NARRATOR: YOUR BODY IS EXTRAORDINARY.

BORN WEAK AND HELPLESS, YOU DEVELOP INTO ONE OF THE MOST SOPHISTICATED LIVING THINGS ON THE PLANET.

HIDDEN WITHIN YOUR BODY ARE ALMOST MIRACULOUS ABILITIES TO TRANSFORM YOURSELF.

YOU HAVE LEARNED TO COORDINATE MILLIONS OF NERVE CELLS TO PRECISELY CONTROL YOUR MOVEMENT.

PNEUMONOULTRAMICROSCOPICSILICO- VOLCANOCONIOSIS.

NARRATOR: REMEMBER TENS OF THOUSANDS OF WORDS... AND EVEN CHANGE YOUR OWN GENETIC BLUEPRINT TO ADAPT TO THE WORLD AROUND YOU.

WE ARE LIVING IN AN EXTRAORDINARY ERA OF SCIENCE, WHERE NEW INSIGHTS ARE REVEALING THE HIDDEN WORKINGS OF YOUR BODY IN WAYS NEVER SEEN BEFORE.

HOW YOU LEARN... GROW... AND SURVIVE.

YOU MAY THINK YOU KNOW WHO YOU ARE... [WOMAN LAUGHING] NARRATOR: BUT IT'S TIME TO THINK AGAIN.

THIS IS "THE AMAZING HUMAN BODY."

AS A BABY, YOU ARE EFFECTIVELY A BLANK SLATE, BARELY ABLE TO MOVE, WITH LITTLE UNDERSTANDING OF THE WORLD AROUND YOU AND UNABLE TO COMMUNICATE WITH EASE.

YET FROM DAY ONE YOU LEARN, AND THE AMAZING THING IS, YOU NEVER STOP LEARNING.

ONE OF THE FIRST THINGS YOU HAVE TO MASTER IS HOW TO CONTROL YOUR BODY.

AND WHEN THEY START LOOKING AROUND, THAT'S AMAZING.

AND THEN THEIR ARMS START TO MOVE AND THEY START THROWING EVERYTHING DOWN OFF THE TABLE TO SEE WHAT THEY CAN DO.

THE MOVEMENTS WENT FROM CRAWLING TO RUNNING TO JUMPING TO FLYING DOWN THE MOUNTAIN.

WHEN THEY STARTED WALKING AROUND, THEY DIDN'T WALK, IT WAS A RUN, AND THEN WE KNEW IT WAS JUST TIME TO PLAY CATCH-UP AND THEY WERE JUST GONNA NEVER STOP GROWING.

YOU JUST HAVE TO HAVE EYES IN THE BACK OF YOUR HEAD ALL THE TIME.

NARRATOR: JUST LEARNING HOW TO STAND AND PUT ONE FOOT IN FRONT OF THE OTHER REQUIRES ENORMOUS DEXTERITY.

WITH EVERY MOVEMENT, YOUR BRAIN TAKES IN HUGE AMOUNTS OF SENSORY INFORMATION, PROCESSES IT AT LIGHTNING SPEED, AND THEN COORDINATES TENDONS, LIGAMENTS, AND MUSCLES.

IT CAN TAKE MONTHS TO MASTER THIS CONTROL, BUT ONCE LEARNED, IT BECOMES AUTOMATIC, BECAUSE ONCE YOU LEARN A SKILL, IT'S ETCHED PHYSICALLY IN THE BRAIN AND RARELY FORGOTTEN.

JUST LIKE RIDING A BIKE.

MAN: I FIRST STARTED RIDING A BIKE WHEN I WAS 4 YEARS OLD, JUST LIKE ANY NORMAL KID.

I THINK I WAS RIDING 'ROUND MY GARDEN, AND THEN FROM THERE I'VE REALLY KIND OF JUST ALWAYS BEEN ON MY BIKE.

NARRATOR: DESCENDING FROM HIGH ABOVE LOCH KATRINE IN SCOTLAND... DANNY MacASKILL SHOWS WHY HE'S CONSIDERED ONE OF THE WORLD'S BEST CYCLISTS.

DANNY: RIDING A BIKE, TO ME, JUST FEELS COMPLETELY NATURAL, AS IF I'M ON MY FEET.

NARRATOR: AS HE RACES DOWN THE SIDE OF THE MOUNTAIN, HE CAN FOLLOW TWISTS... NAVIGATE TURNS, AND OVERCOME OBSTACLES, SEEMINGLY WITHOUT THINKING ABOUT IT.

DANNY: IT ALSO OPENS UP THE WORLD IN A DIFFERENT WAY WHERE EVERYTHING'S AN OBSTACLE.

YOU KNOW, IT REALLY IS SECOND NATURE.

NARRATOR: BUT WHILE DANNY WOWS WITH HIS EFFORTLESS DISPLAYS OF SKILL, WHEN HE'S RIDING, HE'S USING ABILITIES EVERYONE HAS-- GOOD BALANCE.

FAST REACTION TIMES.

AND COORDINATION.

THINGS YOU USE ALL THE TIME, WHETHER YOU ARE RUNNING FOR THE BUS... OR CATCHING A BALL.

THESE ABILITIES ARE WHAT GIVES DANNY HIS EXTRAORDINARY AGILITY ON HIS BIKE.

IN FACT, HE'S SPENT SO MUCH TIME ON TWO WHEELS... THAT HIS BIKE IS LIKE AN EXTENSION OF HIS OWN BODY.

DANNY: IT'S KIND OF SIMILAR TO RUNNING OVER ROCKS ON A BEACH.

YOU JUST KNOW EXACTLY HOW FAR YOU NEED TO SHIFT YOUR FEET TO GET TO EACH ROCK.

IT'S THE SAME FOR ME WHEN I RIDE MY BIKE.

I KNOW EXACTLY HOW MUCH PRESSURE TO PUT ON MY PEDALS.

IT'S ALMOST EASIER FOR ME TO DO IT ON MY BIKE THAN IT IS ON MY FEET.

NARRATOR: TO CYCLE THE WAY HE DOES, DANNY'S BODY IS CONSTANTLY GATHERING INFORMATION FROM THE ENVIRONMENT AROUND HIM, THE SAME WAY YOUR BODY DOES WITH EVERYTHING YOU DO.

EVERY SECOND, TENS OF THOUSANDS OF RECEPTORS IN YOUR HANDS ARE FEEDING BACK INFORMATION TO YOUR BRAIN, ALONG WITH BALANCED DATA FROM THE VESTIBULAR SYSTEM IN THE INNER EAR AND YOUR EYES.

ALL THIS INFORMATION IS COLLATED BY THE CENTRAL NERVOUS SYSTEM AND USED TO COMPUTE YOUR EXACT BODY POSITION.

DANNY'S BRAIN CAN THEN MAKE TINY ADJUSTMENTS TO ARM AND LEG MUSCLES TO MAKE SURE HE CAN STAY IN CONTROL OF THE BIKE.

THIS FEEDBACK LOOP IS AT THE HEART OF ALL YOUR MOTOR SKILLS.

BUT IT DOESN'T JUST HAPPEN.

TO MASTER ANY NEW ACTIVITY, FROM RIDING A BIKE LIKE DANNY DOES TO SIMPLY LEARNING TO WALK AS A TODDLER, REQUIRES PRACTICE.

DANNY: SOME OF THE TRICKS I DO ON MY BIKE CAN TAKE ME, YOU KNOW, DAYS TO LAND, HUNDREDS OF GOES.

AH!

THERE'S A GORSE BUSH.

BUT IN YOUR MIND, YOU KNOW HOW TO DO IT.

YOU KNOW, YOU'VE KIND OF VISUALIZED HOW YOU'RE GONNA LAND THE TRICK.

NARRATOR: NEW MOTOR SKILLS HAVE TO BE LEARNED, ADAPTED, AND REFINED, SO WHAT AT FIRST IS HARD, WITH PRACTICE BECOME EFFORTLESS.

THE FIRST TIME DANNY TRIES A NEW TRICK...

IT'S NOT ENTIRELY SUCCESSFUL.

DANNY: I ALMOST DIED.

OH, MY EAR.

IT LITERALLY ALMOST GOT LIKE TORN OFF.

IT FEELS LIKE IT'S LIKE BLEEDING INSIDE.

NARRATOR: BUT WHEN YOU PRACTICE OVER AND OVER, YOUR BRAIN BUILDS UP STRONG NEURAL CONNECTIONS... DANNY: OH, THAT WAS AMAZING.

AND THEN REINFORCES THEM.

THIS SPEEDS UP THE CONNECTIONS AND IMPRINTS THE SKILL ONTO THE BRAIN... DANNY: HA HA.

NARRATOR: SO IT BECOMES SECOND NATURE.

WHEN YOU PRACTICE, INCREASED ACTIVITY IN THE PATHWAYS, OR AXONS, USED FOR THE NEW SKILL ATTRACTS THE ATTENTION OF SPECIAL CELLS CALLED OLIGODENDROCYTES.

THESE WRAP THEIR BRANCH-LIKE EXTENSIONS AROUND THE AXON AND BUILD A SHEATH OF FATTY PROTECTIVE MATERIAL CALLED MYELIN AROUND IT.

THIS EXTRAORDINARY FOOTAGE SHOWS AXONS AS THEY ARE BEING MYELINATED, SEEN IN GREEN.

THOSE WITHOUT MYELIN ARE SHOWN IN RED.

THIS PROCESS OF MYELINATION SECURES AND INSULATES THE AXON, AND LIKE THE INSULATION AROUND THE CABLE TO YOUR TELEVISION, IT ALLOWS ELECTRICAL SIGNALS TO TRAVEL FASTER, AT SPEEDS OF OVER 500 FEET PER SECOND.

DANNY: READY?

3... 2... 1...COMING.

ALL OF DANNY'S PRACTICE HAS CREATED A VAST NEW SUPER HIGHWAY ENABLING HIM TO PULL OFF THE MANEUVER WITH INCREDIBLE EASE.

MYELIN NOT ONLY SPEEDS UP THE CONNECTIONS, BUT PROTECTS AND STRENGTHENS THE MEMORIES AND SKILLS YOU'VE DEVELOPED SO THAT WHAT YOU'VE LEARNED ISN'T FORGOTTEN.

IT'S CENTRAL TO ALL THOSE MOTOR SKILLS YOU USE THROUGH YOUR DAILY LIFE, LIKE WALKING OR RIDING A BIKE, THINGS THAT EVENTUALLY FEEL AUTOMATIC.

AND THIS EXTRAORDINARY PROCESS IS TAKING PLACE FROM THE TIME YOU ARE BORN.

[MUSIC PLAYING] AS AN INFANT AND TODDLER, YOU ARE MAKING A MILLION NEW NEURAL CONNECTIONS EVERY SECOND, LAYING DOWN NEW PATHWAYS ALL THE TIME... AS YOU LEARN HOW TO GRAB THINGS, HOW TO STAND, HOW TO TAKE YOUR VERY FIRST STEPS.

AND AT AROUND THE SAME TIME AS YOU LEARN TO WALK, YOU ARE LEARNING TO DO SOMETHING EVEN MORE COMPLEX.

HEY, HOW'S IT GOING?

IT'S NICE TO MEET YOU.

NAMASTE.

[SPEAKING NATIVE LANGUAGE] [SPEAKING NATIVE LANGUAGE] ME LLAMO ALEDIA.

[SPEAKING NATIVE LANGUAGE] NARRATOR: YOU DO IT EVERY DAY WITHOUT A THOUGHT.

[SPEAKING JAPANESE] NARRATOR: YET TALKING... [SPEAKING CHINESE] MAN: [INAUDIBLE] LANGUAGE IS A UNIQUELY HUMAN ABILITY.

[SPEAKING NATIVE LANGUAGE] NARRATOR: AROUND THE WORLD, WE SPEAK MORE THAN 6,000 LANGUAGES.

AS AN ADULT, YOU CAN KNOW MORE THAN 75,000 WORDS... [SPEAKING KOREAN] NARRATOR: USING DOZENS OF MUSCLES TO FORM JUST ONE OF THEM.

[SPEAKING NATIVE LANGUAGE] MY FAVORITE WORD.

UH... MY NAME?

[LAUGHS] WOMAN: WATER?

WATER?

NARRATOR: FROM THE MOMENT YOU'RE BORN, YOU ARE SURROUNDED BY LANGUAGE.

WOMAN: SOUP OR WATER?

WATER?

OK. NARRATOR: AND THANKS TO COGNITIVE SCIENTIST DEB ROY, WE CAN ACTUALLY OBSERVE THE INCREDIBLE PROCESS OF A YOUNG CHILD LEARNING TO TALK.

CHILD: [INDISTINCT] MAN: MY WIFE AND I WERE EXPECTING OUR FIRST CHILD, AND WE HAD MANY CONVERSATIONS AROUND, YOU KNOW, WOULD THIS BE POSSIBLE?

COULD WE SET UP OUR HOME AS AN OBSERVATION SPACE AND ACTUALLY CAPTURE THIS KIND OF RICH, LONGITUDINAL RECORD OF OUR OWN CHILD'S DEVELOPMENT FROM BIRTH?

AND THAT'S WHAT WE SET OUT TO DO.

NARRATOR: ROY TURNED HIS HOME INTO A LANGUAGE LAB.

CAMERAS AND MICROPHONES WERE RIGGED IN EVERY ROOM TO RECORD FROM THE MOMENT HIS SON WAS BROUGHT HOME.

OVER 200,000 HOURS OF RECORDINGS WERE MADE.

SO IT'S ACTUALLY POSSIBLE TO WATCH THE ACQUISITION OF A WORD... CHILD: DA DA DA DA.

NARRATOR: LIKE WATER... CHILD: WATER.

WATER.

NARRATOR: IN ASTONISHING DETAIL, BY COMPRESSING 18 MONTHS...

MOM: WATER.

CHILD: WATER?

NARRATOR: INTO 30 SECONDS.

DAD: WATER.

CHILD: WATER.

ALL THE WAY FROM COPYING A SIMPLE RHYTHM... CHILD: WATER.

WATER.

WATER.

NARRATOR: TO THE BIRTH OF A WORD.

WATER.

WATER?

WATER?

WATER.

WATER?

WATER.

MOMMY.

MOM: WATER.

NARRATOR: THE RESEARCH REVEALED THAT CAREGIVERS REDUCE THEIR SPEECH TO SIMPLE WORDS AND PHRASES, ENCOURAGING THE BABY TO LEARN INDIVIDUAL WORDS.

CHILD: CAR.

CAR?

CAR CAR.

NARRATOR: ONCE A WORD WAS ACQUIRED, THE CHILD IS THEN COAXED BY MORE COMPLICATED LANGUAGE INTO CREATING LONGER SENTENCES.

CHILD: BLUE CAR.

YELLOW CAR.

POLICE CAR.

FAST CAR.

FAST CAR.

THAT'S A BIG CAR.

WHAT HAPPENED TO THE POLICE CAR?

THIS IS TRUCK AND A CAR TOGETHER.

NARRATOR: SO FROM LEARNING THE RHYTHM OF WORDS, LANGUAGE DEVELOPS, AND NEW RESEARCH IS REVEALING JUST HOW CRUCIAL YOUR SENSE OF RHYTHM IS IN LEARNING TO TALK.

DEEP IN THE HEART OF MUSIC CITY, SCIENTISTS ARE EXPLORING HOW LANGUAGE DEVELOPMENT AND RHYTHM ARE LINKED.

FIRST, THEY ARE LOOKING AT HOW BABIES RESPOND TO DIFFERENT BEATS.

THANK YOU, RICKY, FOR COMING IN.

HI, CARSON.

HELL0.

WHAT WE'RE GONNA DO IS PLAY SOME CLIPS WITH SOME DIFFERENT MUSICAL PIECES.

AND WE'RE JUST INTERESTED IN HOW CARSON MOVES OR DOESN'T MOVE AND RESPONDS TO THE MUSIC.

[LAUGHTER] NARRATOR: NEUROSCIENTIST DR. REYNA GORDON AND HER TEAM PLAY A VARIETY OF TUNES TO PRE-VERBAL BABIES AGED BETWEEN 5 TO 14 MONTHS.

AND YOU'LL BE WEARING EAR PLUGS AND ALSO EAR PROTECTION SO YOU WON'T HEAR THEM.

NARRATOR: THAT'S TO STOP THE PARENTS FROM MOVING IN TIME TO THE MUSIC AND INFLUENCING THEIR BABIES.

[TUNE PLAYS] THE BABIES REACT, LIKE WE ALL WOULD, AND TRY TO MOVE THEIR BODIES TO THE MUSIC... [DIFFERENT TUNE PLAYS] SHE STARTED DOING SOME REALLY INTERESTING LITTLE CONDUCTING.

[LAUGHS] THOUGH SOME ARE BETTER THAN OTHERS.

[NEW TUNE PLAYS] SO IN AN ADULT, YOU WOULD SEE ADULTS DANCING TO MUSIC, OF COURSE.

WITH INFANTS, THEY DON'T HAVE THIS GREAT MOTOR CONTROL, UM, BUT THEY'RE STILL ATTUNED TO WHAT'S HAPPENING.

AND THERE'S SOMETHING SPECIAL ABOUT THE BEAT IN MUSIC.

I LOVED HOW HAPPY HE WAS, WHEN HE WAS LIKE TAPPING ON HIS TOES.

NARRATOR: THE BABIES MAY NOT BE EXACTLY ON BEAT, BUT AS THE RESEARCHERS PLAY MUSIC WITH DIFFERENT TEMPOS, THEY FOUND THE BABIES CHANGED THE SPEED OF THEIR MOVEMENTS IN RESPONSE TO DIFFERENT RHYTHMS... [MUSIC PLAYS] WITH ARM WAVING... [INDISTINCT SONG LYRICS] TO TOE TAPPING... [TEMPO SPEEDS UP] AND WHOLE-BODY JIGGLING.

[BABY VOCALIZES] OH, MY GOODNESS.

OOH!

BUT I FEEL THIS IN MY BONES.

[SONG CONTINUES] NARRATOR: THIS RESEARCH SHOWS THE ABILITY TO MATCH A BEAT IS SOMETHING YOU ARE BORN WITH.

AND SCIENTISTS THINK IT'S THIS ABILITY TO COPY A RHYTHM THAT ENABLES YOU TO LEARN TO TALK.

♪ OOH OOH ♪ I THINK RHYTHM IS REALLY IMPORTANT IF YOU THINK ABOUT THE TIMING OF LANGUAGE.

IF YOU HAVE A WORD THAT HAS THE STRESS ON THE WRONG SYLLABLE, LIKE IF I SAY SYL-LABLE, IT JUST SOUNDS STRANGE, RIGHT?

HUMANS HAVE VERY GOOD ABILITY TO DETECT THESE VERY TINY DIFFERENCES IN THE RHYTHM OF LANGUAGE.

YOU'VE DONE WONDERFULLY!

OHH!

NARRATOR: SCIENTISTS HAVE DISCOVERED THAT CERTAIN NEURONS IN THE BRAIN FIRE IN EXACTLY THE SAME WAY WHETHER YOU HEAR MUSIC OR PEOPLE TALKING.

DR. GORDON BELIEVES RHYTHM PROVIDES A SCAFFOLD TO HANG WORDS ONTO.

AND IT'S NOT JUST IMPORTANT FOR BABIES LEARNING THEIR FIRST WORDS.

[RHYTHMIC MUSIC PLAYING] SHE RECENTLY DISCOVERED THAT 6-YEAR-OLDS WHO PERFORM BETTER ON MUSICAL RHYTHM TESTS ALSO TEND TO DO BETTER ON A SPOKEN GRAMMAR TEST.

HOW OLD ARE YOU, LUKE?

UM... 6.

6 YEARS OLD?

8.

8.

DID YOU HAVE A BIRTHDAY?

WHEN WAS YOUR BIRTHDAY?

DECEMBER 4, 2008.

NARRATOR: WHILE CHILDREN WITH LANGUAGE IMPAIRMENTS STRUGGLE WITH RHYTHM.

SO IT SEEMS LIKE LANGUAGE AND RHYTHM ARE INTRICATELY LINKED.

DO YOU REMEMBER WHAT YOU DID FOR YOUR BIRTHDAY THIS YEAR?

DID YOU HAVE A PARTY?

WE--WE, UH, A BIRTHDAY'S GONNA BE AT MY SCHOOL, THEN WE GET A PARTY AT MY CHURCH.

SO AT YOUR SCHOOL AND AT YOUR CHURCH?

WHAT DO YOU WANT TO DO?

WHAT DO YOU TRY TO... NARRATOR: THESE CHILDREN HAVE NO OTHER COGNITIVE PROBLEMS.

WHAT THEY HAVE IS CALLED DEVELOPMENTAL LANGUAGE DISORDER, WHERE THEY HAVE DIFFICULTY BOTH PRODUCING AND PROCESSING LANGUAGE.

HOW ABOUT YOUR LITTLE SISTER?

DO YOU DO ANYTHING WITH HER?

UM...

I JUST...I DON'T KNOW.

DON'T KNOW.

HA HA.

AWESOME.

I CAN'T EXPLAIN IT.

I DON'T KNOW HOW TO EXPLAIN IT.

THAT'S OK. NARRATOR: DR. GORDON HAS FOUND THAT IMPROVING THEIR RHYTHMIC ABILITY CAN HELP THEM EXPRESS THEMSELVES.

SO ALONG WITH SPEECH AND LANGUAGE THERAPY, THEY'RE GIVEN VIOLIN LESSONS AND MOVEMENT CLASSES.

WE'RE TRYING TO SEE IF WE CAN USE ALL THESE DIFFERENT INDIVIDUAL MUSIC LEARNING EXERCISES TO EVENTUALLY ACT UPON WHAT WE THINK ARE POTENTIALLY SHARED BRAIN NETWORKS BETWEEN RHYTHM AND GRAMMAR.

NARRATOR: BY BUILDING RHYTHM IN THEIR BRAINS, DR. GORDON IS ATTEMPTING TO HELP THESE CHILDREN FIND THEIR WORDS.

[MUSIC ENDS] THAT WAS WONDERFUL.

MAN: [INDISTINCT] [VOCALIZING] DA DA DA DA.

NARRATOR: HAVING THE WORDS TO COMMUNICATE WITH THE WORLD AROUND YOU... [VOCALIZING] NARRATOR: LIES AT THE CORE OF YOUR HUMANITY.

[VOCALIZING] NARRATOR: YOU SAY YOUR FIRST MEANINGFUL WORDS BEFORE THE AGE OF TWO.

MUMMY.

MUMMY.

WHAT'S THAT?

MAN: THAT'S A MICROPHONE.

YEAH.

NARRATOR: AS YOU GROW, SO DOES YOUR VOCABULARY.

WOMAN: WHAT'S YOUR FAVORITE WORD?

MY FAVORITE WORD IS LOVE.

CANDY.

CRANIUM.

MY FAVORITE WORD... NARRATOR: UNTIL BY ADULTHOOD... THAT'S A GOOD QUESTION.

I'VE NEVER REALLY THOUGHT ABOUT IT.

NARRATOR: YOU CAN HAVE A VOCABULARY OF 75,000 WORDS.

PHILANTHROPIC.

SUCCULENT.

NEANDERTHAL.

I JUST LIKE SAYING IT.

I HAVE TWO.

ONE IS MUNCH, THE OTHER IS STERNOCLEIDOMASTOID.

SPLENDIFEROUS.

I'M NOT SURE IF IT'S A WORD, THOUGH.

NARRATOR: YOU SEEM TO LEARN AND REMEMBER THEM WITH INCREDIBLE EASE.

UH, MY FAVORITE WORD IS ONOMATOPOEIA.

NOT THAT I GET TO USE IT, BUT IT'S SO MUCH FUN TO SAY.

I CAN'T THINK OF A WORD.

I CAN'T THINK OF A WORD.

UH... NARRATOR: BUT IT ACTUALLY REQUIRES ENORMOUS MEMORY AND RECALL.

ACTUALLY, POSSIBLY ONE OF MY FAVORITE WORDS IS COOPERATION.

OR SOMETHING TO THAT EFFECT.

NARRATOR: NOW, FOR THE FIRST TIME, THE SECRETS OF HOW YOU REMEMBER THE THOUSANDS OF WORDS YOU USE EACH DAY ARE BEING UNCOVERED.

BOY: WELL, MY FAVORITE WORD IS PNEUMONOULTRAMICROSCOPICSILICO- VOLCANOCONIOSIS.

THIS WORD IS 45 LETTERS LONG.

IT IS A LUNG DISEASE CAUSED BY INHALING VERY FINE SILICONE DUST IN ASH, SAND, DUST, ET CETERA.

OHH!

NARRATOR: LIKE MOST 7-YEAR-OLD CHILDREN, AKASH LOVES TO LEARN NEW WORDS.

SHOOK.

BURRITO.

BURRITO.

NARRATOR: MOST KIDS HIS AGE ACTIVELY USE AROUND 8,000 WORDS WHEN THEY TALK.

AKASH HAS A VOCABULARY OF MORE THAN 20,000.

HARMONICA!

NARRATOR: NOW HE'S PREPARING TO TAKE PART IN A LOCAL SPELLING BEE, ALONG WITH HIS 9-YEAR-OLD SISTER AMRITA.

HERE'S THE NEXT WORD.

ERGONOMIC.

ERGONOMIC?

ERGONOMIC.

NARRATOR: IN THE WEEKS LEADING UP TO THE COMPETITION, THEY SPEND MORE THAN TWO HOURS A DAY STUDYING WORDS FROM THE LIST OF OVER 1,000 THEY COULD BE TESTED ON.

E-R-G-O-N-O-M-I-C. ERGONOMIC.

OK. NARRATOR: IT'S AN INTENSIVE VERSION OF THE WAY YOU MAKE A LONG-TERM MEMORY OF A WORD, BY HEARING OR SEEING AND UNDERSTANDING THE WORD.

SHAH.

THAT'S... NARRATOR: TO LEARN A NEW WORD, YOU FEED THE BRAIN WITH SENSORY INFORMATION THROUGH YOUR EYES AND, BY USING THE TRICK OF SAYING THE WORD OUT LOUD, THROUGH YOUR EARS.

YOU ALSO NEED TO LEARN THE MEANING OF THE WORD.

THIS INPUT STIMULATES DIFFERENT PARTS OF YOUR BRAIN...

SO THE CONNECTION BETWEEN 3 DISTINCT AREAS MUST BE STRENGTHENED-- THE VISUAL CORTEX AT THE BACK OF THE BRAIN, THE AUDITORY CORTEX ON THE SIDE, AND THE ANTERIOR TEMPORAL LOBE WHERE OUR SENSE OF MEANING RESIDES.

[LETTERS ECHO] THIS GRADUALLY CREATES A MAP FOR EACH MEMORY, A UNIQUE PATTERN THAT IS ENCODED AND STORED BY THE BRAIN.

AND NOW, FOR THE FIRST TIME, THE WAY A MEMORY MAP IS CREATED HAS BEEN FILMED.

THIS EXTRAORDINARY FOOTAGE SHOWS THE FIRST STEPS OF A MEMORY BEING MADE.

THE TINY SPECKS ARE MEMORY BUILDERS, MESSENGER RNA MOLECULES THAT TRAVEL DOWN THE NEURONS TO THE SYNAPSES, THE JUNCTION POINTS WHERE NEURONS MEET.

THE MESSENGER RNA REMAINS AT THE SYNAPSE UNTIL ACTIVATED BY A SENSORY IMPULSE, LIKE THE REPEATED SOUND OF A NEW WORD.

THIS TRIGGERS IT TO PRODUCE NEW PROTEINS THAT STRENGTHEN THE CONNECTIONS IN THE SYNAPSE.

[ECHOING] BEETEWK.

AND THE MORE IT'S ACTIVATED, THE STRONGER THESE CONNECTIONS CAN BECOME, UNTIL THE MEMORY IS PRESERVED.

[ECHOING] BEETEWK.

IT'S THE BASIC MECHANISM FOR CREATING ANY MEMORY.

IF AKASH REALLY WANTS THESE WORDS TO STICK, HE'LL HAVE TO STOP PRACTICING AND SLEEP.

IT'S THOUGHT THAT DURING SLEEP, BRAIN RESOURCES CAN BE REDIRECTED AND SPENT ON STRENGTHENING IMPORTANT MEMORY NETWORKS, PERHAPS DOUBLING YOUR CHANCES OF REMEMBERING.

BUT IT'S ALSO A TIME WHEN YOUR BRAIN IS PARING BACK ON CONNECTIONS THAT YOU DON'T NEED.

SOME BELIEVE IT COULD BE THE REASON YOU SLEEP AT ALL.

THE MORNING OF THE SAN ANGELO SPELLING BEE.

SLEEPING WELL IS ONE THING, BUT AS WE ALL KNOW, RECALLING A MEMORY WHEN YOU NEED IT IS NOT ALWAYS STRAIGHTFORWARD.

BUT AKASH HOPES HE'LL HAVE NO TROUBLE RECALLING THE 1,150 WORDS HE MAY BE TESTED ON.

AKASH: WHAT I LIKE ABOUT DOING SPELLING BEES, ACTUALLY, I HAVE LOTS OF FUN.

I MAKE FRIENDS, AND I ALSO LEARN NEW WORDS.

NARRATOR: AKASH IS THE DEFENDING CHAMPION AND THE YOUNGEST EVER WINNER.

WOMAN: THANK YOU FOR JOINING US TO CELEBRATE THE ACHIEVEMENTS OF THESE FANTASTIC YOUNG SPELLERS.

NARRATOR: THE COMPETITION STARTS WITH 26 CHILDREN, BUT THE NUMBERS DROP QUICKLY.

THE WORD IS CHUTNEY.

CHUTNEY.

C-U-- C-H-U-T-N-Y.

CHUTNEY.

NARRATOR: THE SOUND THEY MOST DREAD... [DING] MEANS THEY'RE OUT.

CONAH.

C-O-N-A.

CONAH.

[DING] COMMA.

SHERRY.

STACCATO.

[DING DING DING] NARRATOR: THIS INCLUDES AKASH'S SISTER AMRITA.

...O-R-I-A.

TRATTORIA.

[DING] FINALLY, AFTER TWO HOURS OF COMPETITION, THERE ARE JUST 4 CHILDREN LEFT VYING FOR THE TITLE.

FACETIOUS.

BOLSHEVIK.

HALAL.

FORETREKKER.

NARRATOR: EACH NEW ROUND BRINGS INCREASINGLY COMPLEX WORDS, AS THE JUDGES TRY AND FIND A WINNER.

METEORITE.

COMANDANTE.

INFINITESIMAL.

DOLIA.

PICKELHAUBE.

TSCHOTCHKE.

NARRATOR: THEN, AKASH IS ASKED TO SPELL BEETEWK.

BEETEWK.

BEETEWK.

NARRATOR: IF HE CAN RECONSTRUCT THE MEMORY MAP CREATED WHEN HE LEARNED THE WORD, HE WILL BE ABLE TO REMEMBER IT AND SPELL IT CORRECTLY.

WHILE YOUR MEMORIES ARE STORED IN THE CORTEX, IT'S THE HIPPOCAMPUS THAT'S THE CRITICAL PART OF YOUR BRAIN IN THIS PROCESS.

IT'S THE RINGMASTER BRINGING TOGETHER THE PARTS OF THE BRAIN INVOLVED IN SEEING, HEARING, AND KNOWING THE MEANING OF THE WORD.

B... UNTIL IT SLOWLY EMERGES INTO HIS CONSCIOUSNESS.

...E-E-T-E-W-K. BEETEWK.

NARRATOR: AKASH IS SAFELY THROUGH.

BUT SO ARE THE OTHER CHILDREN.

MENDIER.

NARRATOR: THE JUDGES RUN OUT OF WORDS ON THE COMPETITION LIST AND TURN TO THE DICTIONARY.

[INDISTINCT] P-L-U... T-E... K-K... MAN: THIS WORD HAS A HOMONYM.

THE WORD IS BOARDERS, AND IT'S "PEOPLE WHO ARE PROVIDED WITH REGULAR MEALS AND LODGING."

UM, MAY I HAVE THE OTHER PRONUNCIATIONS, PLEASE.

THERE ARE NONE.

IT WAS A SURPRISE, 'CAUSE I THINK I NEVER SAW THE WORD BEFORE.

BOARDERS.

CAN YOU PLEASE REPEAT THE WORD AGAIN?

BOARDERS.

NARRATOR: IF AKASH HASN'T COME ACROSS THE WORD BEFORE AND CAN'T MAKE A GUESS BASED ON A SIMILAR WORD, HE WON'T BE ABLE TO CALL ON A MEMORY MAP TO GET THE SPELLING RIGHT.

B-O-R-D-E-R-S.

BORDERS.

[DING] GOOD LUCK TO ALL MY FELLOW SPELLERS.

I HOPE I'LL COME BACK NEXT YEAR.

[APPLAUSE] [CHEERING] [CRYING] THAT'S ALL RIGHT.

IT'S NOT DISAPPOINTING, JUST A TINY BIT SAD.

YEAH.

OTHER THAN THAT, PRETTY MUCH I WILL BE COMING BACK NEXT YEAR.

[MUSIC PLAYING] NARRATOR: WITH EVERY NEW CHILDHOOD EXPERIENCE, YOU BUILD ON YOUR UNDERSTANDING OF THE WORLD, WHETHER THAT'S LEARNING NEW WORDS OR HOW TO DEAL WITH SETBACKS.

BUT ONE OF THE MOST COMPLEX THINGS YOU HAVE TO LEARN IS HOW TO WORK WITH OTHER PEOPLE.

GIRL: BUILD AN ARCH USING ALL OF THE BRICKS.

NARRATOR: AS YOU GROW, YOU LEARN HOW TO COOPERATE AND COMMUNICATE WITH OTHERS... AND WE'RE DONE.

DISCOVERING MORE EFFECTIVE WAYS OF WORKING TOGETHER TO ACHIEVE MORE COMPLEX THINGS.

TO DO THIS, YOU NEED MORE THAN JUST WORDS.

YOU HAVE TO LEARN ABOUT OTHERS' EMOTIONS.

WOMAN: GIVE ME YOUR BIGGEST FROWN.

NARRATOR: SOMETIMES THIS IS STRAIGHTFORWARD, AS SOME EMOTIONS ARE LITERALLY WRITTEN ACROSS YOUR FACE.

THERE ARE 6 CORE FACIAL EXPRESSIONS: HAPPINESS, ANGER, SURPRISE, DISGUST, FEAR... [CRYING] AND SADNESS.

[CONTINUES CRYING] AND WE NOW THAT THAT THERE ARE ALSO AS MANY AS 10,000 MICRO-EXPRESSIONS, MOMENTS THAT FLICKER ACROSS YOUR FACE INVOLUNTARILY IN LESS THAT 1/15 OF A SECOND, EVEN IF YOU ARE TRYING TO CONCEAL HOW YOU FEEL.

BUT IN SOCIAL SITUATIONS, THERE'S ONE FACIAL EXPRESSION THAT HAS MORE POWER THAN ANY OTHER.

HA HA HA HA HA HA HA!

LAUGHING FEELS LIKE A TOTAL RELEASE, AND IT'S A FULL-BODY EXPERIENCE.

I LAUGH ALL THE TIME.

HA HA HA HA HA HA!

HA HA HA HA HA!

WOMAN: IT'S SORT OF A BUBBLING UP AND A KIND OF HAPPY CONVULSION.

HA HA HA HA HA!

I FEEL ENERGETIC.

I FEEL THAT MY BODY'S BOUNCIN'.

HA HA HA HA HA!

[CONTINUES LAUGHING] WOMAN: HELLO, EVERYBODY.

KNOCK KNOCK.

KIDS: WHO'S THERE?

DONE UP.

DONE UP WHO?

[LAUGHING] NARRATOR: LAUGHTER IS SOMETHING THAT ALL HUMANS DO.

IN FACT, INVOLUNTARY LAUGHTER IS HARD-WIRED, AND YOU DO IF FROM AN INCREDIBLY EARLY AGE.

BUT THERE'S ANOTHER KIND-- SOCIAL OR VOLUNTARY LAUGHTER THAT YOU LEARN HOW TO RECOGNIZE AND USE AS YOU GROW.

SO YOU CAN LAUGH TO MAKE SOMEBODY FEEL COMFORTABLE, PUT THEM AT THEIR EASE.

IT CAN BE KIND OF A, UM, NERVOUS THING AS WELL, LIKE THE NERVOUS "HEH HEH HEH."

UM, I USE THAT ALL THE TIME WHEN IT GETS TOO TENSE OR TOO AWKWARD.

WHEN YOU'RE TRYING TO MAKE NEW FRIENDS, I ALWAYS TRY AND LIKE LAUGH AT ALL THEIR JOKES, AND JUST TO LIKE LIGHTEN THE MOOD.

I USE LAUGHTER TO EASE AWKWARD SITUATIONS ALL THE TIME, PROBABLY TO A FAULT.

YOU CAN LAUGH BECAUSE YOU WANT TO DEFUSE A SITUATION, OR EVEN IF YOU CAN'T COMMUNICATE USING WORDS, YOU CAN USE LAUGHTER AS ANOTHER KIND OF LANGUAGE.

THERE'S SO MANY WAYS.

NARRATOR: STUDIES SHOW THAT MOST LAUGHTER HAPPENS IN CONVERSATIONS AND IS ASSOCIATED WITH STATEMENTS AND COMMENTS, NOT JOKES.

[WEAK LAUGH] HA HA HA HA HA.

NARRATOR: THIS TYPE OF LAUGHTER ALSO SOUNDS DIFFERENT TO INVOLUNTARY LAUGHTER.

HA HA HA HA HA HA HA!

NARRATOR: AND YOUR BRAIN APPEARS TO BE ABLE TO TELL THEM APART.

[LAUGHING] NARRATOR: WHEN YOU HEAR REAL LAUGHTER, THE PART OF THE BRAIN MOST ACTIVE IS YOUR AUDITORY CORTEX.

BUT WHEN YOU HEAR SOCIAL LAUGHTER... HA HA HA HA...AH HA HA.

AH... NARRATOR: A DIFFERENT PART OF YOUR BRAIN IS PARTICULARLY ACTIVE... HA HA HA HA.

NARRATOR: THE PART THAT DEALS WITH FIGURING OUT WHAT OTHERS ARE THINKING OR FEELING.

HA HA HA HA HA HAA... [KIDS LAUGHING] NARRATOR: RESEARCH SHOWS THAT WHEN YOU'RE YOUNG, SAY AROUND 6, YOU PROBABLY DON'T HEAR THE DIFFERENCE BETWEEN THE TWO.

BUT AS YOU PLAY IN CHILDHOOD, YOU LEARN TO USE AND RECOGNIZE SOCIAL LAUGHTER, ENABLING YOU TO START MASTERING SOCIAL SITUATIONS BY THE TIME YOU HIT YOUR TEENS.

[INDISTINCT CHATTER] AS TEENAGERS, FRIENDS START TO HAVE MORE APPEAL THAN YOUR FAMILY.

AND THE DESIRE TO BE ACCEPTED BY OTHERS BECOMES PARAMOUNT, WHETHER IN THE REAL WORLD OR ONLINE.

IN FACT, RESEARCH IS REVEALING THAT TEENAGERS ARE BETTER AT LEARNING HOW TO FIT IN SOCIALLY THAN AT ANY OTHER AGE.

THIS CUTTING-EDGE WORK IS BEING DONE AT UCLA's BRAIN MAPPING CENTER BY COGNITIVE PSYCHOLOGIST DR. LAUREN SHERMAN.

WE'RE GOING TO GET YOU SET UP WITH THE INSTAGRAM PART OF THE STUDY, SO HANG TIGHT.

NARRATOR: DR. SHERMAN SCANS THE BRAINS OF TEENAGERS WHILE SHOWING THEM OVER 100 IMAGES FROM SOCIAL MEDIA.

ALL THE SUBJECTS NEED TO DO IS LIKE THEM OR NOT.

ALL RIGHT, WE'RE GOING TO GET STARTED.

IT'LL BE ABOUT 10 MINUTES, AND I'LL CHECK IN WHEN WE'RE DONE, OK?

[BEEP] NARRATOR: BUT WHAT THEY SEE IN THE SCANNER IS NO ORDINARY FEED.

DR. SHERMAN HAS MANIPULATED THE IMAGES SO THAT HALF THE SUBJECTS SEE AN IMAGE WITH A LOT OF LIKES, AND THE OTHER HALF THE SAME IMAGE WITH FEWER LIKES.

IT TURNS OUT, THE SUBJECTS ARE MORE LIKELY TO LIKE A PICTURE IF THEY THINK IT'S POPULAR.

SO WITH EVERYTHING ELSE BEING EQUAL, JUST SEEING THAT THE PHOTO HAD 50 LIKES INSTEAD OF TWO LIKES MADE THEM MORE LIKELY TO GO AHEAD AND CLICK LIKE THEMSELVES.

NARRATOR: THE TEENAGERS WERE HEAVILY INFLUENCED BY THE JUDGMENTS OF OTHERS.

AND WHEN DR. SHERMAN LOOKED AT THE BRAIN SCANS, IT BECAME VERY CLEAR WHY.

WE SEE A RESPONSE IN THE PART OF THE BRAIN CALLED THE NUCLEUS ACCUMBENS, AND THAT'S A LITTLE STRUCTURE IN YOUR BRAIN THAT IS A HUB OF REWARD CIRCUITRY.

[BEEP] IT RESPONDS TO ALL SORTS OF REWARDS.

SO, IF YOU SEE SOMEBODY THAT YOU LOVE VERY MUCH, IF YOU EAT CHOCOLATE, IF YOU HAVE THESE REWARDING EXPERIENCES.

AND WE SAW THAT THIS PART OF THE BRAIN WAS MORE RESPONSIVE WHEN THE PICTURE HAD A LOT OF LIKES.

ALL RIGHT, SO WE'RE ACTUALLY GOING TO PULL YOU OUT BECAUSE WE'RE GETTING DOWN TO TIME.

NARRATOR: IT SHOWS THE TEENAGERS' BRAINS DEVELOPED TO FEEL GOOD WHEN THEY FIT IN WITH THE CROWD.

IT SEEMS THAT ADOLESCENTS ARE PARTICULARLY GOOD AT LEARNING ABOUT THEIR SOCIAL WORLD, THAT THE BRAINS MAY BE ESPECIALLY SENSITIVE TO SOCIAL INFORMATION.

AND SO IT MAY BE THAT ONE OF THE VERY IMPORTANT TASKS OR GOALS OF ADOLESCENCE IS TO LEARN ABOUT YOUR SOCIAL WORLD, AND YOUR BRAIN IS KIND OF HELPING YOU TO DO THAT.

NARRATOR: SO BY LEARNING HOW TO FIT IN, YOU ARE PREPARING YOURSELF FOR WHEN YOU HAVE TO TAKE ON THE WORLD AS AN ADULT.

AS YOU GROW, IT MIGHT SEEM LIKE YOUR BRAIN IS DOING ALL THE LEARNING, AS YOU ACQUIRE THE FUNDAMENTAL SKILLS THAT TRANSFORM YOU FROM A HELPLESS INFANT TO A HIGHLY-SKILLED INDIVIDUAL.

WHETHER THAT'S LEARNING HOW TO WALK, TALK, REMEMBER, OR NAVIGATE A COMPLEX SOCIAL WORLD.

BUT IT'S NOT JUST YOUR BRAIN THAT'S LEARNING.

YOUR BODY DOES, TOO.

WOMAN: I WAS A BALLET DANCER.

AND WHAT BALLET DANCING DOES TO YOUR BODY, FIRST OF ALL, IT KIND OF...

UH, LIFTS YOU UP, 'CAUSE YOU ALWAYS HAVE TO BE IN A VERY STRAIGHT POSITION.

WE HAD THIS THING WE CALLED AN ABS CLUB, SO WE WERE DOING A LOT OF CORE EXERCISES.

I NOTICED THAT MY BODY GOT STRONGER IN THE MIDDLE.

I NOTICED THAT IT GOT LEANER.

YOUR FEET GET A WEIRD TURNOUT, SO YOU KIND OF WALK LIKE A DUCK.

BUT THAT'S WHAT BALLET DANCING DOES TO YOU, BECAUSE YOU HAVE TO BE TURNED OUT ALL THE TIME.

I'M A PITCHER ON MY SOFTBALL TEAM AT SCHOOL, AND SO I USE A LOT OF MY RIGHT ARM AND THERE'S A LOT OF REPETITION, SO MY MUSCLES IN MY RIGHT ARM ARE SLIGHTLY BIGGER THAN MY LEFT ARM.

NARRATOR: YOUR BODY HAS THE INCREDIBLE ABILITY TO LEARN AND ADAPT THROUGHOUT YOUR LIFE.

FOR FREYA CHRISTIE, THIS LEARNING PROCESS IS ALL IN PURSUIT OF A VERY SPECIFIC GOAL.

I DEFINITELY WOULDN'T CAST MYSELF AS A NORMAL TEENAGER.

I DON'T THINK MANY TEENAGERS DO WHAT I DO.

SO I'M VERY FORTUNATE AND LUCKY TO DO WHAT I LOVE.

[SINGERS VOCALIZING] NARRATOR: FREYA IS WORKING TO BE THE BEST PROFESSIONAL TENNIS PLAYER SHE CAN BE.

FREYA: MY ASPIRATIONS, I WANT TO BE A TOP-50 TENNIS PLAYER, ESPECIALLY WIMBLEDON.

BEING FROM BRITAIN, YOU KNOW, IT'S MY FAVORITE GRAND SLAM.

SO, HOPEFULLY ONE DAY, THAT'S THE DREAM.

[SINGERS VOCALIZING] NARRATOR: IN THE PURSUIT OF THIS AMBITION, SHE PLAYS TENNIS YEAR-ROUND.

WHEN SHE'S NOT COMPETING, SHE'S PRACTICING.

I PROBABLY HIT ABOUT OVER 1,000 4 HANDS A DAY.

I'M A PERFECTIONIST, SO I LIKE TO GET EVERYTHING PRETTY SPOT ON.

NARRATOR: EVERY MOVEMENT YOU MAKE EXERTS SURPRISINGLY LARGE FORCES ON YOUR BODY.

EVEN THE SIMPLE ACT OF WALKING CAN EXERT THE FORCE OF TWO-AND-A-HALF TIMES YOUR BODY WEIGHT ON YOUR SKELETON.

THE DEMANDS OF ANY SPORT CREATE EVEN GREATER FORCES ON YOUR BODY, AND AT THE ELITE LEVEL, THE INTENSITY AND FREQUENCY OF ACTIVITY CAN HAVE DRAMATIC EFFECTS.

SO FREYA'S SKELETON HAS LEARNED TO COPE WITH HER INTENSE DAILY WORKOUTS BY GROWING DRAMATICALLY IN ORDER TO REDUCE THE RISK OF BREAKING.

WHILE HER BODY LOOKS THE SAME FROM THE OUTSIDE, THE BONES IN HER RACKET ARM HAVE BECOME THICKER AND CONTAIN MORE BONE MINERAL THAN THE OTHER ARM.

THE LONG BONES, LIKE THE HUMERUS, ARE 20% WIDER.

AND BECAUSE JOINTS TAKE THE BRUNT OF THE TWISTING AND MOTION AS SHE PLAYS A SHOT, THE BONE NEAR HER WRIST AND ELBOW IS NOW 20% BIGGER AND DENSER.

IN FACT, WE ALL HAVE SMALL, BARELY PERCEPTIBLE DIFFERENCES IN THE STRENGTH OF THE BONES IN OUR ARMS, BECAUSE PEOPLE TEND TO FAVOR ONE ARM OVER THE OTHER.

BUT THE DIFFERENCES IN TENNIS PLAYERS ARE ABOUT 10 TIMES GREATER THAN IN NON-PLAYERS.

BUT IT'S NOT JUST YOUR BONES THAT LEARN FROM AND ADAPT TO THE STRESSES AND STRAINS OF LIFE.

IT'S YOUR MUSCLES AS WELL.

MUSCLES THAT WILL NEED TO BE ON TOP FORM TO BEAT ANDREA PETKOVIC, A FORMER WORLD TOP-10 PLAYER.

AH!

NARRATOR: MUSCLES, LIKE YOUR BONES, LEARN FROM THE ACTIVITIES YOU DO EVERY DAY.

[APPLAUSE] IN FACT, SKELETAL MUSCLE IS THE MOST ADAPTABLE TISSUE IN THE HUMAN BODY.

MUSCLE FIBER CELLS CONTAIN MORE THAN ONE NUCLEUS.

WHEN THE MUSCLES ARE WORKED HARD, SPECIAL SATELLITE CELLS ARE ACTIVATED.

THEY DIVIDE.

ONE OF THESE CELLS FUSES WITH THE MUSCLE FIBER ITSELF.

WITH ADDED NUCLEI, THE MUSCLE FIBER CELL BUILDS MORE MYOFIBRILS, INCREASING THE SIZE OF BOTH ITSELF AND YOUR MUSCLES.

JUST LIKE ALL OF US WHEN WE DO PHYSICAL ACTIVITY, FREYA'S MUSCLES ARE LEARNING HOW TO ADAPT AND GIVE HER MORE POWER FOR HER SHOTS.

BUT IN THE END...

SOMETIMES EXPERIENCE WINS OVER POWER.

FREYA: AFTER THE MATCH, WIN OR LOSS, I'M QUITE EMOTIONAL.

I WOULD USUALLY GET BACK ONTO THE PRACTICE COURT AND TRY, YOU KNOW, WORK ON THE THINGS THAT PROBABLY DIDN'T GO SO WELL IN THE MATCH.

NARRATOR: USING THE WAY HER BODY CAN LEARN, SHE'S BUILDING IT INTO THE PERFECT VEHICLE TO PURSUE HER DREAM.

YOUR BODY HAS AN INCREDIBLE ABILITY TO ADAPT TO THE WORLD AROUND YOU, LEARNING TO CHANGE WITH THE DIFFERENT EXPERIENCES YOU FACE.

YOU ARE ALWAYS A WORK IN PROGRESS.

BUT FOR YEARS, IT WAS THOUGHT THAT THERE WAS ONE PART OF YOU THAT WOULD NEVER CHANGE-- YOUR GENES, THE BLUEPRINT FOR YOUR EVERY FEATURE, NO MATTER HOW BIG OR SMALL.

HOWEVER, NEW RESEARCH HAS REVEALED THAT EVEN THEY CAN LEARN AND ADAPT AS YOU GO THROUGH LIFE.

IT'S LONG BEEN KNOWN THAT THE HUMAN BODY CAN FIND IT HARD TO COPE AT HIGH ALTITUDES.

FOR BUILDER MARK BENSON, MAKING THE TRANSITION FROM OHIO TO THE HIGH LIFE IN THE ROCKY MOUNTAINS HAS NOT BEEN EASY.

MARK: WHEN I FIRST MOVED HERE TO SUMMIT COUNTY, ONE OF THE HARDEST THINGS TO DO WAS GO UPSTAIRS.

YOU GO UP TWO FLIGHTS OF STAIRS AND YOU'RE WINDED.

AND I WOULD TIRE MORE QUICKLY JUST LIFTING THINGS.

BY THE END OF THE DAY I WAS READY TO GO HOME AND JUST CHILL OUT AND JUST REST.

NARRATOR: MARK WAS SUFFERING THE PHYSICAL SYMPTOMS OF A LACK OF OXYGEN.

AT 9,500 FEET ABOVE SEA LEVEL, BRECKENRIDGE IS ONE OF THE HIGHEST HABITATIONS IN THE U.S., WITH OXYGEN LEVELS 30% LOWER THAN AT SEA LEVEL.

TO SEE WHAT THIS LACK OF OXYGEN DOES TO THE HUMAN BODY, SCIENTIST DR.

ROB ROACH USES A PRESSURE CHAMBER TO MIMIC CHANGES IN ALTITUDE.

OK, EVERYBODY CLEAR?

[BEEP] READY TO START.

[BEEPING] YEAH.

NARRATOR: ROACH IS GOING TO TAKE MIKE, THE VOLUNTEER, FROM SEA LEVEL TO THE TOP OF A MOUNTAIN IN ABOUT 10 MINUTES.

I CAN FEEL IT GOING UP.

[INDISTINCT] TIME TO SEE.

NARRATOR: THE AMOUNT OF OXYGEN IN EACH BREATH YOU TAKE DECREASES WITH ALTITUDE.

DR. ROACH: HEY, GUYS, WE JUST ARRIVED AT 10,000.

MIKE, CAN YOU SHOW US THE ALTIMETER?

WHAT ARE YOU AT?

84.

NARRATOR: SO BY 10,000 FEET, LEVELS OF OXYGEN ARE 30% LOWER.

AND BY 16,000 FEET, IT'S BEEN CUT IN HALF.

DR. ROACH: HOW DO YOU FEEL, MIKE?

SO I'M REALLY FEELING THE ALTITUDE NOW.

76 AND 136.

DEFINITELY STARTING TO FEEL IT.

THINK I'M A LITTLE DIZZY.

NARRATOR: EACH LUNGFUL OF AIR IS ONLY DELIVERING HALF THE OXYGEN MIKE'S BODY NEEDS TO FUNCTION NORMALLY.

SO TO GET BLOOD TO HIS BRAIN AND ORGANS, HIS BREATHING AND HEART RATE INCREASE.

WHEN WE GO TO ALTITUDE, WE HAVE THE IMMEDIATE RESPONSE.

SOME PEOPLE CALL THAT THE STRUGGLE RESPONSE.

AND THAT IS THE-- "I NEED TO SURVIVE."

NARRATOR: MIKE'S BODY STILL CAN'T GET ENOUGH OXYGEN, AND THE OXYGEN SATURATION LEVEL OF HIS BLOOD DROPS TO A DANGEROUS 72%.

HE IS SUFFERING FROM A LACK OF OXYGEN CALLED HYPOXIA-- ALTITUDE SICKNESS.

OH, THAT WAS WEIRD.

NARRATOR: HE IS WEAK AND CONFUSED.

AND IF HE CONTINUES, HE'LL LOSE CONSCIOUSNESS.

HOWEVER, THE HUMAN BODY HAS AN INCREDIBLE ABILITY TO ADAPT TO ITS ENVIRONMENT.

WE'VE LONG KNOWN THAT IN A MATTER OF DAYS, THE BODY CAN TEMPORARILY LEARN TO ACCLIMATIZE TO ALTITUDE.

BUT IT'S NOW BEEN DISCOVERED THAT OVER TIME, THIS CHANGE CAN BE MADE MORE PERMANENT.

THE HUMAN BODY CAN ADAPT TO ALTITUDE AT A MUCH DEEPER LEVEL THAN PREVIOUSLY THOUGHT POSSIBLE.

AFTER ABOUT 4 TO 5 MONTHS, I REALLY FELT LIKE I COULD, UH, MOVE ABOUT LIKE I HAD PREVIOUSLY WITHOUT GOING, "OHH, I'M WINDED."

NARRATOR: THESE CHANGES HAVE ENABLED MARK TO TAKE ON A NEW CHALLENGE... [SIREN] AS A MEMBER OF THE SUMMIT COUNTY RESCUE GROUP, A SEARCH AND RESCUE TEAM WORKING AT ALTITUDES OF UP TO 14,000 FEET.

THEY TRAIN ONCE A MONTH BECAUSE THEY HAVE TO BE READY TO DEAL WITH ANY DISASTER.

MARK: ANYTIME YOU'RE WORKING WITH A DRILL, WE TRY TO MAKE IT AS REALISTIC AS POSSIBLE.

THEY SAY YOU PLAY THE GAME LIKE YOU PRACTICE THE GAME.

NARRATOR: IT'S HARD PHYSICAL WORK IN A LOW OXYGEN ENVIRONMENT.

FOUND PARTY.

MA'AM, CAN YOU HEAR ME?

ARE YOU OK?

[WOMAN MOANS] CAN YOU SIT BACK?

ARE YOU COMFORTABLE?

NARRATOR: BUT MARK CAN NOW COPE, BECAUSE IN ACCLIMATIZING TO ALTITUDE OVER A LONG PERIOD, HE HAS UNDERGONE A REMARKABLE TRANSFORMATION AT THE MOST BASIC LEVEL.

HIS BODY HAS LEARNED TO RAPIDLY PRODUCE MORE OF WHAT IT NEEDS TO GET OXYGEN AROUND HIS SYSTEM.

WHEN YOU FIRST GO TO ALTITUDE, THE RESULTING LOW LEVELS OF OXYGEN IN THE BLOOD ARE DETECTED BY SPECIFIC CELLS IN YOUR KIDNEYS.

THEY TRIGGER AN INCREASE IN THE PRODUCTION OF ERYTHROPOIETIN, OTHERWISE KNOWN AS EPO, A HORMONE THAT CONTROLS RED BLOOD CELL PRODUCTION.

A FLOOD OF EPO IS RELEASED INTO THE BLOODSTREAM AND TRAVELS TO THE LARGER BONES IN YOUR BODY.

THE EPO STIMULATES EXTRA PRODUCTION OF RED BLOOD CELLS SO THERE ARE MORE VEHICLES TO CARRY OXYGEN AROUND THE BODY.

THIS IS WHAT ENABLES SHORT-TERM ACCLIMATIZATION.

BUT OVER TIME, IT SEEMS THE CHANGES IN MARK'S BODY MAY ACTUALLY BECOME MORE PERMANENT, BECAUSE THE DNA INSIDE HIS GENES HAS ACTUALLY CHANGED AND LEARNED FROM THE ENVIRONMENT.

INSIDE YOUR KIDNEY CELLS, EPO IS NORMALLY PRODUCED AT RELATIVELY LOW LEVELS AS AND WHEN YOU NEED IT.

BUT AFTER PROLONGED EXPOSURE TO HYPOXIA, THE DNA THAT CODES FOR EPO ACTUALLY CHANGES.

A MOLECULE THAT CONTROLS GENE ACTIVITY IS REMOVED SO THAT THE GENE IS SWITCHED ON, BOOSTING THE PRODUCTION OF EPO.

THIS CHANGE MEANS THAT ONCE WE ADAPT TO ALTITUDE LONG TERM, OUR BODIES WILL REMEMBER IT, ENCODED IN OUR DNA, EVEN AFTER WE DESCEND TO HIGHER OXYGEN AVAILABILITY.

OUR DNA HAS LITERALLY LEARNED TO COPE WITH THE EXTREME CONDITIONS AND THEREFORE MAKES IT EASIER FOR US TO ADAPT THE NEXT TIME WE TRAVEL TO HIGHER ALTITUDES.

AND CLUES ARE STARTING TO EMERGE THAT THIS TYPE OF GENETIC LEARNING COULD EVEN BE PASSED DOWN THROUGH TWO OR THREE GENERATIONS.

[MUSIC PLAYING] YOU SPEND A LIFETIME LEARNING THE COMPLEX BUSINESS OF BEING HUMAN.

FROM MOVING EFFORTLESSLY THROUGH SPACE...

COMMUNICATING WITH THE WORLD AROUND YOU... AND SUCCESSFULLY NAVIGATING A COMPLEX SOCIAL WORLD.

YOUR BRAIN IS CENTRAL TO THIS... STORING AND PROCESSING BILLIONS OF PIECES OF INFORMATION EVERY SECOND.

BUT YOUR BODY IS ALSO CONSTANTLY LEARNING FROM AND ADAPTING TO THE ENVIRONMENT AROUND YOU.

AND IT'S A JOURNEY THAT NEVER REALLY STOPS.

WE NOW KNOW THAT YOU ARE CONSTANTLY ADAPTING AND CHANGING...

EVEN AT A GENETIC LEVEL.

YOUR LIFE, MORE FLUID THAN YOU EVER THOUGHT POSSIBLE.

OPENING UP A WORLD... OF ENDLESS POSSIBILITIES.

[MUSIC PLAYING] ♪♪ "THE AMAZING HUMAN BODY" IS AVAILABLE ON DVD.

TO ORDER VISIT SHOP.PBS.ORG OR CALL 1-800-PLAY-PBS ALSO AVAILABLE ON AMAZON PRIME VIDEO ♪♪