Turn, Turn, Turn: Perceiving Global and Local, Clockwise and Counterclockwise Rotations

The processing of Navon figures (Navon, 1977), i.e., hierarchical letter stimuli, has been studied in experimental settings for many years. In particular, they have been studied in the context of visual hemifield studies and yielded an interaction between hemifield and whether a target is at the local or global level, with a right hemisphere advantage for the global level, and a left hemisphere advantage for the targets at the local level (Sergent, 1982). This is a ventral stream process, however, and we were interested in whether there might be a similar interaction for hierarchical motion stimuli, presumably a dorsal stream process. Hence we developed a series of dynamic geometric Navon figures in order to study global/local rotation processing. These figures consist of a global figure (a triangle or a square) made up of local figures (also triangles or squares). Both global and local figures can rotate in either clockwise or counterclockwise directions independently. We found that there is no right or left visual field perceptual advantage for either the global or local levels of these figures. However, curiously enough, we found that there is a significant processing advantage for clockwise motion compared to counterclockwise motion. We also found a highly significant interaction between the detection of a particular rotational motion and the presence or absence of that motion in the figure being examined. Finally, our data strongly support the Global Precedence Hypothesis which says that people generally tend to focus on the global properties of an object before local properties and that processing proceeds in a global-to-local direction.