...Taylor trained seven wild crows to associate a short stick with ineffectiveness; the crows failed to obtain their out-of-reach food with the stick and eventually began to ignore or reject it. Then they were divided into two groups, an innovation group and a training group. The training group learned six activities—such as how to use a short stick to extract a long stick from a toolbox—that together could help them get meat with long and short tools. The innovation group wasn’t taught how to use a short stick to extract a long stick from the toolbox, but did learn other techniques.The Taylor et al. abstract:
When tasked with reaching a snack in a hole using a short stick on a string and a longer stick trapped in a toolbox, all of the crows pulled it off. The three birds in the training group linked the behaviors they had learned into a new behavior. They freed the short stick from the string, used it to dislodge the long stick, and used the long stick to obtain their food. And all four crows in the innovation group figured out the sequence on their own. One crow in the innovation group stared at the setup for less than 2 minutes and then performed the whole trial correctly on her very first attempt.
Apes, corvids and parrots all show high rates of behavioural innovation in the wild. However, it is unclear whether this innovative behaviour is underpinned by cognition more complex than simple learning mechanisms. To investigate this question we presented New Caledonian crows with a novel three-stage metatool problem. The task involved three distinct stages: (i) obtaining a short stick by pulling up a string, (ii) using the short stick as a metatool to extract a long stick from a toolbox, and finally (iii) using the long stick to extract food from a hole. Crows with previous experience of the behaviours in stages 1–3 linked them into a novel sequence to solve the problem on the first trial. Crows with experience of only using string and tools to access food also successfully solved the problem. This innovative use of established behaviours in novel contexts was not based on resurgence, chaining and conditional reinforcement. Instead, the performance was consistent with the transfer of an abstract, causal rule: ‘out-of-reach objects can be accessed using a tool’. This suggests that high innovation rates in the wild may reflect complex cognitive abilities that supplement basic learning mechanisms.