TACTILE PATTERN PERCEPTION
This part of the book is about tactile pattern perception. Most of us tend to think about the performatory role of the hands, that is, we focus on the use of the hands for action and manipulation of objects. However, all of us make use of the sense of touch to obtain information about the shapes of objects we manipulate, and for the detection of two-dimensional patterns. We use our hands while typing on a computer keyboard, and rely on our proprioceptive/spatial "knowledge" about the layout of the keys to permit typing. We can tell when we have hit a key through auditory and tactile feedback. It should be clear that we may know the position of the keys, even though we might not be able to provide oral directions for their location on the board. Nonetheless, we have no difficulty accurately typing while looking at the CRT screen with foveal vision. Very blurry peripheral vision of the keyboard remains, of course, but it is insufficient for identification of the key names. Thus, we often take haptic/tactual skills for granted, while the focus of our attention is directed toward visual matters.
The first chapter in this part, by Appelle, is concerned with pattern perception per se. Most of the research in this field has involved two-dimensional arrays. It is certainly hard to know how much of this information will generalize to three-dimensional configurations, as some researchers believe that the sense of touch is better suited for apprehension of solid, 3-D configurations. We will return to this issue in the concluding chapter of this volume, but we should point out that the study of tactile illusions leads to a general caution in this area. Touch and vision are affected rather differently by orient-