Most sets of sensory stimulation appear to fall comfortably near the middle of the sensual spectrum that goes from sensory deprivation to sensory overload. How we perceive the level of stimulus saturation varies. A stimulus set that was comfortable or even bland one day might appear vibrant or irritating the next. Where on the spectrum of sensory saturation a stimulus set appears to us is highly dependent on what state of mind we are in at the time.
There are many things not directly related to perception that can alter the level of effect a stimulus set has on us at any particular time. If we are physically ill we might be more or less sensitive to certain senses. A sinus infection might clog nostrils so badly that the sense of smell is almost non-existant. The most rancid scents go unnoticed. A high fever might render the optic nerve ultrasensitive to light, and even in a shuttered room it is almost too bright to read. In these cases the actual amplitude of the sense is affected. There is actually more or less stimulus getting to the brain from the stimulating event.
Emotional status can also modulate our sensitivities. When a parent is uncomfortable about their child’s safety simple noises and images can become evidence of impending threat. When a lover is lonely subtle scents and textures can evoke images of their missing partner. In these cases the brain is specifically sensitive to a pattern of sensual clues. The brain is over-processing the information so the stimulus has more effect.
Cumulative sensory stimulation can also modulate our sensitivity to further stimulation. We respond to overstimulation by ignoring additional stimulation. When someone asks a question while you are listening intently to the radio something gets ignored. We can focus on a particular source of sensual information, but in doing so we lose track of other sources. We have sensual blinders. The greater the sensual information the more blinding those blinders become. In other words, the greater the overall level of sensory noise in an environment; the more sensory information we filter out in order to focus on any individual stimulus set.
The fourth effecter that I will focus on here is sensitization by deprivation. Sitting in a quiet room for an extended period of time makes all sound appear louder for quite a while afterwards. After wearing a charcoal canistered respirator for a few hours one is assaulted by “new” scents when it is taken off. Within minutes those “new” scents fade into the background. At a low enough level of stimulation the brain will grasp at anything to process. In the absence of competing stimuli each sensory event garners additional significance.
The first two of these four effectors occur regardless of the stimulation level. The second two effecters are self-referentially tied to the stimulus level and the perception of that stimulus level. The self-referential effecters act as modulators for the perceived stimulus level. If the stimulus level is too close to the sensory deprivation end of the spectrum the brain adds more significance to the stimulus it receives. If, on the other hand, the stimulus level is too high the brain filters out more and more information in order to allow focus to be directed at individual sensory information. Instead of appearing as a spectrum to the mind the range appears to be constant with breakdown points during unique situations where one experiences severe deprivation or severe overload.
To complicate matters more there is distinction in the brain between different senses. Each sense is processed in a unique area of the brain. Although it is possible to receive such terrific overstimulation in one sense that the effects bleed over into other senses that level of overstimulation is extreme and rare. It is more common to have one sense overprescribed while another is being severely filtered. We may notice the fragile fragrance of a well worn perfume at a loud party.
One type of brain training involves attempting a particular activity while consciously dealing with competing sensory information. One can try to listen to and answer questions while music is played in the background. One can try and identify a particular pattern while a multitude of images are presented. This is called sensory overload training, and can supposedly help ingrain mental practices better than simple repetition can.
Another practice is directed sensory focus.
a) Pick a particular type of stimulus (I like using colors).
b) “Look” for that sensory stimulus while performing another activity (I suggest not doing this while walking or driving, at least at first).
c) Use your peripheral attention to search for the stimulus. I use my peripheral vision to look for a color. You could do something like trying a part of your anatomy other than your fingertips to detect a particular tactile sensation.
d) Make a mental note every time you detect the search sensation. You will detect it more often as you search for it (Assuming it exists. the trivial case where the search sensation does not exist at all is not very enlightening.).
e) With practice you will detect the search sensation more often and with greater ease. You have now imprinted a random search process on your brain.
Initially the practice of directed sensory focus can help us understand how our own brains work. With practice directed sensory focus can be used to decrease the stressful aspects of partial over-stimulation.
Be careful. It is difficult to explain to someone that you have knocked them over because you were trying to see the color BLUE out of the corner of your eye and therefore did not see them (especially if they are wearing blue).