Bio Paper Three
Do you hear color? Do you see sounds? If so, does a certain sound have a certain color?
Can you taste sounds? Do you hear a sound when you touch a certain texture? If so,
chances are, you are a synesthete.
But take heart, you are not alone. Synesthesia is actually very common by some
standards. Estimates range from 1 in 100,000 (1) to 1 in 100(2) people are synesthetes.
But the fact that this range is so wide tells us that we really don’t know how many
synesthetes there are.
The word “synesthesia” is a Greek word loosely meaning “the mixing of senses.”
Synesthetes receive signals from not only the sense that is being stimulated by the outside
world, but also from other senses at the same time. But it is not random. A synesthete will
experience the same mix of senses for certain stimuli. For example, in color-graphemic
synesthesia which is the mixing of color with letters and numbers, a certain number or
letter will elicit the same color every time over a period of years perhaps even a lifetime.
In fact, it is so regular, that many synesthetes are not aware that this doesn’t happen for
everybody. They don’t know that their senses are mixing. In our example, the synesthete
who sees the number 4 as red, simply believes that the number 4 is red. This is one reason
that it is so hard to know how many people are synesthetes.
Many synesthetes consider themselves receivers of two-dimensional senses. They feel
endowed by a gift rather than afflicted with a disease. Some even feel sorry for those with
only one-dimensional sensory perception. (1) For instance, some color-auditory
synesthetes see a complete light show with every song. One synesthetic artist paints the
music she hears/sees.(3) The only time it seems to be bothersome is when the synesthete
is receiving unpleasant signals, such as ugly colors with someone’s name, or the taste of
onions with certain words…or when the input becomes too much, but this is rare.
Historically, synesthetes have been considered sick, crazy, schizophrenic, and on and on.
Though synesthesia is totally benign, admitting you have it can have dire consequences.
In modern day America synesthesia is well enough known that for the most part it is not
considered a problem, and at worst a dysfunction. But in other countries around the
world, some synesthetes are institutionalized by their society as if they were insane. (6)
What is synesthesia? What is happening in the brain that this “mixing of the senses” takes
place? Once again, we don’t really know. Though there are a number of possible
answers, there are two major schools of thought about the senses themselves, and
synesthesia may provide the answer as to which one is less wrong.
The Mentalist View: Some scientists believe that as a newborn baby all the senses are
mixed. In other words, the axons from certain sensory neurons are attached to receptor
neurons of another sense. As the baby develops, the synapses align themselves with their
particular sense so as to give the individual one-dimensional sensory input. In a
synesthete, this individualization of the senses remains incomplete; synapses remain
crossed between two senses and the result is synesthesia. Along a similar vein, some
scientists believe the synapses are already complete at birth, and remain either crossed or
not, as in the case of synesthesia. (4)
The Naturalist View: A completely different point of view as to the explanation of
synesthesia and the senses themselves is called the Unitary Thesis. This view holds that
instead of having 5 distinct senses acting independently, we have one sensory organ
which encompasses all the senses and has 5 sub-organs.(5) In this view, it is normal to
mix the senses, which all of us do to some extent. For example in music, major chords are
often described as bright, and minor chords as dark.
The debate between these two schools began in the 1800’s and continues today with no
definitive conclusion in sight. But understanding synesthesia may hold the key to
understanding the senses.
Medical technology may give us some inroads to understanding. Current experiments
have found that color-hearing synesthetes actually have activity in different parts of the
brain when receiving an auditory stimulus. They show activity in the visual cortex when
they hear certain words. The non-synesthete does not display any activity in this part of
the brain even when asked to imagine the synesthete’s connection. (4)
Synesthesia brings up some very important philosophical questions as well. What is real,
and what is imagined? What determines reality? Does the number 4 have a color in
reality? Just because the majority of us would say no, does that mean that in reality it
doesn’t have a color? Could it be that in fact the synesthete is picking up a reality that
most of us miss? Who has the last word in what makes something “real” and what makes
Are synesthetes imagining the second sensory input more than the first? Are they
imagining the color red on the 4 more than they are imagining the 4 itself? If so, their
imagination is very unchanging. Studies have shown that a synesthete’s connected senses
remain connected in the same way over a period of years. Synesthetes who say a 4 is red
and 3 is yellow will say the same thing over time. On extensive tests of this kind
synesthetes repeat the same sensory connections 70-100% of the time after a year. A non-
synesthetic control group who had memorized sensory connections could only repeat the
connection on the test 20-40% or the time. (1) How could it be imaginary and yet the
same every time? But if it isn’t imagined, does that make it real?
Senses that are mixed are not mixed in the same way for different synesthetes. For
instance, two color-graphemic synesthetes who both see the number 4 colored probably
won’t see it with the same color as the other, though both will see their color on the 4
consistently. Does that mean that the color on the 4 is imaginary?
Many synesthetes move through life aware of two different realities, theirs and the rest of
the world’s. (6) This isn’t too hard for a synesthete. They are often gifted people, not only
by the synesthesia itself, but they tend to be drawn to artistic hobbies and professions,
they score well on cognitive assessment tests and memory tests, but not as well on spatial
tests. What does all this mean? Who knows? But the question arises, could synesthesia
actually be connected to some other part of the brain as well as the sensory parts?
As more data is collected, more will be revealed about this mysterious, harmless way of
perceiving the world, and it could be a gateway into more understanding as to the
workings of the senses and the brain.
1) BU Neuropsychology
2) Synesthesia Info
3) Steen-Australian Art Review
4) Neuroscience for Kids
5) Experiments with Synesthesia
6) One’s Own Brain as Trixter