Gestalt

Gestalt (ɡəˈSHtält,-ˈSHtôlt/), a German word meaning "form" or "shape", is defined as "something that is made of many parts but is greater or different than the combination of its parts". The concept of Gestalt and its principles are applicable in cartographic design. Gestalt is a general term that describes a group of objects (physical, biological, or even psychological phenomena) that have a definition as a group that is different from their definitions when they were apart. In regards to cartography, the gestalt effect of a map is the way in which a reader perceives all of the elements of a map as a unified whole. When applied to graphic design, gestalt encompasses many concepts including image continuity, closure, similarity, and figure-ground. By understanding the gestalt effect and the application of its laws in map design, it can improve the overall composition of a map through harmony, contrast, and balance.

Gestalt Theory
Gestalt Theory was first developed in the 1920s by German psychologists Max Wertheimer, Wolfgang Kohler, and Kurt Koffka. Then in 1954, the idea became well-known because of the book Art and Visual Perception: A Psychology of the Creative Eye by Rudolf Arnheim. This theory attempts to describe the manner in which humans see the individual components of a graphical image, and organize the components into an organized whole. The Gestalt Theory seeks to understand individual elements by the value of the whole. .

According to Arnheim, the cognitive processes of gestalt are based on a basic law of visual perception: "Any stimulus pattern tends to be seen in such a way that the resulting structure is as simple as the given conditions permit." In other words, as humans make sense of what they see, one of the fundamental goals is cognitive efficiency: make the world seem as simple and orderly as possible. This is the same principle that underlies other cognitive processes that form the basis of geospatial technology and technique, such as generalization and Classification.

Gestalt theory has identified several cognitive processes by which humans organize the visual field into an organized whole:
 * Emergence is the tendency to perceive the whole before we consciously examine the parts.
 * Invariance is the tendency to perceive a designated whole as constant in its characteristics; essentially, once we perceive a pattern, we often see that pattern as stronger than it really is. For example, in a geologic map, one might make a shade of green (representing a particular geologic formation) transparent over a shaded relief image. If executed well, map readers can see the entire green area as a single consistent color and match it to the legend, even though the relief is making the value of the color vary significantly.
 * Reification is the process of recognition, by which large numbers of small individual visual stimuli are combined into simple wholes that can be associated with known concepts and real-world phenomena. For example, a collection of black dashes can be merged into boundary lines, which are in turn combined to form the shape of a country.
 * Multistability is the ability to see multiple wholes at the same time or quickly alternate between perceived wholes. For example, if a choropleth map of income using a divergent color scheme from orange (poor) to green (wealthy), one can see patterns of wealth and poverty nearly simultaneously by isolating shades of green and shades of orange. This process can also have negative consequences, leading to confusion when the reader cannot decide on which pattern to focus attention. A clear visual hierarchy typically mitigates negative multistability.

Prägnanz or Grouping
A primary part of the cognitive process of making sense of the visual field is the grouping of large numbers of individual visual stimuli into larger wholes and patterns. This notion is crucial in maps, which typically consist of multiple layers, each of which consists of many geographic features. It is expected that readers will be able to recognize patterns in each theme as well as connecting patterns between multiple themes.

Often called the Gestalt Laws of Grouping or the Law of Prägnanz, these six principles are essential in map design for creating patterns:


 * Proximity: objects located close together are perceived as a group.
 * Similarity: objects that look alike (e.g., in shape, pattern, color) are grouped. This is especially important for map symbols.
 * Continuity: when the viewer perceives a visual pattern, he or she may extend the pattern beyond the visual field.
 * Closure: disjoint objects may be combined to create a single recognizable shape.
 * Figure-Ground (Area): when looking at a visual area, some objects may appear more distinguished (figures) and stand out more than the background (ground).
 * Symmetry: the viewer perceives an object as forming around its center and being equal or similar across opposing sides.

Gestalt Principles in Map Design
Gestalt is critically important in map design since maps are compositions of many smaller elements that combine to form a bigger picture. For there to be a sense of gestalt in a map, the different elements of a map must interact in relation to each other using various principles of map design. These principles are not applied in isolation but are used in harmony to help cartographers convey geographic information. Several principles of cartography are aimed at achieving the gestalt effect:
 * Aesthetics: the artistic values of harmony, composition, and clarity of map elements is necessary in order to convey the purpose of the map and invoke emotional responses from map viewers.
 * Figure-ground contrast: the contrast or visual difference between figures or features on a map from the ground or background emphasizes the relationship between layers and figures.
 * Visual hierarchy: the order of importance of geographic features displayed on a map, distinguishing main themes from supporting themes and reference information. A clear visual hierarchy places emphasis on the most important information or intended theme of the map, though reference information is necessary to convey the context of the main themes.
 * Contrast: differences among map features that allows the viewer to easily distinguish between them, usually involving differing colors, sizes, or weights. Contrast distinguishes different layers and values from each other to depict visual hierarchy or display variations of geographic phenomena across space.
 * Balance: the organization of different elements on a map such as relative location, shape, size, and subject matter. A well balanced map displays equilibrium and harmony.