"Another study that winds up in half the textbooks makes the same point, if more subtly. The subjects of the "experiment" were children reared in two different orphanages in Germany after World War II. Both orphanages were run by the government; thus there were important controls in place--the kids in both had the same general diet, the same frequency of doctors' visits, and so on. The main identifiable difference in their care was the two women who ran the orphanages. The scientists even checked them, and their description sounds like a parable. In one orphanage was Fraulein Grun, the warm, nurturing mother figure who played with the children, comforted them, and spent all day singing and laughing. In the other was Fraulein Schwarz, a woman who was clearly in the wrong profession. She discharged her professional obligations, but minimized her contact with the children; she frequently criticized and berated them, typically among their assembled peers. The growth rates at the two orphanages were entirely different. Fraulein Schwarz's kids grew in height and weight at a slower pace than the kids in the other orphanage. Then, in an elaboration that couldn't have been more useful if it had been planned by a scientist, Fraulein Grun moved on to greener pastures and, for some bureaucratic reason, Fraulein Schwarz was transferred to the other orphanage. Growth rates in her former orphanage promptly increased; those in her new one decreased."