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.     

Developmental differences in mental rotation.

A reaction time paradigm was used to investigate developmental differences in ability to rotate and compare imaginal representations. Third grade, fifth grade, and college students (ages 9, 11, and 20 years, respectively) were required to determine whether a letter of the alphabet was presented in its backward or normal position. Letters were presented at 0, 60, 120, 180, 240, or 300° orientations from upright. Subjects were given no advance information about a test letter, or they were given identity and orientation information. In the no information condition, reaction time increased for all age groups as a function of the departure in orientation of the test letter from an upright position. In the advance information condition, reaction time remained uniform across orientation for only the college subjects. The developmental implications of these findings are discussed.     

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.     

The use of genomic microarrays to study chromosomal abnormalities in mental retardation

Mental retardation affects 2 to 3% of the US population. It is defined by broad criteria, including significantly subaverage intelligence, onset by age 18, and impaired function in a group of adaptive skills. A myriad of genetic and environmental causes have been described, but for approximately half of individuals diagnosed with mental retardation the molecular basis remains unknown. Genomic microarrays, also called array comparative genomic hybridization (array CGH), represent one of several novel technologies that allow the detection of chromosomal abnormalities, such as microdeletions and microduplications, in a rapid, high throughput fashion from genomic DNA samples. In one early application of this technology, genomic microarrays have been used to characterize the extent of chromosomal changes in a group of patients diagnosed with one particular type of disorder that causes mental retardation, such as deletion 1p36 syndrome. In another application, DNA samples from individuals with idiopathic mental retardation have been assayed to scan the entire genome in attempts to identify chromosomal changes. Genomic microarrays offer both a genome-wide perspective of chromosomal aberrations as well as higher resolution (to the level of approximately one megabase) compared to alternative available technologies.     

Similarities and differences in visual and spatial perspective-taking processes

Processes for perspective-taking can be differentiated on whether or not they require us to mentally rotate ourselves into the position of the other person (Michelon & Zacks, 2006). Until now, only two perspective-taking tasks have been differentiated in this way, showing that judging whether something is to someone’s left or right does require mental rotation, but judging if someone can see something or not does not. These tasks differ firstly on whether the content of the perspective is visual or spatial and secondly on whether the type of the judgement is early-developing (level-1 type) or later-developing (level-2 type). Across two experiments, we tested which of these factors was likely to be most important by using four different perspective-taking tasks which crossed orthogonally the content of judgement (visual vs. spatial) and the type of judgement (level-1 type vs. level-2 type). We found that the level-2 type judgements, of how something looks to someone else and whether it is to their left or right, required egocentric mental rotation. On the other hand, level-1 type judgements, of whether something was in front of or behind someone and of whether someone could see something or not, did not involve mental rotation. We suggest from this that the initial processing strategies employed for perspective-taking are largely independent of whether judgements are visual or spatial in nature. Furthermore, early developing abilities have features that make mental rotation unnecessary.     

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.     

A longitudinal study of active treatment of adaptive skills of individuals with profound mental retardation.

A longitudinal study indicated that a single group of adults living in a large state institution (O'Berry Center in Goldsboro, North Carolina) benefited from receiving active treatment, although no control group was permitted. After five years, 59 individuals with profound mental retardation improved their skills in six general areas of dressing, grooming, eating, toileting, communication, and social interaction. After five more years of active treatment, 51 persons who had remained in the program maintained their skills in dressing, grooming, eating, and communication. Significant improvement in the use of toilet and a loss in social interaction were observed. Although the participants were 10 years older at the end of this study, their adaptive behaviors, in comparison to the date of entry, either improved or were maintained. Therefore, aging was not associated with decline in skills.     

Environmental postmodernism and rehabilitation of the borderline of mental retardation

The subculture of developmental disabilities services has embraced ideological perspectives from academia in general and from other service sectors, including, in recent years, the educational sector. Prevalent ideological and philosophical perspectives with growing influence within the professional literature and to a lesser degree, the practitioner community, include postmodernist and constructionist doctrine. These perspectives influence the depiction of utility of a wide variety of clinical and programmatic activities that typify services and, generally, impact upon decision making by policy makers, administrators, and possibly, to an important degree, by managers who influence events at the point of clinical and service contact. This article discusses the nature and character of these influences and the issues facing the field, centering on the act of classifying a person with mild mental retardation, as well as uncertainties regarding both the process and consequences of classification. Recommendations are made for an expanded but modified role for adaptive behavior assessment in this process. Copyright © 2001 John Wiley & Sons, Ltd.     

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.     

Stanford-Binet and WAIS IQ differences and their implications for adults with intellectual disability (aka mental retardation)

Stanford-Binet and Wechsler Adult Intelligence Scale (WAIS) IQs were compared for a group of 74 adults with intellectual disability (ID). In every case, WAIS Full Scale IQ was higher than the Stanford-Binet Composite IQ, with a mean difference of 16.7 points. These differences did not appear to be due to the lower minimum possible score for the Stanford-Binet. Additional comparisons with other measures suggested that the WAIS might systematically underestimate severity of intellectual impairment. Implications of these findings are discussed regarding determination of disability status, estimating prevalence of ID, assessing dementia and aging-related cognitive declines, and diagnosis of ID in forensic cases involving a possible death penalty.     

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.