What is the Meaning of Shape? - Gestalt Theory

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GESTALT THEORY, Vol. 33, No.3/4 likely as important as the wheel. The square is, in fact, a basic shape used to measure any kind of object, shape or space. Every shape either regular or irregular is measured in squares (m2 ) or in the 3-D version of the square, cubes (m3 ). The square is the unit and, more generally, the ‘brick’ of all the other shapes. By moving around the gaze and focusing the attention on the shapes, one notices that almost everything has a square shape. Most of the human artifacts are made up of squares or its variations. For instance, houses are composed of windows, floors, tables, televisions and doors that are squares or square-like shapes. As concerns these special phenomenal properties, we will study the meaning of shape starting from the square. 1.2. The Shape before the “Shape”: Grouping and Figure-Ground Segregation Gestalt psychologists were the first to study and develop a theory of shape, considered as an emergent quality. They studied the shape mostly in terms of grouping and figure-ground segregation. (Other Gestalt approaches to shape perception will be discussed in section 3.3.) Rubin (1915, 1921) studied the problem of shape formation in terms of figureground segregation, by asking what appears as a figure and what as a background. He discovered the following general figure-ground principles: surroundedness, size, orientation, contrast, symmetry, convexity, and parallelism. Rubin also suggested the following main phenomenal attributes, belonging to the figure but not to the background. (i) The figure takes on the shape traced by the contour, implying that the contour belongs unilaterally to the figure (see Nakayama & Shimojo, 1990; Spillmann, 2012; Spillmann & Ehrenstein, 2004), not to the background. (ii) Its color/brightness is perceived full like a surface and denser than the same physical color/brightness on the background that appear instead transparent and empty. (iii) The figure appears closer to the observer than the background. Wertheimer (1923, see also Spillmann, 2012) approached this problem in terms of grouping. The questions he answered is: how do the elements in the visual field ‘go together’ to form an integrated percept? How do individual elements create larger wholes? He studied some basic grouping principles useful to answer the previous questions. They are: proximity, similarity, good continuation, closure, symmetry, convexity, prägnanz, past experience, common fate, and parallelism. It is reasonable to consider that figure–ground segregation must operate before grouping (Hoffman & Richards, 1984; Palmer, 1999). For example, dot elements on which grouping acts must be already segregated as a figure from the background, otherwise the visual system would not know which elements to group. Nevertheless, the same elements do not possess the figural properties of holistic organized and segregated figures; rather, they appear as elementary 384
385 Pinna, What is the Meaning of Shape? components necessary to create boundaries. They are not surfaces, but something similar to perceptual ‘bricks’ necessary to create something more holistic. In spite of the apparent differences between figure-ground segregation and grouping, what is phenomenally clear is that both dynamics are so intimately intertwined that a sharp distinction is likely impossible and maybe useless from a scientific point of view. Within Rubin’s and Wertheimer’s works, the problem of shape formation is approached in terms of the main conditions operating in two of the processes (grouping and figure-ground segregation) underlying but preceding the formation of the shape. For example, the unilateral belongingness of the boundaries can be considered as a shape issue before the “shape” meaning. It talked about shape but it did not explain its meaning. Similarly, even if the closure principle can describe the perception of a square, it cannot say anything about its properties and about the way its properties assign the special meanings we have previously described. Furthermore, it cannot explain the square variations described in the next sections. Even if Gestalt grouping and figure-ground principles are part of the problem of shape perception, they do not face directly this problem and, more importantly, they do not answer basic questions like: what is shape? What is its meaning? 2. General Methods 2.1. Subjects Different groups of 12 undergraduate students of architecture, design, linguistics participated in the experiments. Subjects had some basic knowledge of Gestalt psychology and visual illusions, but they were naive both to the stimuli and to the purpose of the experiments. They were male and female with normal or corrected-to-normal vision. 2.2. Stimuli The stimuli were the figures shown in the next sections. The overall sizes of the visual stimuli were ~3.5 deg visual angle. The figures were shown on a computer screen with ambient illumination from a Osram Daylight fluorescent light (250 lux, 5600° K). Stimuli were displayed on a 33 cm color CRT monitor (Sony GDM-F520 1600x1200 pixels, refresh rate 100 Hz), driven by a MacBook Pro computer with an NVIDIA GeForce 8600M GT. Viewing was binocular in the frontoparallel plane at a distance of 50 cm from the monitor. 2.3. Procedure Two methods, similar to those used by Gestalt psychologists, were used.
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