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New Caledonian crows reason about hidden causal agents
Edited by Dale Purves, Duke-NUS Graduate Medical School, Singapore, Singapore, and approved August 16, 2012 (received for review May 24, 2012)
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Abstract
The ability to make inferences about hidden causal mechanisms underpins scientific and religious thought. It also facilitates the understanding of social interactions and the production of sophisticated tool-using behaviors. However, although animals can reason about the outcomes of accidental interventions, only humans have been shown to make inferences about hidden causal mechanisms. Here, we show that tool-making New Caledonian crows react differently to an observable event when it is caused by a hidden causal agent. Eight crows watched two series of events in which a stick moved. In the first set of events, the crows observed a human enter a hide, a stick move, and the human then leave the hide. In the second, the stick moved without a human entering or exiting the hide. The crows inspected the hide and abandoned probing with a tool for food more often after the second, unexplained series of events. This difference shows that the crows can reason about a hidden causal agent. Comparative studies with the methodology outlined here could aid in elucidating the selective pressures that led to the evolution of this cognitive ability.
Footnotes
- ↵1To whom correspondence should be addressed. E-mail: alexander.taylor{at}auckland.ac.nz.
Author contributions: A.H.T., R.M., and R.D.G. designed research; A.H.T. and R.M. performed research; A.H.T. and R.D.G. analyzed data; and A.H.T. and R.D.G. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1208724109/-/DCSupplemental.
Freely available online through the PNAS open access option.
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