ABSTRACTThe authors report two experimental studies which addressed the question of how children with mental handicaps can be taught to generate productive, two‐sign combinations; that is, correctly to recombine signs in a way not previously taught. The basic approach, matrix training, involved teaching a specific subset of sign combinations corresponding to the overlapping diagonal items in a matrix of all possible combinations.In Experiment 1, the matrix items consisted of stimuli produced by combining character and facial expression elements. In Experiment 2, the matrix was formed from colour and object elements. In both studies, matrix training was successful in teaching children to use multiple signs to label the multiple attributes of training items. However, the productive recombination of signs only occurred in Experiment 2, with children who, prior to matrix training itself, had acquired sign labels for the elements which made up the matri