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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The biliary recovery and effect on bile flow and biliary bicarbonate secretion of infused norchenodeoxycholate (nor-CDC), the synthetically prepared C23 homologue of chenodeoxycholate (CDC), were defined in the anesthetized biliary fistula hamster, rat, and guinea pig and compared with those of its taurine conjugate as well as those of the natural C24 bile acid, CDC. In the hamster and rat, nor-CDC was recovered slowly in bile in contrast to its taurine conjugate or CDC. Hepatic biotransformation of nor-CDC was complex. Little amidation with glycine or taurine occurred and the compound was recovered in bile in unchanged form, in the form of hydroxylated derivatives as well as glucuronates and sulfates, the proportion varying in the different species. In contrast, CDC was efficiently amidated with glycine or taurine. The taurine conjugate of nor-CDC was secreted largely unchanged. Nor-CDC infusion caused a striking hypercholeresis in the hamster (108 microliters bile/mumol bile acid in bile) and in the rat (220 microliters/mumol); these values for bile acid-dependent flow far exceed those reported for any other natural bile acid to date in these species. The induced hypercholeresis was of canalicular origin and was accompanied by an enrichment in bicarbonate ion concentration as well as increased bicarbonate output. The taurine conjugate of nor-CDC did not display hypercholeretic properties in the hamster. In the guinea pig, whose native bile is bicarbonate-rich relative to other species, nor-CDC was only mildly hypercholeretic relative to CDC and caused no change in bicarbonate concentration. Thus shortening the side chain of a natural dihydroxy bile acid by a single carbon atom formed a compound that underwent a different hepatic biotransformation than that of most natural bile acids and induced a bicarbonate-rich canalicular choleresis far greater than that which can be explained by current theories of bile formation.

Background: Mass casualty and multi-victim incidents have increased in recent years due to a number of factors including natural disasters and terrorism. The Association of American Medical Colleges (AAMC) recommends that medical students be trained in disaster preparedness and response. However, a majority of United States medical students are not provided such education. Objective: The goal of this study was to evaluate the effectiveness of a 1 day, immersive, simulation-based Disaster Day curriculum. Settings and Design: Learners were first and second year medical students from a single institution. Materials and Methods: Our education provided learners with information on disaster management, allowed for application of this knowledge with hands-on skill stations, and culminated in near full-scale simulation where learners could evaluate the knowledge and skills they had acquired. Statistical analysis used: To study the effectiveness of our Disaster Day curriculum, we conducted a single-group pretest-posttest and paired analysis of self-reported confidence data. Results: A total of 40 first and second year medical students participated in Disaster Day as learners. Learners strongly agreed that this course provided new information or provided clarity on previous training, and they intended to use what they learned, 97.6% and 88.4%, respectively. Conclusions: Medical students’ self-reported confidence of key disaster management concepts including victim triage, tourniquet application, and incident command improved after a simulation-based disaster curriculum. This Disaster Day curriculum provides students the ability to apply concepts learned in the classroom and better understand the real-life difficulties experienced in a resource limited environment.

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