bearded capuchin monkeys
1 place palm nuts in a stable position on a surface before trying to crack them open, revealing their capacity to use
2 information to improve tool use. the results are published february 27 in the open access journal plos one by dorothy fragaszy and colleagues from the university of georgia. the researchers
3 the monkeys' tool-use skills by videotaping adult monkeys cracking palm nuts on a surface they used frequently for the purpose. they found that monkeys positioned the nuts flat side down more frequently than expected by
4 chance. when placing the nuts, the monkeys knocked the nuts on the surface a few times before releasing them, after which the nuts very rarely moved.
the researchers suggest that the monkeys may have learned to
5 this tool-use strategy by repeatedly knocking the nut to achieve the stable position prior to cracking it. they conclude that the monkeys' strategic placement of the nut reveals that the monkeys pay attention to the fit between the nut and the surface each time they place the nut, and adjust their actions accordingly.
in a parallel experiment, the scientists asked
6（被蒙上眼睛的） people to perform the same action, positioning palm nuts on an
7 as if to crack them with a stone or hammer. like the monkeys, the human participants also followed
tactile（触觉的） cues to place the nut flat-side down on the anvil.
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