Gifted Issues Discussion homepage Forums Identification, Testing & Assessment WISC IV and high Processing Speed

Index scores that are consistently in the 137-139 range taken together indicate a FSIQ score higher than the individual scores taken separately because it is rarer to have all the scores that high. This effect isn't due to processing speed "inflating" his scores, because the FSIQ is not an arithmetic average, but rather a measure of the rarity of the score. It is rarer to have many subtests this high than it is to have only one or two.

ETA: A child with high processing speed will appear to be mentally (and physically) "quick", which is often equated with being "smart", so it may be easier for a child like this to get recognition for his intelligence than it would be for a child with similarly high VCI, PRI, and WMI scores but low PSI.