In an experiment, researchers posed simple questions in geometry to children from varied backgrounds. One group consisted of 7-to-13-year-old children of the Mundurucu, an isolated indigenous group in the Amazon basin. The Mundurucu children, who had no formal training in geometry, answered the questions just as quickly and accurately as did French chidlren of the same ages who did have formal training in geometry. In contrast, 5-year-old North American children had much more trouble answering the questions. The researchers concluded that some basic geometric knowledge is innate, but this innate knowledge typically develops only after age 5.