Conceptually Accurate Signed English transliteration: effects of accuracy and lag time on message intelligibility

This paper, the 6th in a series about the level of access afforded to students who use educational interpreters, examines the intelligibility of messages produced by Conceptually Accurate Signed English (CASE) transliterators. Eight highly skilled receivers of CASE evaluated the intelligibility of messages that varied in accuracy and lag time. Results of intelligibility tests showed that (1) overall intelligibility (40%) was considerably lower than average accuracy (58%), (2) accuracy played a smaller role than expected in intelligibility, and (3) the relationship between accuracy and intelligibility likelihood was roughly sigmoidal in shape, with intelligibility likelihood falling fastest as accuracy drops below 65%. Mouthing was the primary factor in intelligibility of all words in the message, explaining 24% of the variance; accuracy accounted for another 6%. The roles were reversed for key words (accuracy accounted for 15% of variance; mouthing explained 6%). Lag time had no contribution after accounting for accuracy and mouthing, but utterances with lag times between 0.5 and 1.5 s were most likely to exceed 70% intelligibility. Future work should investigate sources of transliterator variability (e.g., speechreadability, presentation rate) and other communication options (e.g., American Sign Language) in order to ensure accessibility for all students who use educational interpreters.