If I may ask some clarifying questions:
You describe the subtest scores as superior, but also state DC hit the ceiling in 4 out of the 6 GAI subtests. That would place those subtests in the very superior range. In order for the VCI and PRI to fall in only the superior range, that would suggest that the remaining subtest in each index was significantly lower. Is that the case? Also, if 2 of 3 subtests in VCI and PRI hit the ceiling (max scaled score, usually of 19 for a six or seven year old), then the psych should have considered extended norms, and explained their decision on extended norms one way or the other.
You report a 16 point difference VCI > PRI, generally considered statistically significant. Did the psych comment on this?
PSI factors into the FSIQ through its arithmetic contribution to the sum of scaled scores. There are 10 core subtests in the FSIQ, and two PSI subtests, hence 1/5 of the FSIQ contribution comes from the PSI.
Elsewhere on this forum, we have discussed low PSI a number of times recently. In brief: there are many potential causes of a divergently-low PSI, including difficulties with vision, fine-motor coordination, fatigue, attention, psychomotor retardation as a side effect of medication, anxiety, depression, and perfectionism. Many high cognitive examinees exhibit a conscientious task approach that values accuracy over speed (likely an overlapping category with perfectionism).
