The entire healthy adult population of 19 nonmissionized nomadic Auca Indians of the Ecuadorian Amazon basin were given tests involving the four-colored Kohs Block Design, spatial-relational, lexical, and body and face shapes. The test results reveal a specific grouping of deficiencies in color naming (with preservation of color concept), block design especially related to representation, and construction of certain intrapattern spatial relations and graphic representational skills. This ecologically determined grouping of deficiencies suggests a homology to certain neuropsychological syndromes (E. Stengel, 1948, Journal of Mental Science, 94, 46-58; J. de Ajuriaguerra & H. Hécaen, 1960, Le cortex cérébrale; N. Geschwind & M. Fusillo, 1966, Archives of Neurology, 15, 137-146). Further, specifically deficient components of constructional praxis (A. R. Luria & L. S. Tsvetkova, 1964, Neuropsychologia, 2, 95-107) are proposed to reflect gender-related limitations of daily tasks, suggesting occipital-parietal underuse in Auca men and frontal system underuse in Auca women.