0:00:01.006,0:00:06.156
We have historical records that allow us[br]to know how the ancient Greeks dressed,

0:00:06.180,0:00:07.434
how they lived,

0:00:07.458,0:00:08.980
how they fought...

0:00:09.004,0:00:10.528
but how did they think?

0:00:11.432,0:00:15.872
One natural idea is that the deepest[br]aspects of human thought --

0:00:15.896,0:00:17.768
our ability to imagine,

0:00:17.792,0:00:19.189
to be conscious,

0:00:19.213,0:00:20.444
to dream --

0:00:20.468,0:00:22.087
have always been the same.

0:00:22.872,0:00:24.371
Another possibility

0:00:24.395,0:00:28.118
is that the social transformations[br]that have shaped our culture

0:00:28.142,0:00:31.927
may have also changed[br]the structural columns of human thought.

0:00:32.911,0:00:35.435
We may all have different[br]opinions about this.

0:00:35.459,0:00:38.176
Actually, it's a long-standing[br]philosophical debate.

0:00:38.644,0:00:41.371
But is this question[br]even amenable to science?

0:00:42.834,0:00:45.340
Here I'd like to propose

0:00:45.364,0:00:50.136
that in the same way we can reconstruct[br]how the ancient Greek cities looked like,

0:00:50.160,0:00:52.548
just based on a few bricks,

0:00:52.572,0:00:56.698
that the writings of a culture[br]are the archaeological records --

0:00:56.722,0:00:58.865
the fossils of human thought.

0:00:59.905,0:01:01.079
And in fact,

0:01:01.103,0:01:03.309
doing some form of psychological analysis

0:01:03.333,0:01:06.877
of some of the most ancient[br]books of human culture,

0:01:06.901,0:01:12.856
Julian Jaynes came up in the '70s[br]with a very wild and radical hypothesis:

0:01:12.880,0:01:15.293
that only 3,000 years ago,

0:01:15.317,0:01:20.205
humans were what today[br]we would call schizophrenics.

0:01:21.753,0:01:23.261
And he made this claim

0:01:23.285,0:01:26.586
based on the fact that the first[br]humans described in these books

0:01:26.610,0:01:28.514
behaved consistently,

0:01:28.538,0:01:31.554
in different traditions[br]and in different places of the world,

0:01:31.578,0:01:35.110
as if they were hearing and obeying voices

0:01:35.134,0:01:38.174
that they perceived[br]as coming from the Gods,

0:01:38.198,0:01:39.396
or from the muses...

0:01:40.063,0:01:42.832
what today we would call hallucinations.

0:01:43.888,0:01:46.514
And only then, as time went on,

0:01:46.538,0:01:50.189
they began to recognize[br]that they were the creators --

0:01:50.213,0:01:52.728
the owners of these inner voices.

0:01:53.316,0:01:56.031
And with this, they gained introspection:

0:01:56.055,0:01:58.538
the ability to think[br]about their own thoughts.

0:01:59.785,0:02:03.182
So Jaynes' theory is that consciousness --

0:02:03.206,0:02:06.372
at least in the way we perceive it today,

0:02:06.396,0:02:09.936
where we feel that we are the pilots[br]of our own existence --

0:02:09.960,0:02:12.697
is a quite recent cultural development.

0:02:13.456,0:02:15.242
And this theory is quite spectacular,

0:02:15.266,0:02:16.699
but it has an obvious problem

0:02:16.723,0:02:20.715
which is that it's built on just a few[br]and very specific examples.

0:02:21.085,0:02:22.848
So the question is whether the theory

0:02:22.872,0:02:27.623
that introspection built up in human[br]history only about 3,000 years ago

0:02:27.647,0:02:30.631
can be examined in a quantitative[br]and objective manner.

0:02:31.543,0:02:35.106
And the problem of how[br]to go about this is quite obvious.

0:02:35.130,0:02:38.590
It's not like Plato woke up one day[br]and then he wrote,

0:02:38.614,0:02:40.273
"Hello, I'm Plato,

0:02:40.297,0:02:43.186
and as of today, I have[br]a fully introspective consciousness."

0:02:43.210,0:02:45.503
(Laughter)

0:02:45.527,0:02:48.860
And this still is actually[br]what is the essence of the problem.

0:02:49.467,0:02:53.522
We need to find the emergence[br]of a concept that's never said.

0:02:54.434,0:02:58.744
The word introspection[br]does not appear a single time

0:02:58.768,0:03:00.687
in the books we want to analyze.

0:03:01.728,0:03:05.815
So our way to solve this[br]is to build the space of words.

0:03:06.571,0:03:09.858
This is a huge space[br]that contains all words

0:03:09.882,0:03:12.684
in such a way that the distance[br]between any two of them

0:03:12.708,0:03:15.591
is indicative of how[br]closely related they are.

0:03:16.460,0:03:17.611
So for instance,

0:03:17.635,0:03:20.532
you want the words "dog" and "cat"[br]to be very close together,

0:03:20.556,0:03:24.387
but the words "grapefruit" and "logarithm"[br]to be very far away.

0:03:24.809,0:03:28.705
And this has to be true[br]for any two words within the space.

0:03:29.626,0:03:32.967
And there are different ways[br]that we can construct the space of words.

0:03:32.991,0:03:34.634
One is just asking the experts,

0:03:34.658,0:03:36.554
a bit like we do with dictionaries.

0:03:36.896,0:03:38.324
Another possibility

0:03:38.348,0:03:42.063
is following the simple assumption[br]that when two words are related,

0:03:42.087,0:03:44.436
they tend to appear in the same sentences,

0:03:44.460,0:03:45.913
in the same paragraphs,

0:03:45.937,0:03:47.707
in the same documents,

0:03:47.731,0:03:50.913
more often than would be expected[br]just by pure chance.

0:03:52.231,0:03:54.281
And this simple hypothesis,

0:03:54.305,0:03:55.611
this simple method,

0:03:55.635,0:03:57.242
with some computational tricks

0:03:57.266,0:03:58.655
that have to do with the fact

0:03:58.679,0:04:01.743
that this is a very complex[br]and high-dimensional space,

0:04:01.767,0:04:03.432
turns out to be quite effective.

0:04:04.155,0:04:06.957
And just to give you a flavor[br]of how well this works,

0:04:06.981,0:04:10.893
this is the result we get when[br]we analyze this for some familiar words.

0:04:11.607,0:04:12.792
And you can see first

0:04:12.816,0:04:16.094
that words automatically organize[br]into semantic neighborhoods.

0:04:16.118,0:04:18.335
So you get the fruits, the body parts,

0:04:18.359,0:04:20.784
the computer parts,[br]the scientific terms and so on.

0:04:21.119,0:04:25.341
The algorithm also identifies[br]that we organize concepts in a hierarchy.

0:04:25.852,0:04:27.003
So for instance,

0:04:27.027,0:04:30.624
you can see that the scientific terms[br]break down into two subcategories

0:04:30.648,0:04:32.748
of the astronomic and the physics terms.

0:04:33.338,0:04:35.584
And then there are very fine things.

0:04:35.608,0:04:37.513
For instance, the word astronomy,

0:04:37.537,0:04:39.352
which seems a bit bizarre where it is,

0:04:39.376,0:04:41.424
is actually exactly where it should be,

0:04:41.448,0:04:43.043
between what it is --

0:04:43.067,0:04:44.337
an actual science --

0:04:44.361,0:04:45.897
and between what it describes --

0:04:45.921,0:04:47.413
the astronomical terms.

0:04:48.182,0:04:50.073
And we could go on and on with this.

0:04:50.097,0:04:52.157
Actually, if you stare[br]at this for a while,

0:04:52.181,0:04:54.039
and you just build random trajectories,

0:04:54.063,0:04:57.229
you will see that it actually feels[br]a bit like doing poetry.

0:04:58.018,0:04:59.900
And this is because, in a way,

0:04:59.924,0:05:02.864
walking in this space[br]is like walking in the mind.

0:05:04.027,0:05:05.644
And the last thing

0:05:05.668,0:05:09.708
is that this algorithm also identifies[br]what are our intuitions

0:05:09.732,0:05:13.628
of which words should lead[br]in the neighborhood of introspection.

0:05:13.652,0:05:14.875
So for instance,

0:05:14.899,0:05:18.878
words such as "self," "guilt,"[br]"reason," "emotion"

0:05:18.902,0:05:20.791
are very close to "introspection,"

0:05:20.815,0:05:21.966
but other words,

0:05:21.990,0:05:24.157
such as "red," "football,"[br]"candle," "banana,"

0:05:24.181,0:05:25.633
are just very far away.

0:05:26.054,0:05:28.816
And so once we've built the space,

0:05:28.840,0:05:31.666
the question of the history[br]of introspection,

0:05:31.690,0:05:34.023
or of the history of any concept

0:05:34.047,0:05:38.826
which before could seem abstract[br]and somehow vague,

0:05:38.850,0:05:40.454
becomes concrete --

0:05:40.478,0:05:43.216
becomes amenable to quantitative science.

0:05:44.216,0:05:46.978
All that we have to do is take the books,

0:05:47.002,0:05:48.383
we digitize them,

0:05:48.407,0:05:51.216
and we take this stream[br]of words as a trajectory

0:05:51.240,0:05:53.209
and project them into the space,

0:05:53.233,0:05:56.987
and then we ask whether this trajectory[br]spends significant time

0:05:57.011,0:06:00.003
circling closely to the concept[br]of introspection.

0:06:00.760,0:06:01.956
And with this,

0:06:01.980,0:06:04.092
we could analyze[br]the history of introspection

0:06:04.116,0:06:06.037
in the ancient Greek tradition,

0:06:06.061,0:06:08.663
for which we have the best[br]available written record.

0:06:09.631,0:06:11.886
So what we did is we took all the books --

0:06:11.910,0:06:14.194
we just ordered them by time --

0:06:14.218,0:06:15.970
for each book we take the words

0:06:15.994,0:06:17.955
and we project them to the space,

0:06:17.979,0:06:21.011
and then we ask for each word[br]how close it is to introspection,

0:06:21.035,0:06:22.265
and we just average that.

0:06:22.590,0:06:25.788
And as time goes on and on,

0:06:25.812,0:06:29.064
these books get closer,[br]and closer and closer

0:06:29.088,0:06:30.842
to the concept of introspection.

0:06:30.866,0:06:34.667
And this is exactly what happens[br]in the ancient Greek tradition.

0:06:35.698,0:06:38.825
So you can see that for the oldest books[br]in the Homeric tradition,

0:06:38.849,0:06:42.261
there is a small increase with books[br]getting closer to introspection,

0:06:42.285,0:06:44.491
but about four centuries before Christ,

0:06:44.515,0:06:49.223
this starts ramping up very rapidly[br]to an almost five-fold increase

0:06:49.247,0:06:51.747
of books getting closer,[br]and closer and closer

0:06:51.771,0:06:53.453
to the concept of introspection.

0:06:54.159,0:06:56.583
And one of the nice things about this

0:06:56.607,0:06:57.805
is that now we can ask

0:06:57.829,0:07:01.976
whether this is also true[br]in a different, independent tradition.

0:07:02.962,0:07:06.138
So we just ran this same analysis[br]on the Judeo-Christian tradition,

0:07:06.162,0:07:08.883
and we got virtually the same pattern.

0:07:09.548,0:07:14.183
Again, you see a small increase[br]for the oldest books in the Old Testament,

0:07:14.207,0:07:16.121
and then it increases much more rapidly

0:07:16.145,0:07:17.984
in the new books of the New Testament,

0:07:18.008,0:07:20.040
and then we get the peak of introspection

0:07:20.064,0:07:22.191
in "The Confessions of Saint Augustine,"

0:07:22.215,0:07:24.072
about four centuries after Christ.

0:07:24.897,0:07:26.841
And this was very important,

0:07:26.865,0:07:30.238
because Saint Augustine[br]had been recognized by scholars,

0:07:30.262,0:07:32.434
philologists, historians,

0:07:32.458,0:07:34.536
as one of the founders of introspection.

0:07:35.060,0:07:38.357
Actually, some believe him to be[br]the father of modern psychology.

0:07:39.012,0:07:40.851
So our algorithm,

0:07:40.875,0:07:43.717
which has the virtue[br]of being quantitative,

0:07:43.741,0:07:45.004
of being objective,

0:07:45.028,0:07:47.044
and of course of being extremely fast --

0:07:47.068,0:07:49.465
it just runs in a fraction of a second --

0:07:49.489,0:07:52.992
can capture some of the most[br]important conclusions

0:07:53.016,0:07:55.238
of this long tradition of investigation.

0:07:56.317,0:07:59.968
And this is in a way[br]one of the beauties of science,

0:07:59.992,0:08:03.468
which is that now this idea[br]can be translated

0:08:03.492,0:08:06.063
and generalized to a whole lot[br]of different domains.

0:08:06.769,0:08:11.536
So in the same way that we asked[br]about the past of human consciousness,

0:08:11.560,0:08:14.966
maybe the most challenging question[br]we can pose to ourselves

0:08:14.990,0:08:19.127
is whether this can tell us something[br]about the future of our own consciousness.

0:08:19.550,0:08:21.020
To put it more precisely,

0:08:21.044,0:08:23.460
whether the words we say today

0:08:23.484,0:08:28.681
can tell us something[br]of where our minds will be in a few days,

0:08:28.705,0:08:29.856
in a few months,

0:08:29.880,0:08:31.062
or a few years from now.

0:08:31.597,0:08:34.617
And in the same way many of us[br]are now wearing censors

0:08:34.641,0:08:36.427
that detect our heart rate,

0:08:36.451,0:08:37.720
our respiration,

0:08:37.744,0:08:39.411
our genes,

0:08:39.435,0:08:43.086
on the hopes that this may[br]help us prevent diseases,

0:08:43.110,0:08:46.631
we can ask whether monitoring[br]and analyzing the words we speak,

0:08:46.655,0:08:49.338
we tweet, we email, we write,

0:08:49.362,0:08:54.170
can tell us ahead of time whether[br]something may go wrong with our minds.

0:08:55.087,0:08:56.621
And with Guillermo Cecchi,

0:08:56.645,0:08:59.646
who has been my brother in this adventure,

0:08:59.670,0:09:01.225
we took on this task.

0:09:02.228,0:09:07.760
And we did so by analyzing[br]the recorded speech of 34 young people

0:09:07.784,0:09:10.585
who were at a high risk[br]of developing schizophrenia.

0:09:11.434,0:09:14.315
And so what we did is,[br]we measured speech at day one,

0:09:14.339,0:09:17.581
and then we asked whether the properties[br]of the speech could predict,

0:09:17.605,0:09:20.101
within a window of almost three years,

0:09:20.125,0:09:22.160
the future development of psychosis.

0:09:23.427,0:09:25.793
But despite our hopes,

0:09:25.817,0:09:28.934
we got failure after failure.

0:09:29.793,0:09:33.675
There was just not enough[br]information in semantics

0:09:33.699,0:09:36.492
to predict the future[br]organization of the mind.

0:09:36.516,0:09:38.325
It was good enough

0:09:38.349,0:09:42.524
to distinguish between a group[br]of schizophrenics and a control group,

0:09:42.548,0:09:45.260
a bit like we had done[br]for the ancient texts,

0:09:45.284,0:09:48.278
but not to predict the future[br]onto the psychosis.

0:09:49.164,0:09:50.870
But then we realized

0:09:50.894,0:09:54.982
that maybe the most important thing[br]was not so much what they were saying,

0:09:55.006,0:09:56.679
but how they were saying it.

0:09:57.679,0:09:58.899
More specifically,

0:09:58.923,0:10:01.750
it was not in which semantic[br]neighborhoods the words were,

0:10:01.774,0:10:04.374
but how far and fast they jumped

0:10:04.398,0:10:06.699
from one semantic neighborhood[br]to the other one.

0:10:07.247,0:10:08.978
And so we came up with this measure,

0:10:09.002,0:10:11.391
which we termed semantic coherence,

0:10:11.415,0:10:16.219
which essentially measures the persistence[br]of speech within one semantic topic,

0:10:16.243,0:10:17.772
within one semantic category.

0:10:19.294,0:10:23.341
And it turned out to be[br]that for this group of 34 people,

0:10:23.365,0:10:27.024
the algorithm based on semantic[br]coherence could predict,

0:10:27.048,0:10:29.548
with 100 percent accuracy,

0:10:29.572,0:10:32.079
who developed psychosis and who will not.

0:10:32.976,0:10:35.913
And this was something[br]that could not be achieved --

0:10:35.937,0:10:37.445
not even close --

0:10:37.469,0:10:40.595
with all the other[br]existing clinical measures.

0:10:42.525,0:10:46.104
And I remember vividly,[br]while I was working on this,

0:10:46.128,0:10:48.445
I was sitting at my computer

0:10:48.469,0:10:51.104
and I saw a bunch of tweets by Polo --

0:10:51.128,0:10:54.295
Polo had been my first student[br]back in Buenos Aires,

0:10:54.319,0:10:56.389
and at the time,[br]he was living in New York.

0:10:56.413,0:10:58.501
And there was something in this tweets --

0:10:58.525,0:11:02.026
I could not tell exactly what[br]because nothing was said explicitly --

0:11:02.050,0:11:04.071
but I got this strong hunch,

0:11:04.095,0:11:07.050
this strong intuition[br]that something was going wrong.

0:11:08.347,0:11:11.070
So I picked up the phone[br]and I called Polo,

0:11:11.094,0:11:13.013
and in fact, he was not feeling well.

0:11:13.362,0:11:15.299
And this simple fact,

0:11:15.323,0:11:17.814
that reading in between the lines,

0:11:17.838,0:11:22.100
I could sense --[br]through words -- his feelings,

0:11:22.124,0:11:24.743
was a simple, but very[br]effective way to help.

0:11:25.987,0:11:27.625
What I tell you today

0:11:27.649,0:11:30.157
is that we're getting[br]close to understanding

0:11:30.181,0:11:34.467
how we can convert this intuition[br]that we all have,

0:11:34.491,0:11:35.856
that we all share,

0:11:35.880,0:11:37.077
into an algorithm.

0:11:38.102,0:11:39.563
And in doing so,

0:11:39.587,0:11:44.237
we may be seeing in the future[br]a very different form of mental health,

0:11:44.261,0:11:49.882
based on objective, quantitative[br]and automated analysis

0:11:49.906,0:11:51.615
of the words we write,

0:11:51.639,0:11:53.176
of the words we say.

0:11:53.200,0:11:54.351
Gracias.

0:11:54.375,0:11:58.239
(Applause)