In this monograph, the author, basing his conclusions on a critical analysis of available data, rejects the widely accepted hypothesis that handedness is an hereditary trait. Instead, he proposes that preferred laterality is a complicated, developmental trait with biologic endowment, learning experience, emotional reactions and social influence as prominent determining factors.
He explains the occurrence of left-handedness in 5 to 10 per cent of the population as due to: (1) an inherent deficiency, such as a physical defect in the right member enforcing the use of the left, or mental deficiency, (2) faulty education in the use of the hands and (3) emotional negativism.
Regarding the language centers, Blau proposes that cerebral dominance is determined by function. People are left-brained because they are right-handed, and the reverse is true of sinistrals.
Blau concludes that children should be encouraged in their early years to adopt right-handed habits. He believes that the