Comparison of physical cognition between tool-using and non-tool-using corvids
Zusammenfassung der Projektergebnisse
One of the fundamental issues in the study of human and animal cognition concerns the factors that drove the evolution of intelligence. The ability to use tools has played a long-standing role in this debate. To test this hypothesis, it is necessary to test as many tool-using/non-tool-using species pairs as possible, preferably pairs that are only distantly related between themselves. In a previous project, we were interested in finding out whether the use of tools evolved in conjunction with enhanced cognitive abilities in the physical domain, in a tool-using Darwin’s finch species, the woodpecker finch. To do this, we compared general learning and physical cognitive abilities in the woodpecker finch (Cactospiza pallida) and a closely related non-tool-using species, the small tree finch (Camarhynchus parvulus). We predicted that if tool-use evolved with enhanced specialized cognitive abilities, woodpecker finches should outperform small tree finches in physical tasks but not necessarily in the general learning tasks. Contrary to expectation, the small tree finches performed similarly or better than woodpecker finches in one of the general learning tasks and most of the physical tasks. Thus, the study yielded no evidence that woodpecker finches are better at solving physical tasks than small tree finches and therefore did not provide any suggestion that tool-use is indeed associated with enhanced physical cognition in this species. The goal of the current study was to provide highly comparable data from another new tool-using / nontool-using species pair from a distantly related group using the methods which had been applied in the preceding Darwin’s finches study. This would allow a more complete assessment of the hypothesis that tool-use might generally associated with adaptive cognitive specializations in the physical domain. Using the paradigms previously established with Darwin’s finches, we tested physical cognition and general learning abilities in a new two-species pair: tool-using New Caledonian crows (Corvus moneduloides) and a non-tool-using species, the carrion crow (Corvus corone). New Caledonian crows are well-known for their prolific tool-use in the wild as well as captive studies that have demonstrated their ability to use and modify tools appropriately for a given task as well as remarkable planning and creative problemsolving abilities. We found that while New Caledonian crows did not outperform the carrion crows in general learning tasks, they were more proficient in the cane task, a physical task closely related to tool-use. Thus, in contrast to the previous study on Darwin’s finches, this new study did yield some suggestion for a cognitive enhancement in the physical cognitive domain of tool-use in New Caledonian crows. Thus, based on these two studies, there does not seem to be any generality to the tool-use hypothesis: it seems that some types or contexts of tool-use might foster evolution of this foraging mode in conjunction with enhanced physical cognitive abilities while others may not.
