autism to increase compliance, enhance communicative initiations and responses, and decrease verbal prompt dependence (Mirenda and Santogrossi, 1985; Steibel, 1999). Communication partner training in using visual symbols, with parents, practitioners, and peers has been shown to be relatively simple (Steibel, 1999; Garrison-Harrell et al., 1997; Cafiero, 1995).

Because children with autism have difficulty pointing and show strengths in using contact gestures, they may benefit from using a giving gesture to make choices or indicate a selection from an array of objects or visual symbols. The most widely used exchange system, the Picture Exchange Communication System (PECS) (Frost and Bondy, 1994), is a structured program that teaches the exchange of symbols for communication. PECS is a systematic behavioral program that teaches a child to initiate communicative requests by approaching the communication partner and exchanging the symbol for the desired object. It includes protocols for expanding communication from single to multiple words and for increasing communicative function from requesting to labeling and commenting. Bondy and Frost (1994) reported a case review of a group of preschoolers with autism who were taught PECS. Of 19 children who used PECS for less than 1 year, only two (10%) acquired independent speech, while five used speech with PECS, and 12 children used PECS as their sole communication. Of 66 children using PECS for 2 years, 39 (59%) developed independent speech, 20 developed speech as they used PECS, and 7 used only PECS. Thus, for most preschoolers introduced to PECS, it took more than 1 year after initiating PECS to observe independent speech, and many continued to have very limited spontaneous use of language. Speech tended to develop once the children were able to use 30–100 symbols to communicate (Frost and Bondy, 1994). Furthermore, the overall communication development of the children was strongly related to their overall level of intellectual functioning.

The only other published study using PECS was reported by Schwartz et al., (1998) on 11 children with autistic spectrum disorders who attended an integrated preschool. These children required an average of 11 months to exchange “I want+symbol” sentence strips with adults and 14 months with peers. In this study, 6 (55%) of the 11 children developed functional and complex speech, and the 5 who did not were able to use PECS effectively to communicate. The authors state, however, that their study did not control for maturation or the effects of other components of their school program. Whether comparable outcomes with PECS and the concomitant development of speech would be expected without the specific intervention or with older children is not known.

There is even less research on the effectiveness of other AAC systems used by children with autism. A voice output communication aid (VOCA) is a portable AAC device that produces synthesized or digitized (re-



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