The Effects of Message Encoding Techniques on Recall by Literate Adults Using AAC Systems

The study investigated the information processing demands of three different approaches to message encoding: letter codes based on the first letters of salient words in the message; letter category codes based on the first letters of a category plus a specifier; and iconic codes derived from-the icons and semantic associations proposed by Baker (1982, 1987). Six nonspeaking, functionally literate, physically disabled adults participated in the study. Three counterbalanced conditions, corresponding to the three message encoding techniques, were presented to each subject. Within each condition, subjects were given 15 minutes of study time to learn a list of 30 messages and their two element codes. Half of the messages involved concrete referents; the other half involved abstract concepts. After a 40 minute retention interval spent in conversation with the investigator, the subjects were randomly presented with contexts that necessitated the messages- use and were tested for their recall of the codes. The results indicated that the subjects were significantly more accurate recalling the salient letter codes than the codes within the other two message encoding techniques. The recall of the codes was significantly better for concrete messages than for abstract ones. The findings suggested that the potential to accelerate communication rate through preprogramming messages depends critically on the cognitive demands of the specific encoding technique used.