Modes of CommunicationValerie, Timmy, and Robyn all used various communication modes to convey multi-symbol messages (see Table 3). The percentages of occurrence for each mode varied across children. The children tended to use signs when they did not have access to a concept via their aided AAC systems. This was the case for 96% (48/50) of Valerie’s signs and 94% (50/53) of Timmy’s. For Robyn, most of her signs (i.e., 68%; 23/34) consisted of the sign for HOT, for which she did not have access via aided AAC. For seven of her nine remaining signs, she provided the sign immediately after selecting these same concepts via aided AAC.