In this chapter the Experience Sampling Method (ESM) is used to study the daily fluctuations in the mental state of an agoraphobic patient over the course of a year. This case study illustrates the relevance of the ‘Flow Theory’ (Csikszentmihalyi, 1975, 1985), and the key concept of ‘Optimal Experience’ in mental patients. Optimal experience is the state of mind that arises when high environmental challenges are balanced with high personal skills in facing them (Csikszentmihalyi & Massimini, 1985; Massimini, Csikszentmihalyi & Delle Fave, 1986, 1988). Recent studies show that this positive experiential state is recognized across cultures. The theory holds that in daily life, normal subjects tend to reproduce optimal experience selectively and to look for activities which facilitate this experience and attempt to devote as much time and psychic energy to these activities as possible (Csikszentmihalyi & Rochberg-Halton, 1981). The selected activities may include routine daily tasks, as well as leisure, but as sources of optimal experience, they are basically related to the intrinsic motivation of the subject and are performed for their own sake, regardless of material rewards.

ESM was applied to the study of daily life in a number of different samples and cultures. As deVries (1987) points out, it allows one to ‘overcome the shortcomings of retrospective recall in psychiatric research’. Therefore, it is also suited to sample the experiences in the daily life of ambulatory psychiatric patients between therapeutic sessions.