Incidence and Gender Differences for Handedness among Greek Adolescents and Its Association with Familial History and Brain Injury

Handedness is marked by the preference of one hand over another for fine motor tasks, especially writing. Usually, only one hand is considered dominant; however, there are individuals who exhibit the ability to use both hands equally (mixed-handers). The aim of this study was to identify the incidence for handedness in a sample of Greek adolescents and examine possible gender differences in handedness among these adolescents and their siblings. 634 secondary school students (Mean age 13.38, SD = 1.47) who attended mainstream public schools participated in this study. All students completed the Edinburgh Handedness Inventory (EHI). Students were divided in three groups, namely right-handers (an EHI +50 to +100), mixed-handers (an EHI -49 to +49) and left-handers (an EHI -100 to -50). This process resulted in the classification of 544 adolescents (85.8%) as right-handed, 46 adolescents (7.3%) as left-handed and 44 adolescents (6.9%) as non-lateralized (ambidextrous). Contrary to previous research, the statistical analysis conducted did not reveal any significant differences in the prevalence of handedness between genders. Nevertheless, our data suggest that men might be more prone to ambidexterity. Similarly, although some interesting trends were observed in our data, the statistical analyses performed did not confirm the familial effect upon handedness and the pathological left-handedness hypotheses. The paper concludes with underlining the significance of the evidence presented here and discusses the inconclusive findings often reported in the literature concerning the association of handedness with family history and brain injury.