The interior of architecture is a familiar environment that is easily accessible to everyone. However, establishing the impression of a room consists of many factors, such as color; materials; the designs of walls, floors, and ceiling; positions, colors, brightness, and interspersion of lighting apparatus; color combinations and designs of furniture and curtains. The impression of a room varies by the impression of each item as well as their combinations.

In environmental psychology, researchers have endeavored to formulate relationships between environmental factors (e.g., the color and brightness of the interior decoration and furniture) and their impressions through evaluation experiments to improve interior designs. Typically, examinees are presented with “stimuli” in the form of models (Fig. 1), photographs, or virtual reality images with targeted environmental factors in variation and asked to provide evaluations using sets of bipolar adjectives based on the semantic differential method. (*)

Our laboratory’s recent research examines the relationship between impressions and human behavior. Specifically, we conduct experiments to elucidate the relationship between the lighting effects and people’s gazes on objects using an eye-mark recorder. The results demonstrate that the longer people gaze at an item, the smaller the difference in the luminance ratio. People can see articles for sale even in dark places because they are appealing. For items that are not for sale, the results suggested that people are prone to look in the direction of brighter areas (Fig. 2).

Another attempt of our laboratory is to systematize various impressions by organizing interior evaluation words compiled from previous similar experiments. Many former studies identified three impression factors through analyses of the experiment: activity, potency, and evaluation. We compare the results between the current and previous experiments and analyze them using the evaluation words sampled from the experiments. A good point of systemization is that it eliminates the need to individually formulate numerous impressions and atmospheres.

Moreover, we suggest the use of the three axes (factors), namely, brightness, warmth, and contrast, for evaluating the light environment based on the Color Image Scale formulated by the Nippon Color & Design Research Institute. We intend to quantify evaluations of the light environment through basic experiments. The three axes and the three factors of interior evaluation worlds exhibit similarity. In particular, the perception of brightness is quantified in light environment studies conducted in Japan, and many researchers suggest their formulations. I have been participating in research projects on this topic since I was a student, with the objective of improving the formulation and elucidating the relationships between the two other axes. In addition, the company I conducted joint research with is developing an app using the formulation (Fig. 3).

Simultaneously validating the formulation of the axes and the organization of impression evaluation words will lead to the quantification and formulation of various impressions. Why is formulation needed? The reason is that a difference exists between the environment and state that physically exist through light in terms of physical condition (i.e., light environment) and those that are visually perceived and reproduced in the brain (i.e., visual environment). The formulation also expands the current understanding of human perceptions. In the future, this study intends to expand the research to identify more relationships between the environment and human beings.