Tuesday, January 29, 2008

Developmental Dyscalculia, Part 3

Cognitive Domains: Strategy

Experimental studies of developmental dyscalculia and math disability in children have focused primarily on skill development in arithmetic, which can be divided into two sections: counting knowledge, and strategy and memory development.

Counting is governed by five principles (Gallistel and Gelman, 1992):
(1) the one-to-one correspondence rule, where one word is assigned to each counted object;
(2) the stable order rule, where the order of counting words must be stable across sets of counted objects;
(3) the cardinality rule, which states that final counting word assigned represents the total number of objects in a set;
(4) the abstraction rule, which states that objects of any kind can be counted; and
(5) the order irrelevance rule, which states that items in a set can be counted in any order.

A mastery of counting is essential to discover the most efficient strategies for basic arithmetic procedures such as addition and subtraction, and later, multiplication and division.

In many models of cognitive development, children are depicted as thinking or acting a certain way for an extended period of time. Then, they undergo a brief and sometimes mysterious transition and begin to act and think in a new way. When considering cognitive development, Siegler (1994) prefers to understand change as variable and gradual, with different strategies available to a child as the child’s brain matures. Further, there are some problems where there is really only one logical strategy. After some time experimenting with different strategies, both in progressive and regressive directions, most children will focus on the best, most logical strategy, and lock onto it for much of the remainder of their lives.

Young children’s brains are highly active, with synaptogenesis peaking by age six or so. Following the periods of synaptogenesis there is widespread synaptic pruning, to make the synaptic pathways more efficient and speedy. So it is during this time of great neural change when students are first learning basic mathematics and reading skills. Given the proliferation of neural pathways, it makes sense that the normally developing child will use a variety of different strategies when faced with the same or similar problems. For example, there are at least three common strategies that children can use for addition. The most efficient is direct fact retrieval: 3 + 3 always equals 6. Another is the min strategy, where kids count up from the larger number: 9 +2 = (9 + 1) + 1 = 10 + 1 = 11. A third is decomposition into easily manipulated numbers: 19 + 22 = 19 + 20 + 2 = 39 + 2 = 41. Normally developing children will ultimately lock into one of these or another strategy when faced with a random addition problem.

Siegler’s model provides for two possible explanations for developmental dyscalculia. First, perhaps while the brain is undergoing its normal course of synaptogenesis and synaptic pruning, the child has not had enough experience with the various strategies for arithmetic – so by the time synaptic pruning occurs, it is unclear which neural pathways are stronger or more efficient. That leaves the child unable to become “expert” at any particular arithmetic task, as there is no clear efficient pathway left. Second, perhaps the child has had sufficient opportunity to experiment with the various strategies, but the synaptic pruning processes occur in a somewhat haphazard, non-systematic way, which leaves the child forever locked into a pattern of experimentation and variability. That is, the child does not have the opportunity to lock in on a best-choice strategy because of neural/biological limitations.

While neither of these possibilities precludes the children from gaining efficiency over a long period of time, they leave them behind the rest of their peers, significantly slowed down by the wide variety of problem-solving strategies available to them. These are particularly suitable explanations, given the empirical evidence that children with developmental dyscalculia are generally two grade levels below their peers in arithmetic and mathematics (Shalev, Auerbach, Manor, and Gross-Tsur, 2000).

1. Gallistel, C.R., & Gelman, R. (1992). Preverbal and verbal counting and computation. Cognition, 44, 43-74.

2. Siegler, R.S. (1994). Cognitive variability: a key to understanding cognitive development. Current Directions in Psychological Science, 3, 1-5.

3. Shalev, R.S., Auerbach, J., Manor, O., & Gross-Tsur, V. (2000). Developmental dyscalculia: prevalence and prognosis. European Child and Adolescent Psychiatry, 9(2), 58-64.

No comments: