“…Sometimes, the treatment package that involves speech output is compared to a control condition involving no aac modalities (e.g., Kasari, Kaiser, Goods, nietfield, & Mathy, 2014). Second, two aac treatment packages may be compared to one another, whereby one package includes a speech output technology and the other package includes aac modalities other than speech output (e.g., Boesch, Wendt, Subramanian, & hsu, 2013a). Third, speech output may be isolated as an independent variable to study its specific impact when comparing the presence versus absence of speech output; for example, Parsons and laSorte (1993) studied whether the use of a computer-based SGd with the speech output on would result in greater vocalizations in children with autism than with the speech output off.…”