Season of birth and parental age in right, mixed and left handers

Bulgarian secondary school students (264 right handers, 246 mixed handers and 360 left handers) were investigated concerning subjectʹs month of birth and concerning his motherʹs and fatherʹs age at his birth. Neither the month of birth nor any group of months turned out to be significantly associated with handedness. Similarly, no association between parentsʹ age and handedness was found.