This exploratory study will test a model of residential population density effects on humans. It claims that density in a local area ("Neighborhood") or household influences attitudes and social behavior only if perceived as potentially stressful. Perceptions are a crucial intervening variable between objective environmental conditions and response to them. Second, the model claims that people respond to crowding in two important ways not identified in classical models: 1) by changing their cognitions of local environment and people in it (for example, using "crowded" and "open" to distinguish features of their block and neighborhood) and 2) by adjusting social contact to reduce the feeling of crowding in one's area. Classical models predict abnormal social behaviors and some emotions as consequences of high population density. A sample of residents in two areas of Baltimore will be interviewed about their objective density conditions, perceptions of crowding, feelings of control over environment and opportunities to alleviate crowding, environmental and social cognitions (which may reveal density as an important element), objective social ties, and attitudes about neighborhood residents. The sample sites are chosen to be similar in socioeconomic, ethnic, and housing characteristics, but dissimilar in area population density. An innovative aspect of the interview is a version of the Kelly Repgrid procedure, to measure environmental and social cognitions pertinent to the local area.