Asymmetrical stimulus control and the mirror-image problem

An analysis of the mirror-image discrimination literature revealed a number of inconsistent and paradoxical results. A unifying conception was proposed and it was argued that lateral mirror-image stimuli constitute a special class of problems on which effective performance is related to the introduction of an asymmetrical event into the task. Some implications were derived and tested in two experiments. First, five different response modes were compared for children required to discriminate two lateral or up-down mirror-image stimulus pairs. Acquisition was significantly faster on the latter problems. On the former, it was shown that responding to just one side of the lateral mirror-image stimuli led to significantly faster learning. Subsequent generalization tests indicated control by one part of the stimulus display for those who responded to one side. Next, Ss unable to learn the problem in Experiment I were given further acquisition trials. Only those children given training designed to promote selective stimulus control learned the problem.