| Math learning disability (MLD) is an important area of learning disability, accounting for large percentage of students in the middle school. However, the examination of math learning disability is a relatively new field of study. Now there emerging a leading paradigm for carrying out research on MLD from the viewpoint of information processing, and more and more studies focused on discussing the cognitive processing mechanism of MLD. Some core topics such as the definition and screening methods of the MLD are in dispute, therefore it needs further investigation. The criteria for defining the MLD or math learning disorder of this study is:the math score was lower than 20% of the total score; normal IQ; without the obvious organic deficit, emotional disorder and learning motivation disorder.Based the three-factor model put forward by Baddeley and Hitch (1974), this study designed the experiment tasks of central executive system, visuo-spatial sketchpad and phonological loop, exploring the differences of the three components of working memory (WM) between the 55 MLD students and 56 students who are good at math (with 46 male students and 68 female students, average age is 11.97-year-old). Then, according to the criteria of national math curriculum, math study was further divided into two parts, that is, (a) counting and algebra, (b) space and geometry. Combined the working memory with PASS model theory raised by Das,Kirby and Naglieri (1990), the cognitive processing mechanism of various kinds of math study were investigated. The author tried to build a cognitive structural equation model which exerted the great impact to the study of junior school students.This thesis mainly follows three phases on considering the above issues:In the first study, the author investigated the performance of the MLD students in different components of the working memory. A serial cognitive-behavior computerized tasks were composed to test the WM of the students, such as, the stop signal task and Flanker's tasks testifying the central executive function, N-back and Spatial Figure Position tasks testifying the visuo-spatial sketchpad, the digit span and sentence span tasks which tested the phonological loop. The results showed that the MLD group performed poorer than the normal group in central executive system, visuo-spatial sketchpad and phonological loop, indicating the WM deficits among the MLD students was domain-general. Secondly, the developmental trend of the working memory ability among the junior school students grew with age, but it was fluctuated. Thirdly, the MLD students couldn't finish the tasks with high loaded working memory demand, but they were capable to finish some simple cognitive tasks, what's more, they even performed better than the students who were good at math in the low loaded working memory demand tasks, which meant that the working memory deficit was the core deficit in the MLD.The second study investigated the role played by the WM in different kinds of math studies. The first research found the working memory deficit in the MLD students was domain general, but various kinds of math learning belonged to different cognitive processing mechanism. Then the author designed three experiments in order to specify the research. First, based on the PASS cognitive process, the basic cognitive processing of math study was discussed; then the author divided the math into counting and algebra, space and geometry, analyzing the cognitive characteristics of the MLD students in some specific math leaning area; finally, the author chose the specific math knowledge-- Axial Symmetry and Centro Symmetry tasks from the space and geometry to discover the cognitive feature between the MLD group and the group who were good at math.The main results were summarized below. First, the MLD students had the basic cognitive processing deficit. Simultaneous processing and planning correlated with math achievement closely and simultaneous processing predicted MLD significantly. Secondly, learning of counting and algebra was influenced by the combined role played by the central executive system, visuo-spatial sketchpad and phonological loop; learning of space and geometry was influenced by the central executive system, visuo-spatial sketchpad instead of phonological loop. This indicated that during math study, working memory was not only domain specific but also domain general, i.e. the central executive system, visuo-spatial sketchpad was characterized by domain generality and phonological loop was characterized by domain specificity. At last, visuo-spatial sketchpad predicted the performance of Axial Symmetry and Centro symmetry tasks, then followed by central executive system, and phonological loop had little effect to this task. The results testified the specificity of phonological loop, and the impact to geometry exerted by visuo-spatial sketchpad was obvious.The third study investigated the relationship between the cognitive processing and the academic achievement of junior school students. The results from above two studies showed that working memory and basic cognitive process influenced the math achievement greatly. Then four structural equation models were built to discuss how the three components of working memory, the four basic cognitive processes and cognitive processing speed influenced the academic achievement of junior school students. The results indicated that the model of working memory-simultaneous processing-successive processing (WM-SS) was the best model, which predicted the academic achievement very well. The author suggested this model could be regarded as a new framework for the intelligence theory, which had more advantage than the traditional g-factor intelligence tests.
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