This thesis uses a resource theoretical approach to study and analyze social psychological phenomena in different age-cohorts. Resources are seen as any asset the person has access to in a certain situation. Access to resources are crucial to meet the demands of the surrounding environment. When the resources are sufficient to cope with the surrounding environment there will be a greater freedom of choice to manipulate or to not be unnecessarily manipulated by the environment. In older age cohorts access to resources is lower than in younger age cohorts, where access depends on aging, cohort, and/or historical reasons. The model suggests three different categories of resources: individual, interpersonal, and institutional. Individual resources are exemplified by health, interpersonal by social network, and institutional by social position. The gap between actual and perceived resources can be understood by a construct called the self-reference system. The actual resources and the way these are perceived influence feelings and behavior such as activity level, loneliness, and life satisfaction. This also means that the use of age or age cohorts to explain feeling and behavior often is misleading. It is much more convincing to categorize people according to access to resources rather than to their age. Some aspects of the model were empirically studied in a non-proportional stratified random sample of 130 persons in 5 age cohorts. The results provided strong support to the model. (Author/LLL)