Monthly Archives: May 2007

Mysteries of the Brain Part – 16 – How to Smile

This post was written on Thursday, May 17, 2007


Today’s episode is inspired by a chapter that I read in the book “Phantoms in the Brain” by V.S. Ramachandran. Harindranath Parameshwaran had given me this book to read a couple of years back and I have conveniently forgotten to return it.


If you observe yourself in a picture you will notice that there is something that is not right. It is the smile. Somehow the smile in the picture never comes right. The photographer tells you to smile and you really do try but when you see the picture, it is just not the way it should be. Your family members tell you that it is not natural. In today’s VERITAS we will try to understand this mystery. Hopefully this should put a smile on your face.


To-night, if I may guess, thy beauty wears
A smile of such delight,
As brilliant and as bright
As when with ravished, aching, vassal eyes,
Lost in soft amaze,
I gaze, I gaze!
( Keats)


The problem is that we can smile effortlessly when we see a friendly face or a thing that we like. But when someone else tells us to smile we CANNOT do it. A smile is not as easy as you may think it is. It involves dozens of muscles and the smallest lack of coordination in those muscles will spoil your natural ( and beautiful) smile!


So am I telling you that you do not really know how to smile? Am I telling you that you can only smile when it happens automatically( subconsciously)? Am I telling you that you cannot smile if you try? Yes, I am telling you all these things.


Let’s try to understand the difference between your natural smile and the unnatural one. But for that we will have to understand the brain a little bit.

The limbic system is the emotional centre of the brain. This part of the brain is much more developed in mammals than it is in other animals( like reptiles and fishes). The neo-cortex is the part of the brain that is responsible for thinking, planning etc. This part is there in humans and other mammals but is much more developed in the case of humans and other highly intelligent mammals( chimpanzees and dolphins).


The basal ganglia is a complex assembly of cells whose primary role is to trigger simple(primitive/primary) movements. The actual movement is done by the muscles of the body- the basal ganglia just trigger the muscles to start. The basal ganglia cannot stop a primary movement!
The movement must run its genetically programmed course or be stopped by some other part of the brain. The basal ganglia can only start simple/primitive motions.


The motor cortex is a part of the neo-cortex and is responsible for complex/skilled motions- combing your hair, playing the piano etc. It is a higher system than basal ganglia and tries to control/coordinate each muscle while performing these complex motions.


When you see a person who you like, a signal starts from the limbic system( emotional centre) and tells the basal ganglia to initiate the smile. The basal ganglia start the smile but we know that the basal ganglia cannot stop it. Once it starts it has to complete its full course. So the basal ganglia tells the various muscles of the face to “initiate” the smile “program”. And you have a full beautiful natural smile!


But when you sit in front of a cameraman and he tells you to smile, a different sequence of events occur. The thinking and planning part of the brain( the neo-cortex) knows that the face has to smile so that the picture comes out nice. It sends a message to the motor cortex to do a smile. The motor cortex tells each muscle to smile. However the motor cortex does not know how to smile. It tries to control every muscle of the
face and places too much stress on the lips. It may not even remember that the eyes also have a role. The exact coordination is never reached because the brain is thinking too much about it! The motor cortex fails miserably. And you get a forced, tight and unnatural smile.


So the natural and beautiful smile can only happen if it is initiated by the emotional centre(limbic system) and triggered by the basal ganglia( the part that triggers simple primitive motions). You cannot smile of you decide to do it( via the neo-cortex/motor-cortex pathway).



No time to turn at Beauty’s glance,
And watch her feet, how they can dance:
No time to wait till her mouth can
Enrich that smile her eyes began?
A poor life this if, full of care,
We have no time to stand and stare.


(William Henry Davies)






Go, wondrous creature! mount where Science guides:
Go, measure earth, weigh air, and state the tides:
Instruct the planets in what orbs to run,
Correct old time and regulate the Sun;