ABSTRACT
At the beginning of the twentieth century, the Berlin school of Gestalt psychology headed by Christian von Ehrenfels and Carl Stumpf, with its pioneering members Kurt Koffka, Max Wertheimer, Wolfgang Köhler, Kurt Lewin and Wolfgang Metzger, developed a theory of perceptual organization that is now known as Gestalt theory. This school of thought proposed that the percept of the whole was more than the sum of its parts. At the focus of this idea are the principles of perceptual grouping, consisting of the laws of closure, proximity, similarity, good continuation, symmetry, common fate and good Gestalt. These principles or laws were put forth as general tendencies of perceptual organization that can be best studied when visual images were incomplete or the definition of figure-ground is ambiguous. Perceptual phenomena like figure-ground segmentation (i.e. which parts of the image belong to the object and which belong to the background), bistable percepts (exemplified in the famous Necker cube or the Rubin vase-face figure) and visual illusions of brightness (e.g. the Hermann gird or Ehrenstein figure), motion (the phi-phenomenon and other forms of apparent motion) or perspective (the Ponzo figure) could be better understood if the underlying Gestalt principles were consulted. When viewing a matrix of dots, we tend to perceive a single row of these dots as belonging to a perceptual group when they share a common color, are close in proximity to each other, or when their arrangement leads to the formation of a good shape (indeed the German term Gestalt means shape or form, see Figure 1.1). Phenomenological in nature, the Gestalt approach was influenced also by the insights of Weber and Fechner and their laws of psychophysics. Precise description of perceptual phenomena and the stimulus conditions leading to these phenomena were essential prerequisites for their research in perception. a) Demonstration of Gestalt principle of similarity. The 7 x 7 array of gray dots is aligned to be equidistant. The central row forms a collinear group since their color is slightly brighter than those of the other dots. b) Demonstration of Gestalt principle of good Gestalt. As in Figure 1.1(a), the 7 x 7 array of gray dots is aligned to be equidistant. The central square forms two collinear rows and columns of dots that share a slightly brighter color compared to the background dots (see Chapter 5 by Pinna, and Chapter 7 by Hamburger, Dixon and Shapiro for more detailed accounts of Gestalt principles underlying perceptual grouping). https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780203076323/a746b50f-9ff7-4629-8090-464ce5fdc2de/content/fig01_01_C.jpg" xmlns:xlink="https://www.w3.org/1999/xlink"/>
