New research shows that wild New Caledonian crows can compete with 7-year-old children when it comes to understanding causality, or how one action causes another.
[T]here’s a widely used experiment called the trap-tube task. An animal uses a stick to push or pull a food reward out of a transparent tube, avoiding a small well in the center of the tube where the food would become stuck.
In the first experiment, the researchers replicate an earlier finding that the crows preferentially drop stones into water rather than sand to retrieve their snack. The second and third experiments pitted heavier and lighter objects, and solid blocks against hollow ones. The fourth experiment pitted narrow tubes against wide ones.
The New Caledonian crows actually did pretty well on all of these but the fourth, which they succeeded at, but not in a way that proved they understood the principle.
After these (and a fifth variation similar to the fourth) the researchers attempted a “U-Tube” task, with three tubes, the center being too narrow to drop anything into but having the treat.
Since the tubes were connected, the solution was to drop objects into one of the side tubes – but only one.
Eight year old children can figure this out, but apparently not any of the New Caledonian crows, who just kept dropping objects into both of the side tubes.