WMI and PSI:
short answer:
Working Memory Index and Processing Speed Index. In general though, they are memory and speed.
long answer:
WMI is Working Memory Index, and the tasks in the WISC-IV require a child to recite random combinations numbers forward and backwards, and reorganize combinations of letters and numbers into ABC/123 order. Basically, it's a measure of how your brain can manipulate the data is has for that moment. (This is not the same as long term memory)
PSI is Processing Speed Index, and the tasks in the WISC-IV require a child to match certain symbols in a page of random data, and is somewhat a measure of hand/eye coordination, as well as speed. It also requires good fine motor skills and attention to the task at hand. The other task requires a child to translate a "code" into another form on a written sheet. Both subtests are timed.
