Bilateral Transfer of Motor Skill as a Indicator of Anomalous Dominance Pattern of Lateralization among Mentally Challenged

This research paper is concerned with atypical laterality in the field of perceptual- motor skill among mentally challenged, reveals about the anomalous pattern of lateralisation and severity of cerebral dysfunction in this population. The number of children diagnosed with mental retardation and developmental disorder such as dyslexia, autism, speech and language impairment and attention deficit disorder are increasing as these disorders become better defined in terms of their behavioural and motor characteristics. The studies of brain morphometry were stimulated by the landmark study of Geschwind and Levitsky (1968), which provided evidence of asymmetry in brain structure that correlated with the well established functional asymmetry and found dominance of the left hemisphere for language and motor related activity. Implicit in the notion that mentally challenged persons are associated with anomalous lateralisation pattern or atypical lateralisation pattern. Atypical laterality (i.e. the lack of a clear pattern of lateralisation) has been found to be characteristics of individual with intellectual disability (ID). The evidence has been based on handedness studies which have contain little information about the ability of people with ID to carry out interhemispheric task reflecting bilateral transfer. The present study examined the atypical laterality among mentally challenged person by utilising bilateral transfer of motor skill by transfer paradigm. Right handed mentally challenged (No= 60) and controls matched (N=60) for age and sex were tested for bilateral transfer of motor skills in contralateral hands with a mirror drawing task. The finding indicated that mentally challenged people are significantly deficient relative to match controls in bilateral transfer of motor skills from their non-preferred (left) hand to their preferred (right) hand. Mentally challenged persons were found to perform better with their non- preferred hand than with their preferred hand. A within group comparison revealed that right handed performance was more affected and committed more errors than left hand in these subjects.