On the Wechsler Adult Intelligence Scale v. 4 (WAIS-IV) there’s an index called “processing speed”. It’s composed of two subtests: Coding and symbol search. I never took the WAIS-IV, but I’ve taken earlier versions. These are two of my worst subtests (the others where I am really bad are block design, matrix reasoning and visual puzzles, all of which make up an index called “perceptual reasoning” but that’s another topic). I am guessing that my score on the processing speed subtest would be the equivalent of about 70 – two standard deviations below the mean. WAY SLOW. This would strike anyone who knows me as ridiculous.
One of the things I do is process information fast. Really fast. I was the first one done on every test I ever took – no matter what grade I got, from F to A+. I read quickly. I do arithmetic quickly. (Indeed, when I took the WAIS I did the arithmetic section so fast that I was told it was hard to score it). This speediness isn’t all good – I make silly errors a lot, but slowing down doesn’t help, nor does checking my work.
So, I am very fast and very slow. What’s up with that?
“Processing speed” is not a unitary construct. The thing they are talking about on the WAIS (and the WISC, too) is visual processing speed. And, on this, the score I get on the WAIS is a good reflection of my abilities (or lack thereof). It helps explain why I am bad at so many visual tasks – that is, nonverbal tasks, the tasks that people with nonverbal learning disability are bad at. Now, some people with NLD are also slow processors of verbal information. But not all of us are like that. People vary.
People are complicated. If you want simple, study something else.