Developmental Risk: Evidence from Large Nonright-Handed Samples

Hindawi Publishing Corporation Child Development Research Volume 2013, Article ID 169509, 10 pages http://dx.doi.org/10.1155/2013/169509 Research Article Developmental Risk: Evidence from Large Nonright-Handed Samples Filippos Vlachos,1 Francois Gaillard,2 Kiriazis Vaitsis,1 and Argiris Karapetsas1 1 2 Department of Special Education, University of Thessaly, Argonafton & Filellinon, 38221 Volos, Greece Institute of Psychology, University of Lausanne, Géopolis, 1015 Lausanne, Switzerland Correspondence should be addressed to Filippos Vlachos; Received 29 March 2013; Revised 4 June 2013; Accepted 19 June 2013 Academic Editor: Ross Flom Copyright © 2013 Filippos Vlachos et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The aim of the present study is twofold. First, we tested the view that individuals who do not develop a typically strong behavioral laterality are distributed differentially among the two genders across age. Second, we examined whether left handedness and mixed handedness are associated with an elevated risk of some developmental or cognitive deficits. A special recruitment procedure provided norms of the Rey-Osterrieth Complex Figure (ROCF) copy from large samples of left-handed (𝑁 = 420) and mixedhanded (𝑁 = 72) compared to right-handed (𝑁 = 420) schoolchildren and adults (𝑁 = 545). This graphic task was considered as reflective of the growth of visual-spatial skills and impairment at copying as a developmental risk. Subjects’ hand preference was assessed by the Edinburgh Handedness Inventory. Data analysis indicated that (1) the trend towards consistent right handedness is sex related. Girls are clearly ahead of boys in this lateralization process, and boys are overrepresented in mixed-handed subjects. The greater prevalence of mixed-handed boys compared to girls decreases with age. (2) Performance on drawing the ROCF varies according to age and handedness groups. Mixed-handed subjects scored worse in all age groups. The results are discussed in relation to the hormonal-developmental, neuropathological, and learning theories of lateralization. 1. Introduction Handedness is a significant feature of ontogenetic development. Its consistency and stability provide evidence for brain hemispheric specialization and can be used as an indicator of developmental stages. Lateralization is both cause and consequence of having a brain with two cerebral hemispheres specialized to perform different tasks and work together in order to improve many motor and cognitive tasks. At the first glance, no hand lateralization is observed in young children who have not yet learned to use innate biological asymmetry. However, careful observation of motor behavior in infants already reveals the human specific trend towards dextrality [1, 2]. The study of handedness has been of interest for many years because subtle cognitive and behavioral differences have been demonstrated in relation to various handedness measures [3]. Gender differences in handedness are widely reported. A recent meta-analysis of 144 studies [4] demonstrated that the gender difference in handedness is both significant and robust, indicating that the overall best estimate, albeit not universal, for the male to female odds ratio was 1.23. The purpose of this study is to investigate further the effects of handedness, as a proxy for hemispheric laterality, in terms of gender differences, performance on a cognitive task, and the potential for later cognitive impairment, examining large left-handed and mixed-handed groups of children and adults. Large samples of nonright handers are rare because only 9-10% of the population of schoolchildren is left-handed, and there are even fewer nonlateralized children. In previous studies [5–7], using a special recruitment procedure in order to obtain a large group of left handers (each lefthanded child was matched by age and sex to a right-handed child), we have demonstrated differences between left and right handers on the Rey-Osterrieth Complex Figure (ROCF) test, a popular tool used to test visuospatial-constructional functions [8]. In the present study, we complete this observation by including non-lateralized children. We are also adding 2 a group of adults in order to present the whole cognitive development. A very recent study [9] indicated that there is no single pattern in the development of handedness from 6 to 24 months, and the shift to more robust hand use preferences may be a developmental phenomenon. Inconsistent and unstable handedness has been found in several clinical groups with pathological cognitive development [10, 11]. However, many studies showed no relationship between handedness and cognitive development in samples of normal children [12–16]. These observations show that factors that disrupt cognitive development can also disrupt the development of consistent manual dominance. We can explain this discrepancy between apparently contradictory results by considering progressive handedness to be merely a sign of brain specialization and not a condition of mental development. However, during the school years, consistent and stable handedness appears as a tool for learning fine motor tasks such as writing and for developing the spatial sense necessary for written language and calculation. Although nonlateralized schoolchildren are not delayed in maturation, they lack the advantage that left and right handers have in their learning. This is why nonlateralized schoolchildren are often at risk of being considered as slow learners or as learning disabled as far as visual-spatial abilities are concerned. In this sense, they are subjected to a true developmental risk. Progressive hand preference indicates neurophysiological asymmetry which is genetic and biological in origin [17– 20]. However, some handedness conditions are pathological. According to the theoretical account of pathological lefthandedness syndrome, a subgroup of left handers suffers from a condition that involves an early injury. This syndrome is believed to be caused by a hemispheric lesion that is predominantly left-sided (or bilateral asymmetric), which onsets before the age of 6 and which encroaches upon the critical speech zones of the frontotemporal/frontoparietal cortex [10]. Indeed, the trend towards functional lateralization reveals itself to be sensitive to any cerebral disturbance. The neuropathological hypothesis of handedness would firstly predict that diffused brain injury would result in a lack of hand dominance and, secondly, that lateralized hemispheric damage would produce strong ipsilateral hand dominance. In the first case, patients present a habitus of mixed handedness characterized by low motor performances on both body sides. Research on prematurity, on risk pregnancy, and on dystocia has shown tha (...truncated)