How people come to understand ideas and stories from sensing meaningless physical marks is a fascinating topic as well as being of practical importance. It addresses the relations between perceptual, linguistic and cognitive processes which are at the heart of the question how the human cognitive system operates. To ask how we read by touch opens a further window on these connections, because we know relatively little as yet about how touch works and how it transmits information. The question is not only of scientific interest. Reading by touch is an important alternative and additional source of information when sight is absent, or is lost later in life.
Reading has been called 'visible language' or 'visible speech'. The phrase is interesting, because it emphasizes the linguistic nature of reading. But it also suggests that to read is to understand language by means of vision. There is no comparable phrase such as 'tactile language' or 'felt speech', although reading by touch is the most important means of written communication for blind people. Visual reading is, of course, more common. But there is also a tacit assumption that touch is perceptually much the same as vision, if less clear, and that lower level perceptual processes do not, in any case, need to be included as factors in models of how reading takes place.
The studies on which this book is based suggest an almost opposite view on both points. The studies were motivated originally by research on intersensory processes which showed that touch produces poor spatial and shape information for perception and memory. Such findings raised questions about the basis of perception by touch, and particularly how it relates to language, to which I could find no easy or simple answer. To read means to understand heard language through another sense modality, and involves much the same language skills. But braille takes a relatively long time to learn, and tends to be slow. Nevertheless, reading can become fast and fluent. How does this come about? What makes reading by touch difficult? In what respect does it matter that language is conveyed by touch rather than by vision, and whether the physical inputs are composed of raised dot patterns or of shapes made up of lines and curves? How