An alternative interpretation of the environ mental-load model postulates the concept of cognitive underload. This suggests that many environment-behaviour problems result from too little 16 As Krupat (1985 p. 125) state monotony, whether in the form of dull urban design. or rural isolation, can be just as stressful as any excess of stimulation 17 Some researchers have asserted that the lack of stimulation provided by modern urban settings leads to boredom and con- tributes to problems of juvenile delinquency and vandalism is A fundamental question is whether there is an optimum level of stimulation. The con- cept of adaptation level sheds light on the problem.19 This is the level of stimulation that is perceived as neutral (e.g. not too crowded and not too empty) Individuals at any given adaptation level evaluate the environment as a function of how much it deviates from neutral. Small deviations in either direction are experienced as pleasant but extreme deviations are considered to be stressful. This approach helps to explain why, as a function of dif ferent individuals' adaptation levels, contrasting evaluations are made of the same urban environ- ment; why certain extreme conditions are generally experienced as unpleasant; and how perceptions and evaluations of a city may change over time.