The present study chose as its focus one of the primary reasons of why aptitude-treatment interactions (ATI) are difficult to find: methodological problems in the measurement of aptitude itself. The aptitude selected for this study is sensory modality preferences. Three types of modality data were gathered: norm-referenced (Illinois Test of Psycholinguistic Abilities), criterion-referenced (Individual Achievement Monitoring system), and teacher ratings. Use of the modality data was made under two different interpretations: forced decisions and nonforced decisions. A total of 21 variables were generated under these two interpretative conditions. A Campbell-Fiske convergent-discriminant intercorrelation matrix was formed. The first major question asked of the data was whether the commonly used, task-general ITPA modality assessments relate logically to the task-specific IAMS assessments. The second was whether the forced interpretation is compatible with the nonforced. (Author/CK)