Experimental Study of Aesthetic Evaluation to Multi-color Stimuli Using Semantic Differential Method

Transactions of Japan Society of Kansei Engineering Vol.14 No.1 (Special Issue) pp.37-47 (2015) 16 ORIGINAL ARTICLE Experimental Study of Aesthetic Evaluation to Multi-color Stimuli Using Semantic Differential Method Towards the Construction of an Artificial KANSEI System Siyuan FANG*, Keiichi MURAMATSU** and Tatsunori MATSUI** * Graduate School of Human Sciences, Waseda University, 2-579-15 Mikajima, Tokorozawa-shi, Saitama 359-1192, Japan ** Waseda University, 2-579-15 Mikajima, Tokorozawa-shi, Saitama 359-1192, Japan Abstract: This research aims to clarify the universal rules of the sense of beauty to multi-color stimuli by establishing a computational model specifying the relationships between the initial color information of multi-color stimuli and the aesthetic evaluation. In order to obtain the empirical data based on which the future computational system can be established, two psychological experiments have been conducted using Semantic Differential method. The design of the experiments is based on Leder s psychological model. In Experiment I, three factors, namely Pleasure, Activity and Potency, are extracted. The aesthetic evaluation values for every stimulus are defined as their factor scores (inverse) on Pleasure factor. In Experiment II, five factors, namely Vividness, Complexity, Gentleness, Strength and Wetness, are extracted. Each of them is regarded as corresponding to a simple visual feature. Keywords: multi-color, aesthetic, beauty 1. INTRODUCTION V. S. Ramachandran & W. Hirstein [1] say in their enlightening paper The Science of Art: A Neurological Theory of Aesthetic Experience: any theory of art (or, indeed, any aspect of human nature) has to ideally have three components. (a) The logic of art: whether there are universal rules or principles; (b) The evolutionary rationale: why did these rules evolve and why do they have the form that they do; (c) What is the brain circuitry involved? In this paper, we are going to introduce our approach to the answer to a question of the first kind, that is, what are the universal rules of the sense of beauty to multi-color stimuli. This approach is a quantitative one which aims at establishing a computational model depicting the relationships between the initial color information of multi-color stimuli and the elicited sense of beauty, namely the aesthetic evaluation. It can serve as an academic foundation for future studies of the second and the third kind. The sense of beauty, as an enigmatic phenomenological feeling dwelling in the depth of human mind, has a great variation across people, just as Philip Galanter [2] puts it: the human aesthetic response is formed by a combination of genetic predisposition, cultural assimilation, and unique individual experience. However, according to Chijiiwa [3], color preference around the world is similar to a large extent. In the light of it, it is reasonable to make endeavor to explore the general rules of the sense of beauty to multi-color stimuli. The whole structure of our study consists of two stages. The first stage is the conduction of two psychological experiments through which the empirical data have been obtained. On the basis of the data, the future computational model can be constructed. In the present paper, we will talk about the design and results of the first stage, namely the two SD experiments, as well as the comparison of our results with the results of several experiments by other researchers. 2. ACADEMIC SIGNIFICANCE In view of the following three points, this research possesses noticeable academic significance. Firstly, on the biological plane, different species exploit different information from environment. That is to say, the ability to make use of a certain set of environment information takes a genetic root in the instinct of a species. Applying this idea to our research, the ability to aesthetically evaluate the multi-color stimuli through a certain set of information of the stimuli is an intrinsic performance of the circuit of human brain. We can surmise that the ability plays an important, though still largely unknown, role in the progress of the human evolution, especially in the evolution of the higher cognitive function. Hence the study of the general rules of the sense of beauty to multi-color stimuli can help to better understand this aspect of the human evolution. Secondly, in terms of the manufacturing industry, Chijiiwa [4] considers the target of the science of color as to create a comfortable Received 2014.05.12 Accepted 2014.06.16 Copyright 2014 Japan Society of Kansei Engineering. All Rights Reserved. 37

Transactions of Japan Society of Kansei Engineering Vol.14 No.1 (Special Issue) environment of color. We believe that if we make clear the general rules of the sense of beauty to multi-color stimuli, we can, through the technology of affective engineering, make the environment of our everyday life more attractive and appealing, and therefore lift our living standard in a spiritual sense. Last but not least, according to the research results of cognitive neuroscience, the neural correlates of the sense of beauty encompass a multitude of brain areas which also engage in other functional systems. Delving into the general rules of the sense of beauty to multi-color stimuli may help us better understand how the relevant brain areas work, and thereby shed new light on the study of other functional systems. 3. THEORETICAL BACKGROUND 3.1 Past Research Review on the Scientific Study of the Sense of Beauty The study of the sense of beauty, as a vital part of aesthetics, has long been a profound topic in art study, literature and philosophy. Because of its difficulty in quantification, it had not been studied in a scientific way until the late 19 th century. In 1876, Gustav T. Fechner founded the area empirical aesthetics, which is aimed to explore the general rules underlying the sense of beauty via an original methodology of scientific psychology called psychophysics. His work focuses on the empirical relations between the measurement of a collection of physical features of experimental stimuli and the elicited preference response [2, 5]. In 1933, mathematician Gorge David Birkhoff came up with a formula to calculate the degree of aesthetic pleasure: M=O/C. In this formula, M means the degree of aesthetic pleasure, O the degree of order of the stimulus, and C the degree of complexity of the stimulus. This formula is a quantitative expression of the philosophical idea that beauty derives from unity in variety. Later, Bense and Moles developed Birkhoff s idea by combining it with Shannon s information theory. And Machado, following this line of thought, put forward a formula of aesthetic evaluation based on concepts of digital image compression [2, 5, 6]. In the middle 20 th century, Fechner s behaviorist idea was carried forward by Denial E. Berlyne, who later put forward a theory trying to explain the generation mechanism underlying the sense of beauty. In his theory, he argues that a stimulus may possess a certain degree of arousal potential deriving from its psychological, ecological and collative properties, and the arousal potential can activate the rewarding system and the aversion system in the human mind. The response of the rewarding system is in direct proportion to the elicited hedonic response, while the response of the aversion system is in inverse proportion to the elicited hedonic response. As a result, the hedonic response can be regarded as the sum of the influence of the rewarding system and the aversion system. This behaviorist line of thought was strongly criticized by Rudolf Arnheim from a cognitive prospective, and Martindale conducted a series of experiments the results of which failed to tally with the prediction of Berlyne s theory. Martindale later put forward a neuralnetwork model which was considered to be a more powerful explanatory tool than Berlyne s theory [2, 5]. In the late 20 th century, with the development of cognitive neuroscience, especially the brain-imaging technology such as Positron Emission Tomography (PET) and Functional Magnetic Resonance Imaging (fmri), some researchers began to explore the possibility of introducing the topics in aesthetics into the field of neuroscience. Semir Zeki has originated an interdisciplinary area called neuroaesthetics which is striving to pin down the neural correlates of the sense of beauty and to understand the human aesthetic function by the principles of neuroscience. However, due to the extreme complex nature of the sense of beauty, to date no theory, no matter in psychology or neuroscience, has been able to offer a satisfactory scientific explanation for the working mechanism of the sense of beauty [2, 7]. 3.2 Semantic Differential Method Semantic Differential (SD) method, invented by C. Osgood in 1957, was initially used in the area of social psychology and personality psychology to measure people s attitude to political parties, companies, industrial products, etc., and then became generally employed to measure the affective response to color, figure and music. Before conducting an SD experiment, the experimenter should prepare an answer sheet with a number of pairs of adjective antonyms on it, for example heavy-light, strong-weak, cold-hot. The adjective pairs can be five-scaled or seven-scaled. The experimenter must choose the adjective pairs carefully to make sure that they are suitable for the evaluation of the experimental stimuli. In the process of the experiment, the stimuli are shown, once a time, to the subjects, and the subjects evaluate the stimuli one by one by selecting one scale on each adjective pair. After the experiment, the data across the subjects are averaged and then put into a computing package of factor analysis which can extract the underlying main factors, if any, from the original data. The most 38

Experimental Study of Aesthetic Evaluation to Multi-color Stimuli Using Semantic Differential Method Transactions of Japan Society of Kansei Engineering Vol.14 No.1 (Special Issue) frequently extracted three factors in the literature of psychological researches using SD method are Evaluation, Activity and Potency [8, 9]. In this study, on the ground that the sense of beauty to multi-color stimuli is an extremely delicate feeling which is hard to be verbally expressed, we believe that SD method is a good choice for our experimental purpose. Besides, according to Kawachi [10], it is possible that the main factors extracted by the SD method not only have significance in statistics, but also have neurological meanings, namely, the biological reality. Hence, perhaps SD method can build a bridge between the psychological statistical research results and neuroscience. 3.3 Psychological models In order to construct a computational model of the sense of beauty to multi-color stimuli, it is almost always a perfect idea to refer to the existing psychological models. Past researches have not found any brain area unique to the function of aesthetic evaluation, so the psychological models about the sense of beauty are built on the basis of reductionism, which means that the functional system of aesthetic evaluation is composed of a variety of components working in a parallel distributed processing way. There are two main models concerning the topic: Chatterjee model and Leder s model. Anjan Chatterjee [11] puts forward his model in the paper Prospects for a Cognitive Neuroscience of Visual Aesthetics. This model is based on Marr s theory of visual system according to which the processing of visual information in brain can be partitioned into three stages: Early Vision, Intermediate Vision and Late Vision. The Early Vision stage is responsible for the processing of simple features of visual stimuli, such as color, lightness, figure, movement and location. In the Intermediate Vision stage, these simple features are combined into a multitude of areas. In the Late Vision stage, some of the areas are chosen for further processing. The corresponding memory will be extracted and certain meanings will be given to these areas. According to Chatterjee, the order of visual information processing in the aesthetic evaluation system is the same as the order in Marr s theory. Helmut Leder [12] puts forward his model in the paper A Model of Aesthetic Appreciation and Aesthetic Judgements. In this model, the visual information processing in the aesthetic evaluation system is divided into four stages. The first stage, called Perceptual Analyses, processes the physical features of stimuli, for instance, contrast, complexity, symmetry, color and grouping. The second stage, called Implicit Memory Integration, is responsible for the processing of familiarity, typicality and peak-shift effect of stimuli. In the third stage, called Explicit Classification, the style and the content of stimuli are specified. In the fourth stage, called Cognitive Mastering, an art-specific interpretation or a self-related interpretation is given to the stimuli. Furthermore, parallel to the module of visual information processing, there exists a Continuous Affective Evaluation module which operates the affective evaluation to stimuli. The outputs of each stage of the visual information processing module mentioned above can serve as inputs to the Continuous Affective Evaluation module. In comparison of the above two models, we can find that, generally speaking, the Perceptual Analyses stage in Leder s model corresponds to the Early Vision stage in Chatterjee s model, and the Implicit Memory Integration stage in Leder s model corresponds to the Intermediate Vision stage in Chatterjee s model. Moreover, the Late Vision stage in Chatterjee s model encompasses both the Explicit Classification stage and the Cognitive Mastering stage in Leder s model. Nevertheless, Chatterjee s model does not include a module for affective evaluation as Leder s model does, so Leder s model possesses a stronger explanatory power. Owing to this, in the following parts, we use only Leder s model. From a philosophical perspective, there are two sorts of sense of beauty, one deriving from the content of representative artworks, the other resulting from the instinctive aesthetic evaluative operation responding to certain simple features of visual stimuli, such as figure, color, contrast, lightness, symmetry and complexity. The former is dominated by individual experience, such as cultural background, artistic education received, peer fashion and social class, so it varies largely across people. On the contrary, the latter kind of sense of beauty is mainly genetically circuited, having almost nothing to do with acquired knowledge and life experience, so this kind of sense of beauty is universal across people to a great extent. Applying this classification idea to Leder s model, the first stage corresponds to the latter kind of sense of beauty, in that it represents the inherent universal ability of aesthetic evaluation, and the other three stages correspond to the former kind of sense of beauty, in that all of them are under the influence of individual experience. The objective of this research is to find the universal rules of the sense of beauty to multi-color stimuli, so only the first stage, namely the Perceptual Analysis stage, is relevant to this research. And, as we have expelled artistry from our experimental stimuli by the means introduced in 4.2, the second, the third and the fourth stages actually do not operate in our experiments. 39

Transactions of Japan Society of Kansei Engineering Vol.14 No.1 (Special Issue) 4. EXPERIMENT I 4.1 Objective In the frame of our research, Leder s model can be paraphrased to the effect that the initial color information of the multi-color stimuli is transformed to several simple physical visual features and then the features are utilized by the affective evaluation module as input variables. The output of the module is the aesthetic evaluation. So, in order to construct a computational model simulating Leder s model, we must answer the following questions: What are the simple visual features? How can they be quantified? How can we quantify the result of aesthetic evaluation to each stimulus? In order to solve these problems, two SD experiments have been designed. The first experiment aims at obtaining the quantified results of the aesthetic evaluation to every stimulus. 4.2 Experimental stimuli Many researchers in empirical aesthetics use real artworks, for example, drawings, photographs and sculptures, as stimuli. However, S. Lacey [13] says, in his paper Art for reward s sake: Visual art recruits the ventral striatum : Relative to non-art images, art images activated, on both subject- and item-wise analyses, reward-related regions: the ventral striatum, hypothalamus andorbitofrontal cortex.... the ventral striatum was driven by visual cortical regions when viewing art images but not non-art images, and was not driven by regions that correlated with esthetic preference for either art or non-art images. These findings are consistent with our hypothesis, leading us to propose that the appeal of visual art involves activation of reward circuitry based on artistic status alone and independently of its hedonic value. That is to say, the artistry, namely the artistic status, itself can influence the brain activity. So if the stimuli are real artworks, it is probable that the neural and the ensuing psychological effect caused by the features of artistry will mix up with those caused by pure color information. To avoid that, we choose to use computer-generated multi-color squares as experimental stimuli. Every square consists of 16 (4*4) sub-squares the colors of which are randomly determined. The size of every stimulus is 400*400 (width*height) pixels. We believe in this way the disturbing factor of artistry can be reduced to the minimum. The idea of the image configuration of the stimuli is suggested by Ogawa [14]. In this experiment, the stimuli used are 20 multi-color squares. Figure 1 is an example of them. Figure 1: An example of the experimental stimuli 4.3 Subjects and Adjective Antonym Pairs There are 8 subjects (6 males and 2 females) who are all undergraduate students of Waseda University. Their ages range from 20 to 22. A number of adjective antonym pairs are gathered from the past researches [9, 14-17] pertaining to the study of color. 24 of them are ultimately selected for this experiment. (see the column Original Response Variables of Table 1)[Note 1] Table 1: Rotated factor loadings matrix of Experiment I Factor Identity 1 2 3 Original Response Variables Factors 1 2 3 beautiful-ugly 0.933 0.034-0.009 clean-dirty 0.907 0.051 0.117 graceful-awkward 0.861-0.239 0.144 pleasant-unpleasant 0.859-0.127 0.194 clear-dull 0.85-0.006 0.008 successful-unsuccessful 0.827-0.052 0.25 harmonious-dissonant 0.823-0.39-0.028 true-false 0.759-0.103 0.15 like-dislike 0.715 0.021 0.448 stable-changeable 0.687-0.441 0.264 static-dynamic 0.093-0.938 0.074 ornate-plain -0.167 0.89-0.062 passive-active 0.184-0.868-0.041 cheerful-gloomy 0.185 0.822 0.348 noisy-quiet -0.459 0.821 0.02 positive-negative -0.014 0.792-0.022 warm-cool -0.218 0.719 0.561 light-dark 0.294 0.691 0.51 novel-ordinary -0.276 0.66-0.099 strong-weak 0.014 0.386-0.828 soft-hard 0.246 0.38 0.805 relaxed-nervous 0.377-0.194 0.722 heavy-light -0.444-0.333-0.667 cruel-kind -0.092-0.579-0.6 40

Experimental Study of Aesthetic Evaluation to Multi-color Stimuli Using Semantic Differential Method Transactions of Japan Society of Kansei Engineering Vol.14 No.1 (Special Issue) 4.4 Results The individual subjects evaluation data on the scales of these 24 original response variables for every stimulus are collected and then averaged across the subjects. Then the data are imported into IBM SPSS Statistics (Version 19) for factor analysis. The correlation matrix of the original response variables has 576 elements, and the absolute values of only 218 of them are below 0.3. Hence there exists an inneglectable correlation between the original response variables, in view of which we can say that the data is suitable for factor analysis. The factor loadings matrix is calculated using Principal Factoring method. There are three factors the eigenvalues of which are larger than 1.0. Therefore, these three factors are selected as main factors. The communalities of every original response variable are larger than 0.50, so there are no original response variables which should be deleted before entering the following computational steps because of low communality. Then the factors are rotated though Varimax method for the preservation of the orthogonality among the factors. Table 1 shows the factor loadings matrix resulting from the rotation. The adjective antonym pairs possessing their highest loading on Factor 1 are beautiful-ugly, clean-dirty, graceful-awkward and pleasant-unpleasant, etc., so we can infer that the function of this factor is to evaluate the goodness property of the stimuli. The adjective antonym pairs having their highest loading on Factor 2 are static-dynamic, passive-active, cheerful-gloomy and noisy-quiet, etc., so it is probable that the factor works to evaluate the kinetic state of the stimuli. The adjective antonym pairs with their highest loading on Factor 3 are strong-weak, soft-hard, relaxed-nervous and heavy-light. Hence it is reasonable to infer that the factor represents the measurement of the strength of the stimuli. So, conforming to the conventional nomenclature, Factor 1, Factor 2 and Factor 3 could be respectively named Evaluation, Activity and Potency. However, although this naming method has been used by a lot of researchers for several decades, we think that some improvement can be made. Both the names Activity and Potency have a relatively concrete meaning. In contrast, the meaning of the name Evaluation is rather vague, because the names Activity and Potency, respectively, can also be explained as the evaluation of activity and the evaluation of potency. So semantically speaking, it is hard to agree that the name evaluation has a meaning which is clear enough to distinguish it from the names of the other two factors. In other words, we should ask the question: What on earth is the so-called Evaluation factor evaluating? In order to answer this question, we think it is advisable to make reference to the papers written by Osgood himself. According to Osgood [18, 19] s papers Studies on the Generality of Affective Meaning Systems and On the Ways and Wherefores of E, P and A, we can know that by using the name Evaluation, Osgood actually means that this factor is evaluating the extent of pleasure deriving from the good V.S. bad judgment to the stimuli in the environment. Hence, in this study, we name the factor Pleasure instead of Evaluation. In this experiment, this factor represents the extent of pleasure felt by the subjects to the multi-color stimuli, so we define the results of the aesthetic evaluation to the stimuli as the factor scores (inverse) on Pleasure factor. 4.5 Discussion The results of this experiment, generally speaking, coincide well with the results of several SD experiments on color-combination by other researchers. In Ogawa [14] s experiment, as mentioned in 4.2, the conformation of stimuli used are nearly the same as that in our experiment. In his experiment, three factors, respectively named Evaluation, Activity and Potency, are extracted, which tally with the factors extracted in our experiment. Regarding the adjective antonym pairs used in both Ogawa s experiment and our experiment, like-dislike, pleasant-unpleasant, clean-dirty and harmonious-dissonant belong to Evaluation factor in both experiments. (As mentioned above, Pleasure factor in our experiment has the same meaning as Evaluation factor.) Light-dark, warm-cool, noisy-quiet and ornate-plain belong to Activity factor in both experiments, and heavy-light and soft-hard Potency factor. Nevertheless, strong-weak belongs to Activity factor in Ogawa s experiment but it belongs to Potency factor in our experiment. In Oyama [20] s experiment, which studies the affections elicited by two-color combinations, three factors, respectively named Evaluation, Activity, Sharpness, are extracted. Regarding the adjective antonym pairs used in both Oyama s experiment and our experiment, likedislike belongs to Evaluation factor in both experiments, and static-dynamic and ornate-plain Activity factor. Beautiful-dirty in Oyama s experiment can be regarded as corresponding to beautiful-ugly and clean-dirty in our experiment, and they belong to Evaluation factor in both experiments. Bustling-quiet in Ogawa s experiment can be regarded as corresponding to noisy-quiet in our experiment, and they belong to Activity factor in both 41

Transactions of Japan Society of Kansei Engineering Vol.14 No.1 (Special Issue) experiments. In view of the fact that relaxed-nervous belongs to Sharpness factor in Oyama s experiment and Potency factor in our experiment, it is possible that Sharpness factor in Oyama s experiment corresponds to Potency factor in our experiment. In Horita [15] s experiment, which studies the affective responses to two-color combinations, four factors, respectively named Evaluation, Activity, Potency and Harmony, are extracted. Regarding the adjective antonym pairs used in both Horita s experiment and our experiment, like-dislike, clean-dirty and clear-dull belong to Evaluation factor in both experiments, warmcool, cheerful-gloomy and static-dynamic Activity factor, and heavy-light and strong-weak Potency factor. Although harmonious-dissonant has its highest loading (-0.591) on Harmony factor, it also has a relatively high loading (0.586) on Evaluation factor to which this adjective antonym pair in our experiment belongs. Nevertheless, unlike the results of Ogawa s experiment and of our experiment, light-dark in Horita s experiment belongs to Evaluation factor and soft-hard Activity factor. As to ornate-plain, although Horita classifies it to Harmony factor, its loading on Harmony factor is only 0.392, which is much lower than its loading on Evaluation factor (0.640). On the contrary, this adjective antonym pair belongs to Activity factor in Ogawa s experiment, Oyama s experiment and our experiment. In Kansaku [21] s experiment, which analyzes the color emotion elicited by two-color combination stimuli, four main factors, respectively named Evaluation, Activity, Potency and Warmness are extracted. Regarding the adjective antonym pairs used in both Kansaku s experiment and our experiment, like-dislike, harmonious-dissonant and clean-dirty belong to Evaluation factor in both experiments, light-dark, cheerful-gloomy and ornate-plain Activity factor, and strong-weak and soft-hard Potency factor. As in our experiment, clear-dull has the highest factor loading (0.77) on Evaluation factor in Kansaku s experiment. Static-dynamic, in Kansaku s experiment, has the highest factor loading (0.59) on Potency factor, but it also has a similarly high factor loading (0.56) on Activity factor to which this adjective antonym pair in our experiment belongs. On the other hand, warm-cool, which belongs to Activity factor in Ogawa s experiment, Horita s experiment and our experiment, has high factor loading only on Warmness factor. Heavy-light, which belong to Potency factor in Ogawa s experiment, Horita s experiment and our experiment, has its highest factor loading on Activity factor in Kansaku s experiment. In summary, the three factors extracted in our experiment have counterparts in the set of factors extracted in all of the above four experiments conducted by other researchers. And, with regards to the common adjective antonym pairs used, most of them belong to the same factors in those four experiments as in our experiment. Therefore, it is reasonable to believe that the factors extracted in our experiments possess a high degree of psychological reality. 5. EXPERIMENT II 5.1 Objective The second experiment is devised to make clear the simple visual features which people use when making aesthetic evaluation to multi-color stimuli. To be sure, in Leder s paper, he proposes several candidate visual features in the Perceptual Analyses stage, such as complexity, contrast, symmetry, color and grouping, and their influence on aesthetic evaluation is supported by many past researches. However, the experimental objectives of a number of these researches are distinct from the target of our research, namely the exploration of the universal aesthetic rules to multi-color stimuli, so it is doubtful whether or not those results are applicable to our research. In view of that, it is necessary for us to conduct another SD experiment to specify the simple visual features. 5.2 Subjects and Adjective Antonym Pairs With regards to the adjective antonym pairs, because the objective of this experiment is to specify the simple visual features, only the adjective antonym pairs which are thought to be appropriate to describing the physical aspects of stimuli are chosen. All evaluative adjectives are excluded from the set. Obviously, this set of adjective antonym pairs are much different from that used in the first SD experiment which contains evaluative adjectives. The stimuli used in this experiment are the same as those used in the first experiment. We find no past research containing an SD experiment focusing on the study of descriptive simple visual features functioning in the psychological mechanism of aesthetic evaluation to multi-color stimuli, so there is no existing adjective antonym pair list for this purpose. Hence, we made an original adjective antonym pair list. First of all, we gathered 266 adjective antonym pairs from 60 papers and books on color study. Then, basing on the following three standards: 1) how many times an adjective antonym pair has been used, 2) whether an 42

Experimental Study of Aesthetic Evaluation to Multi-color Stimuli Using Semantic Differential Method Transactions of Japan Society of Kansei Engineering Vol.14 No.1 (Special Issue) adjective antonym pair describes a physical aspect of multi-color stimuli, and 3) whether two adjective antonym pairs have the same meaning, 45 adjective antonym pairs are selected to be used in this experiment. When determining the number of the adjective antonym pairs to be used, we also take into consideration that the duration of the experiment cannot be too long so that the subjects may become fatigued. Then the SD experiment was conducted. 15 subjects (11 males and 4 females) who are all undergraduate students or graduate students of Waseda University took part in the experiment. Their ages range from 20 to 24. After the collection of individual subjects evaluation data on the scales of these 45 adjective antonym pairs for every stimulus, the Cronbach s α coefficients of every adjective antonym pair are calculated. 32 of them are higher than 0.50, which shows that these adjective antonym pairs possess relatively high subject-wise consistency. (see the column Original Response Variables of Table 2) [Note 2]. 5.3 Results After that, the evaluation data on these adjective antonym pairs are imported into IBM SPSS Statistics (Version 19) for factor analysis. The correlation matrix of these original response variables has 1024 (32*32) elements, and the absolute values of only 338 of them are below 0.30. Moreover, its determinant is close to 0.000. Hence there exist inneglectable correlational relationships between the original response variables, which means that the data is suitable for factor analysis. The factor loadings matrix is calculated via Principal Factoring method. There are five factors the eigenvalues of which are larger than 1.0. Therefore, these five factors are selected as main factors. The communalities of every original response variable are larger than 0.70, so there are no original response variables which should be deleted before entering the following computational steps because of low communality. Then the factors are rotated though Varimax method for the preservation of the orthogonality among the factors. Table 2 shows the factor loadings matrix resulting from the rotation. Concerning the first factor, we can see that vividsubdued, distinct-indistinct, clear-vague, clear-dull, conspicuous-inconspicuous, plain-ornate, disregarding the plus-minus signs, have their highest loading on this factor. So we can infer that the stimuli with low factor scores on this factor possess a vivid, bright and eyeattracting appearance. Two adjective antonym pairs descripting the kinetic property of stimuli, namely Factor Identity 1 2 3 4 Table 2: Rotated factor loadings matrix of Experiment II Original Response Variables Factors 1 2 3 4 5 vivid-subdued.945.090.165 -.041 -.103 distinct-indistinct.881.002.013.044 -.019 savory-tasteless.831.333.210.101.160 sweet-unsweet.786.001.370.108.427 clear-vague.761 -.233.096.267 -.373 clear-dull.742.504.183 -.095 -.034 dynamic-static.702 -.406.357.292 -.235 conspicuous-inconspicuous.690 -.386.219.311 -.238 plain-ornate -.679.436 -.224 -.284.351 noisy-quiet.576 -.527.474.097 -.107 neat-disordered.214.907 -.030 -.212 -.025 heterogeneous-homogeneous.017 -.868.120.017.094 plain-thick.242.789.189 -.272.016 smooth-rough.245.786.293.056.098 clam-violent -.046.760 -.002 -.249.378 regular-irregular -.294.757.006.342.156 diversified-monotonous.457 -.730.177.250 -.147 simple-complex -.475.721 -.002 -.157.087 calm-restless -.376.715 -.273 -.166.368 gaudy-plain -.092 -.687 -.060.547 -.054 leisurely-bustling -.524.577 -.111 -.305.379 soft-hard.257.231.875 -.187.076 rounded-angular.027.341.867.044.096 dark-pale.149.004 -.784.464.186 pale-deep.409 -.271.783 -.218 -.106 cold-warm -.394.352 -.771 -.205.177 light-dark.649 -.181.676 -.036 -.195 light-heavy.576.045.675 -.259 -.276 forceful-forceless -.044 -.351 -.350.693.092 strong-weak.348 -.445 -.271.734.033 large-scale-small-scale.425.017 -.042.757 -.247 5 wet-dry -.243.323 -.516 -.005.692 dynamic-static and noisy-quiet, also have high loading on this factor. It is understandable because a conspicuous, vivid-colored and eye-catching appearance is often associated with situations rich of vigor, validity and liveliness. In addition, two adjective antonym pairs pertaining to the taste sense, namely savory-tasteless and sweet-unsweet, also have high loading on this factor. This inter-modality association can be explained by our every day experience that foods which are fresh, high-quality and appetizing, in many cases, accompany a clear, vivid-colored, conspicuous and eye-appealing appearance. On the ground of the analysis, we name the factor Vividness. With regards to the second factor, neat-disordered, heterogeneous-homogeneous, regular-irregular, diversifiedmonotonous, simple-complex and gaudy-plain, disregarding the plus-minus signs, have their highest 43

Transactions of Japan Society of Kansei Engineering Vol.14 No.1 (Special Issue) loading on this factor. So it is reasonable to infer that this factor works to evaluate the degree of complexity of the stimuli, which is generally accepted as being in inverse proportion to the measurement of order, simplicity and homogeneity. Calm-violent, calm-restless, and leisurely-bustling also have their highest loading on this factor. This association can be explained by our everyday experience that intricate stimuli in the environment can elevate our arousal level more easily than the simpler ones, and therefore can give rise to such feeling as nervousness, anxiety or even a sense of being threatened. In addition, plain-thick, which is often used to depict the gustatory sense, and smooth-rough, which is essentially a description of the tactile sense, also have their highest loading on this factor. These inter-modality associations are understandable because a plain dish or a smooth object, for example a pillow, a sofa cushion or a plush toy, always serves to lower our arousal level and brings us a sense of calmness and leisureliness which are also the psychological states induced by a simple, ordered and homogeneous stimuli. On the basis of the analysis, we name this factor Complexity. The existence of this factor gives a support to the hypothesized complexity feature which Leder places in the Perceptual Analysis stage. In terms of the third factor, soft-hard, roundedangular, dark-pale, pale-deep, cold-warm, light-dark and light-heavy, disregarding the plusminus signs, have their highest loading on this factor, which means that the stimuli with a low factor score on this factor are soft, rounded, warm and light in a tactile sense, and of pale and light color in a visual sense. All of these properties contain a sense of gentleness which can make people feel at ease and relaxed. Hence, we name this factor Gentleness. As to the fourth factor, forceful-forceless and strong-weak, disregarding the plus-minus signs, have their highest loading on this factor. From it we can infer that the function of this factor is to evaluate the strength of the stimuli. In addition, large-scale-small-scale also has its highest loading on this factor. This association is understandable because, in our daily life, a giant, huge and mammoth object often holds a great strength. According to the analysis, we name this factor Strength. There is only one adjective antonym pair, namely wet-dry, having its highest loading on the fifth factor, so we name this factor Wetness. In summary, in this SD experiment, five factors, namely Vividness, Complexity, Gentleness, Strength and Wetness, are extracted. We regard each of them as corresponding to a simple visual feature. 5.4 Discussion In the literature of relevant researches, we find no SD experiment aiming at clarifying the descriptive simple visual features engaged in the psychological process of aesthetic evaluation to multi-color combination, so our research can serve as a starting point on this topic. The following part is a comparison of the results of our experiment and the results of two experiments conducted by Gao [22, 23] which study the descriptive features of mono-color stimuli. In Gao s first experiment, two factors are extracted. Adjective antonym pairs vivid-sombre (which can be regarded as corresponding to vivid-subdued in our experiment), dynamic-passive (which corresponds to dynamic-static in our experiment), gaudy-plain (which corresponds to plain-ornate in our experiment), and striking-subdued (which corresponds to conspicuous-inconspicuous in our experiment) are closely related to the first factor. It coincides well with the results of our experiment that vivid-subdued, dynamic-static, plain-ornate and conspicuous-inconspicuous are all belong to the first factor, namely Vividness factor. Although warm-cool, which belongs to the third factor in our experiment, has its highest loading on the first factor in Gao s experiment, in our experiment it also possesses a relatively high loading (-0.394) on the first factor. As to the second factor in Gao s experiment, soft-hard, pale-deep and light-heavy are included in it. Similarly, in our experiment, these adjective antonym pairs also belong to the same factor, namely Strength factor. Transparent-turbid and weak-strong are also included in the second factor in Gao s experiment. On the contrary, in our experiment, they do not belong to the factor which soft-hard, pale-deep and light-heavy belong to. In addition, in Gao s experiment, light-dark has high loading on both factors. Similarly, in our experiment, this adjective antonym pair has high loading on both Vividness factor and Gentleness factor. Distinctvague, in Gao s experiment, also has high loading on both factors. However, its counterparts in our experiment, namely distinct-indistinct and clear-vague, only have high loading on Vividness factor. From this comparison, we can see that the factorial distribution of the adjective antonym pairs used in both experiment tallies well with each other. Gao later conducted another experiment in which the subjects come from seven nations and districts. In this 44

Experimental Study of Aesthetic Evaluation to Multi-color Stimuli Using Semantic Differential Method Transactions of Japan Society of Kansei Engineering Vol.14 No.1 (Special Issue) experiment, three factors are extracted. The first factor, which is closely related to the Activity category of the original variables, and the second factor, which is closely related to the Potency category of the original variables, correspond to the two factors extracted in Gao s former experiment. (We name them as Activity factor and Potency factor in the present paper.) However, warm-cool becomes the only representative variable of the third factor. In view of the results of these two experiments, it is probable that Activity factor and Potency factor are real psychological entities which emerge when people are evaluating mono-color stimuli. It is a quite interesting perspective to compare the factor structure in our experiment and those in Gao s experiments. Activity factor and Potency factor can be regarded as matching Vividness factor in our experiment, and Potency factor corresponds to Gentleness factor and a part of Strength factor in our experiment. But the results of our experiment show two more factors, especially Complexity factor which accounts for a large proportion (26.16%) of the variance of the original variables. We believe that this disparity in factorial structure represents the difference between the set of simple visual features engaged in the psychological process of aesthetic evaluation to mono-color stimuli and that engaged in the aesthetic evaluation process to multi-color stimuli, and Complexity factor represents a simple visual feature characterizing multi-color stimuli. This phenomenon is easily imaginable in that for a stimulus having only one color, the matter of being complex or not does not exist, yet when a stimulus is constituted by a number of colors, the matter of complexity comes into being. In other words, only a heterogeneous thing can have a degree of complexity. As to homogeneous things, the concept complexity is simply not applicable to them. In summary, regarding the adjective antonym pairs used in both Gao s experiments and our experiment, the results tally well with each other, which means that it is reasonable to believe that the factors extracted in our experiment possesses real psychological meaning. The disparity between the factorial structure in Gao s experiments and that in our experiment, we believe, is mainly due to the difference between the set of simple visual features engaged in the psychological process of aesthetic evaluation to mono-color stimuli and that engaged in the aesthetic evaluation process to multi-color stimuli. That is to say, when people evaluate multi-color stimuli, they utilize more simple visual features than when they evaluate mono-color stimuli. 6. CONCLUSION AND FUTURE PLAN In the present paper, we have introduced the first stage of our research which is aimed to clarify the universal aesthetic rules to multi-color stimuli via the construction of a computational model. This stage consists of two psychological experiments using SD method. The stimuli used are 20 16-color combinations. The design of the experiments and the macro structure of the future computational model are based on Leder s psychological model. According to the model, the initial color information of the stimuli are firstly transformed to some simple visual features in the Perceptual Analysis stage of the visual information processing module, and then the features serve as input into the Continuous Affective Evaluation module the output of which is the aesthetic evaluation. The other three stages in the visual information processing module are all under the influence of individual life experience, so they are irrelevant to our research the objective of which is to make clear the universal rules of the sense of beauty to multi-color stimuli. Thus, we only consider the first stage. First at all, in order to quantify the aesthetic evaluation to the stimuli, Experiment I is conducted. In this experiment, three factors, namely Pleasure, Activity and Potency, are extracted. We define the aesthetic evaluation values for the stimuli as their factor scores (inverse) on Pleasure factor. After that, in order to make clear what the simple visual features in Perceptual Analysis stage are, we conducted Experiment II. In this experiment, five factors, namely Vividness, Complexity, Gentleness, Strength and Wetness, are extracted. Each of them is regarded as corresponding to a simple visual feature. The second stage of our research is to build a computational model which links the initial color information, the processing level constituted by the five simple visual features, and the aesthetic evaluation. After completing the construction of the model, knowledge gathered from relevant past researches in the areas such as psychology of emotion, aesthetic psychology, Gestalt psychology, cognitive neuroscience, chromatology and generative art can be combined to elaborate on various facets of the model, and moreover, some inferences and hypotheses may be made to promote future experiments for further investigation. 45

Transactions of Japan Society of Kansei Engineering Vol.14 No.1 (Special Issue) NOTES 1. & 2.: In the two experiments, the adjective antonym pairs were used in Japanese. In writing this paper, we translated them into English. A part of the translation is based on the book Ningen Kogaku Gaido (pp.153-155) edited by T. Fukuda and R. Fukuda [9]. REFERENCES [1] V. S. Ramachandran and W. Hirstein; The Science of Art: A Neurological Theory of Aesthetic Experience, Journal of Consciousness Studies, 6(6-7), pp.15-51, 1999. [2] P. Galanter; Computational Aesthetic Evaluation: Past and Future; J. McCormack and M. d Inverno (Eds.) Computers and Creativity; Springer, Berlin Heidelberg, pp.255-293, 2012. [3] H. Chijiiwa; An Outline of Color Science; University of Tokyo Press, Tokyo, pp.168-170, 2001. [4] H. Chijiiwa; An Outline of Color Science; University of Tokyo Press, Tokyo, pp.216-218, 2001. [5] G. C. Cupchik; A Decade after Berlyne: New Directions in Experimental Aesthetics, Poetics, 15(4), pp.345-369, 1986. [6] P. Machado and A. Cardoso; Computing Aesthetics, Advances in Artificial Intelligence, Lecture Notes in Computer Science, 1515, Springer, Berlin Heidelberg, pp.219-228, 1998. [7] S. Zeki; Artistic Creativity and the Brain, Science, 293(5527), pp.51-52, 2001. [8] T. Oyama; Shikisai Shinrigaku Nyumon; Chuokoron-Shinsha, Inc., Tokyo, pp.213-216, 2004. [9] T. Fukuda and R. Fukuda (Eds.); Ningen Kogaku Gaido; SAIENSU-SHA Co., Ltd., Tokyo, pp.125-173, 2009. [10] Y. Kawachi, et al.; Distributions of neural activities corresponding to psychological structures underlying the impressions of pictures, Technical Report of the Institute of Electronics, Information and Communication Engineers, 108(264), pp.25-30, 2008. [11] A. Chatterjee; Prospects for a Cognitive Neuroscience of Visual Aesthetics, Bulletin of Psychology and the Arts, 4(2), pp.56-60, 2004. [12] H. Leder, et al.; A Model of Aesthetic Appreciation and Aesthetic Judgments, British Journal of Psychology, 95(4), pp.489-508, 2004. [13] S. Lacey, et al.; Art for Reward s Sake: Visual Art Recruits the Ventral Striatum, NeuroImage, 55(1), pp.420-433, 2011. [14] K. Ogawa; Kansei Evaluation by Using Multidimensional Neural Networks Based on Affective Dimensional Model, Master Thesis of Waseda University, p.11, 2011. [15] Y. Horita, et al.; Estimation of the Sensitivity Factor of the 2 Color Combination with Monochromatic Color Sensitivity Factor, Technical Report of the Institute of Image Information and Television Engineers, 21(28), pp.1-6, 1997. [16] M. Suzumi and J. Gyoba; Analyzing the Factor Structure and the Sensory-Relevance of Impressions Produced by Words and Drawings, The Japanese Journal of Psychology, 73(6), pp.518-523, 2003. [17] Y. Horita, et al.; A Study about Oriented Dependability of Two Color Combinations for Kansei Space Construction, Journal of the Institute of Image Information and Television Engineers, 49(8), pp.1087-1089, 1995. [18] C. E. Osgood; Studies on the Generality of Affective Meaning Systems, American Psychologist, 17(1), pp.10-28, 1962. [19] C. E. Osgood; On the Whys and Wherefores of E, P, and A, Journal of Personality and Social Psychology, 12(3), pp.194-199, 1969. [20] T. Oyama; Affections Induced by Two-Color Combinations: Comparisons with those of Single Colors, Journal of Color Science Association of Japan, 25 (supplement), pp.98-99, 2001. [21] J. Kansaku; The Analytical Study of Affective Values of Color-Combinations: A Study of Color Pairs, The Japanese Journal of Psychology, 34(1), pp.1-12, 1963. [22] X. Gao and J. H. Xin; Investigation of Human s Emotional Responses on Colors, Color Research & Application, 31(5), pp.411-417, 2006. [23] X. Gao, et al.; Analysis of Cross-Cultural Color Emotion, Color Research & Application, 32(3), pp.223-229, 2007. 46

Experimental Study of Aesthetic Evaluation to Multi-color Stimuli Using Semantic Differential Method Transactions of Japan Society of Kansei Engineering Vol.14 No.1 (Special Issue) Siyuan FANG Siyuan Fang has been a graduate student in Waseda University, Japan since 2013, majoring in KANSEI cognitive information system at Graduate School of Human Sciences, supervised by Professor Tatsunori Matsui. His main academic interests are KANSEI information science, artificial intelligence, empirical aesthetics and color science. Currently, his research focuses on the application of the technology of artificial intelligence to the construction of an automatic aesthetic evaluation system. Keiichi MURAMATSU Keiichi Muramatsu has been a research associate of the Faculty of Human Sciences, Waseda University, since 2012. He received his Doctor of Human Sciences from Waseda University in 2014. He was a Japan Society for the Promotion of Science (JSPS) Research Fellow (DC2) in 2010-2012. His current research interests are ontological descriptions on the structure of the human mind in the research fields of aesthetics, color science, and learning sciences. Tatsunori MATSUI Tatsunori Matsui has been a Professor of Knowledge Science and Artificial Intelligence Lab at the Faculty of Human Sciences, Waseda University, Tokyo, Japan, since 2004, after contributing for seven years as an Associate Professor to the Graduate School of Information Systems, the University of Electro-Communications, Tokyo, Japan. Currently, his research interests are Kansei Information Science, Artificial Intelligence in Education, Mathematical Analysis for Educational Data, Statistical Science, and more. He is a member of IEEE, ACM, IEICE, IPSJ, JSAI, JSiSE, and more. 47