Grey parrots' {Psittacus erithacus) abilities for visual inferential reasoning by exclusion were tested in 2 experiments. The first replicated the grey parrot study performed in an Austrian Zoo, which in turn replicated that of Premack and Premack with apes. Here parrots watched an experimenter hide 2 equally desirable foods under 2 separate, opaque cups, surreptitiously remove and then, in view of the birds, pocket/eat 1 of the foods, leaving birds to find the still baited cup. The experiment contained controls for various alternative explanations for the birds' behavior, but birds might still have avoided a cup from which something had been removed rather than specifically tracking the eaten food. Thus, in the second experiment, some trials were run with 1 food slightly more preferred than the other, during which 2 items of each type were hidden and only 1 of the items were removed from 1 cup. Sessions also included Experiment 1-type trials to see if birds tracked when and when not to use exclusion. Thus birds would be rewarded for attending closely to all the experimental aspects needed to infer how to receive their preferred treat. Three of 4 birds succeeded fully.
展开▼
