Price,
Gavin R., and Daniel Ansari. "Dyscalculia:
Characteristics, causes, and treatments." Numeracy 6.1 (2013): 2.
While preparing the third presentation in
the series "mathematics and cognitive abilities" I came upon this
paper. It is written very clearly, and I
highly recommend it. Here are some
interesting findings from this paper:
Dyscalculia
characteristics:
·
Poor
retrieval of arithmetic facts from long term memory.
By third grade, typically developing children have developed a store of
arithmetic facts in memory, from which they can quickly recall the solution to
a given problem. Children with
dyscalculia, on the other hand, typically fail to develop such fluent
fact-retrieval mechanisms, continuing to employ procedural strategies long
after their typically developing peers have progressed to memory-based strategies. One of the immature procedural strategies
children with dyscalculia use is "count all", in which the child
displays two addends on his fingers or by drawing lines, and then counts the
fingers or lines from 1. As an indicator
of the severity of the fact-retrieval deficit in children with dyscalculia,
typically developing children have been found to recall an average of three
times as many arithmetic facts as those with dyscalculia.
·
Poor
number sense. This difficulty is proven by research finding
such as:
o
Israely scholars Avishai Henik and Orly
Rubinsten reported a lack of
facilitation from numerical information in
children with dyscalculia during a numerical stroop task. In this task, the child is presented with two
digits differing in physical size (e.g. 3 5 or 3 5). The child determines as
fast as he can which digit is physically
larger. When there is congruence between
digit physical size and numerical value (like
this: 3 5), reaction time in
typically developing children is faster than when digit size and value are incongruent.
Children with dyscalculia don't show
this effect. It's not clear whether the
reason for this is that the underlying semantic representation of quantity is
impaired in children with dyscalculia, or whether they have a deficit in the
link between the semantic representations and their symbolic referents (i.e.,
Arabic digits).
·
Children with dyscalculia have slower reaction
time to determine which of two digits (having the same physical size) has a
larger numerical value.
·
Children with dyscalculia also have a
qualitatively different “distance
effect”. The distance effect refers
to the behavioral phenomenon that, as the distance between two numbers being
compared decreases (e.g., 2 – 9 versus 7 – 9), reaction times and errors
increase. In other words, numbers that are closer together are harder to
compare than numbers that are further apart. The numerical distance effect
(NDE) is taken by many researchers to reflect the integrity of the underlying
representation of numerical magnitude along a “mental number line” with a
larger NDE indicating a less-precise or more noisy representation. In support
of this idea, the NDE decreases in size over the course of development,
suggesting an ontogenetic increase in the precision of the number sense.
Children with DD have been shown to have larger NDEs than typically developing
children, in much the same way that typically developing children show a larger
NDE relative to adults, suggesting that DD children may have a less-refined,
immature representation of numerical magnitude compared to their typically
developing peers. Recent evidence suggests that the magnitude of the
developmental delay in the precision of this representation may be on the order
of five years, with DD children showing numerical-representation precision
equivalent to typically developing children five years their junior.
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