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Clever crows or unbalanced birds?

Dymond, S. and Haselgrove, M. and McGregor, A. (2013) 'Clever crows or unbalanced birds?', Proceedings of the National Academy of Sciences of the United States of America., 110 (5). E336.


Taylor et al. claimed that New Caledonian crows are capable of reasoning about “hidden causal agents.” Their recorded increases in hide inspections and abandoned trials in the unknown causal agent (UCA) condition relative to the human causal agent (HCA) condition, which were used to infer the presence of “causal reasoning” ability, are, however, confounded by a fundamental methodological limitation. Test trials of the two experimental conditions were administered in a fixed order: The HCA trials always preceded the UCA trials. To overcome the likely impact of order effects, it is customary for researchers to experimentally cross the manipulation of interest with the order of testing, a practice called counterbalancing. Thus, although it is unclear why counterbalancing was not employed, it is plausible that performance on UCA trials was influenced by prior exposure to HCA trials. This being the case, the findings of Taylor et al. are uninterpretable.

Item Type:Article
Full text:(AM) Accepted Manuscript
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Publisher statement:Copyright © 2014 National Academy of Sciences. Article available in PNAS Online at
Date accepted:No date available
Date deposited:28 April 2014
Date of first online publication:January 2013
Date first made open access:No date available

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