Five of the six figures shared some property. The participants
had to guess which figure did not belong. (In their language the
Mundurucú described it as "the ugly one.") For example, one set
included a pair of nonparallel lines amid five pairs of parallel
lines. Another set had six triangles, only one of which had no
right angle. In the second test, each participant was given a
map showing where to find an object hidden under one of three
boxes. The Mundurucú don't typically use maps, but they are
adept at navigating their river valley home in the Brazilian
state of Pará. The boxes in the test were arranged in right
triangles or isosceles triangles on the floor. The maps
correctly reproduced these geometric relations. Stars on the
maps marked the locations of the hidden objects. Dehaene finds
it significant that the U.S. and Mundurucú children had similar
scores while U.S. adults outperformed Mundurucú adults. The
results suggest that "the concepts of geometry are grounded in
extremely basic mechanisms in th