1. Department of Communication Sciences and Disorders, Northeastern University, Boston, MA, USA
2. Department of Otolaryngology and Communication Enhancement, Autism Language Program, Boston Children’s Hospital, Waltham, MA, USA
3. Centre for Augmentative and Alternative Communication, University of Pretoria, Pretoria, South Africa
4. MGH Institute of Health Professions, Charlestown, MA, USA
5. Department of Linguistics, Massachusetts Institute of Technology, Cambridge, MA, USA