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What might cause a discrepancy in FSIQ on WISC-III and WISC-IV over a 4 year period of 37 points?

Twice exceptionality might. If the original test was given when the child was young, the numbers might have been inflated or deflated due to environmental factors (or anxiety or lack of comfort with strangers/the tester if the first IQ score was significantly lower).

Scores btwn the WISC-III and IV are also not going to be exactly spot on. I understand that kids who were tested on both versions often got a lower # on the WISC-IV, not to the extent you have here, but somewhat lower. I don't know if this is due to the Flynn Effect or just the later test scoring lower, or what.

What Cricket said. Also a bad day. Or long term effects of a bad situation.

I'd want to look closely at the subtest scores - are there any large dips in the lower FSIQ testing, and if so, is it possible that your child simply either checked out, lost interest, didn't follow directions or something like that on that one subtest?

I don't have any experience with the WISC3, but I *think* that the WISC-IV FSIQ is more heavily influenced by timed subtests. Is it the WISC-IV score that is lower? If so, are the processing scores relatively low on the WISC-IV compared to VIQ and PRI? If they are, a GAI can be calculated which doesn't include Processing Speed and Working Memory - is that closer to the WISC3 FSIQ?

Last thought, any number of things could influence test #s on any given day. My dd10 had a score on the WPPSI that was 20+ points higher than FSIQ on the WISC-IV just two years later. I think I asked about that here once and received a number of different possibilities why it might have happened. In her case, it wasn't just one-two subtests lower here or there, it was consistently lower across all subtests. I've been told in the past that in our area, there are testers who artificially inflate IQ test scores sometimes to qualify kids for GT programs or because they believe the parents want to see a higher IQ. This wasn't the case with us - we were having our dd evaluated for anxiety and hadn't even realized she'd be given an IQ test, and we also didn't anticipate that she'd score as highly as she did. So I always wondered about it a little bit, particularly after the WISC-IV came back lower. I do think, that in our dd's case, that first test was artifically high. She's been through another round of testing with WJ-III recently and those scores are more in line with the WISC-IV results.

Best wishes,

polarbear