Handedness and birth stress in children and young adults with learning or behavioral difficulties

A literature review by Searleman et al. (1989) suggested that a relationship between the presence of pre- and perinatal complications and handedness does not exist or is very small in normal subjects. Such a relationship might very well be stronger in certain diagnostic groups, however. In the present study, 234 children and young adults with learning and/or behavioral difficulties and with normal intelligence served as subjects to investigate the relationship. Non-right-handers appeared to have suffered more from two specific birth stressors, rhesus antagonism and breathing problems. They also had more problems with spoken language, whereas no relationship was found between handedness and a composite birth stress score. The problems of valid inference making are discussed in terms of statistical power and chance relationships, and it is suggested that stringent interpretations of statistical test results should be avoided in this and other studies. It is concluded that in the diagnostic group of children and young adults investigated here, the effect of pre- and perinatal complications on the development of handedness is either absent or small.