>> Let's take a little look into the physical development
that happens during infancy and toddlerhood.
So I think it's important to note that this probably the age
that has received the most attention because the changes are really dramatic and we can see them.
Where the changes in the womb were even more dramatic,
but they happened where we couldn't see them.
But now we watch this baby go from this tiny little wrinkly pretty much helpless human
to a fully functioning yet tiny, in a tiny packaged human being.
There is some debate about whether or not the significance of this stage has been overstated.
But I think most would agree this is a really important time to pay attention to.
So one of the things that's happening during these early years is rapid growth second only
to prenatal development, right?
So average of that seven and a half pounds and 20 inches at birth, doubles that weight
by four months, triples it when they turn one, and then is almost 26 to 32 inches tall.
And by two their weight has quadrupled.
And it's important to note that sleep plays an important role with this because during sleep is
when the hormones that regulate growth are released.
And we're going to talk more about sleep in a different video.
One of the dramatic things that's happening physically during this time period are the
changes in the brain.
So when you're born your brain is about a quarter of the adult weight of an adult brain.
But by age two that is up to a whopping 75 percent.
And that is because of synaptic blooming and myelination
of the central nervous system, right?
So you have all your brain cells but they're not connected
to each other, and they're not very efficient.
So those connections or the synapses are being made.
And then that fat or that myeline is coating the axons of your neurons
to allow your neural activity to be more efficient.
If you think about those of you have an understanding of how electricity works,
when you insulate your wires it becomes more efficient
because you lose less of your electricity.
A similar thing with neurons.
Another hallmark of physical development during this time period are reflexes.
So most of the things that infants are born able to do are reflexes.
Some of these are purely for survival.
Some probably are kind of vestiges of past evolution.
Some we're not exactly sure.
We think maybe they're practice for later development.
But here are images that come from a table in the chapter.
They show some of the more important reflexes.
So babies will reflexively suck anything that's put in their mouth.
If you stroke the cheek of a baby they will turn their head towards it as if
to seek it out to nurse or to suck.
They instinctually grasp whatever's placed in their hand.
And they don't have the ability to voluntarily release it.
They have a startle reflex or the Moro reflex where they fling their legs and arms
out when they're startled which is part of why many people believe in swaddling
because it helps kind of stifle that Moro reflex.
If you stroke the bottom of a baby's foot their toes will fan out which is the Babinski reflex.
There is the tonic necks or the sword fighter reflex or the fencing reflex.
You can see that they kind of bend one arm up
and put the other arm out when they're laying there.
And then there's also the stepping reflex.
If you put a young baby's feet flat on the floor they will reflexively take steps.
And there are other reflexes at work that we also have, breathing, blinking,
swallowing, those are also all reflexes.
So all of us keep some reflexes.
Some of them disappear completely and they go away never to be seen again.
Some disappear and then are replaced
with voluntary behavior later like the stepping, right?
So that reflex stops but later you voluntarily step.
So I think it's also important to look at kind of the progression
of what happens with motor development.
So there are two ways to look at this or two aspects.
We have gross motor and we have fine motor.
Gross motor is things that use our whole bodies or our arms and legs and that tend
to move our body parts or our body through space.
And this chart comes out of the chapter, and so you can kind of see the progression.
They go from learning to hold their head up and beginning to push their bodies up at two months
to rolling over at six months to getting into a seated position without help,
maybe standing without help at about a year.
By 18 months most children are walking.
They can pull toys, they can start to help undress themselves
which is also a fine motor skill so some of them cross over.
And by two years they can stand on their tiptoes.
They are beginning to run.
So, again, they go from barely being able to --
well, when they're very first born they don't even hold their head up, to running
and really having all of the basic large motor or gross motor skills.
And then the other aspect to look at is fine motor, right?
And when we talk about fine motor we tend to be talking about what we do with our fingers.
That also includes things that you do with your toes and your mouth, but we tend to focus
on the hands when we look at in child development or early childhood education.
So, again, if you remember back to that reflex at two months they don't have a lot
of control over fine motor at all.
It's all reflexive.
They slowly learn to control their arms which then allows them to control their hands
which then allows them to control their fingers.
If you remember that relates back to that proximodistal trend of development, right?
So I'm going to focus on what's closest to the trunk first and then go outwards.
And so you see that progression coming down to when by nine months they're able
to start self-feeding finger foods, right?
Maybe even a little bit earlier than that.
They love to put stuff in their mouth.
By 18 months they're scribbling, they're drinking from a cup.
They may be able to start to eat with a spoon although that's going
to be messy for years to come.
By two they can start to build with blocks.
They can pour and dump, and they can zip and unbutton
if the zippers and buttons are large enough.
So lots of important milestones are happening here.
And the last aspect I want to look at in these early years
for physical development is sensory capacities, right?
So vision is the one sense that we are born with that's fairly poor.
Because vision requires light to develop, and there's very little light in the womb.
And so where good adult vision is 20/20, when you're born your vision is about 20/400
which means what you or I could see 400 feet away has to be 20 feet away from them to be able
to see to kind of help you understand what 20/20 and 20/400 refer to.
They see the best around 8 to 16 inches from their face which is perfect for nursing
or feeding because that puts their face about that far away from their caregiver's face.
And they have poor color vision at birth.
This rapidly changes.
Within months their vision's almost to adult level.
Their color vision fully develops, and they also get the ability to have depth perception
which means they can judge depth and distance using their eyes.
The other senses are mostly well developed at birth.
They are responding to sounds in the womb.
And one of the great things is that they can hear all sounds
in all languages when they're born.
And that lasts until about seven or eight months when they start to stop hearing the sounds
that they don't hear on a regular basis.
They prefer their mother's voice and smell.
And you can see here that they've got some taste preferences, right?
And if you can see the babies tend to like the sweet.
They're a little unsure about the sour, and they're not real fond of the bitter.
So that's a little bit about the physical development during the first two years of life.