In accord with legal concepts, the study hypothesized that laypersons would be able to distinguish between authority over exclusive-use vs. common-use areas and personal effects in exclusive-use vs. common-use areas. The study also hypothesized that the interpretation of 'common authority' would be influenced by the presence vs. absence of the co-resident and that the type of intruder (social, commercial, civil authority, or criminal justice authority) would influence responses to requests for entry. These hypotheses were tested using a fully between-subjects factorial design (N=160). Results support the first three hypotheses. Subjects understood the concept of a warrantless search and distinguished between 'exclusive-use' areas and 'common-authority' areas at the level of rooms within the shared residence. Subjects' interpretation of 'common authority' for third-party consent purposes was influenced by the physical presence of the co-resident. If the co-resident was absent, 'common authority' was interpreted as independent-consent power. There was no consensual interpretation of 'common authority' when the co-resident was present and protected the proposed search. Results suggest situational dependence of lay understandings of 'common authority' over jointly used areas. 1 table, 47 references. (Author abstract modified)