Stimuli really is important!
One of the biggest challenges to home programming in behavior therapy is that often cash constrained parents are responsible for coming up with the new toys to teach new skills. This is actually a huge problem. According to L.J. Kamin, if you use a stimulus to teach a response and then try to teach a new response with the same stimulus, you have actually blocked the new learning by using the old stimuli. In young children where teaching new concepts is the objectives, each objective should have very different stimuli associated with it. The blocking effect is well documented. So agencies which supply behavior therapists should also apply stimulus materials which support their curriculum, otherwise they could actually be retarding the learning of the very students they aim to help!