Abstract
Eight moderately retarded children were trained on a simultaneous two-choice discrimination problem and a series of discrimination-shift problems. The procedure required the subjects to perform overt observing responses to produce elements of the discriminative stimuli, making it possible to measure directly changes in attention to different aspects of stimuli during learning. The patterns of change in observing responses were generally in line with descriptions of attentional changes derived from two-process theories of discrimination learning; for example, the frequency of irrelevant observing responses was high during the presolution period during extradimensional shifts but was low during intradimensional shifts. Contrary to current theories, extradimensional shifts caused an immediate increase in irrelevant observing responses, and intradimensional shifts usually caused an increase in relevant observing responses. Subjects responded to later shift problems by initially increasing both relevant and irrelevant observing responses, then withholding irrelevant observing responses.