0:00:01.102,0:00:06.180
We have historical records that allow us[br]to know how the ancient Greeks dressed,

0:00:06.180,0:00:07.458
how they lived,

0:00:07.458,0:00:09.159
how they fought ...

0:00:09.159,0:00:11.211
but how did they think?

0:00:11.535,0:00:16.094
One natural idea is that the deepest[br]aspects of human thought --

0:00:16.094,0:00:17.976
our ability to imagine,

0:00:17.976,0:00:19.306
to be conscious,

0:00:19.306,0:00:20.681
to dream --

0:00:20.681,0:00:22.701
have always been the same.

0:00:23.092,0:00:24.601
Another possibility

0:00:24.601,0:00:28.351
is that the social transformations[br]that have shaped our culture

0:00:28.351,0:00:32.428
may have also changed the structural[br]columns of human thought.

0:00:33.096,0:00:35.627
We may all have different[br]opinions about this.

0:00:35.627,0:00:38.344
Actually, it's a long-standing[br]philosophical debate.

0:00:38.724,0:00:42.335
But is this question[br]even amenable to science?

0:00:43.116,0:00:45.555
Here I'd like to propose

0:00:45.555,0:00:50.160
that in the same way we can reconstruct[br]how the ancient Greek cities looked like

0:00:50.160,0:00:52.777
just based on a few bricks,

0:00:52.777,0:00:56.835
that the writings of a culture[br]are the archeological records --

0:00:56.835,0:00:59.467
the fossils of human thought.

0:01:00.199,0:01:01.390
And in fact,

0:01:01.390,0:01:03.570
doing some form of psychological analysis

0:01:03.570,0:01:07.184
of some of the most ancient[br]books of human culture,

0:01:07.184,0:01:13.028
Julian Jaynes came in the '70s with[br]a very wild and radical hypothesis ...

0:01:13.028,0:01:15.444
that only 3,000 years ago,

0:01:15.444,0:01:20.857
humans were what today[br]we would call schizophrenics.

0:01:21.883,0:01:23.575
And he made this claim

0:01:23.575,0:01:26.752
based on the fact that the first[br]humans [inscribing] these books

0:01:26.752,0:01:28.792
behaved consistently,[br]

0:01:28.792,0:01:31.708
in different traditions[br]and in different places of the world,

0:01:31.708,0:01:35.444
as if they were hearing and obeying voices

0:01:35.444,0:01:38.394
that they perceived[br]as coming from the Gods,

0:01:38.394,0:01:40.413
or from the muses --

0:01:40.413,0:01:43.673
what today we would call hallucinations.

0:01:44.012,0:01:45.476
And only then,

0:01:45.476,0:01:46.780
as time went on,

0:01:46.780,0:01:50.361
they began to recognize[br]that they were the creators --

0:01:50.361,0:01:53.078
the owners of these inner voices.

0:01:53.510,0:01:56.273
And with this they gained introspection:

0:01:56.273,0:01:59.221
the ability to think[br]about their own thoughts.

0:01:59.965,0:02:03.378
So Jaynes' theory is that consciousness --

0:02:03.378,0:02:06.538
at least in the way we perceive it today,

0:02:06.538,0:02:10.225
where we feel that we are the pilots[br]of our own existence --

0:02:10.225,0:02:13.164
is a quite recent cultural development.

0:02:13.545,0:02:15.337
And this theory is quite spectacular,

0:02:15.337,0:02:16.769
but it has an obvious problem

0:02:16.769,0:02:20.761
which is that it's built on just a few[br]and very specific examples.

0:02:21.085,0:02:22.872
So the question is whether the theory

0:02:22.872,0:02:27.913
that introspection built up in human[br]history only about 3,000 years ago

0:02:27.913,0:02:31.283
can be examined in a quantitative[br]and objective manner.

0:02:31.779,0:02:35.338
And the problem on how[br]to go about this is quite obvious.

0:02:35.338,0:02:37.724
It's not like Plato woke up one day

0:02:37.724,0:02:38.910
and then he wrote,

0:02:38.910,0:02:40.596
"Hello, I'm Plato

0:02:40.596,0:02:43.487
and as of today I have a fully[br]introspective consciousness."

0:02:43.487,0:02:45.307
(Laughter)

0:02:45.637,0:02:49.097
And this still is actually[br]what is the essence of the problem.

0:02:49.624,0:02:54.071
We need to find the emergence[br]of a concept that's never said.

0:02:54.680,0:02:58.942
The word introspection[br]does not appear a single time

0:02:58.942,0:03:01.559
in the books we want to analyze.

0:03:01.971,0:03:06.398
So our way to solve this[br]is to build the space of words.

0:03:06.794,0:03:09.998
This is a huge space[br]that contains all words

0:03:09.998,0:03:12.959
in such a way that they distance[br]between any two of them

0:03:12.959,0:03:15.842
is indicative of how[br]closely related they are.

0:03:16.460,0:03:17.456
So for instance,

0:03:17.456,0:03:20.857
you want the words dog and cat[br]to be very close together,

0:03:20.857,0:03:24.688
but the words grapefruit and logarithm[br]to be very far away.

0:03:25.008,0:03:29.298
And this has to be true for any[br]two words within the space.

0:03:29.748,0:03:33.109
And there are different ways that we[br]can construct the space of words.

0:03:33.109,0:03:34.802
One is just asking the experts,

0:03:34.802,0:03:37.199
a bit like we do with dictionaries.

0:03:37.199,0:03:38.623
Another possibility

0:03:38.623,0:03:40.688
is following the simple assumption

0:03:40.688,0:03:44.640
that when two words are related[br]they tend to appear in the same sentences,

0:03:44.640,0:03:46.214
in the same paragraphs,

0:03:46.214,0:03:48.049
in the same documents,

0:03:48.049,0:03:51.509
more often than would be expected[br]just by pure chance.

0:03:52.448,0:03:54.305
And this simple hypothesis,

0:03:54.305,0:03:55.792
this simple method,

0:03:55.792,0:03:57.266
with some computational tricks

0:03:57.266,0:03:58.679
that have to do with the fact

0:03:58.679,0:04:01.995
that this is a very complex[br]and highly dimensional space,

0:04:01.995,0:04:04.458
turns out to be quite effective.

0:04:04.458,0:04:07.127
And just to give you a flavor[br]of how well this works,

0:04:07.127,0:04:11.321
this is the result we get when[br]we analyze this for some familiar words.

0:04:11.607,0:04:12.816
And you can see first

0:04:12.816,0:04:16.278
that words automatically organize[br]into semantic neighborhoods.

0:04:16.278,0:04:17.362
So you get the fruits,

0:04:17.362,0:04:18.359
the body parts,

0:04:18.359,0:04:19.360
the computer parts,

0:04:19.360,0:04:20.359
the scientific terms

0:04:20.359,0:04:21.357
and so on.

0:04:21.357,0:04:25.699
The algorithm also identifies[br]the reorganized concepts in a hierarchy.

0:04:26.027,0:04:27.027
So for instance,

0:04:27.027,0:04:30.648
you can see that the scientific terms[br]break down into two subcategories

0:04:30.648,0:04:33.608
of the astronomic and the physic terms.

0:04:33.608,0:04:35.881
And then there are very fine things.

0:04:35.881,0:04:36.878
For instance,

0:04:36.878,0:04:38.054
the word astronomy,

0:04:38.056,0:04:39.870
which seems a bit bizarre where it is,

0:04:39.870,0:04:41.768
is actually exactly where it should be,

0:04:41.768,0:04:43.219
between what it is --

0:04:43.219,0:04:44.630
an actual science --

0:04:44.630,0:04:46.165
and between what it describes --

0:04:46.165,0:04:47.912
the astronomical terms.

0:04:48.366,0:04:50.097
And we could go on and on with this.

0:04:50.097,0:04:52.181
Actually if you stare at this for a while

0:04:52.181,0:04:54.034
and you just build random trajectories,

0:04:54.034,0:04:55.725
you will see that is feels well --

0:04:55.725,0:04:58.286
actually it feels a bit like doing poetry.

0:04:58.286,0:04:59.286
And this is because,

0:04:59.286,0:05:00.288
in a way,

0:05:00.288,0:05:03.482
walking in this space[br]is like walking in the mind.

0:05:03.901,0:05:05.778
And the last thing

0:05:05.778,0:05:09.938
is that this algorithm identifies[br]what are our intuitions

0:05:09.938,0:05:14.002
of which words should lead[br]in the neighborhood of introspection.

0:05:14.002,0:05:15.072
So for instance,

0:05:15.072,0:05:18.982
words such as self, guilt,[br]reason, emotion,

0:05:18.982,0:05:21.102
are very close to introspection,

0:05:21.102,0:05:22.102
but other words,

0:05:22.102,0:05:24.432
such as red, football, candle, banana,

0:05:24.432,0:05:26.072
are just very far away.

0:05:26.262,0:05:28.882
And so once we've built the space,

0:05:28.882,0:05:31.945
the question of the history[br]of introspection,

0:05:31.945,0:05:34.277
or of the history of any concept

0:05:34.277,0:05:39.055
which before could seem abstract[br]and somehow vague,

0:05:39.055,0:05:40.754
becomes concrete --

0:05:40.754,0:05:43.656
becomes amenable to quantitative science.

0:05:44.481,0:05:47.137
All that we have to do is take the books,

0:05:47.137,0:05:48.612
we digitize them,

0:05:48.612,0:05:51.420
and we take this stream[br]of words as a trajectory

0:05:51.420,0:05:53.452
and project them into the space,

0:05:53.452,0:05:57.087
and then we ask whether this trajectory[br]spends significant time

0:05:57.087,0:06:00.361
circling closely to the concept[br]of introspection.

0:06:00.911,0:06:02.152
And with this,

0:06:02.152,0:06:04.263
we could analyze[br]the history of introspection

0:06:04.263,0:06:06.183
in the ancient Greek tradition,

0:06:06.183,0:06:09.304
for which we have the best[br]available written record.

0:06:09.711,0:06:12.131
So what we did is we took all the books --

0:06:12.131,0:06:14.517
we just ordered them by time --

0:06:14.517,0:06:15.994
for each book we take the words

0:06:15.994,0:06:18.194
and we project them to the space,

0:06:18.194,0:06:21.165
and then we ask for each word[br]how close it is to introspection,

0:06:21.165,0:06:22.728
and we just average that.

0:06:22.728,0:06:25.986
And then we understand[br]that as time goes on and on,

0:06:25.986,0:06:29.088
these books get closer,[br]and closer and closer

0:06:29.088,0:06:31.062
to the concept of introspection.

0:06:31.062,0:06:35.387
And this is exactly what happens[br]in the ancient Greek tradition.

0:06:35.968,0:06:39.146
So you can see that for the oldest books[br]in the Homeric tradition,

0:06:39.146,0:06:42.540
there is a small increase with books[br]getting closer to introspection,

0:06:42.540,0:06:44.816
but about four centuries before Christ,

0:06:44.816,0:06:49.376
this starts ramping-up very rapidly[br]to an almost five-fold increase

0:06:49.376,0:06:51.938
of books getting closer,[br]and closer and closer

0:06:51.938,0:06:54.319
to the concept of introspection.

0:06:54.319,0:06:56.679
And one of the nice things about this

0:06:56.679,0:06:57.829
is that now we can ask

0:06:57.829,0:07:02.498
whether this is also true[br]in a different independent tradition.

0:07:03.026,0:07:06.248
So we just ran this same analysis[br]on the Judeo-Christian tradition,

0:07:06.248,0:07:09.178
and we got virtually the same pattern.

0:07:09.741,0:07:14.445
Again you see a small increase[br]for the oldest books in the Old Testament,

0:07:14.445,0:07:16.326
and then it increases much more rapidly

0:07:16.326,0:07:18.169
in the new books of the New Testament,

0:07:18.169,0:07:20.518
and then we get the peak of introspection

0:07:20.518,0:07:22.521
in the work Confessions[br]of Saint Augustine,

0:07:22.521,0:07:24.721
about four centuries after Christ.

0:07:25.051,0:07:26.985
And this was very important,

0:07:26.985,0:07:30.351
because Saint Augustine[br]had been recognized by scholars --

0:07:30.351,0:07:31.481
philologists,

0:07:31.481,0:07:32.632
historians --

0:07:32.632,0:07:35.298
as one of the founders of introspection.

0:07:35.298,0:07:38.595
Actually, some believe him to be[br]the father of modern psychology.

0:07:39.155,0:07:41.157
So our algorithm,

0:07:41.157,0:07:43.804
which has the virtue[br]of being quantitative,

0:07:43.804,0:07:45.066
of being objective,

0:07:45.066,0:07:47.332
and of course of being extremely fast --

0:07:47.332,0:07:49.636
it just runs in a fraction of a second --

0:07:49.636,0:07:53.138
can capture some of the most[br]important conclusions

0:07:53.138,0:07:55.940
of this long tradition of investigation.

0:07:56.547,0:08:00.142
And this is in a way[br]one of the beauties of science,

0:08:00.142,0:08:03.617
which is that now this idea[br]can be translated

0:08:03.617,0:08:06.496
and generalized to a whole[br]lot of different domains.

0:08:06.920,0:08:11.807
So in the same way that we asked[br]about the past of human conciousness,

0:08:11.807,0:08:15.132
maybe the most challenging question[br]we can pose to ourselves,

0:08:15.132,0:08:19.269
is whether this can tell us something[br]about the future of our own consciousness.

0:08:19.717,0:08:21.186
To put it more precisely,

0:08:21.186,0:08:23.601
whether the words we say today

0:08:23.601,0:08:28.797
can tell us something of where[br]our minds will be in a few days,

0:08:28.797,0:08:29.962
in a few months,

0:08:29.962,0:08:31.907
or a few years from now.

0:08:31.907,0:08:34.813
And in the same way many of us[br]are now wearing censors

0:08:34.813,0:08:36.524
that detect our heart rate,

0:08:36.524,0:08:37.936
our respiration,

0:08:37.936,0:08:39.712
our genes,

0:08:39.712,0:08:43.268
on the hopes that this may[br]help us prevent diseases,

0:08:43.268,0:08:46.788
we can ask whether monitoring[br]and analyzing the words we speak --

0:08:46.788,0:08:47.786
we tweet,

0:08:47.786,0:08:48.789
we email,

0:08:48.789,0:08:49.793
we write --

0:08:49.793,0:08:54.759
can tell us ahead of time whether[br]something may go wrong with our minds.

0:08:55.301,0:08:56.834
And with Guillermo Cecci,

0:08:56.834,0:08:59.962
who has been my brother[br]in this adventure,

0:08:59.962,0:09:01.517
we took on this task.

0:09:02.489,0:09:08.054
And we did so by analyzing the recorded[br]speech of 34 young people

0:09:08.054,0:09:11.168
who were at a high risk[br]of developing schizophrenia.

0:09:11.568,0:09:14.502
And so what we did is we[br]measured speech at day one

0:09:14.502,0:09:17.743
and then we asked whether the properties[br]of the speech could predict,

0:09:17.743,0:09:20.238
within a window of almost three years,

0:09:20.238,0:09:22.919
the future development of psychosis.

0:09:23.570,0:09:26.039
But despite our hopes,

0:09:26.039,0:09:29.568
we got failure after failure.

0:09:29.928,0:09:33.801
There was just not enough[br]information in semantics

0:09:33.801,0:09:36.844
to predict the future[br]organization of the mind.

0:09:36.844,0:09:38.556
It was good enough

0:09:38.556,0:09:42.883
to distinguish between a group[br]of schizophrenics and a control group,

0:09:42.883,0:09:45.555
a bit like we had done[br]for the ancient texts,

0:09:45.555,0:09:49.108
but not to predict the future[br]onto the psychosis.

0:09:49.320,0:09:51.109
But then we realized

0:09:51.109,0:09:55.135
that maybe the most important thing[br]was not so much what they were saying

0:09:55.135,0:09:57.322
but how they were saying it.

0:09:57.778,0:09:59.138
More specifically,

0:09:59.138,0:10:02.012
it was not in which semantic[br]neighborhoods the words were,

0:10:02.012,0:10:04.611
but how far and fast they jumped

0:10:04.611,0:10:07.076
from one semantic neighborhood[br]to the other one.

0:10:07.336,0:10:09.065
And so we came up with this measure,

0:10:09.065,0:10:11.624
which we termed semantic coherence,

0:10:11.624,0:10:16.427
which essentially measures the persistence[br]of speech within one semantic topic,

0:10:16.427,0:10:18.770
within one semantic category.

0:10:19.445,0:10:23.502
And it turned out to be[br]that for this group of 34 people,

0:10:23.502,0:10:27.465
the algorithm based on semantic[br]coherence could predict,

0:10:27.465,0:10:29.630
with 100 percent accuracy,

0:10:29.630,0:10:32.700
who developed psychosis and who will not.

0:10:33.178,0:10:36.150
And this was something[br]that could not be achieved --

0:10:36.150,0:10:37.733
not even close --

0:10:37.733,0:10:41.123
with all the other[br]existing clinical measures.

0:10:42.779,0:10:46.401
And I remember vividly[br]while I was working on this,

0:10:46.401,0:10:48.750
I was sitting on my computer

0:10:48.750,0:10:51.219
and I saw a bunch of tweets by Polo --

0:10:51.219,0:10:54.385
Polo had been my first student[br]back in Buenos Aires

0:10:54.385,0:10:56.413
and at the time he was living in New York.

0:10:56.413,0:10:58.613
And there was something in this tweets --

0:10:58.613,0:11:02.273
I could not tell exactly what[br]because nothing was said explicitly --

0:11:02.273,0:11:04.293
but I got this strong hunch,

0:11:04.293,0:11:07.873
this strong intuition[br]that something was going wrong.

0:11:08.510,0:11:11.094
So I picked up the phone[br]and I called Polo,

0:11:11.094,0:11:13.300
and in fact he was not feeling well.

0:11:13.582,0:11:15.544
And this simple fact

0:11:15.544,0:11:18.004
that reading in between the lines[br]

0:11:18.004,0:11:22.224
I could sense through words his feelings,

0:11:22.224,0:11:25.196
was a simple but very[br]effective way to help.

0:11:26.154,0:11:27.905
What I tell you today

0:11:27.905,0:11:30.587
is that we're getting[br]close to understanding

0:11:30.587,0:11:34.607
how we can convert this intuition[br]that we all have,

0:11:34.607,0:11:36.125
that we all share,

0:11:36.125,0:11:37.801
into an algorithm.

0:11:38.264,0:11:39.840
And in doing so,

0:11:39.840,0:11:44.489
we may be seeing in the future[br]a very different form of mental health,

0:11:44.489,0:11:50.073
based on objective, quantitative[br]and automated analysis

0:11:50.073,0:11:51.934
of the words we write,

0:11:51.934,0:11:53.470
of the words we say.

0:11:53.470,0:11:54.738
Gracias.

0:11:54.738,0:11:56.736
(Applause)