File:Cognitive-Processes-Associated-with-Sequential-Tool-Use-in-New-Caledonian-Crows-pone.0006471.s001.ogv

English: This video shows Betty's first exposure in Experiment 1 to the three-tool problem (Tertiary), which was her fourth testing trial in total. Correct sequence of actions: first use tabletop tool (freely available in the arena) to retrieve any of the three medium-length tools from tool-tubes (first three tool-tubes from left); then use medium-length tool to retrieve longest tool from tool-tube (fourth tool-tube from left); then use this long tool to obtain food reward from food-tube (in front). Observed behaviour: Betty does not attempt to probe for food, but immediately uses the tabletop tool to retrieve a medium-length tool. She then appears to look into the food-tube, without probing, before using the tool to extract the longest tool. Finally, she uses this tool to retrieve the reward from the food-tube. It is noteworthy that she seems to actively dispose of each tool as its role in the sequence is completed, and she also turns the tools around in order to place the cross-piece distal, where it is most effective as a hook-like instrument.