Multidimensional item analysis of ability factors in spatial test items

Two strategies for solving spatial test items, drawing differently on general ability and visualization, have been shown. These strategies may not only be a matter of individual predilection, but item features may lend themselves more to one or the other strategy. Newly developed techniques for factor analysis and the Mplus program allows items to be analysed as categorical variables together with summarized test results as continuous variables, which enables analyses of the dimensionality of single test items. Five spatial tests in the Computerized Swedish Enlistment test battery were analysed for a representative sample of 18-year old male conscripts (n=14,925). The items were fitted one by one for each of the five spatial tests together with the rest of the tests into a hierarchical model of intellectual abilities with general (G), verbal (Gc′), spatial ability (Gv′) and test specificity (Tspec′) as latent variables. All models showed good fit and the items were found generally to load higher on G than on Gv′, except for some of the items on the test with limited response time. No systematic increase in G loadings with increasing item difficulty, indicating a shift to an analytical strategy, was revealed.