The gestalt principle of perception is the concept that the human mind sees patterns in incomplete representations of objects or concepts and is able to deduct the nature of the whole from these patterns. It is in direct opposition to the approach of Atomism in psychological theory, which states that human perception is based on being able to break down concepts or objects into fundamentally basic parts that are identifiable. Types of perception for the human mind were first being studied intensely in the late-19th century by psychology, and the gestalt principle of perception arose at the time to challenge Atomism. It was promoted in the 1920s by such renowned thinkers as Johann von Goethe, Ernst Mach, and Max Wertheimer. The most basic of underlying gestalt principles is that the human mind perceives meaning based on the higher brain context of what its senses witness more than it relies on the full sensory content before it.
The way that the human mind achieves perceptual organization of its surroundings may remain an incomplete mystery indefinitely, though psychology as of 2011 has a foundational understanding of how it works. Gestalt principles are founded upon four basic premises about how people think. These involve the ideas of similarity, continuation, proximity, and closure.
The concept of similarity means that the human mind groups together objects and occurrences that have basic traits in common, and sees higher connections between them that make them appear as a unified whole. Continuation involves a visual trait where the eye is led to follow a certain pattern to its end to find meaning in an object, which is often based on simple lines or curves present in natural and man-made environments. Proximity is related to continuation, and is a tendency in thinking to group together objects that are physically near each other as being parts of a larger whole, such as a series of small blocks aligned next to each other perceived as making up one larger block.
Closure is one of the more fundamental aspects of the gestalt principle of perception, which states that the mind essentially “fills in the blanks” when an incomplete picture or pattern is observed. The mind has a tendency to give incompleteness a greater meaning, based partly on assumptions from memory and experience about what the missing elements would be. There is also a natural tendency with human perception for the mind to orient itself in an environment based on directions of up and down, which are referred to as figure and ground. Objects are differentiated from a platform upon which they are assumed to rest, or a background upon which they are superimposed. This tendency is so innate to the gestalt principle of perception that, when perspective is removed such as in a weightless environment in space or underwater, the human mind can become disoriented and confused.
A convenient way to imagine how the two opposing theories of Atomism and the gestalt principle of perception differ is in considering how someone “sees” a tree. The Atomism approach states that someone first sees the individual components — the leaves, branches, trunk and so on — and then assembles them all in the mind to realize that it is a tree. The gestalt principle of perception states that the entire tree is seen first, even if significant parts of it are missing from view or are distorted, and its individual components like leaves or fruit are not usually or immediately present on a conscious level.