One could say there is no reason for this article, everyone knows its discoveries already- a baby’s cry is uniquely able to grab attention.

But recent research has explained, in many ways, why this is so.  Even if the conclusion is already known, the story is fascinating.

And, it is told well in a recent NY Times article:  https://nyti.ms/2x4IJ1v

The Punch Line

We start with the stated conclusion, a human babies crying packs a punch- to everyone.  Just think about the last airplane trip you took, and how everyone in the plane has not choice but squirm in their seats if they hear your baby cry.   These passengers have never met your baby, and likely never will, but hearing that sound forces everyone to stop and respond, if only by cringing.

All the more so for we the parents of our babies.  It is a piercing sound like no other.  It forces our brain to stop thinking about whatever we thought was important, and turn our attention to our baby.

One study actually recorded the electrical activity in the brain of adults two ways.  One was by use of MRI brain scans that can light up images of which parts of the brain are actively firing signal as any point in time.  The other was by study of the brain’s level of electrical activity in people undergoing neurosurgery while awake.  In these settings, actual electrodes can be placed on the surface of the brain while the person is awake and able to respond to things they see or hear.

In both studies, adults were exposed to dozens of sounds, only one of which was an infant’s cry.

In both studies, within 47 milliseconds of hearing an infant cry, three interesting areas of the brain leapt into electrical activity:

1. The area of the brain that decides if information is urgently important or not- twice as fast as this area responds to other sounds.
2. The area of the brain charged with deciding how much emotion should be attached to incoming information.
3. The area of the brain that control movement.

None of the other dozens of sounds played did this.

And 47 milliseconds, how fast is that?  You may not know this but TV is, like movies, a sequence of flashing still images that roll so fast they look like one moving image.  The time it takes for one image on TV to flash into the next image, a time so short no one can see this happening, is 50 milliseconds.

It also turns out that 50 milliseconds is how long it takes each of us to decide if we like a website or not.

THE PUNCH LINE:  Nothing in daily life seems to make the brain jump up, sound the alarm, brace for moving to solve a problem quite like the cry of a baby.

How far back does the power of a baby’s cry go?

120 million years.

How do we know?  The fossil record demonstrates that it was 120-150 million years ago when the first liveborn mammals were born and when the first birds appeared.

Prior to this moment, all life emerged ready to go, all on its own.  The first forms of life, single-celled bacteria, do not really mature.  A fully grown-up bacteria simply splits in two, and voila, two fully grown-up bacteria now exist.  The first one offers no help to the second.

Just so with very early forms of multi-celled animals such as sponges and jellyfish.  Eggs evolved and may have been cared for during hatching, but once hatched, newborns are on their own, think about the baby turtles rushing to the sea with no parent in sight to help.

With the emergence of fish, some parental actions after hatching occur, but the repertoire is limited.

But curiously, two very different forms of life developed highly complex parenting around the same time, birds and mammals.

Both came from the dinosaurs, and both moved towards several innovations, apparently independently of each other:

1. Becoming warm-blooded, with material on the skin to keep warm- feathers for birds, fur or hair for mammals
2. Changing the heart to a 4 chambered organ
3. Feeding and caring for their babies.

Think about a newborn robin, or a newborn puppy.  Both cannot live without being fed by their parents.  For birds, that feed is actually food.  For mammals, it is breast milk.

That is what brought about the cry of the baby.  Bacteria and baby turtles never cry, for all sorts of reasons, but one big one is that no one would care.  Even if a baby clam or snake could cry, no mother clam or snake would respond.   But if a baby bird chirps in a crying sort of way, or if a baby deer cries, a mother bird or mother deer will indeed show up and help save their life, feed them.

Isn’t it curious that as soon as life evolved to give birth to young dependent on their parents for food, that cries first appeared?

And that makes babies crying about 120 million years old.

What is it about the baby’s cry that is so unique?

Baby cries evolved about 120 years ago, but for the last 60 million years, there has been little change.

A formula evolved- a certain acoustic sound emerged, and a certain fit to the brain of the parent evolved with it.

That is, baby cries have a certain acoustic signature, and as noted above, that signature makes the adult brain leap to attention and get moving like no other sound short of catastrophe.

That pairing, sound and brain response, once evolved, has worked ever since and has changed very little.

Want to see if this is true?  Click on this link https://nyti.ms/2x4IJ1v

It’s the NY Times article on baby’s crying that this post gratefully is based on.   Go down about 1/3 of the way down the article and you will see an play button for an audio clip that is framed with the headline Which Cry is Human.   If you can, click on the play button without reading the caption and see if you can tell which of these baby cries is human.  I could not.

So what is the acoustic signature of the mammal’s baby’s cry?

It has two parts, like any serious piece of music:

• The fundamental.  Most music is composed of sounds vibrating at set speeds, or frequencies.  A nice sound typically consists of a slow speed that is multiplied.  So the sound is a slow speed, and the same sound at twice the speed, and three times the speed, you get the idea.   Well, in a complex blend of such sounds, where all are multiples of the slowest speed in the mix, the slowest speed is called the fundamental.   All baby’s cries have a steady, unchanging fundamental.
• A melody.  You can imagine a sound of one frequency does not change.  But, melodies do.  They change frequencies.  A higher frequency creates a higher note, a lower frequency a lower note.   Men have voices with lower frequencies, and women with higher frequencies.  A melody happens when a bunch of different frequency flow.  We like melodies where the changing frequencies make a pattern that is pleasing, and that happens when the varying frequencies tend to be clean fractions of each other.  For example, one note might be 1/5 as fast as the other.  That turns out to be a very pleasing combo.   Babies cries have frequencies that go up and down, but their combos are extremely unpleasant.

Not only are the babies’ cries’ frequency a disturbing mix, but the fundamental provides a constant backdrop of sound that allows for the mismatch to really jump.   And, all mammals’ brains are wired to go crazy when this mix is hears.

Some sounds in our lives have been invented to be just as irritating, and they work.  They use the same structure of a steady fundamental and screeching rises and falls in changing frequency- a horrible melody- to set our minds on fire.  One great example of a modern invention that acoustically is very similar to our baby’s cry- the police and ambulance siren.  And it works, right?

What about the baby, how does she or he know how to create this concoction of dire sound?

It turns out that the infant cry is created by a very small number of nerves around the spot where the directive to breathe is crafted in the brain.   This spot in humans is unknown, but in mice it’s in the part of the brain just below the main brain, in us that would be the area between brain and spinal cord, still in the skull.

In mice we know that if you remove as few as 17,000 nerves in this one spot, the baby mouse will breathe just fine, but will not be able to cry.

And, most incredibly, if you remove the baby mouse’s ability to cry, the mother no longer nurses with bad outcomes.

Across the eons, the cry of the baby, which we all experience as a most horrible thing, turns out to be essential to every baby’s survival.

The cry turns out to be a good thing.

BOTTOM LINES

1. All newborns and infants cry.  That cry goes away once talking takes it place.
2. Far from a desperate Hail Mary, the cry of the baby is a highly crafted complex device to make sure they get fed and cared for, when they need it.   Baby cries appeared in animal life about 120 million years ago.  Modern humanity first appeared about 1/3 of 1 million years ago.
3. Our baby’s cry is a finely crafted unique sound and it evolved along with the parent’s brain.  Cry and brain, they evolved together to ensure that this unique sound creates a uniquely urgent response.
4. This highly evolved sound, the cry of a baby, is remarkable similar across very different, but mammalian, species.

The cry of our baby turns out to be a wonder to behold, if impossible to enjoy and impossible to resist responding to.

The only babies that cry are those whose parents feed them after birth.  Baby bacteria (there actually are none), clams, snakes, sponges, do not cry.  The only animals that feed their young are birds and mammals (one exception are the discus fish), and all their babies cry.

We all experience it as a horrible experience, and it took millions of years for that cry to achieve its power, but in point of fact, it is one of the most extraordinary devices life has created to allow the birth of totally dependent babies as seen in birds and mammals.

And, there is no denying that the lifeforms that give birth to the most dependent babies go on to be some of the most intelligent forms of life.

So, yes we all must respond to the cry of our baby, that’s the whole point of the cry.

But as we shake when we hear our baby cry, maybe it lifts the burden a touch to wonder at it all.

To your health,
Dr. Arthur Lavin