Feldhütter, I.; Schleidt, M.; Eibl-Eibesfeldt, I.: Moving in the beat of seconds: Analysis of the time structure of human action. Ethology and Sociobiology 11 (6), pp. 511 - 520 (1990)
Scientists studying a rare population of tool-using chimpanzees have found that aging can have a profound impact on their abilities—but not all chimps decline equally.