Rightward directional bias in art produced by cultures without a written language.

In this study, we coded art painted on rocks located in southern Africa, which was painted with a mixture of ochre, blood, and clay by the San, a Neolithic culture with no written language. These images depict a mixture of humans and animals in a variety of contexts, including (but not limited to) hunts and dances. We calculated a laterality index for the collected available art from each region, finding that although there was variability across regions in the direction of the laterality scores, most regions contained a majority of figures facing rightward. This is in stark contrast with reports of artists drawing leftward facing animals and human profiles (an effect that is influenced by native language writing system direction, gender, and handedness), but interestingly our sample also contained regions with strong leftward biases. Our results are, however, in accord with studies that report people preferring images that depict left-to-right motion, as well as the left-to-right bias in depicting transitive actions, an effect that seems to result from greater right hemispheric activation in scene processing and interpretation. Thus, this study shows that in the absence of a writing system, right-lateralized neural architecture may guide the hands of artists.