String-pulling in the Greater Vasa parrot (Coracopsis vasa): A replication of capacity, findings of longitudinal retention, and evidence for a species-level general insight factor across five physical cognition tasks

Spontaneous solving of an insight-based means-end reasoning task (the string-pulling problem) is observed in an adult male captive bred Greater Vasa parrot (Coracopsis vasa Shaw, 1812), with an efficiency of 66%, replicating previous work in a singleton context. This case report adds to the existing literature on this species by also demonstrating longitudinal retention, specifically the same bird was found to be able to re-solve the simple form of the problem after a period of seven years (the bird was first tested in 2013, and re-tested in 2020), with an efficiency of 43% (the difference between efficiencies was not significant, χ2 = 0.991, p = .319). In a second analysis, species-level data across five patterned string-pulling tasks involving 14 parrot species were reanalysed, revealing that the Greater Vasa parrot exhibited the greatest general competence among those evaluated. A ‘general insight factor’ (GIF) was also found across taxa, the loadings onto which exhibit positive and large-magnitude associations with the correlation between fission-fusion flocking intensity and indicator level performance (r = 0.831), and also positive small and modest-magnitude associations with the correlation between relative brain size and indicator-level performance, and the magnitude of average pair-wise species differences in performance across indicators (r = 0.219 and 0.365 respectively). Finally, the theoretical implications of these findings are discussed. •Greater Vasa parrots are prospectively highly intelligent but critically understudied•An individual is found to spontaneously solve the string-pulling problem, and to be able to re-solve it after seven years•This replicates previous findings, and expands on them•A general insight factor is identified among 14 parrot species•Covariance associates strongly with fission-fusion intensity, weakly with brain size and species differences