Aesthetic preference for the vertical composition of single-object pictures was studied through a series of two-alternative forced-choice experiments. The results reveal the influence of several factors, including spatial asymmetries in the functional properties of the object and the typical position of the object relative to the observer. With asymmetric side views of objects, people generally prefer objects typically located below the observer's viewpoint (e.g., a bowl or swimming stingray) to be below the center of the frame and objects typically located above the observer's viewpoint (e.g., a light fixture or flying eagle) to be above the center of the frame. In addition, people generally prefer symmetric views of those same objects from directly above or directly below to be closer to the center of the frame. We suggest that these results can be unified by the hypothesis that people prefer the object's "affordance space" to be centered within the frame. (Contains 8 figures and 4 footnotes.)