ABSTRACT
The defining aspect of the multitrait-multimethod (MTMM) is the elegant combining of experimental design within a nonexperimental context. The central design feature of the MTMM matrix is that traits and methods are crossed. That is, the same method or instrument is used to measure all the traits for each person. There is a design to the collection of individual-difference scores. As documented by Kenny and Kashy, the use of the confirmatory factor analysis to estimate the parameters of an additive model has been disappointing. It may be advisable to develop simple models for the estimation of MTMM models. The MTMM matrix represents one of the most important discoveries in the social and behavioral sciences. It is as important an invention in the behavioral sciences field as the microscope is in biology and the telescope is in astronomy. It continues to provide great insights into the nature of individual differences in the social and behavioral sciences.
