Objective: This study evaluated the effects of an idiosyncratic stimulus (Legos plastic blocks) on vocal stereotypy by a child with pervasive developmental disorder during functional analysis sessions conducted in analogue and natural settings.
Methods: The presence and absence of the idiosyncratic stimulus was controlled in a multielement experimental design that incorporated four functional analysis conditions.
Results: The background presence of the idiosyncratic stimulus was associated with a higher percentage of vocal stereotypy in all functional analysis sessions in both settings when compared with phases where the stimulus was absent.