The Science of Touching and Feeling | David Linden | TEDxUNC

my god there are a lot of you here so

thank you for having me thank you for

letting me close out your conference

sound because I'm the last speaker I

think I should talk for a moment about

what I think that being human is I've

been listening to all these wonderful

presentations and I think if there's a

summary it's that to be human is to be

emotional to feel things and for all of

us the sense of touch is intrinsically

emotional and we don't need scientific

investigations to know that we can just

look at our common expressions that we

use every day I'm touched by your

concern I didn't mean to hurt your

feelings I can't stand that slippery

politician you can guess which one I

mean could be any of them really when we

encounter someone who's emotionally

clumsy we call her tactless literally

she lacks touch so how does this

connection between emotion and the sense

of touch form and it begins to form very

early in life

and we know that if you're born blind

without sight that you can develop a

great mind and a great body and have a

great life and likewise if you're born

deaf you can develop a great mind and a

great body and have a great life but if

you're born with the biological

components for a sense of touch but you

do not receive touch during your infancy

and when you're a toddler than a

disaster unfolds and we know this mostly

from what happened in orphanages in

Romania during the Ceausescu regime in

the 1970s and what followed in the 1980s

and these were situations where there

were grossly understaffed orphanages

there was no one to hug or hold or


or be loving in a tactile way towards

these children and they develop horrible

compulsive self soothing rocking motions

later they had attachment disorders

cognitive delays and it wasn't just

neuropsychiatric problems their growth

was stunted and they had problems with

the development of their

gastrointestinal systems and their

immune systems and we know that this is

because of touch deprivation because in

some cases volunteers came in and gave

just 30 minutes a day of loving touch a

little hugging a little limb

manipulation and that was enough to

completely reverse all of these

deleterious effects but only if it

occurred in the first two years of life

it happen if the intervention came after

age two all those problems would persist

for the rest of life now the critical

role of touch in childhood development

wasn't always understood as a matter of

fact in the 1920s John B Watson the

founder of the psychological movement

called behaviorism advised parents never

touch your children never hug them if

you must when they have done an

extraordinarily good job at a difficult

task Pat them on the head give them a

handshake at the end of the day now of

course today most parents don't raise

their children this way but it's a very

different situation outside of the home

where we have promulgated no touch

policies for supervisory adults like

teachers and coaches that while

well-meaning have had a disastrous

effect when a kindergartner reaches to

get a reassuring hug from the teacher

and the teacher isn't allowed to have to

stand their stock still that is not a

social good an opportunity to create

bonds of trust and cooperation and

empathy is lost and you might say well

okay understand babies are really

sensitive kids are sensitive but what's

your once you're an adult does all this

touchy-feely stuff really matter and the

answer is yes it does touch is social

glue it's what binds sexual partners

into lasting couples it's what

ion's parents and their children and

siblings it binds together people in the

community in the workplace in two

effective teams we know that doctors who

appropriately touch their patients

during an exam are rated as more caring

and more importantly their patients have

better better medical outcomes and lower

stress hormone levels in terms of actual

teams we know that in the National

Basketball Association there was a

wonderful study was done by dr. kelmer's

group at UC Berkeley and what he did is

he got video tapes of all the NBA games

of all the teams in the first half of

the season and then he had people look

at them and score all of the celebratory

touch all the Pat's on the rear end on

the chest bumps on the high fives and

everything that people do to celebrate a

basket and he came up with an index of

celebratory touch for each team and he

asked does that index for the first half

of the basketball season predict

anything about what's going to happen in

the second half of the season and the

answer is the teams that engage in more

celebratory touch both win more games in

the second half of the season and more

importantly they play in a more

cooperative fashion for example the star

would be more likely to pass off the

ball to another player who had a better

shot so what I'm drawing what am I

trying to tell you here it's not that

touch is good or even that touch is

important rather it's that the specifics

of our touch experience from skin to

nerves to brain are weird and strange

and counterintuitive and these strange

and counterintuitive facets of touch

profoundly affect our human experience

and our human society and let's explore

that point number one we think of touch

as being a unified sensation we

experience it as a unified sensation but

actually it's created by many different

specialized sensors working in parallel

so what do I mean if we looked in your

skin we would see many different kinds

of nerve endings each one a micro

machine specialized to transfer a

certain kind of information we'd find

one nerve ending for heat and another

for cold one for pain

and one for each one for sexual

sensation vibration pressure texture

fine tactile form there are nerve

endings specialized for all these things

and the density of these nerve endings

in different parts of your skin gives

rise to the way you experience touch on

different parts of your body for example

if you want to read Braille dots which

require appreciating fine tactile form

you're likely to use your fingertip

because your fingertip is very

well-endowed it has a high density of

the nerve ending called a Merkel ending

which is the best ending for detecting

fine tactile form and for some reason

you can't use your hand you can read

Braille dots with your lips because they

also have lots of merkel endings or your

tongue which also has lots of merkel

endings and I can I can see your

expressions out there in the audience

some of you are thinking I got some

other parts of my body that are kind of

sensitive could I use those and the

answer is no you cannot use the cornea

of your eye to read Braille dots ah so

you know when you get a piece of grip in

your eye it hurts like crazy but it's

very hard to tell precisely where in

your eye it is and this is because while

your eye is sensitive it's not

discriminative but that is to say you

can't read tactile form with your cornea

because it lacks Merkle endings and of

course I knew what you really think

about your think about your genitals


can you read Braille with your genitals

no you can and it's the same reason you

don't have Merkel endings in your

genitals so you can't read Braille there

it won't work now I know that all of you

want to do citizen science and this is a

cool thing right you don't want to take

my word for it so you're going to be out

on Franklin Street later tonight you're

going to wait till no one's around at

the ATM and you're going to test it

yourself all I ask is that bring a

disinfecting wipes for when you're done

point number two there is no sensation

without emotion the two go hand-in-hand

so all these streams of information that

I told you about

are coming to your spinal cord and

they're coming to your brain and they

distribute into two different systems

one of them in a region called the

somatosensory cortex is all about the

facts it's the discriminative system it

tells you where my body am I being

touched and in what fashion and how

intensely then there's a completely

separate system in a brain region called

the posterior insula and that's your

emotional touch system that's what gives

different kinds of touches their

particular emotional tone so for example

if I were to sneak up on you and whack

you on the thumb with a hammer you would

go out [ __ ] oh that hurts that's

awful my thumb is throbbing um however

if you had damage to your posterior

insula you would have a condition called

pain Easton boliya and then if I whacked

you on the thumb with a hammer you would

say in a very flat emotionless voice yep

that hurts all right it's on my thumb

it's throbbing now the pain would have

no emotional resonance for you

whatsoever because you need the

posterior insula to field out now what

about the converse what if you had

damage throughout your somatosensory

cortex it's a pretty rare thing but it

can occasionally happen then if I whack

you on the thumb with a hammer you would

say oh that's terrible that hurts so

badly and I'd say oh I'm so sorry where

does it hurt and you'd say I have no

idea so the point here is that we're

used to thinking of certain sensations

of having an intrinsic emotional tone

but this is a trick our brain plays on

us right we have the sensation of it's

the thumb that hurts and the negative

emotional tone that goes with that pain

only because these two different brain

systems are active at the same time

point number three point number three is

that we are hard-wired to pay attention

to sensations including touch sensations

that originate in the outside world but

discount ones that originate from our

own motion and so what do I mean imagine

that you're walking down the street and

as you walk down the street you're

moving your limbs and your torso and

your clothes are moving against your


and you're not thinking about it at all

it doesn't enter your consciousness one

bit those sensations are strongly

suppressed whereas if you imagine you're

stopped on the street corner and now

those same sensations come on your body

oh you'd be very very attentive to them

they would have great salience uh why is

that it's because we're hardwired to

suppress the sensations that result from

our own motion and this makes

evolutionary sense right because the

outside world that's where the things

are that we might want to eat that we

might want to mate with that we might

want to run away from so we want to pay

more attention to the outside world

then to the consequences of our own

motions and and the crucial medical

issue that is tied up with this is why

it is that it's so very hard to tickle

yourself right so when you go to tickle

yourself electrical signals are flowing

from the motor cortex in your brain down

to the muscles of your arm and your hand

to produce that tickling motion but

those a copy of those signals is going

to a part of the brain called the

cerebellum and the cerebellum transforms

those into inhibitory signals and feeds

them in to the somatosensory cortex the

fact-based touch Center and suppresses

suppresses those sensations and that's

why you can't tickle yourself very

easily there was a few people I'm sure

in this audience there's probably a

dozen people who will say yeah I can

tickle myself but it's pretty rare we

know however that people who sustained

damage to the cerebellum and interrupt

this hardwired circuits can indeed

tickle themselves now I'd like to

conclude so we like to think that we're

driving the bus and by that I mean we

like to believe that we can take in

reliable information through our senses

about the ex outside world and if

necessary make entirely rational non

emotional decisions about that

[ __ ] it's not true our senses are

not designed to give us the most

accurate representation of the outside

world rather they mess with the data

they emphasize some things and they

diminish others and by the time you're


aware of it that sensory information has

always been already been blended with

your emotional state and it's been

blended with expectations and I'm both

talking about your own personal

expectations that you have accrued

through your individual life experience

as well as the genetic expectations that

you have accrued through your DNA

through hominin evolution and your brain

serves it all up to you as real thank

you very much your attention