Volume 2 Issue 2 - November 9, 2007
A Gestalt-like perceptual measure for home page design using a fuzzy entropy approach
Shih-Wen Hsiao,Jyh-Rong Chou

Department of Product Design, Fortune Institute of Technology, Kaohsiung 831, Taiwan, ROC
Email: swhsiao@mail.ncku.edu.tw

International Journal of Human-Computer Studies 64, pp. 137-156, 2006.

“Gestalt” is a German word concerning “form”, “shape”, or “whole configuration”. The Gestalt theory explains how we organize mental figure-like images and how we perceive images through various types of sensory input such as visual, auditory, and olfactory stimuli. Gestalt psychology provides an important perspective in human perception. The founders of Gestalt psychology (e.g., Wertheimer, Köhler, and Koffka) believe that a perception cannot be meaningfully decomposed into its elementary components. They propose that the basic units of perception are themselves the perceptions-the “Gestalts” (or Gestalten) are the fundamental units. Indeed, the basic Gestalt theme is embodied in the often-applied summary phrase: ‘The whole is different from the sum of its parts; the whole is greater than the sum of the parts’. Many of the Gestalt principles stated earlier, along with several corollaries, have been codified under the general label of the law of Prägnanz, also known as the law of the good figure. This law can be considered as the precursor of the global-minimum principle which refers to the tendency to perceive the simplest and most stable figure of all possible perceptual alternatives. The general law of Prägnanz incorporates the effects of the Gestalt grouping principles. In home page design, organizing the visual pattern on the basis of Gestalt grouping principles can lead to efficient and simpler perceptions, and can also make users understand the page better. There are seven Gestalt grouping principles that assist in arranging forms; they are as follows: proximity/nearness, similarity, uniform connectedness, good continuation, common fate, symmetry, and closure. Gestalt theory emphasizes that the overall impression from visual perception consists of smaller parts. Interaction gestalts are similar to visual gestalts in human computer interaction (HCI). A home page consists of both visual and interactive elements, thus having gestalt properties.

Since cognitive psychology has sought to improve our scientific understanding of the fundamental properties of the human information processing mechanism, it can be used to assist us in dealing with the problems of human-computer interaction (HCI). Applied cognitive psychology attempts to bridge the gap between the properties of cognition as studied in the more abstract laboratory tasks and those phenomena that are characteristic of cognition in the tasks of everyday life. In HCI, much emphasis is put on cognitive usability of web interfaces and the aesthetic perception of interfaces. In general, there is a directional difference between cognitive usability and aesthetic perceptions. Cognitive usability has only one direction most of the time, in the sense that the higher the usability, the better the interface. However, with respect to aesthetic responses, the more beautiful interface is not necessarily the better interface, as aesthetic perceptions are multi-directional in the sense that different aesthetic impressions are preferable in different situations. A home page is considered as an entry interface composed of diverse visual elements designed to directly engage the user in the cognitive and aesthetic interaction. The variability of user perception and appropriateness of visual elements are intangible. Different people may have different cognitive responses to the same home page, and even the same people may have different cognitive responses at different times to the identical home page. Gestalt psychology is one of the useful tools in appraising mental figure-like images of home page design, but the Gestalt-like perception is difficult to measure objectively and uniformly with only observations in a rating scale by respondents. The perception concerning a home page design is not content, graphics, text, or language alone, but all of these elements combined. In this research, we propose a Gestalt-like perceptual measure method by combining Gestalt grouping principles and fuzzy entropy. Similar to the multi-directional property of aesthetic perceptions, the purpose of this proposed method is not to evaluate the grades of alternatives, but to measure the Gestalt-like perceptual degrees for home page design.

In order to test the performance of this proposed method, we implemented an empirical study in this research. The experiment consisted of two parts: (1) a pilot test to identify the importance (weights) of the criteria, and (2) the Gestalt-like perceptual measure of the selected home pages. In Part 1 of the experiment, twenty existing home pages were selected from the world-wide universities, which were primarily textual and graphic designs as well as English versions. Through the analytic hierarchy process (AHP) operation, the weights of evaluated criteria were identified. In Part 2 of the experiment, six existing home pages of the six national universities in Taiwan were selected as test cases on which to try out our method for determining their Gestalt-like perceptual measure. All the selected home pages were also textual and graphic designs as well as English versions. The six home pages selected from the national universities in Taiwan are shown in Figure 1. According to the Gestalt grouping principles, five factors are selected as the parameters for Gestalt-like perceptual measure, because the principles of uniform connectedness and common fate are less appropriately distinguished and evaluated with regard to a home page design so they are neglected. The hierarchy structure of the criteria based on the evaluated factors of the Gestalt-like perceptual measure is shown in Figure 2. The membership function curves of these six home pages obtained with the selected five Gestalt grouping principles shown in Figure 2 is shown in Figure 3. When these membership grades are further used to evaluate these six home pages with the following Gestalt-like perceptual degree formula we constructed in this study (Eq. 1), the grade of the Gestalt-like perceptual measure, D(G), for each home page can be found.
(1)

where 0≤D(G)≤1 , and the higher the D(G) is the closer the measured home page is to the complete Gestalt-like perception.

The experimental study has shown a credible result. In addition to measuring the gestalt perception of a Web page design, the proposed method can also be applied to related design fields such as plane design and other visual interface design. Human perception is an extremely complex process involving certain degrees of uncertainty, imprecision or vagueness and referring to the non-quantifiable, subjective, and affect-based experience. It is difficult to be objectively and uniformly measured by a conventional approach. In this research we constructed a mathematical model for human perceptual measure, as well as proposed a Gestalt-like perceptual measure method based on the Gestalt grouping principles and a fuzzy entropy approach. Due to the characterization and quantification of linguistic fuzzy operations associated with the membership function and fuzzy entropy function, the proposed method can objectively and equitably support the Gestalt-like perceptual measure. This is very important for applying a mathematical model to related social and behavioral studies.

This proposed method can help us to mathematically measure human perception in the perspective of Gestalt theory for works. Furthermore, it enables web page/interface designers to appraise the Gestalt-like perceptual degree of web page design as well as to comprehend whether their work can be better understood and more easily navigated by users. In conclusion, this research contributes to our knowledge by employing the theory of Gestalt psychology in the field on human-computer interaction. We believe that the Gestalt-like perception plays a role in evaluating the quality of interface design, and is relevant to aesthetic preferences and cognitive usability in HCI areas. Further research should focus on exploring the relationship among Gestalt-like perception, aesthetic preferences, and cognitive usability, which is helpful to supporting these perspectives in HCI performance as well as can assist us in deriving some guidelines for designing more beautiful, perceptible, and usable web pages.
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