronouns, and articles,

and prepositions and so forth,
that did matter.

Now think about this.

Here people are writing about
deeply disturbing issues,

and the actual topics that dealt with
tragedies, devastation, horrible things,

the topics themselves
and the words associated

with those topics made no difference.

Instead these little words
like "I" and "the" and "and" did matter.

I'd been looking for the obvious,
but in fact

I'd been paying attention
to what people were saying,

but not how they were saying it.

So how do I go about
analyzing "what" versus "how"?

Well, it turns out that they're
different kinds of classes of words

that look at this distinction,
and one of them is

if you're looking at
what people are writing about,

you look at what are called content words.

These are nouns and regular verbs
and adjectives and some adverbs.

These are the stuff of thought,
these were the stuff of communication.

We were trying to talk to somebody.

Google and search terms
are all based on these content words.

The other group of words
are a class of words

that are generally called
function words.

And function words are made up
of the most boring words you can imagine.

They're made up of pronouns:
"I", "me", "he", "she";

prepositions: "to", "of", "for";
auxiliary verbs: "am", "is", "have".

I'll have to wake you up if I keep talking
about these function words.

But it turns out these
function words are really interesting,

because, first of all, there's only about
five hundred function words in English,

so they account for far less than 1%

of all the words we know,
we hear, we read.

Nevertheless, they reflect 55% to 60%

of all the words that 
we are surrounded with,

they're everywhere,
but we don't pay attention to them.

In English and in other languages,
they're the shortest words there are,

and when they're spoken
or when you're reading,

they zip into your brain
at the speed of less than 0.2 seconds,

meaning that they're processed
essentially non-consciously.

But there's something
even more interesting about them,

they are social,
they are profoundly social.

Let me give me an example,
let's say you're walking along,

you see a note on the ground,
you pick it up and it says,

"I am placing it on the table."

Well, that kinda makes sense,
kinda doesn't.

"I'm placing it on the table".
There's 2 content words:

"placing" and "table";

all the rest are function words:
"I", "am", "it", "on", "the".

Now the reason this doesn't
make sense to most of us is

who was "I"?
No idea.

"Am" implies present tense.
When was it written?

"It"? Pfft, no idea what "it" is.

"On the table", "the table"
means it's a table

that the author knew about

and the intended recipient
of this note knew about,

but nobody else did.

And, in fact, this note only 
has meaning to the author

and the recipient of the note

at a particular time,
in a particular location.

And, in fact, if I took 
that note to this author now

6 months later and say,
"What's this all about?"

There's a good chance 
that the author will say,

"No idea."

Function words are social,

they tell us about the author,

they tell us about the relationship

between the author and the recipient

and the relationship between
the author and the topic itself.

And this is the heart of what
I want to talk to you about today.

By analyzing function words,
we start to get a sense

of who people are,
what their relationships are,

how they think about theirselves
and how they connect with others.

Yeah, there're a lot of function words,

and honestly, I could talk for 
several hours about function words.

But I'm going to spare you that
and just focus on a couple today,

to just give you a flavor
of why they're so interesting.

Let's start off with pronouns,

and let's start off 
with third-person pronouns

like "he", "she", "they".

Now it turns out some people
out there in the world

use these third-person pronouns
at high rates

and other people at low rates.

What kind of person would use them?

Well, you have to think about pronouns
and all function words

in terms of where are
people paying attention.

If you are using
these third-person pronouns,

by definition you're paying 
attention to other people.

You care about other people,
you're thinking about other people,

and people who use these at high rates

are much more socially engaged.

We can analyze emails,
tweets and so forth

and get a sense of someone's
social engagement

just by looking at this.

How about first-person singular pronouns,
"I", "me" and "my"?

OK, using the attentional arguments,

someone who's attending
to their thoughts, feelings,

behaviors, to themselves in some way
would use these words more.

What kind of person
do you think uses "I" words the most?

I hope, you're sitting there,
you're thinking,

"Well, somebody who's 
self-centered, self-important,

narcissistic, hungry for power 
and high in status."

You would be completely wrong.

In fact the person who is
highest in status

uses "I" words the least.

Let me rephrase that,

the higher anybody is in status,
the less they use "I" words;

the lower someone is in status,
the higher they use "I" words.

Now, I discovered this
by analyzing emails,

instant messages, 
natural conversations,

business groups and so forth.

And the effects were huge.

I looked at these results 
and I thought,

"Wow, this must be true
for other people

but it can't possibly be true for me."

You know I love everybody equally.

So I go in and analyze 
my own emails.

I'm the same as everybody else,

I look at the email that I get
from an undergraduate student,

"Dear Dr Pennebaker,
I would like to know

if I could possibly meet with you

because I think I need
to change my grade."

And I write back, "Dear Student,
Thank you so much for your email.

Unfortunately, the way
the grade systems work, blah, blah, blah."

I look at my email to the dean.

"Dear Dean, I'm Jamie Pennebaker
and I would like to ask you

if I could do this and if I could 
do that and I could do this."

And the dean writes back,
"Dear Jamie,

Thank you so much for your email..."
and so forth.

Now everybody is being completely polite,
nobody's putting anybody down.

This is the language 
of power in status;

it tells us where people
are paying attention.

A high status person is
looking out at the world,

the low status person tends
to be looking more inwardly.

What about others' states?

Let's move beyond status,
let's look at emotional states.

You would think 
that someone would be

paying more attention to themselves

if they're in pain. It could be
physical pain or emotional pain.

In fact, if we look at people
who are depressed,

we've done many studies on this,

and we know that people 
who are depressed

pay attention to themselves more

and they used the word "I" more.

In fact one of our very first studies
looked at the poetry

of suicidal and non-suicidal poets.

Now, we did this research
where we went through,

analyzed their poetry,

and initially I thought,
"Well, the big difference is

in the degree that they use 
negative, emotion words."

Not true.

Suicidal and non-suicidal poets

all use negative emotion 
words at high rate.

I think it's part 
of the job description.

(Laughter)

The big difference was
their use of the word "I".

Suicidal poets use the word "I" more.

Consider this poem,
this is by Sylvia Plath

who later committed suicide.

Listen to the way that 
she uses the word "I"

and first-person singular.

I'm taking some lines from her poem
"Mad Girl's Love Song".

I shut my eyes and
all the world drops dead;

I lift my lid[s] and all is born again.

(I think I made you up inside my head.)

I fancied you'd return the way you said,

But I grow old and I forget your name.

(I think I made you up inside my head.)

You can almost see Plath

embracing her sorrow,
her misery and so forth

and you can compare her writing
with other poets, non-suicidal poets

who write about lost love.

When they do, you can almost see 
them holding it off from a distance,

so they're looking at it from a more 
distant, third-person perspective.

Now, there's a really interesting,
important theory within psychology

about depression.
And people who are depressed

are thought to be people who are
very high in self-awareness or self-focus.

And part of this is
they also tend to be extremely honest.

In fact, there are many studies 
showing that they have this deficit

and they're not able to have
positive illusions about ourselves.

Those of us who aren't depressed
get by every day

by holding these insane illusions
about the life.

But these people are brutally honest.

Now this made me wonder:

throw away depression
for just a second.

Could we turn this entire thing
upside down

and find out if depressed people

or if we could use a computer program
as a linguistic lie-detector.

I mean for anybody.
So in fact we did some studies,

where we brought people
in the lab,

we induced them to lie 
or tell the truth,

we analyze court transcripts 
of people who were all found guilty,

half of whom were 
later exonerated,

and the effects were 
really quite impressive.

We did a pretty good job at telling

if someone who was telling
the truth versus lying,

and one of the best words
was the use of the word "I".

People who tell the truth

use the word "I" more, 
owning what they're saying.

Liars are tending to hold off,
distancing themselves.

Now, lie-detection and depression,

status, are all some things 
that we can look at,

but one of the things that 
I'm most interested in now

is looking at groups,

looking at the relationship 
between two people.

Can you tell how two people
are getting along

by analyzing the way that they're
using function words with each other?

And the answer is "yes".

We'd look at the percentage 
of each class of words

and we come up with the metric
that we call language style matching.

And the more that two people are matching
in their function word use,

the more they're on the same page,

the more they're talking
about something in the same way.

Now one place we started 
to look at this

was with speed dating.

Now, I should tell you
I love speed dating,

(Laughter)

I would never do it in a million years,

(Laughter)

but I encourage all of you
to go do speed dating

and when you do,

invite a researcher along

because there is 
no paradigm that is better.

We've been involved
in speed-dating projects

where people come in

and in their 4 minute date,
we tape-record it,

they know we are,

and then we transcribe 
the way they talk.

The more they match
in their language,

the more likely they are
to go out on a date.

We can predict
who will go on a date

at rates slightly better than
the people themselves can.

We've done studies
with young dating couples.

To be in our study, 
they had to give us

10 days of their instant 
messages or IM's.

And then what we do
is we analyze their IM's

with this style matching,

and we do much, 
much better than they do

at predicting if they'll be
together 3 months later.

(Laughter)

The fact is, is these words
are telling us how individuals

and pairs of people are connecting.

What about groups?

Now this is an area
that we're now working at.

We're looking at working groups,

some are groups 
that we've worked with,

people from the business school,

we'd look at people in 
the get-to-know-you groups,

we do educational groups.
And what we're finding is

by looking at a group of, 
say, 5 or 6 people,

we can now get a sense 
of how productive the group will be,

and also how cohesive
the group will be,

simply by looking 
at the style matching.

Now here's where things are
starting to get interesting:

by tracking a group 
that's interacting

and say they're all 
interacting online,

we can have a computer monitoring
how the group is behaving.

Imagine for example,

you are in this group,

and a computer coach 
comes to your group

every now and then,
and a message comes and says,

"You guys are not paying attention
to one another,

you need to be more attentive to what
the other people are saying," or

"You guys for the last few minutes
have strayed off topic,

try to get back on topic,"
or that loud mouth in the group,

the computer comes in and says,
"John, for the last 5 minutes

you said 50% of the words,
why don't you stand back

and encourage others to talk?"
(Laughter)

Well, we have now created
a program that does this,

and we've now tested it out
with hundreds of groups

and we are getting 
very promising results.

Now, you can start to see
why I'm so excited

about this world of function words,

that we're now taking this
in all these directions,

that I never would've thought about.

We've been looking at it in terms
of looking at historical records.

Can you tell if a particular explorer
committed suicide or was murdered?

We've done a project on that.

Can you look at a company 
and get a sense

of how their internal 
communications are working?

How well they are connecting
with the people

in their company or with their clients.

We look at corporate earnings reports
or the quarterly phone calls

to get a sense of the internal
group dynamics of the company.

We've worked with the government

to try to get a sense 
of terrorist groups

and if they are likely 
to behave badly.

We've helped people sort out
their love lives.

You can start to see that

by harnessing the power 
of these function words,

we can get a sense 
of individuals and groups

and how people are connecting.

Now, what I would urge you to do,

I'd like you to go home tonight

and I want you to start looking
at your emails,

your tweets, your IM's or whatever,

and in doing that, 
what I hope you start to see is,

first of all you learn 
a little bit more

about your relationships with others,

but more than anything,

I hope you'll learn 
a little bit about yourself.

Thank you very much.

(Applause)