Tactile Slit Scanning of Letters

Various attempts have been made to present visual pattern information via hearing and touch. Most of this research has been aimed at the development of reading machines for the blind. The results are of psychological interest as they relate to the problem of substitution of one sense modality for another. A common aural reading system consists of a vertical slit behind which is a row of photocells, a transport system to move letters horizontally past the slit, and a set of audio-oscillators triggered by the photocells (Freiberger & Murphy, 1961 ). The device is arranged so that the bottom parts of letters will trigger low tones, middle parts trigger medium tones, and upper parts trigger high tones. Thus, a row of letters being scanned will sound like a varying collection of chords for the duration of scan time. After prolonged practice, single letter recognition was about 81% and paragraphs were read at an average of 10 words per minute (Abma, et al., 1960). Recent unpublished work at the National Physical Laboratory in Teddington, England, found a tactual system, using .5-in. high letters embossed on heavy paper, to be superior to two aural devices, both in speed and accuracy of recognition. Using a self-paced scanner, which permitted S's control of the rransport velocity of letters and which presented letters in their entirety, 98.4% accuracy was achieved with a speed of 3.65 sec. per letter. When transport velociry was mechanically controlled, so that the whole letter was available to S for 0.5 sec., accuracy of discrimination was 72.16% after a brief practice period and was still superior to the scores obtained on their tests of aural machines. Earlier studies of tactile reading by Austin and Sleight employed Masonite letters, symbols and numbers about .5 in. high. The forms were mounted on a disk which rotated 360°, exposing one whole letter rhrough a rectangular opening in a covering plate. Their first study compared 46 letters, symbols, and numerals for difficulty (1952a). The second study employed those forms which had produced 90% accuracy. In only eight sessions, their Ss learned to discriminate the test material with 100% accuracy at a rate of 3.52 sec. per letter ( 1952b). All of the above tactile research involved presentation of entire letters. The auditory systems, employing slit scanning of a letter, require a temporal integration by S. The one known attempt to employ tactile slit scanning was