Another factor comprehension does not share with the core VCI subtests on the WISC-V is the amount of language comprehension necessary to answer the questions. Similarities and Vocabulary both consist of very brief stimuli (one or two words), which may make a difference for some children.
Also, Co is somewhat related to personal experience, unlike the other three verbal subtests, which are more academic in nature. It may be that a six-year-old hasn't had sufficient experience of the world to have encountered some of the situations addressed in Co.
This would actually answer a lot of my questions. DC does not have a broad range of experience and I often have to explain things that many kids already know. DC is homeschooled [after a few disastrous years of preschool] and has always been oblivious to any/everything that wasn't of specific interest [you know: math, science, natural history or gaming] ...
I'm often amazed at the words DC does NOT know ... especially considering DC's vast vocabulary. It all comes down to life experience/exposure.
With respect to your comment about 'brief stimuli': is there a relationship [correlation/causation] between ADHD/attention issues and lower scores on the comprehension subtest? There are days I'm convinced DC's ADHD dx is incorrect and others I totally buy into it ...
