Enhanced cognitive ability has been shown to impart fitness advantages to some species by facilitating establishment in new environments. Enhanced cognitive ability may be an adaptation driven during the establishment process in response to new environments or, alternatively, may reflect a species' characteristic. We used an intraspecific-comparative paradigm to examine the cause of a successful mammalian invader and urban dweller, Eastern grey squirrels’ (Sciurus carolinensis) cognitive ability (novel problem solving, motor memory and spatial learning) using well-established tasks. Free-ranging squirrels residing in rural and urban habitats in native environments (US) were compared with their counterparts living in non-native environments (UK). The four groups of squirrels showed comparable performance in most measures, suggesting that the previously reported ‘enhanced’ performance is likely a general characteristic of this species. Despite this, some cognitive abilities such as solving novel problems in grey squirrels has undergone mild variation during the adaptive process in new environments.

Enhanced behavioural flexibility has been linked to relatively large brain size and social complexity. Aras exhibit both properties. We tested parrots of A. ambiguus and A. glaucogularis in a serial reversal learning paradigm, in which all the individuals completed an acquisition, and 10 reversal learning phases. Behavioural flexibility (and thus learning performance) was measured as the number of errors per trial. We also conducted social observations on individuals’ social interactions. We found that both species made significantly fewer errors per trial during each reversal phase and over the course of ten reversal phases. All individuals gradually developed a generalised learning strategy i.e., ‘win-stay-loose-shift’, and thus showing ‘learning to learn efficiently’. Our results also support the Social Intelligence Hypothesis whereby individuals’ learning performance was positively related to social interaction. These results show that the two Ara species demonstrate behavioural flexibility, and social complexity provides one explanation for varied individual learning performance.