ORIGINAL PAPER Means–end comprehension in four parrot species: explained by social complexity

Abstract A comparative approach is required to investi-gate the evolutionary origins of cognitive abilities. In this paper, we compare the performance of four parrot spe-cies, spectacled parrotlets (Forpus conspicillatus), rainbow lorikeets (Trichoglossus haematodus), green-winged macaws (Ara chloroptera) and sulphur-crested cockatoos (Cacatua galerita triton) in standardized string-pulling and string-choice paradigms. We varied the spatial relationship between the strings, the presence of a reward and the physical contact between the string and the reward to test different cognitive skills requiring means–end comprehension. The species tested showed a high individual and inter-specific variation in their ability to solve the tasks. Spectacled par-rotlets performed best among the four species and solved the most complex choice tasks, namely crossed-string task and broken-string task, spontaneously. In contrast, macaws and cockatoos failed to identify the correct string in these two tasks. The rainbow lorikeets were outperformed by the par-rotlets, but outperformed in turn the macaws and the cock-atoos. The findings can be best explained by the variation in social complexity among species, rather than in their ecology