Now I'm going to throw another angle on processing speed into the mix: what we think of as visual-motor processing speed of the WISC/WAIS/WPPSI coding/symbol search variety is probably more of a measure of efficiency with rote skills (though other kinds of processing speed strength are likely to bleed over). There are some other cognitive skills which we might consider processing speed as well, but which are somewhat distinct from the PSI-type, and include varying levels of reasoning.
For example, on the WJ, there is a subtest called decision speed. Visually and motorically, it's very similar to symbol search and its WJ analog, visual matching, but instead of simple matching of visual forms, one has to identify conceptual matches (albeit simple ones) quickly.
Retrieval fluency can also be considered a type of processing speed: timed object, letter, number, or word naming tasks, with or without visual cue.
