Processing speed and the Block Design subtest on WAIS

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27 Aug 2010, 6:18 pm

My scores on the Block Design subtest on WAIS have always been roughly the same. I always score either a 6 or 7 on block design, which is in the low average range. Aside from Object Assembly and the Visual Puzzles subtests, block design has always been my lowest score out of all subtests on all versions of WAIS. Object Assembly is no longer used on the latest version of WAIS (IV) and I suppose that is because the OA subtest had the lowest reliability coefficient (.68 I believe) out of all the WAIS subtests. The Visual Puzzles subtest is now included on the latest version of WAIS and it is considered more reliable than Object Assembly. I suppose that is due (at least in part) to the fact that the Visual Puzzles subtest does not involve motor skills.

Considering processing speed (especially visual processing it would seem) has always been a weakness for me, I am assuming my poor performance on block design has something to do with my scores on that subtest since it is timed. This is not to say I believe my visual-constructional skills would be good even if I had no problems with processing speed, but I think my performance on this subtest would be somewhat better if processing speed wasn't an issue. I'll use the most recent block design subtest I took as an example.

I arranged most of the block patterns correctly within the alloted time frame. It did take me nearly all the alloted time to do so on quite a few of the patterns however. I only failed to arrange the blocks correctly within the alloted time frame on the very last pattern displayed in the WAIS booklet. I received a six on this particular block design subtest, which is in the low average range. My processing speed index score on this WAIS was 86, which is just on the cusp of borderline.

The thing that seems somewhat odd to me is that I scored a seven on one block design subtest and my processing speed index score on that WAIS was 108. That is over one standard deviation higher than my processing speed index score on this latest WAIS. Now i'm pretty sure my processing speed still could've been a factor on that block design subtest in spite of my higher processing speed index score. For one thing....I believe the index score is an estimate of one's processing speed overall and therefore may not indicate much in and of itself regarding any deficits in VISUAL processing. I'm just wondering how speed is taken into account on the block design subtest.

For example.....say two people assemble all, or at least most, of the block patterns correctly within the alloted time frame. If one does so within a minute and the other arranges them correctly within 25 seconds, i'm almost certain the first person would receive the lower score. Am I correct here or is there something i'm missing in terms of how they calculate the results of the block design subtest? Furthermore, how can they determine that someone has a fundamental problem with visual-constructional skills/reasoning when the cause of the problem may have everything to do with a deficit in processing speed? It seems like they're largely basing all this on processing speed and that doesn't strike me as very fair. Should person X be viewed as someone with greater difficulties in visual-constructional skills than person Y simply because it takes person X longer to correctly complete the tasks that supposedly measure these skills?

In a practical real-world sense....speed certainly does matter when it comes to these things. But how can clinicians differentiate between actual problems with visual-constructional REASONING and mere deficits in visual processing speed? It seems to me that they don't make this distinction very well. My neuropsychologist wasn't very clear as to whether my low performance on block design was simply reflective of deficits in visual processing speed or if I have significant deficits in visual-constructional reasoning itself.


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Joined: 16 Jul 2010
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27 Aug 2010, 7:00 pm

My personal view is that a lot of these tests are good but imperfect.

Some of these tests give false results when given only one time to those who have subtle neurological challenges such as:

ADHD Inattentive
Central auditory processing disorder
Petit mal/absence/complex partial/TLE and so on
Imperfect peripheral vision
Constructional apraxia
Mild dyspraxia
Sports concussions/subtle brain injuries
Subtle cerebral palsy

and so on.

Sometimes there can be a noticeable difference in scores when these tests are given:

in a med-free state


when using an effective medicine for a neurological challenge such as epilepsy or ADHD.

Generally speaking, these tests should be given (for those with the above kinds of challenges) at least twice or more over a period of several years, however, many health care plans will not do this.

Many health care plans today will not test for autism, Asperger, ADHD, central auditory processing disorder, or dyspraxia at all.

Many of these tests are designed as mass production tests and given to the masses as such.

These tests simply fail to give the best answers to those with subtle neurological challenges unless they are given more than once under varying conditions.

That's my understanding.


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27 Aug 2010, 8:27 pm

I think Processing Speed isn't an actual literal description of how fast you process information, but rather a score derived by calculating a number based on two or different subtests. Just because it's called "processing speed" doesn't mean that it reflects some kind of absolute determination of processing speed.

Which makes sense because there are many different forms and kinds of processing speed. I process many things quite slowly, and yet my score on Block Design was my highest subscale score. Because it dealt with an area that I happen to be good at. I'm quite good at dealing with patterns of shapes, which is what it tests. If someone were to test the way I process categories (I don't know the best word for it, but like identifying "table" and "dog" and things like that), it would be a much slower processing speed than the way I process something closer to the raw stimuli without having to evaluate them to determine "what" they are.

Someone recently posted something about how "processing speed" is really a combination of a zillion different skills, and depends on which part of your brain is doing the processing, what it's processing for, what information is being processed, and what the person is going to do with it. It's not a singular thing, and the Processing Speed part of the IQ test should really just be called "Digit Symbol Coding + Symbol Search" because that's all it is.

My test didn't have Symbol Search that I'm aware of. But Digit Symbol Coding was my worst score on the entire test, well into the lowest range of possible subscores (don't remember it exactly). Which means that it's quite likely that my Processing Speed score, if calculated, would be in the MR range. And yet my Block Design score is either above average or high average, can't remember which.

All of which is to say, the reason your Processing Speed score and your Block Design score aren't the same is because they measure entirely different things. Processing Speed is determined by your performance in Digit Symbol Coding and in Symbol Search. Block Design is determined by, well, Block Design. Digit Symbol Coding and Symbol Search don't measure the same thing that Block Design measures. Which is why you have high Processing Speed and low Block Design and I have the opposite. Totally different subtests.

"In my world it's a place of patterns and feel. In my world it's a haven for what is real. It's my world, nobody can steal it, but people like me, we live in the shadows." -Donna Williams


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Joined: 16 Nov 2014
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18 Nov 2014, 5:48 pm

I had the testing done, but have not gotten written results yet.
I had difficulty with the block design, I could only finish about the first 5 or6 within the time frame.
Then I got frustrated because no matter how much time I had, I could not figure it out.
The examiner had me try again, and I had two minutes but couldn't do it.
So Id like to know what this means!
What would a very low score mean?


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Joined: 16 Nov 2014
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18 Nov 2014, 6:01 pm

I got49 raw score on coding


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Joined: 22 Feb 2012
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18 Nov 2014, 6:18 pm

Funny story. When I did that test the tester had to step out of the room and come back later. I was still working on the same puzzle when he came back.

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Joined: 27 Jan 2015
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27 Jan 2015, 6:08 am

The thread is obviously quite old, but I have input that might be of use. My wife studied psychology and used me as a test subject when practicing IQ testing. I don't remember any of the scores as most of them would be highly suspect due to the subjectivity given our relationship. The block design test is a very objective test though, there are no judgements to be made by the tester apart from timing. The scoring is based on timing. If you complete the image correctly within the first 30 seconds for example you'll get the highest score. Then the next highest score is if you complete it in the first 60 seconds and so on.

I sometimes thought about that test because her professor specifically said she'd never had anyone get a perfect score or complete all images correctly within the shortest possible timeframe. She was therefore quite interested when my wife told her I had actually done just that. I had taken an IQ test with a professional once before a number of years prior. The block design test was also a subject of discussion then. I scored higher on it than should have been "possible". That was the psychologist's explanation at least. And during both tests I had the same, very strange feeling, that I was cheating on the test. For some reason I felt like there was no way it was supposed to be this easy. What my method was I don't remember but I think I saw the image as a grid so it was just a question of placing each of the blocks in the grid in the same order they were on the image. Which made it feel like I was being asked to count to 10 or tell how many fingers the tester was holding up!

Some of the other parts of the test felt completely opposite, especially some of the verbal and auditory ones. Just disgustingly difficult. Like when you're given a series of letters and numbers like hl9a47v and you have to order them like 479ahlv. Keeping 7 or 8 letters in my mind, given via auditory instructions and then arranging them like that...I felt like I could've pissed my pants it was so physicially hard.

Anyways, two much of a rant, just have always wondered about that block design test part and never mentioned it before.


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Joined: 4 Feb 2014
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27 Jan 2015, 6:35 am

I've always scored low on the block design test, yet high in coding.