1. Miles of Smiles- Jay Mejia
How is it that we smile and why are some smiles so bad? Picture yourself at your
8th birthday party. The lights are off, and in comes the parade of family and friends
singing your praises, birthday cake ablaze. That picture is still hanging on the mantle,
your 8 year old smile stretched from ear to ear.
Compare this to a few growth spurts and pimples down the line: amidst the sea of
hormones and excessive cologne. Picture you and your first real date trying to pose for
the camera. “No, no, no…smile!” says the photographer for the fourth time. Awkwardly,
you force a smile, which to this day, makes you cringe each time you look at that picture.
What differentiates these two smiles? Like most things in life, the answer lies within the
brain.
The evolution of the modern brain is best compared to the automobile’s evolution
over time. An automobile is essentially just a wheeled motor vehicle with its own
engine. And though the modern cars we drive today don’t look anything like a 19th
century Benz Motorwagen: bearing 3 wheels, no windows, and a small combustion
engine, it is commonly regarded as the first real automobile.
A 19th century Motorwagen is analogous to the primitive brain; scientists often
call it the reptilian brain. This brain controls only the most basic functions necessary to
life, ranging from circulation to respiration.1 These functions are present in all species
with nervous systems. Damage to this most basic part of the brain usually results in
death.
By the time the first affordable automobile, the Model-T, was made 20 years later,
cars had evolved. The Model-T sported 4 wheels along with doors and windows.
Similarly, the limbic brain gave rise to new developments on top of basic brain functions
for the first mammals. With the limbic brain came memory formation, motivation, and
emotions. 1,2
One hundred years after the Model-T, we are living in the age of the modern car.
Today, when you go for a drive, you can rest assured that your car will have seatbelts,
airbags, and Bluetooth. In the modern brain, the newest addition is the neocortex. The
neocortex is only present in humans and primates. It allows for almost infinite learning
capabilities as well as reasoning and complex decision-making. 1

2. Though a smile is nothing more than the contraction of certain facial muscles,
internally, two very different systems can produce the look. Imagine driving to work in
the morning. If there’s traffic on the highway there’s always the option of taking back
roads to get to work. You ultimately get to the same place but you used a different route.
On your birthday, you felt true happiness. Being an emotion, “real” happiness
stems from the limbic part of our brains in structures like the hippocampus and amygdala.
Requiring no conscious thought, this type of smile is an autonomic response. 3
In your high school prom picture, the cringeworthy “smile” was not a limbic
smile but a forced smile; instead of following a subconscious, autonomic route this smile
took the alternate route through the neocortex. This route involves a lot of conscious
thought and voluntary motion trying to break down the smile into its components. 4
And so amidst the annoyed demands of the photographer to show teeth, lower
lips, and have symmetry, the real smile gets replaced with a fake one that uses conscious
movement of the face. This is the reason many people can’t smile on cue; they spend too
much time planning the individual movements with their neocortex instead of allowing
the limbic brain to smile. This also happens when you are smiling for a picture but the
photographer takes longer than expected. Conscious thought takes over and your smile
starts to look scary. Those who can smile on cue have learned to mimic their limbic brain,
though it takes practice and can never be a true replication. 4
Clinically, patients who have suffered a stroke in the neocortex area devoted to
voluntary movement of the face, tend to have a drooping of the muscles in the side
opposite the lesion. If asked to smile, their smile looks more like a sideways S than the
familiar C-shape. However, if the patient is told a joke, or a loved one walks into the
room to greet them, a genuine smile is suddenly seen spanning cheek to cheek- true
happiness. If the patient is asked to smile immediately after or even to hold their smile in
place, their smile subsides and returns to the droopy S-shape. 4
In 1862, this limbic, “true” smile was best described by French doctor Guillaume
Duchenne who, after intensely studying several hundred smiles, concluded that a true
limbic smile involved contraction of the muscles in the corners of the mouth as well as

3. the orbicularis oculi muscles which raise the cheeks and form “crows feet” around the
eyes. Since most people cannot voluntarily contract the orbicularis muscles, it’s a telltale
sign of a true smile. 5
A true smile takes little work. In fact, over-thinking a smile can ruin one. The next
time you find yourself on a date, note their smile. Is it one of Duchenne’s limbic smiles,
meaning happiness even at the subconscious level or do you note the hesitation, the
voluntary initiation of movement, the lack of crow’s feet? The answer’s always in the
brain though you may want to take it at face value.

4. Works Cited
1. Nolte, John. The Human Brain: An Introduction to its Functional Anatomy. 6th ed.
N.p.: Mosby, 2008 . Print.
2. Caine, Renate N., and Geoffrey Caine. Making Connections: Teaching and the Human
Brain. Nashville: Incentive Publications, 1990. Buffalo State U. Web. 26 Jan. 2014.
3. Czerner, Thomas B. What Makes You Tick? The Brain in Plain English. Vol. 1. N.p.:
Wiley, 2001. Web. 26 Jan. 2014.
4. Ramachandran, V.S., and Sandra Blakeslee. Phantoms in the Brain: Probing the
Mysteries of the Human Mind. N.p.: William Morrow and Company, Inc., 1998. Print.
5. de Boulogne, Duchenne. Mechanism of Human Physiognomy. Vol. 1. Cambridge:
Cambridge University Press, 1990 . Print.