if "chunking" is not used?
This answer neatly explains what chunking is
Chunking is a strategy for more efficiently storing information by changing the way you encode or process it. Effectively, you're arranging/re-arranging information in a way that makes sense to you. Chunking refers to breaking it up into meaningful lots. For example:
Suppose you had a digit span task. Normal capacity is 7 plus/minus 2 digits. I was presented the following digit span numbers:
11111111111111111111111112221111111111111111111111111
I could store it as: 1-1-1-1… however, by the time I got to the end, the information I encoded at the start would have decayed.
So instead of trying to store it that way, I could break it up into the meaning parts: twenty-five 1s, three 2s, twenty-five 1s.
Wow! Did I just increase my digit span to over 53 digits? No, not quite. I just changed the way the information was encoded.
By chunking information, one can store more information by more efficiently structuring it.
That said.
Does the digit span test draw on any executive functions besides working memory, if "chunking" is not used?
Yes, it does.
It actually becomes a better measure of executive function. And working memory.
First, is there a reason why you're looking at digit span? I ask because it's not a good measure of working memory capacity/executive function. Also, your use of digit span may be leading to a number of misconceptions about what is going on during the WM task, and it's because the digit span task is biasing your understanding of it.
To begin with, any digit span test requires executive function. This is because at a bare minimum, you need to be paying attention to new information. You need to rehearse it. You need to store it.
Instead, if you would like to get a better conceptual idea of what working memory tasks are trying to measure then have a look for the "N-back task". You should be able to download it. Recommendation: Try to "walking yourself through" the sorts of things you need to do in order to perform the task. It's a hard task. In fact, they don't recommend it be used to actually test WM because performance is too unreliable to be used as a measure of WMC.
I'm not sure I believe that the digit span is a test of a single raw cognitive function.
e.g. surely we don't need to "chunk" for perceptual speed to play a role: would that be helped by other executive functions?
What you're asking ought to be inferable from first principles.
First, you need to look at positive manifold. See all those intercorrelations? They're all positive. When you move them around, however, you identify the way that different tasks build up on one another.
The easiest way top make sense of this is to look at Carroll's Three Stratum Model. The single abilities are right at the bottom. But our digit span test is at stratum II
I'm not sure I believe that the digit span is a test of a single raw cognitive function.
There is no such thing as test of a "single raw cognitive function". For example, the closest to what I presume you're thinking of is say, a reaction time task. This is called an elementary cognitive task (ECT). But it's not like reaction time is comprised of a "single raw cognitive function". Instead, (and I think this is what you mean is) this is meant to tap into independent processes as maximally possible.
But more to the point, digit span is meant to be a measure of WMC. It's "higher up" in terms of requiring that there is integrity of simpler cognitive processes below it.
It's a higher-order task. It's simply not possible to tap a single raw cognitive function. Even without looking it up, I know that it has to be tapping into numerical ability.
This is what a good test of WMC will be tapping into. However, digit span doesn't do this, because it's only going to be loading on the phonological loop:
e.g. surely we don't need to "chunk" for perceptual speed to play a role: would that be helped by other executive functions?
I think I know what you're getting at. Let's just way that, perceptual speed has to have some role, because if you're, say, looking at a computer screen, light hits your eyes, the travels through the optive nerve and to your brain, Then you create a mental representation somewhere, and then perform higher order processing on it. But if you're asking will it affect it any meaningful way? Then no. But more importantly, one shouldn't design a cognitive task that does.
There are good and bad tasks. A well designed test of WM is will not try to "tap into" perceptual speed, because if you did poorly in that task, you would not know if it was due to a bottleneck in WMC (which you want) or perceptual speed. This is particularly relevant if somebody has a brain injury where damage in more elementary cognitive process renders then incapable from even performing the task.
