filled. Also, a dentist's office without patients (or the possibility of patients) would be a meaningless artifact. So, a behavior setting is a self-referenced (internally interdependent and self-defined) entity that consists of one or more standing patterns of behavior. Just as the standing pattern is synomorphic with the artifacts in the milieu, so are standing patterns synomorphic with other standing patterns in the behavior setting. We see in the eminent ecological psychologist, Roger G. Barker's conception, an elegant and stable view of the nested interrelationships that exist within our common experience. The pieces fit, and in their fitting we see the larger structure-in-a-context that is necessary for making claims about development, causality, or purpose. Ecological units Ecological units exist at the interface between the ecological environment and certain practice of molar behavior. These units exist in the physiological, social, psychological, and behavioral realms and share three common attributes: they are self-generated, as opposed to resulting from the observer's or researchers interest or manipulation; they have a time-space locus; and they have a boundary separating the internal pattern of the unit from the external pattern of surround. An ecological unit is a composite of an environment piece and a behavior piece. They are hybrid artifacts that exist as quasi-objective entities, much like Searle's "observer-relative features of the world". An example that Barker used in 1968 is a road—a road is a track (physical feature) used for travelling or carrying goods (expression of 'molar behavior'). The coupling of a molar behavior to an environmental feature (affordance) is the mechanism through which the reciprocal relations between different levels of nested or related phenomena occur. The ecological unit is the foundation for the concept of a 'behavior setting' which was defined above. More generally, it seems that this notion captures the relationship of any organism to its niche and is captured by Reed in his 1996 discussion of the 'affordance'. Barker also develops a useful analogy for conceptualizing this relation, as well as preparing readers for later claims about behavior settings. He observes that 'molar behavior' is to the 'ecological environment', just as 'visual perception' is to 'light'; i.e., in order to understand visual perception, you have to understand light, independent from visual perception. If we were only to look at the eye-optic channel at the instant that light hit the receptor surface, we would know nothing of depth of field, focus, or perspective.