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If you ask evolutionary biologists

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when did humans become humans,

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some of them will say that,

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well, at some point
we started standing on our feet,

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became biped and became
the masters of our environment.

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Others will say that because our brain
started growing much bigger,

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that we were able to have
much more complex cognitive processes.

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And others might argue
that it's because we developed language

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that allowed us to evolve as a species.

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Interestingly, those three
phenomena are all connected.

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We are not sure how or in which order,

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but they are all linked

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with the change of shape of a little bone
in the back of your neck

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that changed the angle
between our head and our body.

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That means we were able to stand upright

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but also for our brain
to evolve in the back

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and for our voice box to grow
from seven centimeters for primates

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to 11 and up to 17 centimetres for humans.

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And this is called
the descent of the larynx.

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And the larynx is the site of your voice.

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When baby humans are born today,
their larynx is not descended yet.

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That only happens
at about three months old.

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So, metaphorically, each of us here

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has relived the evolution
of our whole species.

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And talking about babies,

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when you were starting to develop
in your mother's womb,

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the first sensation that you had
coming from the outside world,

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at only three weeks old,
when you were about the size of a shrimp,

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were through the tactile sensation

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coming from the vibrations
of your mother's voice.

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So, as we can see, the human voice
is quite meaningful and important

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at the level of the species,

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at the level of the society --

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this is how we communicate
and create bonds,

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and at the personal
and interpersonal levels --

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with our voice, we share much more
than words and data,

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we share basically who we are.

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And our voice is indistinguishable
from how other people see us.

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It is a mask that we wear in society.

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But our relationship with our own voice
is far from obvious.

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We rarely use our voice for ourselves;
we use it as a gift to give to others.

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It is how we touch each other.

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It's a dialectical grooming.

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But what do we think about our own voice?

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So please raise your hand

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if you don't like the sound of your voice
when you hear it on a recording machine.

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(Laughter)

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Yeah, thank you, indeed,

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most people report not liking
the sound of their voice recording.

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So what does that mean?

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Let's try to understand that
in the next 10 minutes.

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I'm a researcher at the MIT Media Lab,

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part of the Opera of the Future group,

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and my research
focuses on the relationship

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people have with their own voice
and with the voices of others.

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I study what we can learn
from listening to voices,

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from the various fields,

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from neurology to biology,
cognitive sciences, linguistics.

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In our group we create
tools and experiences

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to help people gain a better
applied understanding of their voice

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in order to reduce the biases,

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to become better listeners,

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to create more healthy relationships

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or just to understand themselves better.

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And this really has to come
with a holistic approach on the voice.

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Because, think about all
the applications and implications

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that the voice may have,
as we discover more about it.

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Your voice is a very complex phenomenon.

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It requires a synchronization
of more than 100 muscles in your body.

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And by listening to the voice,

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we can understand possible failures
of what happens inside.

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For example:

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listening to very specific
types of turbulences

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and nonlinearity of the voice

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can help predict
very early stages of Parkinson's,

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just through a phone call.

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Listening to the breathlessness
of the voice

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can help detect heart disease.

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And we also know that the changes of tempo
inside individual words

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is a very good marker of depression.

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Your voice is also very linked
with your hormone levels.

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Third parties listening to female voices

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were able to very accurately
place the speaker

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on their menstrual cycle.

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Just with acoustic information.

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And now with technology
listening to us all the time,

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Alexa from Amazon Echo

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might be able to predict
if you're pregnant

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even before you know it.

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So think about --

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(Laughter)

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Think about the ethical
implications of that.

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Your voice is also very linked
to how you create relationships.

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You have a different voice
for every person you talk to.

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If I take a little snippet
of your voice and I analyze it,

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I can know whether you're talking
to your mother, to your brother,

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your friend or your boss.

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We can also use, as a predictor,
the vocal posture.

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Meaning, how you decide to place
your voice when you talk to someone.

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And you vocal posture,
when you talk to your spouse,

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can help predict not only if,
but also when you will divorce.

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So there is a lot to learn
from listening to voices.

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And I believe this has to start
with understanding

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that we have more than one voice.

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So, I'm going to talk
about three voices that most of us posses,

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in a model of what I call the mask.

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So when you look at the mask,

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what you see is a projection
of a character.

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Let's call that your outward voice.

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This is also the most classic way
to think about the voice,

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it's a way of projecting
yourself in the world.

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The mechanism for this projection
is well understood.

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Your lungs contract your diaphragm

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and that creates a self-sustained
vibration of your vocal fold,

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that creates a sound.

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And then the way you open and close
the cavities in you mouth,

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your vocal tract is going to
transform the sound.

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So everyone has the same mechanism.

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But voices are quite unique.

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It's because very subtle differences
in size, physiology, in hormone levels

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are going to make very subtle
differences in your outward voice.

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And your brain is very good

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at picking up those subtle differences
from other people's outward voices.

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In our lab, we are working
on teaching machines

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to understand those subtle differences.

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And we use deep learning to create
a real-time speaker identification system

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to help raise awareness
on the use of the shared vocal space --

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so who talks and who never
talks during meetings --

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to increase group intelligence.

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And one of the difficulties with that
is that your voice is also not static.

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We already said that it changes
with every person you talk to

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but it also changes generally
throughout your life.

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At the beginning
and at the end of the journey,

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male and female voices are very similar.

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It's very hard to distinguish

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the voice of a very young girl
from the voice of a very young boy.

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But in between, your voice
becomes a marker of your fluid identity.

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Generally, for male voices
there's a big change at puberty.

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And then for female voices,

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there is a change at each pregnancy
and a big change at menopause.

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So all of that is the voice
other people hear when you talk.

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So why is it that we're so
unfamiliar with it?

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Why is it that it's not
the voice that we hear?

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So, let's think about it.

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When you wear a mask,
you actually don't see the mask.

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And when you try to observe it,
what you will see is inside of the mask.

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And that's your inward voice.

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So to understand why it's different,

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let's try to understand the mechanism
of perception of this inward voice.

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Because your body has many ways
of filtering it differently

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from the outward voice.

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So to perceive this voice,
it first has to travel to your ears.

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And your outward voice
travels through the air

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while your inward voice
travels through your bones.

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This is called bone conduction.

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Because of this, your inward voice
is going to sound in a lower register

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and also more musically harmonical
than your outward voice.

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Once it travels there,
it has to access your inner ear.

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And there's this other mechanism
taking place here.

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It's a mechanical filter,

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it's a little partition
that comes and protects your inner ear

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each time you produce a sound.

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So it also reduces what you hear.

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And then there is a third filter,
it's a biological filter.

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Your cochlea -- it's a part of your
inner ear that processes the sound --

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is made out of living cells.

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And those living cells
are going to trigger differently

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according to how often
they hear the sound.

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It's a habituation effect.

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So because of this,

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as your voice is the sound
you hear the most in your life,

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you actually hear it less
than other sounds.

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Finally, we have a fourth filter.

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It's a neurological filter.

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Neurologists found out recently

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that when you open your mouth
to create a sound,

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your own auditory cortex shuts down.

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So you hear your voice

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but your brain actually never listens
to the sound of your voice.

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Well, evolutionarily
that might make sense,

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because we know cognitively
what we are going to sound like

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so maybe we don't need
to spend energy analyzing the signal.

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And this is called a corollary discharge

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and it happens for every motion
that your body does.

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The exact definition
of a corollary discharge

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is a copy of a motor command
that is sent by the brain.

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This copy doesn't create any motion itself

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but instead is sent
to other regions of the brain

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to inform them of the impending motion.

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And for the voice, this corollary
discharge also has a different name.

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It is your inner voice.

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So let's recapitulate.

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We have the mask, the outward voice,

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the inside of the mask, your inward voice,

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and then you have your inner voice.

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And I like to see this one
as the puppeteer

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that holds the strings
of the whole system.

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Your inner voice is

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the one you hear
when you read a text silently,

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when you rehearse
for an important conversation.

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Sometimes is hard to turn it off,

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it's really hard to look at the text
written in your native language,

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without having this inner voice read it.

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It's also the voice
that refuse to stop singing

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the stupid song you have in your head.

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(Laughter)

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And for some people
it's actually impossible to control it.

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And that's the case
of schizophrenic patients,

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who have auditory hallucinations.

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Who can't distinguish at all
between voices coming from inside

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and outside their head.

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So in our lab, we are also
working on small devices

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to help those people
make those distinctions

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and know if a voice
is internal or external.

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You can also think about the inner voice
as the voice that speaks in your dream.

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This inner voice can take many forms.

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And in your dreams, you actually unleash
the potential of this inner voice.

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That's another work
we are doing in our lab:

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trying to access
this inner voice in dreams.

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So even if you can't always control it,

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the inner voice --
you can always engage with it

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through dialogue, through inner dialogues.

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And you can even see this inner voice

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as the missing link
between thought and actions.

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So I hope I've left you
with a better appreciation,

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a new appreciation of all of your voices

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and the role it plays
inside and outside of you --

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as your voice is a very critical
determinant of what makes you humans

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and of how you interact with the world.

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Thank you.

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(Applause)