Developing the Alphabetic Principle to Aid Text-Based Augmentative and Alternative Communication Use by Adults With Low Speech Intelligibility and Intellectual Disabilities

Abstract

Purpose: We explored alphabet supplementation as an augmentative and alternative communication strategy for adults with minimal literacy. Study 1's goal was to teach onset-letter selection with spoken words and assess generalization to untaught words, demonstrating the alphabetic principle. Study 2 incorporated alphabet supplementation within a naming task and then assessed effects on speech intelligibility.

Method: Three men with intellectual disabilities (ID) and low speech intelligibility participated. Study 1 used a multiple-probe design, across three 20-word sets, to show that our computer-based training improved onset-letter selection. We also probed generalization to untrained words. Study 2 taught onset-letter selection for 30 new words chosen for functionality. Five listeners transcribed speech samples of the 30 words in 2 conditions: speech only and speech with alphabet supplementation.

Results: Across studies 1 and 2, participants demonstrated onset-letter selection for at least 90 words. Study 1 showed evidence of the alphabetic principle for some but not all word sets. In study 2, participants readily used alphabet supplementation, enabling listeners to understand twice as many words.

Conclusions: This is the first demonstration of alphabet supplementation in individuals with ID and minimal literacy. The large number of words learned holds promise both for improving communication and providing a foundation for improved literacy.

Figure 1.

Computer screen displays for one trial of onset-letter selection training.

Figure 2.

Flowchart of training and testing sequence within a single word set.

Figure 3.

The percentage of correct onset-letter selections in the comprehensive tests for Mark and Jimmy. Panels represent word sets and are arranged from top to bottom in the order in which they were trained with each participant. The first phase line indicates the completion of sound to letter training. The second phase line indicates the completion of spoken-word to onset-letter training.

Figure 4.

The percentage of correct onset-letter selections in generalization tests for Mark and Jimmy. Rimes within the word pairs are shown along the x-axis, and the onsets are shown within the field of each graph. For example, Mark's first word pair was sip/tip. White triangles show pretest data, and bars show generalization (untrained word pairs). Solid gray bars represent added word pairs (not pretested). For Mark's final five word pairs, we tested first without feedback (black bars), and then without feedback on every test trial.

Figure 5.

Mean overall speech-intelligibility percentages for Aaron, Mark, and Jimmy in the speech-only condition and in the speech-with-alphabet-supplementation condition.