Basically, there are two approaches in visual landscape assessment; objective and subjective. Objective approach to visual landscape assessment assumes that visual quality of the landscape is an inherent characteristic and physical attributes of the environment determine its aesthetic value. On the contrary, subjective approach assumes that visual quality is in the eye of beholder and aesthetic value of an environment can be determined through subjective evaluation. There are also studies which have integrated both objective and subjective approaches.
Zube et al. (1982) identified four research paradigms on landscape assessment and perception which are; expert, psychophysical, cognitive and experiential paradigms (Taylor et al., 1987).
The expert paradigm: this paradigm is based on expert judgments of visual quality of landscapes. Evaluation of landscape quality depends on formal characteristics of the landscape such as landform, vegetation, color, texture etc. Another assumption of this paradigm is that natural ecosystems have the greatest aesthetic value. This paradigm is criticized for the lack of user environment and being incompatible with users’ perceptions (Lekagul, 2002). Furthermore, S. Kaplan (1988a) points out that experts perceive visual environment different to other people, and expert judgments are "a dubious source of objective judgment" about what other people really care about in the landscape.
The psychophysical paradigm: In psychophysical paradigm, in contrast to expert paradigm visual quality of the landscape is evaluated by the general public or special interest groups. The main assumption of this paradigm is landscapes have a stimulus property which is external to the observer who perceives the landscape without conscious thinking. Ranking and sorting are widely used techniques in visual assessments within this paradigm.
The cognitive paradigm: The cognitive paradigm focuses on why people prefer particular landscapes. The research is directed mostly towards developing a theoretical basis. In contrast to psychophysical paradigm, cognitive paradigm assumes that cognitive processes influence aesthetic judgments. Mostly verbal evaluation techniques, such as semantic differential analysis and adjective checklists, have been used to evaluate preferences and meanings. Most of the evolutionary theories on environmental perception (e. g. prospect – refuge theory and information processing theory) form a basis for this paradigm. However, this paradigm neglects the physical environment and rather focuses on meanings associated with landscapes (Taylor et al., 1987).
The experiential paradigm: This paradigm focuses on human-environment interaction. Human experiences affect the landscape’s perceived value. This approach is commonly used in "sense of place" studies and mainly by geographers. However, experiential approach is more subjective than cognitive and psychophysical paradigms; therefore reliability and validity of the results are hard to be measured (Taylor et al., 1987).
Although paradigms explained above may seem completely different from each other, each contributes to overall comprehension of environmental perception. In terms of design and planning, the expert paradigm has been the most used approach in visual landscape assessment. However, there is a certain need for involvement of public or users in order to create enjoyable places for people. Fenton & Reser (1988) criticize that human geographers and landscape architects tend to use atheoretical and apsychological methods while psychologists use mainly theoretically derived psychometric methods. Professional differences might make it difficult to find a common basis for theoretical and methodological research. Nevertheless, collaboration of disciplines involved in environmental perception studies is essential to resolve some of the conflicts.