ИСТИНА

To improve our knowledge on animal’s cognition we investigate the cognitive abilities of birds with different level of brain complexity using a whole complex of cognitive tests. We investigated the numerical competence in hooded crows (Corvus cornix L.) and crossbills (Loxia curvirostra) under a relative numerousness judgments paradigm (Zorina & Smirnova 1996a, 1996b; Obozova et al., 2009). Most the crows and one crossbill were found to be able to perceive and exactly estimate graphic arrays, containing up to 20 items, and to form the concept "larger than" based on numerical rather than other quantitative futures. The “same/different” concept formation was investigated in hooded crows and Amazonian parrots (Amazona amazonica) using simultaneous matching-to-sample procedure. It was shown that both crows and parrots are able to transfer the matching rule to the novel, unfamiliar stimuli оf novel categories, demonstrating the acquisition of the abstract “same-different” concept (Smirnova et al., 2000). The same matching-to-sample procedure was used to investigate bird’s ability to analogical reasoning. Both crows and parrots, which had been previously learned generalized matching-to-sample task based on physical resemblance between stimuli, spontaneously match analogical sameness of relations-between-relations even though they were not differentially rewarded during the test trials. This finding demonstrates that these birds, as well as apes, can percept and judge sameness at conceptual level, including relations between relations (Zorina & Smirnova 2005; Obozova, unpublished data). To estimate the level of means-end-relations comprehension in birds with different level of brain complexity, hooded crows, common crossbills, blue tits (Cyanistes caeruleus) and great grey owls (Strix nebulosa) were offered a series of string-pulling tasks. Consequently, out of these species, only hooded crows, which have a higher level of brain complexity, are probably able to comprehend the functional properties of the strings. The fact that corvids and parrots on the one side, and anthropoids on the other side, have similar abilities to successfully solve numerous cognitive tests supports the hypothesis (Krushinsky 1990; Emery & Clayton, 2004) about the convergent evolution of brain and cognition in birds and primates.