Word Prediction
Three language representation methods are used in AAC:
1) Single Meaning Pictures;
2) Alphabet-based methods; and
3 Semantic Compaction.
Each method has its own attributes, strengths and weaknesses. Alphabet-based methods can be further divided into:
a) Spelling;
b) Word prediction; and
c) Orthographic word selection (direct access to printed whole words).
Of the various ways to characterize communication performance, people who use AAC can achieve the performance of naturally speaking individuals in every area except one: communication rate. For this reason a major emphasis in AAC device development and AAC service delivery is communication rate.
For nearly everyone who uses AAC, faster is better.
In the early days of microprocessors and personal computers, it was possible to implement word prediction systems and this was done. The expectation was that the clear and significant keystroke savings would translate into enhanced communication rate. However, when research was done the results were generally surprising. Research studies showed that the keystroke (selection) savings was offset by increased time per keystroke. The net effect was no statistical rate enhancement. This was true even for slow selection methods (row-column scanning). Three peer reviewed papers appeared in 1994 with these results. AAC Institute has obtained the necessary permissions to be able to make them available here. We are not aware of any research that has attempted to replicate these studies or has been published showing different results.
Links to other peer reviewed research relating to word prediction are invited. If permission can be obtained, other papers will be added to this site.
AAC service delivery professionals, families and individuals who use AAC who are measuring communication performance are reporting results that are consistent with the above research. Communication rate using word prediction ranges from slighty slower than spelling to slightly faster. Item L in the sample AAC Performance Report shows word predication to be 5.5 words per minute as opposed to spelling at 4.4 words per minute for this individual. (This individual was a young adult with cerebral palsy with an associate degree. The language sample was collected after three months of experience with this AAC system. The previous system provided access to spelling and word prediction.)
To learn more about available tools to support this important personal component of evidence-based practice, visit the AAC Institute home page and look under Products.
While word prediction may not include significant enhancement of communication rate, other benefits may be valuable to some people who use AAC. The keystroke (selection) reduction associated with word prediction may save energy and thus reduce fatigue. However, it may be prudent to use word prediction only for extended vocabulary access. Careful consideration should be given to analyzing the significant performance compromise that use of word prediction may represent for core vocabulary access relative to other methods that offer similar keystroke reduction with potentially much higher communication rate.
To learn about other methods that offer keystroke reduction similar to word prediction, but actually result in communication rate enhancement, consider taking the free Self-Study Program course on AAC Symbols and Language Representation Methods.
* "This article has been reproduced and originally appeared in [RESNA’s Assistive Technology, 1994, volume 6]. For purchase, subscription and membership information, contact RESNA, Suite 1540, 1700 North Moore Street, Arlington, VA 22209-1903.”
** Copyright ©2004 Institute of Electrical and Electronics Engineers. Reprinted from IEEE Transactions on Rehabilitation Engineering. Vol. 2, No. 3.
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*** Made available with permission. Taylor & Francis Group AAC is the official journal of ISAAC (International Society for Augmentative and Alternative Communication). www.informaworld.com/AAC
