Clever crows or unbalanced birds?

Abstract

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.