THE COMPLEXITY OF OUR PERCEPTIONS

Because it is possible to isolate particular sensations and study them in detail, as we have attempted to do here, it must not be assumed that we customarily experience them in so simple a manner. Even at birth the human nervous system is a tremendously complicated affair. There are cross connections among the senses. From the very first most of our sensations seem to us completely bound up with other processes. A pure sensation is a very rare occurrence. A color is nearly always the color of something—of cloth or leather or paper or liquid. All of the objects which have colors have textures also. They look rough or smooth or glossy or dull. And the color and texture seem inalterably mixed together. It is only when we look at a rainbow or the rays of a spectroscope that we see a color which does not appear to be an integral part of some object.

Tones seem to belong less to the objects which produce them—to exist by themselves to a greater degree. Yet it is much more difficult to produce a simple tone than a pure color. In this case the trouble lies not so much with the nervous system as in the physical stimulus itself. There are not as many audible tones as there are discernible colors and odors, but there are some eleven thousand of them. The tone got from a musical instrument is not, however, a simple tone or a pure sensation. It is a combination of many tones, some of which are more intense than others. These extra tones or partials are produced by the musical instrument itself and they cannot be eliminated because a musical instrument is essentially a complicated vibrating body. With each vibration it produces over-tones as well as a principal tone. It is the different intensities of the partial tones which give timbre to instruments. It is by their characteristic timbres that we are able to distinguish a G struck on a piano from the G of an organ or a violin or a saxophone.

Because it is so difficult to produce simple tones, psychologists have been unable to discover a great deal about our sense of audition. The physical side of sound has been adequately investigated, but we have to resort to musical terminology when we try to describe the sensations which are produced.

We have already discovered, then, in the case of the three lower senses, our perceptions appear so unified that we seldom realize that they are complex. Wetness seems to be a unique experience until we recognize that it is composed of cold and pressure. So completely blended are our tastes and smells that a severe cold in the head is required for their conscious separation. And psychologists had to wait for years, until a soldier had a strange cortical injury, before they learned how complicated a process is tactual localization.