Different Multi-Symbol MessagesValerie, Timmy, and Robyn demonstrated increases in their productions of different two symbol combinations during the intervention phase (see Table 2).Data were also collected on the ratio of the number of different symbol combinations acrossall sessions, compared with the total number of symbol combinations across all sessions. The higher the ratio, the greater the diversity: a ratio of 1.0 would indicate that a child never produced the same multi-symbol message twice throughoutthe course of the investigation; conversely, a ratio of 0.1 would indicate that a child frequently produced the same symbol combinations (i.e., only 1 in 10 symbol combinations had not been produced previously). Valerie, Timmy, and Robyn’s ratios were 0.67, 0.78, and 0.73, respectively.