This conflict with the model of cognition led to a
refinement of the cognitive model, splitting apart the proficiencies of conceptual
composition (the original depth construct minus the Justified level) and conceptual
justification (involving the number of steps in the causal chain).
To model this multidimensional set of proficiencies, a confirmatory multidimensional
item response model was used (Adams et al. 1997). The results (Fig. 9) illustrated that the
two proficiencies—conceptual composition and conceptual justification—are nearly
uncorrelated (r=0.11), a striking result and one that would not have been discovered had
the data not been analyzed with an explicit model of cognition in mind, one that can be
compared with the other cornerstones of assessment and revised if necessary