The effect of explicit cultural bias on lateral preferences in Tunisia

Hand, eye and foot preferences in Tunisia were examined in relation to age, gender and geographic location. We analyzed 1291 questionnaires from 653 men and 638 women, aged 8 to 74 years. Despite the cultural pressure against the use of the left hand for food-related activities, the overall frequency of left-hand writers (10.9%) was comparable to that found in the Western world. The frequency of left-hand writers was higher for subjects with one left-handed parent, and even higher for subjects with two left-handed parents than for subjects whose parents were right handed. The frequency of left-hand writers dropped to 5.9% in the older age-group; it was found to be higher in Tunis, the largest and most Occidental city, than in other cities, while left-hand eating was lower in the South than in the Center or in the North. The frequency of left-footers also dropped in the older age groups and was higher in Tunis than in other cities. Eye preference, consistency of preferred-hand use, crossed hand-eye laterality, crossed hand-foot laterality and gender-related differences in lateral preferences were all comparable to Western results. These data suggest that lateral preferences are partly influenced by a genetic factor, but that handedness (and to a lesser degree footedness) emerges from the intricate interaction of several factors including genetic and cultural influences.