All IQ tests try to measure intelligence from different... angles.
From what I have read (
http://alpha.fdu.edu/psychology/wisciv_gloadings.htm) the Vocabulary subtest on the WISC-IV is most correlated with g, but it is also a measure of crystallized intelligence (
http://alpha.fdu.edu/psychology/wisciv_gfgc.htm), the things you know/learned.
And I have been mulling those for a while. Because my son got the WISC-IV at school in November 2010 and the DAS-II as part of a private assessment in March 2011 (WISC couldn't be repeated). His perceptual scores remained stable, but his vocabulary jumped from 8 (WISC-IV Vocabulary subtest) to 13-14 (DAS-II Naming Vocabularies and Word Definitions). The first test was at the beginning of first grade after a year in a Spanish immersion program when we kept our rule of no English at home (our home language is neither English nor Spanish). The second test was after 6 months of intensive after-schooling in English at home (the school assesment having shown him to be below grade level in English, blamed on lowered exposure), including lots of reading.
I am not 100% sure how comparable those tests are, but based on descriptions they seem fairly similar. The fact that 6 months of hot-housing could raise a child from the 25th to the 90th percentile left me scratching my head, because I had totally internalized the "IQ is a measure of ability, not achievement" meme.
