While developing a rendering, an artist strives for interest by creating differences that emphasize the degrees of importance of its various parts. These differences result from compositional considerations - some features are emphasized, and others are subordinated. This creates both primary focal points and secondary areas of interest that help move the eye around the rendering.
Areas become dominant when they are emphasized by contrasts that make them stand out from the rest. Contrast draws attention like the spotlight in a dramatic production or crescendo in a musical piece. In general, the greater the contrast, the greater the emphasis and the more dominant the area becomes.
Renderings that neglect varying degrees of dominance seem to imply that everything is of equal importance, resulting in a confusing rendering that gives the viewer no direction and fails to communicate.