Each person's senses differ in their sensitivity and perceptual interpretation.
Synesthesia is the capacity for a stimulus in one sense to evoke an image or response in another sense.
Smell and taste are synesthetically associated to one another in most people.
The smell of an apple prepares the brain for the taste of an apple when you bite into one.
With your nose stopped up, mashed apples and mashed potatoes taste almost the same.
Natural synesthetes blend their senses in unusual ways.
Some synesthetes "taste" words, "feel" flavors and "see" sounds.
For instance, one woman 'saw' a long chain in the air as a kitten purred.
A ringing phone displayed to her diamond-shaped blocks in the air.
Another woman heard the word Massachusetts and she 'tasted' newspaper, or she heard the word New York and received a 'taste' of toast.
One peculiar case involved a man that tasted something sour only to 'feel' a pointed shape.
When he tasted a certain sauce, he said it 'felt' angular.
Perhaps a more common form of synesthesia involves seeing colors when certain musical notes are played.
Some composers "suffered" from this malady and made use of it.
Russian composers Aleksandr Scriabin and Nikolai Rimsky-Korsakov both "sound painted" many of their compositions in an elaborate system of matches between colors and keys.
In fact, research has shown that synesthetes reflect a consistency in their sound to color experience.
Studies have shown that during episodes of synesthesia, blood flow to the higher cortex decreases dramatically, which indicates at least the phenomena is not involving the cortical areas where your imagination is running wild.
One example where a synesthete experienced "dark purple triangles" when he listened to a "clicking sound" revealed no activity in the visual cortex center at all.
In fact, most research indicates an increased blood flow in the lower limbic region of the brain during synesthetic episodes.
The Russian mnemonist, Shereshevskii, appeared to have no limit to what he could memorize with the help of his natural synesthetic abilities.
Every sound that he heard evoked visual images of distinct form, color and taste.
He could repeat learned material in reverse order, and recall it without difficulty even years later.
Since synesthetes usually have better memories, developing a synesthetic skill can no doubt enhance your own memory.
As an exercise to simulate a synesthetic experience, scratch a partner's back through his shirt while he consciously attends to the activity.
Let him listen to the sound of the scratching and inwardly feel the sensation with intensity.
Now while your partner has his eyes closed, scratch your own back.
Allow your partner to hear the sound of the scratching while "feeling" the sensation of it for himself at the same time.
Then reverse your roles.
Vary the tactile and sound combinations, but each time have your partner feel it first and imagine it afterwards.
Now take the word IMPROVEMENT and think of it for a minute.
Say it aloud and play with it.
Use it in several phrases.
Roll the word on your tongue.
Is it stale, fresh or aromatic?
How does it feel?
Is it long, short, fat or skinny?
Does it have a texture of smooth, soft, hard, pointed, mushy or prickly?
How heavy is it?
Does it evoke visual or auditory images?
Just as squeaking chalk on a blackboard evokes goose bumps on some people, pleasant music can evoke other sensory impressions if you allow yourself that capacity.
Many people already associate high-pitched sound with bright colors and low-pitched sounds with more somber hues.
Now assume a comfortable position and relax yourself completely.
Now have someone play a provocative piece of classical music that you're not already familiar with.
As the music begins, open up all your senses to it.
Imagine that your skin is hearing and feeling the texture of each note as the music flows over and through you.
Imagine your nose is smelling the flavor of it, and your mouth is drinking in each tone, and tasting the savor of it.
Visualize an array of colors swirling around you in brilliant hues as the music is played.
Use your powers of visualization and let the music sweep through all of your senses.
Allow a kinesthetic involvement, and move your hands and body if you wish.
Write down what each note smells, tastes or feels like in emotional way.
In this way, the limbic system can orchestrate a fusing of the senses for the right brain's musical experience.
With continued practice, a synesthetic appreciation of music will eventually develop in you.
Play various notes on a piano or other instrument individually and interpret each as resembling sweet, bitter, sour or neutral.
What color would you choose to associate with each note?
Do you perceive any visual images or forms when the notes are played?
When you eat something in the future, consciously 'attend' to the activity.
Notice the smells commingling with the tastes.
Discern how flavors feel to you.
Whatever you do during the day, imagine a mixing to take place in your sensory involvement.
Although true synesthetes do not imagine their synesthetic episodes, this exercise will bring you as close as possible to what synesthetic sensations are like.