The realm of sensation comprises six familiar kinds of phenomena and a few more that often go unnoticed. Each has characteristic qualities that make it possible to distinguish one kind of sensation from the others. For the novice as well as the experienced contemplative it is fascinating and useful to investigate the senses. Let us look at the six primary modes of sensation in turn.
- The field of visual sensation is more or less round, highly detailed at the center, which corresponds to the fovea centralis of the retina, and more or less coarse everywhere else. Although the detection of color, edges, texture, movement, distance, dark/light gradation, etc., are functions of sight that are processed in separate areas of the brain, the visual field nevertheless appears as a collection of recognizable entities. Visual perception is often accompanied by the strong sense of an observer who looks out at the world from a position somewhere behind the eyes. That illusion is probably due to the perception of depth that results from binocular vision. The sensory field of sight seems to be outside the body, as compared with the other sensory fields that are felt to be on or in it. This phenomenon sheds light on the tendency to locate oneself (much the time) within the body.
- Audition seems to occur for the most part in the vicinity of the ears although attention and imagination will often “move” in the apparent direction of the sound.
- Odors are sensed in the nose, and
- Flavors on the tongue.
- Tactile sensations, which include temperature, pain, itching, and various signals originating in the viscera, seem to be within or distributed over the surface of the body. Other sensory phenomena, such as balance, and the mapping of the body’s parts in relation to each other and the whole in relation to objects in the environment, are seldom even noticed in the course of everyday life.
- Thoughts, feelings, judgements, etc., may or may not have an apparent or putative location. (The conventions of folk-topography have them mostly in the head, sometimes in the heart, depending upon cultural norms). Verbalized thought often seems to arise, as represented audition, at an inner “ear.” Certain kinds of thoughts will be accompanied by the mental equivalent of images or sounds. Represented flavors and odors are less common.
These, then, are the principal means by which we gather information about the environment and our own bodies. But whatever the actual number of senses we may count as contributing to a given moment of experience, the raw data is so great and so diverse that if it were to be taken as a whole, it would be unintelligible. Before that data can be of use to us, impulses originating in the sense-receptors will be shunted about the nervous system, often by multiple pathways, and processed in various ways before they issue in behavior or cognitive events.
Sensory perception is highly organized, and that is the oddest and most interesting thing about it. All six of these modes of sensation occur simultaneously, although it is moot whether one is ever aware of all six with true simultaneity. We are able to distinguish each of the sensory modes from all the others. More wonderful yet, we do not perceive a vast field of chaotic, intermixed sensory phenomena, nor unidentifiable blobs or clusters of visual, auditory, and tactile sensation. We perceive wholes. We perceive things. By the time data of the senses are integrated—and it is a very short time—they have undergone filtering, sorting, pattern recognition and completion, comparison, and labeling, so that we “instantly” recognize them for what they are, except on rare occasions such as when we are suddenly awakened from a deep sleep.
Some of the processes that allow us to recognize things, as opposed to merely sensing them, are the results of evolution, others of learning. They are currently the objects of study by psychologists, neuroscientists, and evolutionary biologists. We meditators can fruitfully study them “from the phenomenal side,” as some philosophers would have it.
In “meditation” we can temporarily suspend or undo selected elements of that information-processing network. To put it another way, we train ourselves to disable the higher cognitive functions by increments, beginning with self-consciousness and working our way “down” through the various layers (about which more in future posts) until we are near to the sensory foundation. Then we simply (!) observe.
In the following posts I will describe a few exercises that helped me to get started in my exploration of this terrain.