Abstract

Object manipulation can be a comparative scale of cognitive development in primates including humans. Combinatory manipulation is a precursor of tool-using behavior and regarded as a milestone in the cognitive development. Although all four species of great apes exhibit combinatory manipulation at least in captive settings, their tool-use propensities in the wild differ significantly. Notation system of object manipulation was applied in the tasks of nesting cups, stacking blocks, or crackingnuts and enabled the detailed analysis on the characteristics of action grammar in humans and nonhuman primates. Precise analysis on the patterns of object manipulation revealed the commonality and difference in the level of cognitive development among the four species of great apes and humans.