The paper introduces the notion of ecological validity in laboratory studies on man-environment relations. Ecological validity refers to the extent to which a stimulus/response-combination indicates what it is claimed for a species. This requires species-typical stimuli, special-typical responses, and a species-typical experimental context. The concept does not necessarily require an experimental design with a representative sample of species-typical stimuli and responses, but it requires stimuli containing rich (and controlled) information, responses that fit clearly to the task at hand and do not require special training. Several examples from laboratory studies using pictures, mockups, large screens, or virtual reality facilities are given.