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Using the Aesop's Fable Paradigm to Investigate Causal Understanding of Water Displacement by New Caledonian Crows

Figure 1

Diagrams of the apparatus used in each of the 6 experiments.

In each experiment birds dropped objects into tubes to obtain an out of reach food reward. Each experiment involved either a choice of two tubes or a choice of two objects. The apparatus was presented on a table in the centre of a large testing cage, as pictured. A: Experiment 1, Sand-filled tubes v Water-filled tubes, B: Experiment 2, Sinking v Floating objects, C: Experiment 3, Solid v Hollow objects, D: Experiment 4, Narrow v Wide tubes, E: Experiment 5, High v Low water levels in Narrow and Wide tubes, F: Experiment 6, U-tube, a concealed connection links one of the outer tubes with the rewarded central tube.

Figure 1

doi: https://doi.org/10.1371/journal.pone.0092895.g001