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E Leeuwenberg

Publications and source records attributed to E Leeuwenberg.

13 recordsLinked to original sources
PubMed1994

From geons to structure. A note on object representation.

Two models of object perception are compared: recognition by components (RBC), proposed by Biederman, and structural information theory (SIT), initially proposed by Leeuwenberg. According to RBC a complex object is decomposed into predefined elementary objects, called geons. According to SIT, the decomposition is guided by regularities in the object. It is assumed that the simplest of all possible interpretations of any object is perceptually preferred. The comparison deals with two aspects of the models. One is the representation of simple objects--various definitions of object axes are considered. It is shown that the more these definitions account for object regularity and thus the more they agree with SIT, the better the object representations predict object classification. Another topic concerns assumptions underlying the models: the identification of geons is mediated by cues which are supposed to be invariant under varying viewpoints of objects. It is argued that such cues are not based on this invariance but on the regularity of actual objects. The latter conclusion is in line with SIT. An advantage of RBC, however, is that it deals with the perceptual process from stimulus to interpretation, whereas SIT merely concerns the outcome of the process, not the process itself.

Attention↗
PubMed1994

Integrating global and local aspects of visual occlusion.

The phenomenon of visual occlusion has frequently been studied by means of two-dimensional line drawings. These drawings may elicit various interpretations. Sometimes a mosaic of shapes is seen, sometimes a shape that partly occludes another shape. In the latter case, observers often have a clear idea about the form of the partly occluded shape. Local and global pattern aspects both seem to be decisive with respect to the preferred interpretation. An attempt is made to integrate these aspects by applying the global-minimum principle to the perceptual complexity of three distinct components of those pattern interpretations: (i) The internal structure, dealing with each of the shapes separately, (ii) the external structure, dealing with the positional relation between these shapes, and (iii) the virtual structure, dealing with the occluded parts of the shapes. The perceptual complexity of each of these three components can be expressed in terms of structural information. The hypothesis that the perceptually preferred interpretation is the one for which the total information load is minimal is tested on many patterns stemming from different studies on pattern completion.

Form Perception↗
PubMed1991

Unity and variety in visual form.

Some stimuli are perceived as unitary patterns, and others as dual or plural patterns. Such 'unity-and-variety' phenomena are explained by various process approaches of perception, such as the global precedence hypothesis, the preattentive orientation detection assumption, and the recognition-by-components model. However, these three approaches, which will be discussed in this paper, each explain a different subset of these phenomena. It will be argued that not only these three subsets but also other unity-and-variety phenomena can be explained from just one point of view by adopting the descriptive minimum principle. This principle states that the preferred interpretation of a pattern is reflected by the simplest of all possible representations of that pattern. The highest hierarchical level in the simplest pattern-representation will be called the 'superstructure' of the pattern. The superstructure of a pattern neither refers necessarily to the largest or global pattern component, nor is assessed necessarily in a primary stage in the perception process. Yet, it will be argued that the superstructure is decisive in determining whether a shape is perceived either as unitary or as dual.

Attention↗
PubMed1986

A test of the minimum principle requires a perceptual coding system.

The minimum principle states that a perceiver will see the simplest possible interpretation of a pattern. Some theorists of human perception take this principle as a core explanatory concept. Others, especially Rock and Hochberg, hold the view that a perceptual minimum principle is untenable. Rock presents a great number of demonstrations which, in his opinion, rule out the minimum principle. Hochberg states that 'impossible' figures especially present a difficulty for this principle. It is argued here that, in order to test the minimum principle, a method is needed to describe interpretations of patterns in such a way that they can be ordered according to simplicity. To achieve this, Leeuwenberg's coding system was used. The analyses reported here of the patterns which Rock produces as evidence against the principle show that, contrary to Rock's claim, the way these patterns are preferentially perceived provides strong support for the minimum principle. Next, it is demonstrated that interpreting certain patterns as 'impossible' figures is not incompatible with the principle. Finally, it is argued that a test of the minimum principle is necessarily conflated with two other hypotheses, one concerning the metric of simplicity and one concerning the task conception of the experimental subjects.

Depth Perception↗
PubMed1985

Birkhoff revisited: beauty as a function of effect and means.

The beauty of visual patterns is quantified, starting from the assumption that beauty is maximal when a maximum of effect is attained with a minimum of means applied. Birkhoff has based his theory of beauty on this assumption, but his specification of means and effect differs from the one presented here. In our conception, effect is specified as the number of independent regularities (R) of a pattern not accounted for by the simplest interpretation of the pattern. This variable is closely allied to the concept of conjunctive ambiguity. The irregularities of a pattern that are not constrained by additional regularities (P) make up the means term of the means-effect analogy. An index of beauty (M) is defined, M = R - P. It is shown that there is substantial correlation between M and preference judgments for a set of Birkhoff's polygons. It is further demonstrated that M has relevance to describe properties of the relation of beauty to complexity, data of experiments on the aesthetic attractivity of combinations of patterns, and preferences for certain proportions of simple figures above others.

Art↗
PubMed1983

Analysis of ambiguity in visual pattern completion.

It is possible to construct an ambiguous line drawing representing several objects partly hidden behind another object. This article deals with two problems: (a) What are the necessary and sufficient conditions for ambiguity to occur? (b) How can the response frequencies of the completions of ambiguous drawings be explained? Whether completions occur or not, the predictions based on the coding theory, better termed the structural information theory, have been discussed in a previous article (Buffart, Leeuwenberg, & Restle, 1981). It is shown here that the theory also specifies the conditions for ambiguity to occur. The theory describes all possible interpretations of a drawing and selects those interpretations or completions to which subjects will respond. A direct relation between the response frequencies and the possible theoretical descriptions of each response is shown to exist. Two one-parameter models describing the behavior of subjects each fit the response frequencies measured in two experiments with 25 drawings. It is argued that the type of ambiguity that is studied in both experiments generally appears during the perceptual process. The character of the theoretical descriptions indicates that guidance of perceptual behavior by interpretations might occur.

Adolescent↗
PubMed1981

Coding theory of visual pattern completion.

It is possible to construct a line drawing that represents one object partly hidden behind another, and most subjects complete the interrupted figure and see the hidden object as whole. This article is addressed to two problems: (a) What are the necessary and sufficient conditions for such figural completion to occur, and (b) exactly what will be seen behind the occluding figure---that is, what completion will be made? Leeuwenberg's coding model for line drawings was used to analyze a number of such figures, along with the hypothesis that figural completion occurs whenever it results in a simplification of final code of the whole figure. Data from previous experiments along with results from two new experimental studies were collected and shown to agree with this hypothesis. Of various possible figural completions or "mosaic" interpretations, subjects chose the ones resulting in the simplest overall code. However, the above conclusions are correct only if "simple" is precisely defined as the smallest information load in a completely reduced code. Other possible theories of figural completion, both structuralist and Gestalt, may invoke familiarity, particular "cues," like T-shaped intersections, simplicity of the hidden figure, symmetry, and good continuation. All such possibilities were considered in the experiments and shown to fail, wrongly predicting at least one figure. The coding-theory analysis, on the other hand, made correct predictions for all of the 25 figures used.

Cues↗
PubMed1981

Grounding the figure.

Coding rules can be formulated in which the shortest description of a figure-ground pattern exhibits a hierarchical structure, with the ground playing a primary and the figure a secondary role. We hypothesized that the process of perception involves and assimilation phase followed by a test phase in which the ground is tested before the figure. Experiments are described in which pairs of consecutive, superimposed patterns are presented in rapid succession, resulting in a subjective impression of seeing one pattern only. In these presentations, the second pattern introduces some deliberate distortion of the figure or ground displayed in the first pattern. Maximal distortions of the ground occur at shorter stimulus onset asynchronies than maximal distortions of the figure, suggesting that the ground codes are processed before figure codes. Moreover, patterns presenting the ground first are more likely to be perceived as ground, regardless of the distortions, than patterns presenting the figure first. This quasi masking or microgenetic approach might be relevant to theories on :mediations of immediate, or direct" perception.

Discrimination Learning↗