Stankov, L. (1978). Fluid and crystallized intelligence and broad perceptual factors among 11 to 12 year olds. Journal of Educational Psychology, 70(3), 324-334.
http://dx.doi.org/10.1037/0022-0663.70.3.324
Gave a battery of 36 visual and auditory tests to 113 primary school children. Second-order analysis of the data yielded 2 well-defined factors representing Fluid (Gf) and Crystallized (Gc) Intelligence and 2 perceptual factors corresponding to General Visualization (Gv) and General Auditory Function (Ga). Perceptual factors were not clearly separated from broad intellective factors at this age level. (18 ref) (PsycINFO Database Record (c) 2016 APA, all rights reserved)