Effects of an idiosyncratic stimulus on functional analysis of vocal stereotypy in two settings.

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.

CONCLUSIONS

The presence or absence of specific stimuli can alter the results of a functional analysis and produce inaccurate conclusions about the environmental conditions that occasion problem behavior.