Experimental Factors Related to Aptitude-Treatment Interactions

have suggested that no single instructional process provides optimal learning for all students. Given a common set of objectives, some students will be more successful with one instructional program and other students will be more successful with an alternative instructional program. Consequently, a greater proportion of students will attain the instructional objectives when instruction is differentiated for different types of students. Glaser (1967) and others pointed out that psychologists have been too optimistic in their expectations of formulating general laws of learning and have not given sufficient attention to individual differences. In his APA presidential address, Cronbach (1957) encouraged psychologists in the experimental and correlational disciplines to combine their interests and methods to observe experimental effects for subjects of different character-istics and to conduct investigations to find aptitude-treatment interactions (ATIs). The goal of research on ATI is to find significant disordinal inter-actions between alternative treatments and personological variables, i.e., to