Читать книгу The Form Within - Karl H Pribram - Страница 73

We are able to perceive objects as the result of relative movement of ourselves within the world we navigate. Thus, objects can be regarded as constructions by our brain systems that are computing the results of those movements.

When I use the term “construction,” I do not mean that what we navigate is not a real world. When I hit my shin on the bed rail, I don’t doubt, no matter how sleepy I may be, that the navigable world of bed rails is real. This lack of doubt forms a belief that is based on our early experience.

I first understood how a belief is involved in our perception of an objective world while at a conference held at Esalen, the famous West Coast spa and retreat. The situation was somewhat bizarre, as the theme of the conference was brain anatomy. During the conference, we were introduced to some of the New Age exercises. One of these involved all of us stodgy scientists being blindfolded and going around the campus feeling bushes, flowers, and one another’s faces. It was a totally different experience from our usual visual explorations and resulted in my becoming aware of the distinctiveness of perceptions derived from different sensory experiences.

It immediately occurred to me that as babies, we experience our mothers and others around us in different ways with each of our various sensory systems. Each of these experiences is totally different. As we quickly learned at Esalen, our visual experience of a person is very different from our auditory experience of that person, and different still from our experience of touch or of taste! Somewhere along the line, as we process these various inputs, we make a leap of faith: all these experiences are still experiences of the same “someone.” In the scientific language of psychology, this is called the process of “consensual validation,” validation among the senses.

As we grow older, we extend this faith in the unity of our experiences beyond what our various sensory explorations tell us, and we include what others tell us. We believe that our experiences, when supported by those of others, point to a “reality.” But this is a faith that is based on disparate experiences.

The English philosopher Bishop George Berkeley became famous for raising questions regarding this faith. He suggested that perhaps God is fooling us by making all of our experience seem to cohere, that we are incapable of “knowing” reality. Occasionally other philosophers have shared Berkeley’s view, which is referred to in philosophy as “solipsism.” I suggest that, distinct from the rest of us, such philosophers simply didn’t make that consensual act of faith when they were babies.

An extreme form of consensuality is a psychological phenomenon called “synesthesia.” Most of us share such experiences in milder form: red is a hot color, blue is cool. Some thrilling auditory and/or visual experiences actually make us shiver. Those who experience synesthesia have many more such sensations—salty is cool; peppery is hot— to a much greater degree.

The usual interpretation is that connections between separate systems are occurring in their brains, “binding” the two sensations into one—connections that the rest of us don’t make. Instead, it is as likely that synesthesia is due to a higher-order abstraction, similar to the process previously described where I asked those students to raise their hands if they wear glasses and also blue jeans. Eyeglasses and blue jeans are conjoined in their response. In my laboratory at Stanford, we found that many receptive fields in the primary visual cortex respond not only to visual stimuli but also to limited bandwidths of auditory stimulation. Still other conjunctions within a monkey’s receptive field encoded whether the monkey had received a reward or had made an error. Other investigators have found similar cross-modal conjunctions, especially in motor cortexes of the brain. A top-down process that emphasizes such cross-modal properties could account for synesthesia such as the experience of bright sounds without recourse to connecting, “binding” together such properties as hearing and seeing from two separate brain locations.

Our faith arising from consensual agreement works well with regard to our physical environment. Once, when I was in Santiago, Chile, my colleague, the University of California philosopher John Searle rebutted the challenge of a solipsist with the statement that he was happy that the pilot of the plane that brought him through the Andes was not of that persuasion. The pilot might have tried to take a shortcut and fly right into a mountain since it “really” didn’t exist.

When it comes to our social environment, consensuality breaks down more often than not. Ask any therapist treating both wife and husband: one would never believe these two inhabited the same world. The film Rashomon portrays non-consensuality beautifully. In later chapters, I will examine some possibilities as to how this difference between social and physical perceptions comes about.

I am left with an act of faith that states that there is a real world and that our brain is fitted to deal with it to some extent. We would not be able to navigate that real world if this were not so. But at the same time, well fitted as our brains are, our experience is still a construction of that reality and can therefore become misfitted by the operation of that brain. It is the job of brain/behavioral science to lay bare when and how our experience becomes fitting.

In the section on communication we will look at what has been accomplished so far. From my standpoint of a half-century of research, both brain and behavioral scientists have indeed accomplished a great deal. This accomplishment has depended on understanding how the brain makes it possible for us to more or less skillfully navigate the world we live in. This in turn requires us to understand brain functions in relation to other branches of science. Thus, a multiple front of investigators has developed under the heading of “cognitive neuroscience.” This heading that does not do justice to the breadth of interest, expertise and research that is being pursued. For perception, the topic of the current section of this book, the link had to be made primarily with physics. In this arena, theory based on mathematics has been most useful.