Causal reasoning in New Caledonian crows: Ruling out spatial analogies and sampling error

A large number of studies have failed to find conclusive evidence for causal reasoning in nonhuman animals. For example, when animals are required to avoid a trap while extracting a reward from a tube they appear to learn about the surface-level features of the task, rather than about the task's causal regularities. We recently reported that New Caledonian crows solved a two-trap-tube task and then were able to immediately solve a novel, visually distinct problem, the trap-table task. Such transfer suggests these crows were reasoning causally. However, there are two other possible explanations for the successful transfer: sampling bias and the use of a spatial, rather than a causal, analogy. Here we present data that rule out these explanations.