COMMUNICATION BY ELECTRICAL STIMULATION OF THE SKIN.

Abstract : For the past two years, a project has been underway to construct an electrocutaneous code, to teach this code to a group of subjects, and to evaluate its usefulness. A code was constructed in which stimuli were varied in three stimulus dimensions. There were ten loci, the ten fingertips, two stimulus durations, and two stimulus intensities. Each signal in the code was characterized by one of the ten loci, one of the two durations, and one of the two intensities. This arrangement resulted in the stimulus alphabet of 40 signals. Twenty-six of these signals were paired with the 26 letters of the alphabet. The remaining signals were paired with punctuations and with frequently recurring letter groups such as 'ing', 'er', and 'and'. Subjects have received training in the reception of this code for over a year. On the reception of unfamiliar prose, a few subjects have shown word rates as high as 20 words per minute. Three of these better subjects were each given fifteen random permutations of the code signals, and their performance was summarized in a stimulus - response matrix. Work was also begun on another electro-cutaneous code in which signals were formed from patterns of simultaneously applied dc pulses. Although this work is still in the pilot stage, preliminary results suggest signals formed in this way may be much better than those formed by combining stimulus dimensions with respect to reaction time. Reaction times to signals in the locus pattern code appear to be two or three times as short as the reaction times to signals in the tri-dimensional code.