I See, Therefore I Think - The Role of Observed Realities on Cognition in Rooks (Corvus frugilegus) and African Grey Parrots (Psittacus erithacus)
Within the avian order, corvids and psittacines are those for which evidence of complex cognitive abilities abounds, but rarely are the same tasks given to both. One such ability is secondary representation: entertaining mental models of multiple versions of reality. Secondary representation is likely a pre-requisite for several other abilities, including mental time travel, theory of mind, and self-awareness. While evidence of such abilities is found in both families, direct comparisons are lacking. This makes it impossible to judge if their representational abilities are equivalent and likely to underlie these complex abilities. To generate comparative data, two concepts thought to require secondary representation are examined. Firstly, five rooks (Corvus frugilegus) were presented with object permanence (OP) tasks comparable to previous studies with African grey parrots (Psittacus erithacus). Like parrots, one rook also demonstrated full Stage 6b (multiple invisible displacements), including evidence of representation, whereas other individuals ranged between Stage 5a (single visible displacements) and 6a (single invisible displacements). Individual differences, past experiences, and behavioural characteristics are posited to underlie the lower performance of some, especially given existing data in other corvids, which display advanced OP and food caching. Secondly, another ability requiring secondary representation is mirror self-recognition (MSR), but evidence from birds is contested and contradictory: Often, they do not behave consistently with either self-recognition or perceiving a conspecific, or appear to recognise themselves in only some contexts. I posit this to be due to the interference of mirrors on the ultraviolet (UV) portion of light, which birds see and use for mate choice, foraging, and possibly individual recognition. For the first time, two rooks and two African grey parrots were given a series of mirror-stimulation tasks intended to target their visual perception of surfaces causing different levels of UV interference. Although individual differences influenced the results, it was evident that all birds attended to the differences between surfaces: they treated “mirrors”, as a group, separate from “glasses”, and appeared to also distinguish between different types of glass, as well as probably between types of mirrors. This, coupled with other significant results and effects of the UV light readings available during sessions, suggests the influence of UV light and its interference may be relevant in mirror studies, and should be studied further. Although there were species differences, rooks and parrots performed comparably in OP and mirror-stimulation tasks. Together with the existing literature of complex abilities in both families, this supports the presence of secondary representation in them, and that methodologically equivalent tasks can and should be presented to both families for better comparative data.
animal cognition, psychology, comparative cognition, birds
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