Training EMR children to solve missing minuend problems errorlessly: Acquisition, generalization, and maintenance

The present study evaluated an errorless procedure for teaching EMR students to solve missing minuend problems (i.e., missing number problems starting with a minus sign). The study consisted of two experiments, with two phases of training in each. The first phase was directed at establishing a nonnumerical, differentiated response to a prompt, the shape of which was gradually transformed to make the discriminative stimulus. The second phase was designed (a) to extend the control of this stimulus to the required numerical operations, and (b) to gradually eliminate the first trained nonnumerical components of the response chain and the experimental conditions (presence of the experimenter and immediate feedback) used for acquisition training. Five subjects participated in Experiment I, and four in Experiment II. The results indicated that seven subjects acquired the target skill in a nearly errorless fashion in 75 to 172 minutes of individual training time. The two other subjects required several programmatic alterations before completing the training. Their total training time was much longer, that is, 212 and 318 minutes, respectively. Moreover, the obtained findings revealed that whenever measured, the acquired skill transferred to similar, more advanced problems, and was maintained over periods ranging from several weeks to several months. The technical aspects are discussed in terms of the literature on stimulus control by prompts. Attention is also given to the educational relevance of the acquired skill.