Date of Award


Degree Name

Doctor of Philosophy



First Advisor

Dr. Alan D. Poling

Second Advisor

Dr. Richard Malott

Third Advisor

Dr. Ron Van Houten

Fourth Advisor

Dr. Mitch Weisbrod


Autism, PECS, manding, adults, vocal speech, twins


This study examined the effectiveness of a Picture Exchange Communication System (PECS) on increasing manding (i.e., making requests) and spontaneous vocalizations. Participants were a set of identical twin adult women, both with a diagnosis of autism. The main dependent variable was the number of mands emitted by the participants while utilizing PECS. During each phase of training, participants had to meet a specific criterion before receiving a preferred item. Once the participants met the criterion for each phase of PECS training, a new phase began. Spontaneous vocalizations were tracked during each phase of training to determine if, as previous studies have shown in children, spontaneous vocalizations increase during Phase IV of PECS training. Additionally, the percentage of sessions that were terminated as a result of aggressive responding were also tracked.

A multiple-baseline across participant design was used in this research, with the training phases being implemented at different times for the two participants. Participants were assessed on their overall manding abilities (pointing, nodding, signing) as well as their use of pictures prior to the start of baseline. During baseline the participants averaged 0% use of pictures to mand for desired items. After PECS training was completed, the use of pictures to mand for desired items averaged 96.63% for participant 1 and 98.26% for participant 2. Two weeks, four weeks, and six weeks after training was completed, probe sessions were conducted to ensure that the participants had maintained their ability to communicate using PECS, and the participants averaged 100% usage of pictures to mand for desired items during the probe sessions. These results suggest that PECS, which has previously proven useful in teaching children with autism to mand, is also effective with adults. In contrast to previous findings with children, however, many of whom began to spontaneously verbalize during PECS training, the two adult participants in the present study did not verbalize. Participant 1 showed an overall decrease in the percentage of sessions terminated due to aggressive responding throughout training. Further research to examine the value of PECS training in teaching manding with adults, and to examine whether such training can generate vocalizations, is warranted.

Access Setting

Dissertation-Open Access