Atkinson, R. K., Levin, J. R. et al. (1999). Matrix and mnemonic text-processing adjuncts: Comparing and combining their components. Journal of Educational Psychology, 91(2), 342-357.

The comparative text-processing benefits of matrix structures, mnemonic representations, and their combination were examined in 3 experiments (1 with college students, 2 with 5th graders). The study's major findings permit the following conclusions: First, contrary to previous research on the topic, 2-dimensional matrices (whether in a verbal or pictorial format) produced only limited positive effects on students' text-learning performance, relative to either corresponding linear outlines or text alone. Second, and in contrast, appropriate mnemonic representations (whether individually presented or embedded in a matrix) did prove to be highly effective text-learning facilitators of students' memory and application in both individual- and group-testing situations, both immediately following instruction and on 1-week delayed tests. Third, relatively little advantage of the mnemonic matrix over individual mnemonic representations was detected.