would be impossible to manipulate all of them in a single experiment so that we could look at their combined effects. The field researcher accepts the larger challenge of dealing with data as they occur in real-life settings. Imposing a great deal of constraint on subjects' responses is not always desirable, either. Allowing subjects to behave as they usually would provides a much richer picture of the complex, multiple relationships among behaviors, and results from these studies may have more external validity, or generalizability, than laboratory demonstrations.