More but not less uncertainty makes adult humans' tool selections more similar to those reported with crows.

In this study, we examined whether adult humans' tool selections in a stick-and-tube problem might resemble previously published results of crows' selections if people had more experience solving the problem or were presented with a more ambiguous problem. In Experiments 1a and 1b, when given multiple opportunities to select a stick from a set of 10 to retrieve a candy located either 8 or 16 cm from the opening of a tube, the participants always selected a stick that was long enough to retrieve the candy; however, they did not generally select either the stick whose length matched the object's distance or the longest stick in the set-two outcomes reported in studies with crows. In Experiment 2, participants who were allowed only a brief period of time to study the problem selected a longer stick than did participants allowed unlimited time to do the same. However, only when the candy's distance was 16 cm did these people reliably select the longest stick in the set. It seems that increasing, but not decreasing, people's uncertainty about a problem can make humans' tool selections more similar to those reported with crows.