The effect of two procedures on spontaneous signing with Down's syndrome children.

In this study, two procedural aspects were investigated with regard to their effect on spontaneous use of manual signs with three Down's syndrome children. First, two modes of presenting reinforcement for spontaneous sign requesting were compared. Second, the effect of a least-to-most prompting procedure was evaluated. Within a randomization design, a statistically significant difference was observed between the two modes in favour of the one in which only a part of the sign-requested reinforcement was initially presented. Within a mixed design of reversal and multiple baseline, introduction of the least-to-most prompting procedure resulted in an increase of the spontaneous use of the target signs, while withdrawal of the procedure resulted in a decrease.