That's not a problem that's exclusive to the CogAT, though, polarbear. The neuropsych had almost the same explanation for my DS5's relatively low score on the Picture Concepts subtest of the WPPSI. (Block Design 17, Matrix Reasoning 15, Picture Concepts 8)
I've just been skimming this thread (never heard of CoGat outside this forum) but your post jumped out at me. My DS also had Picture Concepts notably lower than the other subtests in PRI (in WISC-IV). He also had Comprehension notably lower than the other subtests in VCI.
I'm always interested in hearing possible explanations. Is it measuring an actual weakness, or is there a flaw in test design, or is it just noise? (Maybe a topic for another thread.)
