Using the Aesop's fable paradigm to investigate causal understanding of water displacement by New Caledonian crows.

Understanding causal regularities in the world is a key feature of human cognition. However, the extent to which non-human animals are capable of causal understanding is not well understood. Here, we used the Aesop's fable paradigm--in which subjects drop stones into water to raise the water level and obtain an out of reach reward--to assess New Caledonian crows' causal understanding of water displacement. We found that crows preferentially dropped stones into a water-filled tube instead of a sand-filled tube; they dropped sinking objects rather than floating objects; solid objects rather than hollow objects, and they dropped objects into a tube with a high water level rather than a low one. However, they failed two more challenging tasks which required them to attend to the width of the tube, and to counter-intuitive causal cues in a U-shaped apparatus. Our results indicate that New Caledonian crows possess a sophisticated, but incomplete, understanding of the causal properties of displacement, rivalling that of 5-7 year old children

Measurement of low energy charge correlations in underdoped spin-glass La-based cuprates using impedance spectroscopy

We report on the charge kinetics of La_2CuO_4 lightly doped with Li and Sr. Impedance spectroscopy measurements down to 25mK and from 20Hz to 500kHz reveal evidence for low energy charge dynamics, which slow down with decreasing temperature. Both systems are acutely sensitive to stoichiometry. In the case of Sr substitution, which at higher carrier concentration evolves to a high temperature superconductor, the ground state in the pseudogap-doping regime is one of spatially segregated, dynamic charge domains. The charge carriers slow down at substantially lower temperatures than their spin counterparts and the dynamics are particularly sensitive to crystallographic direction. This is contrasted with the case of Li-doping.Comment: 4 pages, 4 figure

History dependent magnetoresistance in lightly doped La_{2-x}Sr_{x}CuO_{4} thin films

The in-plane magnetoresistance (MR) in atomically smooth La_{2-x}Sr_{x}CuO_{4} thin films grown by molecular-beam-epitaxy was measured in magnetic fields B up to 9 T over a wide range of temperatures T. The films, with x=0.03 and x=0.05, are insulating, and the positive MR emerges at T<4 K. The positive MR exhibits glassy features, including history dependence and memory, for all orientations of B. The results show that this behavior, which reflects the onset of glassiness in the dynamics of doped holes, is a robust feature of the insulating state.Comment: 4 pages, 4 figures, International School and Workshop on Electronic Crystals (ECRYS-2011); to appear in Physica

Low-temperature ferroelectric phase and magnetoelectric coupling in the underdoped La_2CuO_(4+x)

We report the discovery of a ferroelectric ground state below 4.5 K in highly underdoped La_2CuO_(4+x) accompanied by slow charge dynamics which develop below T~40 K. An anisotropic magnetoelectric response has also been observed, indicating considerable spin-charge coupling in this lightly doped "parent" high temperature copper-oxide superconductor. The ferroelectric state is proposed to develop from polar nanoregions, in which spatial inversion symmetry is locally broken due to non-stoichiometric carrier doping.Comment: 7 Pages, 6 Figures, supplementary materia

Performance in Object-Choice Aesop's Fable Tasks Are Influenced by Object Biases in New Caledonian Crows but not in Human Children

The ability to reason about causality underlies key aspects of human cognition, but the extent to which non-humans understand causality is still largely unknown. The Aesop's Fable paradigm, where objects are inserted into water-filled tubes to obtain out-of-reach rewards, has been used to test casual reasoning in birds and children. However, success on these tasks may be influenced by other factors, specifically, object preferences present prior to testing or arising during pre-test stone-dropping training. Here, we assessed this 'object-bias' hypothesis by giving New Caledonian crows and 5-10 year old children two object-choice Aesop's Fable experiments: sinking vs. floating objects, and solid vs. hollow objects. Before each test, we assessed subjects' object preferences and/or trained them to prefer the alternative object. Both crows and children showed pre-test object preferences, suggesting that birds in previous Aesop's Fable studies may also have had initial preferences for objects that proved to be functional on test. After training to prefer the non-functional object, crows, but not children, performed more poorly on these two object-choice Aesop's Fable tasks than subjects in previous studies. Crows dropped the non-functional objects into the tube on their first trials, indicating that, unlike many children, they do not appear to have an a priori understanding of water displacement. Alternatively, issues with inhibition could explain their performance. The crows did, however, learn to solve the tasks over time. We tested crows further to determine whether their eventual success was based on learning about the functional properties of the objects, or associating dropping the functional object with reward. Crows inserted significantly more rewarded, non-functional objects than non-rewarded, functional objects. These findings suggest that the ability of New Caledonian crows to produce performances rivaling those of young children on object-choice Aesop's Fable tasks is partly due to pre-existing object preferences.This research was funded by the European Research Council under the European Union's Seventh Framewor k Programme (FP7/ 2007-2013)/ERC Grant Agreement No. 3399933, awarded to NSC (funding RM, SAJ, EL & NSC). AHT was funded by a Rutherford Discovery Fellowship from the Royal Society of New Zealand

New Caledonian crows rapidly solve a collaborative problem without cooperative cognition

There is growing comparative evidence that the cognitive bases of cooperation are not unique to humans. However, the selective pressures that lead to the evolution of these mechanisms remain unclear. Here we show that while tool-making New Caledonian crows can produce collaborative behavior, they do not understand the causality of cooperation nor show sensitivity to inequity. Instead, the collaborative behavior produced appears to have been underpinned by the transfer of prior experience. These results suggest that a number of possible selective pressures, including tool manufacture and mobbing behaviours, have not led to the evolution of cooperative cognition in this species. They show that causal cognition can evolve in a domain specific manner-understanding the properties and flexible uses of physical tools does not necessarily enable animals to grasp that a conspecific can be used as a social tool

Diagrams of the apparatus used in each of the 6 experiments.

<p>In each experiment birds dropped objects into tubes to obtain an out of reach food reward. Each experiment involved either a choice of two tubes or a choice of two objects. The apparatus was presented on a table in the centre of a large testing cage, as pictured. A: Experiment 1, Sand-filled tubes v Water-filled tubes, B: Experiment 2, Sinking v Floating objects, C: Experiment 3, Solid v Hollow objects, D: Experiment 4, Narrow v Wide tubes, E: Experiment 5, High v Low water levels in Narrow and Wide tubes, F: Experiment 6, U-tube, a concealed connection links one of the outer tubes with the rewarded central tube.</p