Exploratory behavior, physiological arousal and experimental aesthetics were amongst the main interest areas of psychologist David E. Berlyne (1924-1976). He developed a psychobiological approach towards aesthetics. According to Berlyne, environmental perception is a process of exploratory behavior and information transmission which are triggered by the amount of conflict or uncertainty in the environment (Chang, 2009). Berlyne’s theoretical framework involves two main concepts; arousal potential and hedonic response. He identified four factors, which he called "collative properties" that determined the arousal potential of a stimulus; (i) complexity (diversity of the elements in the environment), (ii) novelty (presence of novel elements), (iii) incongruity (extent of any apparent ‘mis-match’ between elements), and (iv)surprisingness (presence of unexpected elements) (Ungar, 1999). The arousal potential of the stimulus results in hedonic response in the observer. Berlyne (1972) hypothesized that there is an inverted U-shaped relation between collative properties and hedonic response; increase in arousal also increases pleasure up to a point, however beyond a certain point hedonic response will lessen (Galanter, 2010; Nasar, 1988a). Thus medium degree of arousal potential has a positive effect on preference, while low or high degrees of arousal potential cause negative response (Martindale, 1996).
Wohlwill’s studies on environmental aesthetics are based on Berlyne’s theory. Both Berlyne and Wohwill regarded arousal and hedonic value as an important aspect of aesthetic response (Nasar, 1988b) Similar to Berlyne, he proposed that there was an optimal level of information in a landscape and too much information was stressful while too little information was boring (Mok et al., 2006). He also extended Berlyne’s arousal theory and hypothesized (1974) that there is an adaptation level where environmental stimulation is at optimal degree for an observer and larger changes in the adaptation level produce negative response (Bell et al., 2001; Ungar, 1999). Adaptation level depends on an individual’s past experiences, thus it differs from person to person and furthermore changes in time if exposed to a different level of stimulation (Bell et al., 2001).