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Home > AAC Features > Selection Set > Message Retrieval Strategies 3. Message Retrieval StrategiesOnly the smallest devices show all the available vocabulary at once. Devices with a larger capacity can only show some vocabulary and require the user to "retrieve" words that are not readily visible at first. An individual who is not able to use a retrieval method, or does not use it proficiently, will be unable to use that additional vocabulary during communication. There are three different ways that users can "retrieve" vocabulary in AAC devices:
A. Levels and Overlays
Levels and overlays are most often used with communication boards and books and low-tech voice output devices. Some devices can store only one level of vocabulary, represented on a single overlay with symbols.
Some devices store more vocabulary, but someone has to change the paper overlay to view the new symbol set AND change the "level" in the device, typically by pressing a sequence of buttons.
B. Dynamic DisplaysDynamic display systems are similar to devices with levels and overlays, but the levels and displays change automatically with the touch of a button. When the user touches a certain symbol, the display changes to show the next level of choices. For example, if the user selected the food symbol, he might get a choice of drinks, meals, and snacks.
According to Blackstone (1994), dynamic displays can be challenging for AAC users because of demands on memory, visual attention, and decision-making skills. If you've ever gotten lost while browsing through multiple open windows on the Web, you may understand why.
Some devices with dynamic displays have very small screens, such as the Hand Held Voice below. This means that the same amount of vocabulary would require far more screens for the individual to navigate through.
C. Encoding
Encoding is a technique in which the user retrieves a word, phrase or sentence by selecting a predetermined sequence of items. Codes can be based on numbers (e.g. 1-2-3 = I love you) or alphabet letters (e.g. ILY = I love you) or letters and numbers (e.g. I3 = I love you) or symbols (e.g. EYE + HEART = I love you). There are many different ways to encode information. The best strategies organize information in a logical fashion with easy-to-remember codes for retrieval. If you've ever used keyboard shortcuts on your computer, you know it's much easier to remember ones like Control-S (to save a document) and Control-C (to copy something) than F8 (who knows what it does?). Symbols are reported to be even more memorable than numbers and letters. It has been reported that encoding places demands on the user's cognitive, perceptual, and learning abilities as the code sequences are learned. (Dowden & Cook, 2002)
There's some evidence that encoding-based systems can become automatic to the user. He or she can learn to make the movements to produce the message without thinking consciously about the location of keys on the display. This phenomenon has been observed in both devices with static, unchanging displays (e.g., Minspeak symbol displays) as well as in devices with no displays (e.g., Morse code-based system). This is likely to speed up message composition. D. Combination of Retrieval MethodsPrentke Romich's Pathfinder™ device combines two retrieval methods: dynamic displays and encoding.
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