Oriental pied hornbills have levels of object permanence comparable to monkeys

Two animal behaviorists from the National University of Singapore have discovered, through testing, that oriental pied hornbills have levels of object permanence comparable to monkeys. In their article published in the journal Biology lettersRuitong Yao and Elias Garcia-Pelegrin, describe how they tested levels of object permanence in several captive eastern pied hornbills.

Object permanence is the ability to remember or know that something still exists even if it is out of sight. Previous research has shown that only two bird species possess such an ability; corvids and parrots. In this new effort, the research team discovered that a third species, oriental pied hornbills, also possess this ability.

To learn more about object permeance in oriental pied hornbills, the researchers tested six of the birds housed at a testing facility at the National University of Singapore. They chose to test birds because previous research showed that they demonstrated a form of object permanence in nature: males bring treats to females and hatchlings although they cannot see them because they are hidden behind protective constructions. Each of the birds was tested in several ways, with the tests becoming progressively more difficult.

All tests involved first training the birds to show where a treat was by pecking at it or in its direction. The birds were then placed one by one in a cage with a screen through which they could watch while the researchers handled and hid the treats under small red cups. After each manipulation, the bird was asked to indicate where it thought the treat was by pecking through the mesh of one of the red cups.

At first, a treat was placed under a cup while a bird watched, then asked to indicate which cup hid the treat. In subsequent steps, a treat was placed under various cups and then moved to other cups before asking the bird where it was.

The final test involved invisible movement, where a bird was allowed to observe a treat placed under a box, and then it could not see where the treat was moved, but it had not been moved at all. After showing the birds that the treat was not under a cup, half of the birds began pecking at the box, assuming it had been left there.

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