Based on Daniel Berlyne's theory on perception and motivation and especially on the categories of stimulation he distinguishes, part of a large research project was devoted to an attempt to explain the process of landscape evaluation. The Kaplan's Landscape Preference Model was interpreted as an application of Berlyne's category of collative simulation. Taking also in account the effects of Berlyne's category of ecological stimulation, a causal model was hypothesized to explain the process of landscape perception and evaluation. The results look promising and are in line with the theory used. The process was studied for people extremely familiar with certain parts of their environment as well as for people unfamiliar with landscapes that were shown by slides.