Examining the benefits of naturalness forms an important part of environmental psychology research, with exposure to naturalness associated with restoration and positive affective quality. But the work of this thesis shows that it is not always clear what is meant by naturalness. Study A (N = 243) revealed several elements of naturalness which cannot be explained by current research, suggesting more work is needed to examine what constitutes naturalness. An in-depth literature review of the operationalisation of naturalness in 95 papers emphasised this need, demonstrating: 1) the interchangeable use of terms for naturalness; 2) a reliance on dichotomous variables; 3) a lack of explicit definitions; and 4) a lack of distinction between perceived and ecological naturalness.

Addressing these gaps in the literature, a survey was used to develop a new conceptualisation of lay perceived naturalness. Respondents (N = 846) were asked what they thought made a place natural and inductive content analysis used to develop a theme structure to represent these. A card sort study (N = 23) was used to improve this structure. Sixteen themes and 138 subthemes summarised lay perceptions; serving to broaden the conceptualisation beyond that of current research. Some of the most frequently mentioned themes/subthemes reflected those of existing literature, including the absence of humans and their influence, and vegetation. Several novel themes/subthemes were identified (e.g. smells, touch, weather); of use in future research. Humans, their influence and things also formed part of the concept of naturalness, demonstrating the difficulty associated with pitching humanness against naturalness.

Quantitative analyses showed that various subthemes of lay perceived naturalness were perceived as restorative and of positive affective quality: including elements such as sounds, plants, and water being associated with relaxing environments; and an absence of humans being associated with perceived restoration. These form the basis of recommendations for environmental design.