Family History of Handedness and Language Problems in Mexican Reading-Disabled Children

Behavioural Neurology (1996), 9, 119-126 Family history of handedness and language problems in Mexican reading-disabled children E. Matute 1 , S. Guajardo-Cardenas 1 and M-de-L Ramfrez-Duenas 2 1Departmento de Estudios en Educacion, Universidad de Guadalajara, Guadalajara, Jalisco, Mexico and 2Division de Genetica, Centro de Investigaciones Biomedicas de Occidente, Instituto Mexicano del Segura Social, Guadalajara, Jalisco, Mexico Correspondence to: E. Matute, Departmento de Estudios en Educacion, CUCSH. Universidad de Guadalajara, Hidalgo 935, Sector Hidalgo C:P:44100, Guadalajara, Jalisco, Mexico. A sample of 120 Spanish-speaking children, 60 with reading disabilities and 60 normal readers was studied. Individual and family history of handedness, language problems, and reading disabilities were analyzed in each case. The results suggest that reading disabilities are more common among boys, that associated language problems are frequent and that handedness is not a significant factor. Insofar as family history is concerned, there were more affected families and relatives in the reading disabled group than in the control group. Finally an association was established between the variables of handedness and language problems. Keywords: Children - Dyslexia - Genetics - Reading disabilities INTRODUCTION A specific reading disability like dyslexia is one of the most common educational problems (Malatesha and Dougan, 1982). The schoolchildren who suffer from it are otherwise at least average in cognitive skills, and emotional and social experiences, and this disability is not attributable to other handicapping conditions (Hynd and Cohen, 1983). Early research on reading disability gave rise to the hypothesis that an association exists between learning problems and imperfect cerebral dominance, linked mainly to a high frequency of left- or mixedhandedness (Orton, 1928, 1937). Even though there is more recent research about this subject (Porac and Coren, 1981), the questions remain unanswered. Geschwind and Behan (1982) reported an association between left-handedness, certain disorders of the immune system and dyslexia, which is stronger in males. On the other hand, it has been established that some children with reading disability had language problems early in development (Pirozzolo, 1985). Hecaen et ai. (1981) suggested that bilateral language representation is more common among left-handed subjects with a family history of left-handedness. Possibly, this type of representation favors a greater incidence of reading problems. Studies on the genetics of reading disability demonstrated that at 0953-4180 © 1996 Rapid Science Publishers least in certain SUbtypes, a family aggregation exists (Van Strien et ai., 1990; DeFries and Decker, 1992). Nevertheless, no conclusive relationship has been established between reading disability, handedness, and language problems. Furthermore, a hypothesis exists about the relationship between the language orthography and the reading problem tipology. Taking English and Spanish, the former is a partially logographic reading system (depth ortography) and the latter uses a more graphophonemic reading system (shallow orthography). Taking account of this hypothesis, some differences in reading errors have been shown between Spanish and English speaking brain-damaged dyslexic adults (Ardila et ai., 1989; Ardila, 1991) and between German and English speaking dyslexic children (Wimmer, 1994). The language and cultural characteristics of the subjects may influence different variables. We studied a sample of reading-disabled and normal readers among Mexican children (Spanish speakers). A possible association between reading disability, handedness and language problems was analyzed, as well as the family history in question. Since there are almost no studies on Spanish-speaking dyslexic children, and because the structure of the Spanish Behavioural Neurology. Vol 9 • 1996 119 E. MATUTE ET AL. language is different from that of English, where the spelling is more transparent (meaning that there is a high grapheme-phoneme consistency) the present studies are of particular value. METHODS The reading disabled group (RDG) was made up of 60 children, randomly selected from the 'Centro Psicopedag6gico de Guadalajara', belonging to the 'Departmento de Educaci6n Especial, Unidad de Servicios Educativos a Descentralizar'. They ranged from second to sixth grade of elementary school; 12 from each grade were included. WISC-RM IQ ranged from 86 to 120. All of them were diagnosed previously as specifically reading disabled, and obtained only low scores on reading and writing with the Guias de Evaluaci6n Psicopedag6gicas and PPCILEM which are unpublished Mexican tests designed to detect specific learning failures. The Control Group (CG) was made up of randomly selected children from the same sex, grade and school as that of the RDG; only children with good school performance and no recognized learning difficulties were included in the CG. The reading profiles of the two groups obtained through the reading of a story of 290 words were considerably different in relation to the reading speed and the number of words misread but not in relation to omitted words (Table I). TABLE I. Comparisons between the reading disabled (RDG) and control group (CG) for text reading RDG Variable Words/min Words misreaded Words omitted CG Mean S.D. Mean 51.12 22.34 86.53 26.98 -7.83 0.00001 21.63 15.37 10.05 7.80 5.20 0.00001 7.35 20.08 3.98 1.65 2.98 S.D. p< N.S. Personal and family data were obtained for each case in two ways: (1) Centro Psicopedag6gico Records; (2) a questionnaire to the parents of each child, including identification data, medical, educational and personal background. With regard to the language problems, the parents were asked if their child had had a delay or problems in learning to talk and if it had undergone language therapy. Family information included: parents' identification data, educational and social level, occupation, a twogeneration pedigree and reports (only by parental 120 Behavioural Neurology. Vol 9 • 1996 reference) of handedness, reading disability, and language problems in parents and siblings. This information was obtained by a questionnaire. The 120 children were examined using the following tests. First, a handedness test: hand use was evaluated with eight items to identify hand dominance, four of them required only one hand (to catch a ball, to write, to brush his or her hair, to take a spoon), and four required the participation of both hands (to twist ajar open, to open a Coke bottle, to take a hat and to put it on a doll, to thread a needle). The dominating hand in each task was registered, and a percent of handedness was calculated (number of right-hand dominant tasks/total tasks x 100 = %) and expressed as handedness coefficient (HC); those children with HC between 100 to 88 were classified as right-handed, those (...truncated)