Principal Components Factor analysis for the items of the JCCES Verbal Ability part

In an attempt to study the structure of the Verbal Ability scale of the JCCES, I've factor analyzed the items of both the Verbal Analogies (VA) subtest and the General Knowledge (GK) subtest all at once. Factor analysis is a common method of examining the patterns of relationships among a set of variables and is a widely used analytical approach in order to evaluate the existence and the structure of any latent constructs among a set of items, or tests (Cronbach, 1990; Kamphaus, 2001). For exploring the presence of latent traits among the items of the JCCES verbal subscale the method of principal components was chosen, with a varimax rotation (Kaiser's normalization) for interpreting the results. For better interpretability, two factors were retained. The first one has an engeinvalue of 21.62, and the second one has an engeinvalue of 5.86.
The results are given in Figure 1. As it can be seen, the items of both subtests are relatively well arranged in ascending order of difficulty, and share pretty much the same space in the low to middle range of ability. However, the half-circle is split into two distinct curves when it comes to a certain level of examinees' performance. One can easily notice that although the easier items of both questionnaires are relatively grouped all together on the left side of the figure, the harder problems on the right side of the figure are getting farther and farther according to difficulty level.
These findings suggest that even though the items' sensitivity to ability is relatively homogeneous up to a certain level of performance, it appears to be heterogeneous in the high range of cognitive abilities. The difference in the representation of latent constructs is here somewhat negligible in persons' with low to superior ability in comparison to the way it appears for instance in intellectually gifted individuals. Such a phenomenon is seen as close to the asymmetry of g describes by Evans (1999, 2000). This author observed that scales are more highly intercorrelated at the bottom end of the spectrum of g than at the top end.

References.
  Cronbach, L. J. (1990). Essentials of psychological testing (5th ed.). Boston, MA: Addison-Wesley.
  Evans, M. G. (1999). On the asymmetry of g. Psychological Reports, 85, pp 1059-1069.
  Evans, M. G. (2000). Implications of the Asymmetry of g for predictive validity. American Psychological Association / Yale University Conference on Intelligence.
  Kamphaus, R. W. (2001). Clinical assessment of child and adolescent intelligence (2nd ed.). Needham Heights, MA: Allyn & Bacon.