Posted by Collin

In Reply to: Learning Disabilities FAQ posted by Ted Rosenberg

Obviously, defining a learning disability isn't easy, however, it
isn't necessarily impossible either. I think this particular FAQ
while having some good points but unfortunately also perpetuates a
number of common misconceptions about disabilities in general.

Let me illustrate.

Hearing disability -- Any individual that in some aspect of hearing
has ability to hear substantially below the average distribution of
the ability of people to hear.

What I'm talking about here --- is that if you take a population of
people and were to measure their distribution of hearing -- you would
probably expect it to be bell shaped curve. However, if you find an
excessive number of individuals that form a second lower hump on the
hearing ability curve, (which could manfest by a large gap in
abilities between two parts of distribution) then you have identified
a disability. One common misconception is that persons with below
average hearing have a hearing disability. This is simply not true,
as then half the population would by definition have a hearing
disability. Nor can we say that individuals say those within the
bottom 1% have a hearing disability -- as this is an arbitrary line
is no different that 50% one we picked eariler and every population
would have a hearing disability. Nor would setting it at .01% help.
The problem is that individuals with very poor hearing might still be
part of the normal population if that population has wide variance of
hearing ability.

Thus, the identification of a disability requires two facets.

1) demonstration that this individual has ability in some aspect
substantially below that of the general population.

2) that some real phenomena other than natural variation of ability is
the cause of this substantially lower ability.

Statistically what this is really saying, is that there are two
distinct populations, with different characteristics. Technically,
at some point it should be possible to identify by some
characteristics, measurements, properties of those individuals whether
they below to a particular population or not. Sort of like some
people have type A blood, and some have type B blood. There may
exist variation of blood properties within type A, and there may be
variation within blood properties within type B, but fundamentally
type A and B blood are different.

See further comments on the points below.

Ted Rosenberg wrote:

>The broadest definition of Learning Disabilities
>
>http://www.state.ia.us/educate/programs/ecese/cfcs/docs/ld_tech.pdf
>
>1) Learning disability can be differentiated from other disabilities.

In my mind, a true learning disability by its definition means that
the persons are capable of performing the task, only they have
difficulty learning to do so . This means that once they have
learned the task -- they will be able to perform it within normal
variation of performance in the population.

A disability that isn't a learning disability will mean -- we can't
ever learn to do it. For example, if I'm born without vocal cords,
then my disability will prevent me from ever learning to sing. That I
can be fitted with a mechanical voice box that might let me sing -- is
a different story, just indicates that some disabilities can be
overcome with proper assistance and environment.
>
>2) Many students experience learning problems or learning failures, but
>not all of these are the result of a learning disability.

Failture can be result of something other than intrinsic ability. It
may have to do with the environment or something like that. This just
highlights that performance -- that is the actual learning progress
is not necessarily a good measure of a learning disabiity. One
student may actually be outperforming the class averge but if this
student is putting in 10 times the effort (time, study, drill, etc.)
then student may still have a disability.

Often we see teachers saying-- Johnny can't have a disability , look
Johnny near the top of the class. Hogwash, if the other students were
as motivated, working as hard as Johnny, been drilled and tutored as
intensely as Johnny they probably be miles above him.
>
>3) Operational criteria can be delineated and reliably applied to
>identify a learning disability.

Much of what passes as operational criteria is pseudo science. Take
typical definitions of ADD and the like. In order to demonstrate that
say figeting is as a characteristic of ADD, you have to show that the
figeting is correlated with or is distributed with some property of
ADD individuals that lies outside natural variation curve. The
problem is simply that if we take say a sample of 1000 students at
random of say a certain school system, we were to measure the amount
of figeting and plot a distribution, we may find a broad distribuiton
curve where the top percentiles of the population figet 10 to 50 times
that of say the population average. However, if this distribution is
clear -- smooth curve, monitonically decreasing, one has to wonder if
this part of the population isn't just normal -- they just happen to
have random features that give them a higher fidget rate.
Contrarily, if we were to perform this experiment and discover that
we have basically have two independent curves, says one with variation
in figeting running from .1 to 10 x times normally, and then a large
gap and second smaller hump with distribution running say from 75 to
200x average, we would have clear indication that the second group of
individuals has something fundamentally different about them.
>
>4) Persons with a primary disability diagnosis of learning disability
>have intellectual ability in the average to above average range.
>
Intellectual ability above average -- should be irrelevant to learning
disability criteria. Typically, we only identify individuals with
higher intellectual ability -- because we feel that anyone that smart
ought to be able to perform better than they are doing. Unless,
intellectual ability is correlated with the disability in question
then we expect 50% of the people with that disability to have below
average, and 50% to have above average disabilty. Lets suppose we
put this in perspective. Say, I have a disability of a shorter leg,
and this causes me to run substantially slower than the average
population. Would we say that individuals which happen to have less
than average intellectual ability but happen to have the same shorter
leg -- and poor running are not handicapped and don't have a
disability !?

Now, I think this has been partly clouded because it has been found
that intellectual ability is generally positively correlated with
performance (with higher intellectual ability generally enhancing
performance). Example, high intellectual individuals often excell at
sports, music, art. The strange part is that in some disabilities
such as dyslexia and ADD -- the percentage of persons with that
disability that have higher than average intelligence appears to be
much higher than expected. In short, there are studies that indicate
that 80% of say dyslexics have IQ's above 120. This could be an
artifact of detection -- in that low IQ individuals are not classified
as having dyslexia or it may be intrinsic feature of the dyslexic
population. Repeated studies have found that the effect -- is pretty
consistent ... dyslexics are on average have much higher IQs than the
general population -- now generally believed to be a characteristic of
that population. However, this doen't mean that there aren't
dyslexics with say low IQs.

>6) Learning disability is unexpected or unpredicted learning failure in
>language, reading, writing, or mathematics.
Why limit it to these particular skills? Couldn't we have learning
disability in sports, in skiing, basketball, soccer, music, etc.
There are many skills that indiviudals might have a learning
disability in. Such as ability to recognize other people, ability to
jump skipping rope, ability to run, ability to learn to drive an
autobile, etc.
>
>7) Learning disability is intrinsic to the individual as demonstrated by
>deficits in one or more of the basic cognitive processes essential to
>learning.
We probably all believe that there is an underlying physical causes --
however, often the defective basic cognitive process isn't so easy to
identify. The causes can be genetic or they can be enviromental
( exposure to pesticide has been shown to be correlated with ADD and
other learning disabilities.) or they may be combination of both.
>
>8) Severe discrepancy between expected and actual performance is only
>one>criteria for determining a learning disability. Agreed.
>
>9) Learning disability is not synonymous with underachievement. Agreed.
>
>10) Consideration of data from multiple sources on multiple variables is
>necessary for determining a learning disability.
Usually true. However, again this is a broad statement with no
basis. Some learning disabilities might be easily identified from a
few variables. Sometime in the future, testing for dyslexia or ADD
could be as simple as a single blood test for a combination of genetic
markers. Or it may involve something as simple as a brain scan
performming some simple task -- to determine if the characteristics of
ADD behavior clearly show up. As with some test, there may be some
false positives and false negatives ... but not all tests suffer from
this.
>
>11) Persons with a learning disability exhibit intraindividual
>differences across academic domains with distinguishable strengths and
>weaknesses.
Isn't this true of everyone? Don't we all have distinquishable
strengths and weaknesses. Again, its an irrelevant factor.

Collin

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