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New Caledonian crows learn the functional properties of novel tool types.

ABSTRACT: New Caledonian crows were presented with Bird and Emery's (2009a) Aesop's fable paradigm, which requires stones to be dropped into a water-filled tube to bring floating food within reach. The crows did not spontaneously use stones as tools, but quickly learned to do so, and to choose objects and materials with functional properties. Some crows discarded both inefficient and non-functional objects before observing their effects on the water level. Interestingly, the crows did not learn to discriminate between functional and non-functional objects and materials when there was an arbitrary, rather than causal, link between object and reward. This finding suggests that the crows' performances were not based on associative learning alone. That is, learning was not guided solely by the covariation rate between stimuli and outcomes or the conditioned reinforcement properties acquired by functional objects. Our results, therefore, show that New Caledonian crows can process causal information not only when it is linked to sticks and stick-like tools but also when it concerns the functional properties of novel types of tool.

SUBMITTER: Taylor AH

PROVIDER: S-EPMC3237408 | biostudies-literature | 2011

REPOSITORIES: biostudies-literature

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New Caledonian crows learn the functional properties of novel tool types.

Taylor Alex H AH Elliffe Douglas M DM Hunt Gavin R GR Emery Nathan J NJ Clayton Nicola S NS Gray Russell D RD

PloS one 20111214 12

New Caledonian crows were presented with Bird and Emery's (2009a) Aesop's fable paradigm, which requires stones to be dropped into a water-filled tube to bring floating food within reach. The crows did not spontaneously use stones as tools, but quickly learned to do so, and to choose objects and materials with functional properties. Some crows discarded both inefficient and non-functional objects before observing their effects on the water level. Interestingly, the crows did not learn to discrim ...[more]

PMID: 22194779

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Project description:BackgroundUsing tools to act on non-food objects--for example, to make other tools--is considered to be a hallmark of human intelligence, and may have been a crucial step in our evolution. One form of this behaviour, 'sequential tool use', has been observed in a number of non-human primates and even in one bird, the New Caledonian crow (Corvus moneduloides). While sequential tool use has often been interpreted as evidence for advanced cognitive abilities, such as planning and analogical reasoning, the behaviour itself can be underpinned by a range of different cognitive mechanisms, which have never been explicitly examined. Here, we present experiments that not only demonstrate new tool-using capabilities in New Caledonian crows, but allow examination of the extent to which crows understand the physical interactions involved.Methodology/principal findingsIn two experiments, we tested seven captive New Caledonian crows in six tasks requiring the use of up to three different tools in a sequence to retrieve food. Our study incorporated several novel features: (i) we tested crows on a three-tool problem (subjects were required to use a tool to retrieve a second tool, then use the second tool to retrieve a third one, and finally use the third one to reach for food); (ii) we presented tasks of different complexity in random rather than progressive order; (iii) we included a number of control conditions to test whether tool retrieval was goal-directed; and (iv) we manipulated the subjects' pre-testing experience. Five subjects successfully used tools in a sequence (four from their first trial), and four subjects repeatedly solved the three-tool condition. Sequential tool use did not require, but was enhanced by, pre-training on each element in the sequence ('chaining'), an explanation that could not be ruled out in earlier studies. By analyzing tool choice, tool swapping and improvement over time, we show that successful subjects did not use a random probing strategy. However, we find no firm evidence to support previous claims that sequential tool use demonstrates analogical reasoning or human-like planning.Conclusions/significanceWhile the ability of subjects to use three tools in sequence reveals a competence beyond that observed in any other species, our study also emphasises the importance of parsimony in comparative cognitive science: seemingly intelligent behaviour can be achieved without the involvement of high-level mental faculties, and detailed analyses are necessary before accepting claims for complex cognitive abilities.

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New Caledonian crows learn the functional properties of novel tool types.

Publications

New Caledonian crows learn the functional properties of novel tool types.

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