Introduction Changes in attention must be reflections of underlying neurophysiological change. While one set of objects or factors occupies the center of attention, more peripheral factors in the environment may still influence behavior. The relative influence of peripheral factors reflects the focus of attention, and a narrowed focus of attention (i. e., a decreased influence of peripheral factors) seems related to some neurophysiological component of acute stress. The existence of such a relationship can be demonstrated best by uncovering its details, and such details would be most useful. The better one understands how physiological changes influence attention, the better one can predict and control the effects of drugs and emotions. This paper describes a search for details of the relationship between narrowed attention and physiological change. We first studied the connection between attention and physiological change by observing the way people judge sizes.1We had our subjects adjust the