In experiments on individual differences in learning, knowledge prerequisites and learning strategies have been shown to be important factors. The author questions whether learning optimization should rely on direct measures from outside the learner or should elucidate and strengthen the individual's capacity for learning decisions. He proposes to study more intensely the learner's (micro) decisions and ways to support them. As a starting point, Ausubel's meaningful-learning theory is analyzed, and a concept of cognitive structure is proposed. With the hypothesis that the optimal information sequence depends upon the individual's idiosyncratic cognitive structure, a system for studying these interrelationships and their determinants is proposed. (Author/AA)