A study of the tactual and visual reception of fingerspelling

A method of communication in frequent use among members of the deaf-blind community is the tactual reception of fingerspelling. In this method, the hand of the deaf-blind individual is placed on the hand of the sender to monitor the handshapes and movements associated with the letters of the manual alphabet. The purpose of the current study was to examine the ability of experienced deaf-blind subjects to receive fingerspelled materials, including sentences and connected text, through the tactual sense. A parallel study of the reception of fingerspelling through the visual sense was also conducted using sighted deaf subjects. For both visual and tactual reception of fingerspelled sentences, accuracy of reception was examined as a function of rate of presentation. In the tactual study, where rates were limited to those that could be produced naturally by an experienced interpreter, highly accurate reception of conversational sentence materials was observed throughout the range of naturally produced rates (i.e., 2 to 6 letters/s). In the visual study, rates in excess of those that can be produced naturally were achieved through variable-speed playback of videotapes of fingerspelled sentences. The results of this study indicate that performance varies systematically as a function of rate of presentation, with scores of 50% correct on conversational sentences obtained at rates of 12 to 16 letters/s (i.e., rates roughly double to triple normal speed). These results suggest that normal communication rates for the visual reception of fingerspelling are restricted by limitations on the rate of manual production. Although maximal rates of natural manual production of fingerspelling correspond to the presentation of a new handshape on the order of once every 150-20 ms, the data from the sped-up visual study suggest that experienced receivers of visual fingerspelling are able to receive sentences at substantially higher rates of fingerspelling (which are, in fact, comparable to communication rates for spoken English).