Gestalt psychology means unified whole. Gestalt psychology does not look at things as individual elements but as a whole. The three main founders who established the school of gestalt psychology were Max Wertheimer, Kurt Koffka as well as Wolfgang Kohler. The foundations of the Gestalt psychology are perception, memory and learning. Some of the principles of Gestalt psychology are isomorphism, productive thinking as well as reproductive thinking which will be elaborated in this essay. One of the main contributions of Gestalt psychology is Gestalt therapy which focuses on helping an individual understand their internal self and the difference of what they experience and interpretation of events.
Gestalt is a psychology term which means "unified whole". It refers to theories of visual perception developed by German psychologists in the 1920s. Instead of approaching psychology as atoms or elements according to Wundt's theory, Gestalt psychology, discovered by Wertheimer, a German, on the other hand, focuses on human experiencing psychological events as a whole. This essay will be focusing on some of the founders of Gestalt psychology and how it has been interpreted and developed over the years from 1880 to 1967, followed by the principles of Gestalt psychology leading to modern day contribution of Gestalt psychology.
Historical Developments
There were 3 main founders and contributors of Gestalt psychology. They were Max Wertheimer, Kurt Koffa and Wolfgang Kohler. Max Wertheimer used to study law but his interest soon shifted to philosophy and psychology. He developed a keen interest on perception after observing how the flashing of lights at train station created an illusion of movement. He was at the University of Frankfurt where he worked with Kurt Koffka and Wolfgang Kohler and the three of them established a school of Gestalt Psychology also known as the school of thoughts. Wertheimer had an enormous influence on other areas including sensation and perception as well as experimental psychology. He also wrote a book on productive thinking shortly before his death in October 1943 and was later published. Kurt Koffka graduated with a doctorate in psychology at the University of Berlin. Later he went on to University of Frankfurt where he started working closely with Wertheimer and Kohler. Koffka primary interest of study was on colors. It focuses on the interrelation of brightness and color, the difference of colors with short and long wave-lengths and also the question of ground and figure. He wrote an article on "Perception: An Introduction to Gestalt Psychology" in 1922. He later went on to being a professor at Smith College where he remained till his death. There he worked on the principles of Gestalt psychology mainly focusing on memory, perception and learning. Wolfgang Kohler graduated with a doctorate from the University of Berlin under the supervision of Stumpf. He later went on to the University of Frankfurt where he worked together with Koffka and Wertheimer. He pursued perceptual ideas through his studies with chimpanzees as director of the Canary Island Anthropoid Station in 1913. He went to become a professor at a University of Berlin taking over Stumpf and left for the U.S as he publicly criticized the Nazis. He became an American citizen and finally became the president of the American Psychological Association in 1959. Kohler contributed substantial literature work to the field of psychology. He wrote and lectured extensively on his animal research and on the understanding of human perception.

Principles
Isomorphism means similar shapes. Isomorphism suggests that there is a clear pattern in the gestalt patterning of stimuli and of the activity in the brain while a person actually perceives the stimuli. For example, if there is a surface filled with color, as individual perceive it, the brain will convert a separate and different color at every distinct space and within that space's surface to a particular resolution. Each point of that surface is not experienced in isolation but in its proper occurring space to every other point in the perceived surface. This shows that the pattern of a person's conscious experience or perception is structurally similar to the patterns of the activity of the brain. The isomorphism discussed in gestalt theory is mainly functional isomorphism. Behavior of a system as if it was physically similar in shape. It can only be assumed as the exact geometrical configuration of the brain but cannot be observed phenomenological.
Productive thinking will lead to an understanding of the relationships between the objects in a problem which will in turn lead to an abstract thought process which can be applied to future problems. Productive thinking is used when there is no obvious answer to the problem. It basically requires the individual to think out of the box to get to the answer. For example, in the Two String Problem experiment, participants were asked to enter a room where to strings were tie at each end of the room and was impossible to grasp both at the same time. At the same time a pair of pliers was also found in the room. Participants were asked to tie both strings together. This situation required participants to perceive the relationship between the objects and relate it to the question that they were asked. The way to resolve this problem was to use the pliers to act as pendulums to give the strings some weight so that it can be further extended and participant can then pull these extended strings towards each other and tie it. Participants were also required to think out of the box, to use the pliers as pendulums instead of tools. Reproductive thinking requires the individual to use the solution of the similar problems that the individual have solved previously to solve current problem. However, reproductive thinking method can only be applied if the individual can recognized the similarity between the two problems and are able to recall it which taps into the long term memory.
Contribution
One of the contributions of Gestalt psychology is Gestalt therapy. Gestalt therapy focuses raising an individual's needs, senses, feelings as well as boundaries. It contributes to the individual well-being and self-respect. It emphasizes strongly on contact, connection and respectful meetings. According to Lewin's theory, an individual is actually a part of society and there cannot be an isolation of an individual as Gestalt has always been focusing on the whole rather than individuals. However, in the context of human being, every one of us are formed by atoms with specific individual characteristic but when put in a larger structure, humans are dependent of each another. This is called, paradigm of individualism.
Gestalt therapy borrows a few of the concept from pragmatism like the concept of human experience, and also one of the gestalt experiments in which insights are encouraged to emerge and be tested within the creative activities of the therapy session. In gestalt therapy, the therapist and the patient will engage together to a point where they develop a phenomenal field and this in turn becomes the focus of the therapy. It focuses on what the patient is feeling at that moment in time and what the patient is thinking at that point of time. The therapist must also be trained to find the patterns in the experiences of the patients through contacting with them. Contact in this context would be what the therapist observed in the session with patient; felt, sensed, perceived, observed and known qualities. The therapy teaches the patient the difference between what they truly experience and what was just the interpretation of events. Gestalt therapy helps patients gain a better understanding of how their emotional and physical bodies are connected. Understanding the internal self is the key to understanding actions, reactions and their behaviors. Gestalt therapy is a form of self-discovery and it gives patients the necessary skills to face stressful situations.

Gestalt psychology has impacted the field of psychology to a huge extent mainly in terms of perception, memory and learning. Principles of Gestalt psychology like isomorphism, productive thinking and re productive thinking had proven to be the few best psychological theories that have been implemented to date. Since gestalt have progressed so much till date, gestalt therapy have been established and it aimed in helping individual understand their internal self in order for them to understand their actions, reactions as well as behaviors.

References:

Köhler, Wolfgang. The Task of Gestalt Psychology. Princeton, NJ: Princeton University Press, 1972.
McConville, Mark. Adolescence: Psychotherapy and the Emergent Self. San Francisco, CA: Jossey-Bass Publishers, 1995.

Ellis, Willis D. (1938)1950 A Source Book of Gestalt Psychology. London: Routledge. → Contains excerpts from the technical contributions of gestalt psychology which were first published in Psychologische Forschung between 1921 and 1938.

Heider, Fritz 1958 The Psychology of Interpersonal Relations. New York: Wiley.

Helson, Harry 1964 Adaptation-level Theory: An Experimental and Systematic Approach to Behavior. New York: Harper.

Henle, Mary (editor) 1961 Documents of Gestalt Psychology. Berkeley: Univ. of California Press.

Henle, Mary 1965 On Gestalt Psychology. Pages 276-292 in Benjamin B. Wolman and Ernest Nagel (editors), Scientific Psychology. New York: Basic Books.