Testing Luria's Model: A Reply to Naglieri and Das

We respond to Naglieri and Das' criticisms of the methodology used in a study designed to explore the simultaneous-successive-planning (S-S-P) model (Cowart & McCallum, 1988). That study represents the first attempt to partial trait and method variance using the multi-trait-multi-method technique (for the S-S-P model). Principal limitations cited by Naglieri and Das were noted in the original study. In this article we address those and other limitations raised by Naglieri and Das and conclude that our original concern is still valid. That is, the methods typically used to assess these processing constructs, particularly simultaneous and successive processing, confound their interpretability. Consequently, future efforts to assess the constructs should address the need to separate and determine the relative contributions of method vs. trait (to the total variance).