GeneralizationOnly those children who reached criterion during intervention participated in the generalizationphase. Both Valerie and Timmy exceeding criterion during this phase (i.e., 16 and 18 combinations and 17 and 23 combinations, respectively). Thus, Valerie and Timmy (a) generalized production of multi-symbol messages to new play routines, and (b) did not require aided AAC models to produce multi-symbol messages within these playscenarios.