Modularity,mental retardation and speed of processing

This paper briefly outlines Anderson's (1992) theory of the minimal cognitive architecture underlying intelligence and development and briefly discusses its application to understanding mental retardation and specific cognitive deficits. An experiment on the relationship between face perception and mental retardation serves as an illustration of how the theory might be informative about the relationship between intelligence and cognitive architecture.     

Verbal ability and mental processing speed

The notion that verbal ability is related to mental processing speed was examined using tasks that systematically varied in semantic content. Subjects’ reaction times were measured in five tasks involving arrow matching, physical identity word matching, or taxonomic identity word matching. The findings indicated that matching tasks using different decision rules and different stimuli were all related to verbal ability. In fact, reaction time for subjects required to judge whether two arrows pointed in the same direction was the best predictor of verbal ability. One explanation of the results is that speed of information processing (a general factor) may be the important component of verbal ability which is measured by seemingly different matching tasks.     

Verbal ability and mental processing speed

The notion that verbal ability is related to mental processing speed was examined using tasks that systematically varied in semantic content. Subjects' reaction times were measured in five tasks involving arrow matching, physical identity word matching, or taxonomic identity word matching. The findings indicated that matching tasks using different decision rules and different stimuli were all related to verbal ability. In fact, reaction time for subjects required to judge whether two arrows pointed in the same direction was the best predictor of verbal ability. One explanation of the results is that speed of information processing (a general factor) may be the important component of verbal ability which is measured by seemingly different matching tasks.     

Processing speed and mental retardation: Deadline procedures indicate fixed and adjustable limitations

Brewer and Smith (1984) showed that control mechanisms mediating speed-accuracy regulation contribute to retarded-nonretarded differences in processing speed, with poorly controlled trial-to-trial RT adjustments underlying the greater RT variability of retarded individuals. In Experiment 1, response deadlines controlled processing time, thus minimizing the influence of such control mechanisms. The obtained speed-accuracy relations showed that retarded subjects were unable to match nonretarded subjects' accuracy when responding as rapidly, thus indicating structural limitations on processing speed. The results of Experiment 2 showed, however, that significant adjustments to retarded subjects' processing speed--exceeding those produced by practice--are achievable. Extended training at a short deadline led to tighter control of RT adjustments, with substantial improvements in mean RT when subjects transferred to a self-paced RT task.     

Simple mental addition in children with and without mild mental retardation.

The speeded performance on simple mental addition problems of 6- and 7-year-old children with and without mild mental retardation is modeled from a person perspective and an item perspective. On the person side, it was found that a single cognitive dimension spanned the performance differences between the two ability groups. However, a discontinuity, or "jump," was observed in the performance of the normal ability group on the easier items. On the item side, the addition problems were almost perfectly ordered in difficulty according to their problem size. Differences in difficulty were explained by factors related to the difficulty of executing nonretrieval strategies. All findings were interpreted within the framework of Siegler's (e.g., R. S. Siegler & C. Shipley, 1995) model of children's strategy choices in arithmetic. Models from item response theory were used to test the hypotheses.     

Ministry and mental retardation

Conclusion This has been an attempt to show how the parents of the mentally retarded inspired me to take a second look at my theological views, to show the method I used, and to give a few instances out of many in which my theological views have been affected. If space had allowed, it would have been good to show how this human predicament can cast new light on our theological thinking about grace, redemption, and many other categories. On the other hand, each of us has a chance to pursue in depth any single doctrine, using the added perspective of this particular crisis situation.Each of us has the original theological perspective which we had before beginning our pastoral involvements with the mentally retarded and their families. Then, as we focus on this human situation we become aware of an added theological perspective that helps us to take a second look from a different viewpoint. We then find our original view has been reinforced, modified, or enlarged. It is my feeling that a pastor who becomes involved with these particular persons-who need his services very much—will find a golden opportunity to grow theologically.If any of us feel we know all we need to know about God and life and man, this would be a good time to become involved in a pastoral way with a mentally retarded person and his family and get to know them well.     

Culture and mental retardation

The Psychological Record -     

Psychometric g and mental processing speed on a semantic verification test

The Semantic Verification Test (SVT) consists of brief, simple statements, which are either true or false, about various arrangements of the letters ABC (e.g. B after A). Mean reaction time (RT) for confirming or disconfirming the various statements varies according to their complexity. In independent studies of university students and Navy recruits, RT and other response latency parameters (intraindividual variability and movement time) from SVT performance show significant correlations of about -0.40 with nonspeeded tests of psychometric g. The mean RTs of adults to the various SVT item types are highly related to the mean error rates on these item types when the SVT is taken by elementary school children as a nonspeeded paper-and-pencil test. RT is correlated with the general cognitive ability factor (g) and not with the test-taking speed factor that is found in speeded paper-and-pencil tests. The degree of correlation between RT and psychometric g does not show any regular relationship to differences in the SVT item-type's complexity or difficulty as indicated by mean RT.     

Neuropsychological evaluation and rehabilitation in mental retardation

A discussion is provided of issues related to neuropsychological assessment of mentally retarded individuals. The first matters considered are test selection in relation to mental age and diagnostic issues. Various methods of evaluation are then considered, including assessment of orientation to sound and visual stimuli, language comprehension, right-left discrimination, and abstract and symbolic processes. Methods are also reviewed for detailed evaluation of language functions including testing for aphasia and for academic skills such as reading, writing, and calculation, as well as for spatial and constructional abilities. A section is devoted to use of neuropsychological assessment for rehabilitation of various disorders such as congenital aphasia, alexia, and spatial-constructional disorders.     

Cognitive correlates of laterality in mental retardation

Correlations of various laterality score for 202 persons with cognitive test scores in the seventies of mental retardation are presented.     

High speed memory scanning in mental retardates: evidence for a central processing deficit

Third-grade, high-school, and adult normal subjects and two diagnostic categories of educable mental retardates (cultural familials and encephalopathies) were tested in a Sternberg-type “memory scanning” recognition task. All five groups showed the characteristic linear increase in correct reaction time as the number of items in the memorized set increased. The slopes of the linear functions, however, were steeper for the two retardate samples than for the normal samples, suggesting a central processing deficit which could not be attributed to a lag in development.     

Word-attack skills in individuals with mental retardation

This article assesses the state of the literature on word-attack skills and phonological awareness (PA) in individuals with mental retardation, in light of progress towards the development of effective teaching procedures. The literature contains promising findings. Studies have shown PA to be correlated with word-attack skills in individuals with mental retardation, as has been shown conclusively in typically developing children. This suggests that instruction in PA would facilitate the acquisition of word-attack skills in individuals with mental retardation, as it does with typically developing children. As of yet, however, very few experimental studies designed to demonstrate effective teaching procedures for PA and word-attack skills have been published. This research field might evolve most effectively and efficiently by following a two-step research program. First, test new teaching procedures in a series of small-N studies, each study incorporating modifications of teaching procedures based on the results of the previous study. Once procedures prove effective at this level, the resources necessary to pursue large-scale studies can be used to their best advantage.     

The involvement of epigenetic defects in mental retardation

Mental retardation is a group of cognitive disorders with a significant worldwide prevalence rate. This high rate, together with the considerable familial and societal burden resulting from these disorders, makes it an important focus for prevention and intervention. While the diseases associated with mental retardation are diverse, a significant number are linked with disruptions in epigenetic mechanisms, mainly due to loss-of-function mutations in genes that are key components of the epigenetic machinery. Additionally, several disorders classed as imprinting syndromes are associated with mental retardation. This review will discuss the epigenetic abnormalities associated with mental retardation, and will highlight their importance for diagnosis, treatment, and prevention of these disorders.     

Measuring behavior in genetic disorders of mental retardation

As researchers have examined the so-called "behavioral phenotypes" of different genetic mental retardation conditions, the measurement of behavior becomes increasingly important. From earlier, more global examinations of noteworthy behaviors or profiles, recent researchers have moved from reliance on a single, all-encompassing questionnaire to more multimethod, multireporter approaches. This paper summarizes strengths and weaknesses in utilizing parent-report questionnaires and checklists; psychiatric nosology and specific psychiatric questionnaires; observational studies; reports from individuals with mental retardation themselves; profile analyses of psychometric test and subtest scores; and "grouping" analyses of items (factor analysis) and people (cluster analysis). Although we advocate a mixture of approaches to behavioral assessment, in future work researchers will require more theoretically driven methods for studying behavior, greater acknowledgment that the child's behavior is simply one event in ongoing interactions-transactions with other people, and more attention to age-related changes in behavioral phenotypes.