Rachel and Stephen Kaplan of University of Michigan are leading researchers in the field of environmental psychology. They have many published works on human-environment relationship. Kaplans’ information processing theory (1979) is amongst the most influential and well-known theories on landscape preferences. Information is the fundamental concept of their approach. Information has been central to human experience and survival throughout the evolution of human being (Kaplan et al., 1998). Not only we need to gain information to make sense out of the environment, but an individual also values environments with promising information for exploration (Kaplan et al., 1998; S. Kaplan, 1975). Understanding of an environment aids an individual to know what is going around and feel secure. On the other hand, people want to explore by seeking more information and look for new challenges (Kaplan et al., 1998). Furthermore information is important to people’s ability to function well in the environment (Maulan et al. , 2006). Aesthetics reflects the functional potential of things and spaces (S. Kaplan, 1988a).
We gather information from our environment through our senses, mostly through visual sense. Kaplans’ theory suggests that information is derived through the contents and the organization of the environment. Organization of an environment is an important variable in perception since it affects the degree of making sense. S. Kaplan (1975) states that acquisition of knowledge should be related to environmental preference. Results of their studies show that scenes with large expanses of undifferentiated land covers, dense vegetation and obstructed views are low in preference (Kaplan et al., 1998). They suggest that if visual organization of spaces is homogenous within an environment, then it suggests that nothing is going on. Besides, there is little to focus on and sameness causes difficulty in keeping interest in the environment. On the other hand although dense vegetation has a rich content, it lacks of clear focus which confuses one. People also are discomforted when the view is blocked, they feel insecure because it is hard to tell what to expect. On the contrary scenes with spaced trees and smooth ground have been found to be high in preference. They
explain that in contrast to large expanses and obstructed views; such combinations of settings provide a clear focus and invite entry.
Based on their results, the Kaplans developed a preference matrix which comprises of four informational factors which affect preferences of landscape (Figure 2). These factors are; coherence, complexity, legibility and mystery. Coherence and complexity of a setting can be understood as soon as when one enters or views the setting, thus they happen in the picture plane (2D) and they are perceived immediately. In contrast, to perceive legibility and mystery degrees of a setting requires time, an involvement with the environment. Hence, they are inferred factors and this inference about the third dimension occurs in longer (a few milliseconds longer) and unconsciously.
2- 
D
3- D
Coherence: Coherence of a setting is about the order and organization of its elements. If a place is coherent, then people can easily make sense out of the setting. Kaplan et al. (1998) suggest that coherence can be achieved through repeat of themes and unifying textures; however limited degree of contrast is also helpful. Coherence is similar to gestalt principles of organization that states elements are perceived in groups rather than parts (S. Kaplan, 1975).
Complexity: Complexity refers to the degree of diversity of landscape elements. The more complex an environment is, the more information it involves. According to Kaplans’ theory, greater variety in a setting would encourage exploration. They argue that coherence and complexity shouldn’t be confused since a highly coherent setting can still also be very complex.
Legibility: The concept of legibility is about orientation. Way-finding is important for an individual in terms of feeling secure and safe. It is about reading the environment and making sense out of it. Distinctiveness contributes to legibility of an environment. Hence, landmarks or focal points may increase the legibility of a setting. However, one has to experience the setting first, in order to realize what is distinctive and what is not. Spaciousness also supports legibility by increasing the individual’s range of vision (S. Kaplan, 1975). S. Kaplan, (1975) points out that fine texture is also a legibility component; the finer the texture, the easier to distinguish figures from ground.
Mystery: Mystery is the component of preference related to exploration. It is about the setting’s potential of promising information. Mystery requires an inferential process (S. Kaplan, 1975). Mystery motivates people for exploration in order to gain new information. There are various ways to create mystery in a landscape. Kaplan et al. (1998) suggest that a curved path or vegetation that partially obstructs the view can add mystery to an environment.
The Kaplans suggest that we prefer environments that involve all of the four components explained above. They also emphasize that information needs to be central in environmental
design and management. However, handling and managing information can also be stressful for people. According to Kaplan et al. (1998), our capacity for directed attention is limited, and mental fatigue occurs if one is forced to receive and manage information above his capacity. Mental fatigue may cause difficulties in or loss of concentration, impulsive actions, anger and irritability. Hence, the designers should be aware of the risks of creating settings that offers too many information.
