The early characteristics of groups of children, aged 7 to 8 years, identified with reading disability (RD) only, behavior problem (BP) only, RD and BP, and neither RD nor BP, were compared by temperament and behavior indices, gathered in 5 periods between infancy and 6 years of age, at the Department of Psychology, University of Melbourne, Australia. The RD children with and without BP were different from each other from early childhood. BPs of both the BP-only and the comorbid group distinguished them from the non-BP groups at an early age. In contrast, the RD-only children were similar to the normal comparison group up to school age, except for lower maternal education and more difficult temperament. The early detection of RD could not rely on behavioral measures. Children at risk for developing pure RD were predominantly girls, and low educational stimulation from low maternal education was the only risk factor. The gender composition of the two RD groups differed, the RD-BP boys showing the most problems. Boys with difficult temperament, poor mother-child relationship, lower educational stimulation and relative social disadvantage were at risk of early development of BPs and later diagnosis of RD. 
COMMENT. This study suggests different developmental pathways for pure RD children and those with comorbid BPs. Sex differences were also evident, boys showing more behavioral problems and more difficult temperament from 1-3 years, more hostile-aggressive and hyperactive behavior from 3-4 years, and lower school readiness and task orientation.
Twin-sibling differences in ADHD children with reading and speech problems were reported from the Prince of Wales Hospital, University of New South Wales, Australia . Male twins had the highest rate of ADHD, speech and reading problems. The reading deficit in male twins becomes more marked in adolescence while that in female twins decreases. Pre- and perinatal insults were not the explanation for an increased incidence of ADHD among twins.