I'm summarizing the paper A Practice-Based Approach to Group Identification in Nonverbal Learning Disorders (http://www.informaworld.com.proxy.lib.uiowa.edu/smpp/content~db=all?content=10.1080/09297041003631444) (subscription needed)

Apparently, people with Nonverbal Learning Disorder has too much internal diversity in their disabilities, and even the usual VIQ>PIQ measure didn't seemed to be too predictive. "[W]e believe that we lack a basic agreement about the nature of the problem that we need to investigate."

The authors mainly grouped people with NLD into 3 subtypes:


The Processing Efficiency Group (PROC-EFF), who "problems synchronizing the necessary elements (visual and verbal) to process (input) and produce (output) at an appropriate cognitive rate or tempo." The writers later refer to this as "wading in molasses" and mentioned that it may sound like ADD-Inattentive or Sluggish Mental Tempo; the difference being in this kind of NLD the attention deficit is not universal.
The Concept Integration Group (CONC-INT), which is "due to underlying deficits in the integration of concepts; they are unable to weave together elements to create a “whole” mental representation." In my opinion, this is pretty AS-sounding, especially the writer's portray of such a patient is probably also AS.
The Social Adaptation Group (SOC-ADAP), which "characterized in terms of the most salient impact of their linear style in the everyday world. This style limits online processing of the multiple, rapidly changing cues that are necessary for effective social functioning. Its most dramatic manifestation is thus in social adaptation."

The writer enrolled 435 children with NLD for analysis. The three groups, in order, were in the 27:47:27 ratio. ADHD was overrepresented in neither group.

In general terms of function, the investigators found that the CONC-INT group has lower functioning than the other groups. The difference i functioning between PROC-EFF and SOC-ADAP groups are not significant.

The writers thought the PROC-EFF group are slow verbal processors, but data rejected that hypothesis.

On the COMP-INT group, the results also rejected the writers' expectation of them "[having] significantly greater deficits in spatial processing functions, specifically perceptual reasoning and spatial organization," when appropriate testing results are adjusted for their lower Functional IQ.

As for the SOC-ADAP group, they did found some issues, they did get more anxious in front of teachers and parents compared to the other two groups.

Their conclusions:


Current processing speed measures seemed to missed out the "wading in molasses" issue;
FIQ seemed to be predictive of the COMP-INT subtype;
While the SOC-ADAP subtype have social adaptations that are easily observd, they are not easy to be tested.
NLD should be subtyped, but work should be done on how to subtype.

I'm kind of NLD-ish (probably more processing speed subtype according to this, but I don't really see myself as SCT either . . . mostly I have terrible working memory, especially for spatial information).

This is the first article that's touched on something that I've often wondered about regarding the original NLD literature: *VIQ* in the original groups were barely "average", and often borderline (so that FIQ was borderline at best), with organic syndromes like Williams not excluded. . .

I hate making this generalization (b/c I'm not always comfortable with the idea that the FIQ or IQ in general actually corresponds to intellectual functionig), but I often wonder if the concept formation issues can be overcome somewhat in ppl who function at an overall higher intellectual level.

This is the first article that's touched on something that I've often wondered about regarding the original NLD literature: *VIQ* in the original groups were barely "average", and often borderline (so that FIQ was borderline at best), with organic syndromes like Williams not excluded. . .

This paper mentioned that some other researchers have doubts about the existence of NLD as Rourke described (ie what is defined right now)-- when NLD was first described, it was considered one of the first two major types of LD and was intended to be sub-categorized (as verbal LDs are). Rourke's stance that NLD cannot be further subcategorized is highly disputed.


I hate making this generalization (b/c I'm not always comfortable with the idea that the FIQ or IQ in general actually corresponds to intellectual functioning), but I often wonder if the concept formation issues can be overcome somewhat in ppl who function at an overall higher intellectual level.
Let's see what do you define as "concept formation"...

I think one of the most confusing things about NLD is that it seems to encompass a huge array of problems. Since there are no definitive criteria for diagnosis, you can find statements of 'absolutes' about people with NLD that contradict each other, depending where you look.

I'm glad to see research being done on differentiating some of the groups who fall under this broader category, but I find these subtypes a bit too restrictive. I, for example, would fit best in the social one, but the issues which led to my NLD 'diagnosis' are certainly not limited to the social.

The one thing that seems to unify descriptions of NLD is the existence of a significant gap between performance and verbal IQ. I've certainly got that, but I also have significant variations between my performance on the subtests within each category, doing above average on some performance and below on some verbal. So, I wonder how useful the performance and verbal scores themselves are, given that they don't represent my performance in that domain generally, but are an average of scores that are all over the place.

This is one of my issues with IQ tests generally, actually, the subtests seem like they could tell you something fairly useful, the verbal and performance seem to tell you rather a lot less, and the 'full scale score' seems, at least if a person didn't score similarly across the board, a number that tells you pretty much nothing.

I'm glad to see research being done on differentiating some of the groups who fall under this broader category, but I find these subtypes a bit too restrictive. I, for example, would fit best in the social one, but the issues which led to my NLD 'diagnosis' are certainly not limited to the social.
The writer thinks it's more like 3 syndromes.

The one thing that seems to unify descriptions of NLD is the existence of a significant gap between performance and verbal IQ.
As I mentioned above, not really.

By "concept formation" I simply mean aspects of cognition like the ability to generalize, and not take things literally. I think that, in some cases, the idea that NLDers have issues with thinking abstractly may have something more to do with intellectual functioning rather than specific deficits. I know that I think "differently" from most people. Even though I can think abstractly, I think I may do so in a different way from most. So I have to wonder if I'm doing the "intellectual" equivalent of say, a blind person's visual brain being taken over by tactile stimuli.

By "concept formation" I simply mean aspects of cognition like the ability to generalize, and not take things literally.
My concept formation is awful, and I know it already seriously affected my language (See the thread I opened on this board).

I can't seem to get the article through any database I have access to, but from what you posted it sounds like they're saying that the VIQ>PIQ wasn't predictive of the nature of the problems the people they were studying had.

The study, it seems, was of people identified as NLD, and from everything I've read, the most agreed to, and consistently applied criteria is a big gap between verbal and performance IQ, which means that it is very likely that all the people in the study had such a gap. Again, I haven't read it, so I could be wrong, and would welcome more details.

As far as the three syndromes thing goes, again, it's hard to say without reading the article, but it sounds like it's largely an arbitrary division. Perhaps an attempt to impose some order on the catch category of NLD.