Our senses and our world, part two

Because of light, we see things around us—and even things, such as stars, that are far from us. Because of sound, we hear things. Sound travels as waves through air and water and even through solid substances. When those waves reach our ears, our eardrums and the tiny bones behind them move, and nerves carry messages about those movements to our brains. Loud sounds and soft sounds, high sounds and low sounds, brief sounds and continuing sounds—all these are faithfully reported to our brains. Sometimes we enjoy the sounds we hear. Sometimes they warn us of dangers to which we must react. Sometimes we ignore what we hear. Even while we sleep, even while in a coma, we continue to hear, because our ears (unlike our eyes) have no muscles. Therefore, we should never assume that a person in the room with us cannot hear the things we say.

Our hearing is not identical, even as our seeing is not identical. Some people hear higher pitches than other people; some people hear lower sounds than other people. My sister and her household once had a singing refrigerator—all day and all night, it alternated through three high-pitched tones, not shrill and piercing tones, but sounds that were present to those who could hear them. Her husband and their daughter could not hear the refrigerator sing. They thought my sister was inventing a story when she mentioned its song. When my children and I commented on the song, my brother-in-law and niece thought we were joining my sister in her joke. They could not hear those three sounds. As a result, they assumed that no such sounds existed.

We smell various scents when small particles of matter in the air reach our noses. Flowery perfumes, smoke, food cooking on the stove, freshly-cut grass, the plastic in a new car—all have distinctive odors that we notice when those particles enter our noses. Taste works like smell, except that we taste only the things that we put into our mouths. Sugar is sweet, acidic foods are sour, alkali foods are bitter, and salt is, well, salty. Chocolate is both sweet and bitter; lemonade is both sweet and sour. Whenever we taste something, our tongues report to our brains what we are eating, and our brains decide how much we like what we are eating. Most flavors combine both scent from the nose and sensations from the tongue, which is why food tastes different when our noses are obstructed due to colds or allergies.

The skin on our bodies includes nerve endings that tell us about the things we touch. These distinguish hot and cold, sharp and dull, soft and firm, and various other distinctions. They also report the intensity of contact, presenting pain when the touch is dangerous. The nerve endings in our skin are constantly reporting to our brains everything that touches them. The brain then decides how to react to the information it is receiving from our skin.

Our brains, then, are constantly responding to a variety of messages about sight, sound, scent, taste, and touch. Our brains are constantly judging which information to ignore and which information requires a response. If we are focused on one situation—if, for example, we are reading—the brain will ignore many of the other messages about sound and scent and touch that it receives. On the other hand, if we are reading and then smell smoke and hear the wail of the smoke detector, the brain decides to ignore the written message and to react to the other messages. While driving a car, we pay attention to many things: the road conditions, the behavior of other vehicles, and the signs and signals along the road, for example. We might listen to the radio, but the sound of a siren diverts our attention. If we smell gasoline, we wonder whether the source of that odor is from our vehicle, from the old pick-up truck next to us on the road, or from the gas station we just passed. If the ride is bumpy, we wonder if the pavement is rough or if a tire is going flat. We will notice other things—that car that just passed us has a license plate from Wisconsin; the price of gasoline went up four cents since yesterday. Our brains note some of the things reported to them, respond immediately to some, note others for later reflection, and ignore and forget many of the things our senses report. At any moment, our brains are discounting much sensory information as irrelevant—the touch of clothing on our arms, the ticking of the clock, the color of the floor and the walls, the lingering scents from our last meal. Our world is too busy; we could not survive if we continually noticed every sight and sound and scent and touch and tried to respond to all that information. And all this does not begin to address other information available to us, including memories and abstract concepts. J.

Our senses and our world, part one

We experience the world around us through our senses. Traditionally, we are attributed with five senses: sight, hearing, touch, taste, and smell. Taste and smell are similar enough in nature that they often are lumped together as one sense. At the same time, modern physiologists speak of other senses which we possess, such as the sense of balance. These additional senses tell us about our own body rather than about the outside world, so we can set those aside as we explore philosophy.

Still other people mention additional senses or sense-like perceptions. They suggest that we gather information about the world in ways that transcend the usual five senses. They speak of a sixth sense or of Extra-Sensory Perception (ESP). unfortunately, scientific investigation into those additional senses usually reveals either fraud or mere coincidence. Much of what we attribute to a sixth sense comes more from information acquired through the five senses and from rational (if often less than conscious) consideration of that information gathered in the present or remembered from the past.

So we are left with sight, hearing, touch, and taste-and-smell. Each of those involves input from the world beyond our bodies. Sight involves light, perceived by our eyes and reported to our brains. Hearing involves sound, perceived by our ears and reported to our brains. Touch involves contact with our skin, perceived by nerve-endings in our skin and reported to our brains. Taste and smell involve small particles that reach receptors in our mouths and noses that report to our brains what they perceive. In all these cases, our brains receive this information, evaluate its importance, and generate a response—ranging from ignoring the information to enjoying the experience, remembering the source of the stimulus so it can be repeated or avoided, or even rushing to flee from the cause of the stimulus.

Over the centuries, philosophers meditated on sight and discussed its significance. They pondered whether a color—white, for example, or red—was an essential part of an object or merely a characteristic of an object. They asked whether a color, such as white or red, can exist apart from an object. (Is the idea of whiteness real, or is it merely a label applied to all objects that have the characteristic of being white?) They debated how colors are perceived by our minds, and they asked whether we all see the same thing when we look at an object.

Modern scientists tell us that light comes in various wavelengths. Whiteness is a combination of wavelengths, which scientists demonstrate by shining white light through a prism, which breaks the light into the colors of the rainbow. Red and orange and other colors are distinct wavelengths of light. We see light emitted by some objects—the sun, of course, and flames, and wires or bulbs of light that glow due to electric current. Other objects reflect light. If the source of the light is red, the objects that reflect that red light will all look red. But white light shining on objects will have some wavelengths absorbed by the object and others reflected. As a consequence, when white light shines, we will see red objects and green objects and blue objects and many other colors as well.

Certain trees and other broad-leafed plants change color. In the spring and summer, they have green leaves. That green is caused by chlorophyl, which absorbs other wavelengths of light but reflects green light. In autumn, plants stop producing chlorophyl, and other chemicals in the leaves reflect other wavelengths of light—red, orange, yellow, or brown. Those leaves then fall off the plants and die, and in the spring new leaves are produced to replace them. We see different colors of leaves at different times of the year because of different chemicals in the leaves which reflect different wavelengths of light.

Arguably, an object in the dark has no color, because it is reflecting no light. An apple or tomato in the drawer of a closed refrigerator has the potential to be red, but it is not red when it is in the dark. (Yes, I know that apples and tomatoes last longer when they are not refrigerated, but the example is still valid.) Open the door of the refrigerator, let light shine on the apple or tomato, and they are red. They do not lose their ability to be red by being in the dark. But potential color is real color only when light is reflected by an object.

We see more than color. We also see shapes and sizes and other qualities of the objects within our view. Our brains are adept at interpreting what we see, even when what we see is a distortion of what is really there. This fact has caused some philosophers to wrestle almost endlessly with the relationship between sight and reality. For example, in the center of my reading room is a square table. Only by standing directly over it and looking down at it do I really see a square. From my favorite chair, or from the doorway, the table would not seem to be square. A photograph or painting from either perspective would contain a tabletop with four sides, but those four sides would not form a square. Yet not only do I recognize that the table is square from every other perspective; a visitor to my house, looking from the doorway into the reading room, would recognize that the table is square. Partly because we have two eyes (which provides some perception of depth) but more because our brains are effective at interpreting what our eyes report, we see the true shape of objects even when our perspective should distort the shape of those objects.

In the same way, I know that the person standing next to me is much shorter than a distant tree, even though the tree occupies much less of my field of vision than the nearer person. Our brains have awareness of depth perception and of the fact that distant objects are bigger than they appear. Therefore, our brains are fooled only when we cannot know either the size or distance of an object. Ancient philosophers and scientists thought that the sun was both smaller and nearer than it really is, because at the time they had no way of measuring its true size or its true distance. In most cases, though, people are able to estimate the size of seen objects accurately because of knowledge and experience of the world and of the way it works.

Yet our eyes can be fooled. A spoon in a glass of water appears to be bent because of the difference between the way light flows through water and through air. Distracted and preoccupied, our minds sometimes miss sights that our eyes have recorded or wrongly interpret what they eyes report. And, naturally, we cannot see things when something else is in the way—we cannot see the apple in the refrigerator when the refrigerator door is closed. Our experience of the world, as gained through sight, remains limited.

And we do not always see what other people see. In 2015, a woman photographed a dress in a store and sent the digital photograph to her daughter. The dress was blue and black, but when the daughter saw the photograph, she thought she was looking at a photograph of a white and gold dress. Over the following months, millions of people saw the same photograph. Even looking at the same photograph on the same device at the same time, some saw a blue and black dress, while others saw a white and gold dress. Our minds process information received from the eyes in a variety of ways, drawing clues about color and shape and size from many past experiences and impressions. Living in the same world, we do not always experience the same thing. Reality does not change from person to person—the real dress was blue and black. But perception and interpretation can lead to differences, sometimes such significant differences that we appear to be living in different worlds. J.