Using a combined blocking procedure to teach color discrimination to a child with autism.

A combined blocking procedure was used to teach a child with autism to select two colors on request. First, two color cards were placed at fixed locations on a table and the experimenter repeatedly requested the child to touch one of the colors. After 10 consecutive correct selections, the child was asked to touch the other color. Blocks of trials with each color were systematically thinned until requests were presented randomly with few errors. Subsequently, the location of the selection cards was systematically alternated until the child was able to touch the correct card when both requests and card positions were presented in random fashion.