It's so neat she did so well on the symbol search. As polarbear said symbol search requires simpler hand motions than coding so that could be it, especially if she is a messy writer.
In addition to do really well on coding ideally one keeps multiple things in one's memory, and switches back and forth between them without mixing them up. Whereas in symbol search one doesn't have to use memory for such long stretches.
So the big difference between her scores on the two processing subtests could be due to several things or a combo:
1. Could be random such as chatted during the coding. There is not any time to spare on it.
2. Could be her actual hand control or her motor planning ability is poor. If so she would likely be either a uniformly slow printer, or not horribly slow but letters are sometimes illegible especially later ones as she tires. How is her motor planning or fine motor skills with other activities besides writing? Cutting with scissors, or tying shoes or lacing beads?
3. Could have trouble with memory, not memory for facts or events but the type of memory where you remember several things at the same time and manipulate them. Example: memorizing a list of what people are in what hotel room number and then being able to visit them in a particular order. But for the wisc it's a visually presented data.
4. Could have trouble switching. Perseveration is the extreme of this. Check out all the varieties of perseveration.
5. Perfectionism. If you worry you aren't doing it right you waste time checking or don't rely on your memory as much as you could. The amount of memory involved isn't huge but if you know you have a terrible memory (like me) you would probably waste a lot of time checking. It would take more time to check the coding and you'dbe more likely to lose exactly where you are, I think.
According to the wisc results it seems facile and easy use of memory, juggling memories in her head, is her weakest area. But maybe perfectionism or a fluid ability to switch back and forth complicates it?
Not sure how all that impacts spelling or punctuation.
PS... I have no training just read about the wisc processing because my DS has fine motor issues.
