Visual hierarchy is the order in which the human eye perceives what it sees. This order is created by the visual contrast between forms in a field of perception. Objects with highest contrast to their surroundings are recognized first by the human mind. The term visual hierarchy is used most frequently in the discourse of the visual arts fields, notably so within the field of graphic design.
The concept of visual hierarchy is based in Gestalt psychological theory, an early 20th-century German theory that proposes that the human brain has innate organizing tendencies that “structure individual elements, shapes or forms into a coherent, organized whole.” The German word Gestalt translates into “form,” “pattern,” or “shape” in English. When an element in a visual field disconnects from the ‘whole’ created by the brain’s perceptual organization, it “stands out” to the viewer. The shapes that disconnect most severely from their surroundings stand out the most.
The brain disassociates objects from one another based upon the differences between their physical characteristics. These characteristics fall into four categories: color, size, alignment, and character. The category of color encompasses the hue, saturation, value, and perceived texture of forms. Size describes the surface area of a form. Alignment is the arrangement of forms with respect to their direction, orientation, or pattern. Character is the rectilinearity and curvilinearity of forms. Forms that have differences in these characteristics contrast each other.
Visual hierarchy is an important concept in the field of graphic design, a field that specializes in visual organization. Designers attempt to control visual hierarchy to guide the eye to information in a specific order for a specific purpose. One could compare visual hierarchy in graphic design to grammatical structure in writing in terms of the importance of each principle to these fields.
Fluorescent color contrasts highly against most naturally occurring colors. Fluorescent substances achieve this contrast by emitting light. Forms of this type of color are almost always high in visual hierarchy. Tennis balls are fluorescent green for the perceptual ease of players, match officials, and spectators.
Camouflage patterns diminish the contrast between themselves and their surroundings. Camouflage describes a form that mimics the physical characteristics of its environment. These patterns are difficult and sometimes impossible to perceive. Certain animals and military forces have both developed their own camouflaged patterns as mechanisms of defense.