More than one way to see it: Individual heuristics in avian visual computation

Comparative pattern learning experiments investigate how different species find regularities in sensory input, providing insights into cognitive processing in humans and other animals. Past research has focused either on one species’ ability to process pattern classes or different species’ performance in recognizing the same pattern, with little attention to individual and species-specific heuristics and decision strategies. We trained and tested two bird species, pigeons (Columba livia) and kea (Nestor notabilis, a parrot species), on visual patterns using touch-screen technology. Patterns were composed of several abstract elements and had varying degrees of structural complexity. We developed a model selection paradigm, based on regular expressions, that allowed us to reconstruct the specific decision strategies and cognitive heuristics adopted by a given individual in our task. Individual birds showed considerable differences in the number, type and heterogeneity of heuristic strategies adopted. Birds’ choices also exhibited consistent species-level differences. Kea adopted effective heuristic strategies, based on matching learned bigrams to stimulus edges. Individual pigeons, in contrast, adopted an idiosyncratic mix of strategies that included local transition probabilities and global string similarity. Although performance was above chance and quite high for kea, no individual of either species provided clear evidence of learning exactly the rule used to generate the training stimuli. Our results show that similar behavioral outcomes can be achieved using dramatically different strategies and highlight the dangers of combining multiple individuals in a group analysis. These findings, and our general approach, have implications for the design of future pattern learning experiments, and the interpretation of comparative cognition research more generally

DNA copy number changes define spatial patterns of heterogeneity in colorectal cancer

Genetic heterogeneity between and within tumours is a major factor determining cancer progression and therapy response. Here we examined DNA sequence and DNA copy-number heterogeneity in colorectal cancer (CRC) by targeted high-depth sequencing of 100 most frequently altered genes. In 97 samples, with primary tumours and matched metastases from 27 patients, we observe inter-tumour concordance for coding mutations; in contrast, gene copy numbers are highly discordant between primary tumours and metastases as validated by fluorescent in situ hybridization. To further investigate intra-tumour heterogeneity, we dissected a single tumour into 68 spatially defined samples and sequenced them separately. We identify evenly distributed coding mutations in APC and TP53 in all tumour areas, yet highly variable gene copy numbers in numerous genes. 3D morpho-molecular reconstruction reveals two clusters with divergent copy number aberrations along the proximal–distal axis indicating that DNA copy number variations are a major source of tumour heterogeneity in CRC

Preoperative prism adaptation test in normosensoric strabismus

In 19 patients with normosensoric esotropia, the squint angles measured with the alternate cover test were compared with those after prolonged prismatic correction of the squint angle and with those after prolonged occlusion of one eye. All patients showed an increase of the squint angle after prism adaptation. The angle was generally smaller after diagnostic occlusion of one eye than after prism adaptation. We assume that the increase in the squint angle after prism adaptation is caused by an anomalous sensorial relationship between the two eyes that was not detected with the usual psychophysical tests. Surgery tailored to the squint angle after prism adaptation seems advisable in patients with normosensoric esotropia

Czech Social Reform/Non-reform: Routes, Actors and Problems

In this contribution, the author first considers the characteristics of the Czechoslovak communist welfare state and its theoretical alternatives. Throughout the reform process, dependency on both corporatist and socialist regimes won out, while residualist efforts were promoted in the beginning, but were later held back. The author then considers the possible actors involved in social reforms. In this respect, when proceeding from a general to a more concrete level, thought should first be devoted to the social classes and their ideologies, and second to political parties and their leaders. The author goes on to summarise the particular problems and traps in individual sections of the Czech social system. While no objection to decent standards of social protection and health care could be raised, the poor efficiency of their achievement should evoke concern. The author concludes by reflecting on the possible specificities of Czech social reform in comparison with the other countries undergoing reform and the EU. The current lethargy of the Czech welfare system corresponds to a “frozen edifice”, just as in most Western countries. However, such stagnation is apparently acceptable to both the politicians (who mask it in reformist rhetoric) and the population (which learned to master taking advantage of the generous welfare state) and thus is basically sustainable in the long run.http://deepblue.lib.umich.edu/bitstream/2027.42/40037/3/wp651.pd

Multi-Particle Collision Dynamics -- a Particle-Based Mesoscale Simulation Approach to the Hydrodynamics of Complex Fluids

In this review, we describe and analyze a mesoscale simulation method for fluid flow, which was introduced by Malevanets and Kapral in 1999, and is now called multi-particle collision dynamics (MPC) or stochastic rotation dynamics (SRD). The method consists of alternating streaming and collision steps in an ensemble of point particles. The multi-particle collisions are performed by grouping particles in collision cells, and mass, momentum, and energy are locally conserved. This simulation technique captures both full hydrodynamic interactions and thermal fluctuations. The first part of the review begins with a description of several widely used MPC algorithms and then discusses important features of the original SRD algorithm and frequently used variations. Two complementary approaches for deriving the hydrodynamic equations and evaluating the transport coefficients are reviewed. It is then shown how MPC algorithms can be generalized to model non-ideal fluids, and binary mixtures with a consolute point. The importance of angular-momentum conservation for systems like phase-separated liquids with different viscosities is discussed. The second part of the review describes a number of recent applications of MPC algorithms to study colloid and polymer dynamics, the behavior of vesicles and cells in hydrodynamic flows, and the dynamics of viscoelastic fluids

Head of State of Exception

During the escalation of the “German Autumn” in 1977 the Federal German government resorted to a specific form of crisis management that had been described as an undeclared state of exception. It was Federal chancellor Helmut Schmidt in the first place who oversaw the anti-terrorist measures in the situation room where the executive branch ruled for six weeks beyond any parliamentary control. This article examines the role that Helmut Schmidt had played for the creation of a “subjective state of exception” (Julius Hatschek) and how this could be seen as stemming from Schmidt’s earlier experiences and handling of crisis situations dating back to the 1960s. In this regard it has to be asked with Giorgio Agamben, if in the West German case, the state of exception had become the rule

Exclusion Performance in Dwarf Goats (Capra aegagrus hircus) and Sheep (Ovis orientalis aries)

Using a comparative approach, we investigated the ability of dwarf goats and sheep to use direct and indirect information about the location of a food reward in an object-choice task. Subjects had to choose between two cups with only one covering a reward. Before making a choice, subjects received information about the baited (direct information) or non-baited cup (indirect information). Both goats and sheep were able to use direct information (presence of food) in the object choice task. After controlling for local enhancement, we found that goats rather than sheep were able to use indirect information (i.e., the absence of food) to find a reward. The actual test setup could not clarify whether individual goats were able to inferentially reason about the content of the baited cup when only shown the content of the non-baited cup or if they simply avoided the empty cup in that situation. As browsing species, feral and wild goats exhibit highly selective feeding behaviour compared to the rather unselective grazing sheep. The potential influence of this species-specific foraging flexibility of goats and sheep for using direct and indirect information to find a food reward is discussed in relation to a higher aversion to losses in food acquisition in goats compared to sheep

Is caching the key to exclusion in corvids? The case of carrion crows (Corvus corone corone)

Recently, two corvid species, food-caching ravens and non-caching jackdaws, have been tested in an exclusion performance (EP) task. While the ravens chose by exclusion, the jackdaws did not. Thus, foraging behaviour may affect EP abilities. To investigate this possibility, another food-caching corvid species, the carrion crow (Corvus corone corone), was tested in the same exclusion task. We hid food under one of two cups and subsequently lifted either both cups, or the baited or the un-baited cup. The crows were significantly above chance when both cups were lifted or when only the baited cup was lifted. When the empty cup was lifted, we found considerable inter-individual variation, with some birds having a significant preference for the un-baited but manipulated cup. In a follow-up task, we always provided the birds with the full information about the food location, but manipulated in which order they saw the hiding or the removal of food. Interestingly, they strongly preferred the cup which was manipulated last, even if it did not contain any food. Therefore, we repeated the first experiment but controlled for the movement of the cups. In this case, more crows found the food reliably in the un-baited condition. We conclude that carrion crows are able to choose by exclusion, but local enhancement has a strong influence on their performance and may overshadow potential inferential abilities. However, these findings support the hypothesis that caching might be a key to exclusion in corvids

Insect herbivores should follow plants escaping their relatives

Neighboring plants within a local community may be separated by many millions of years of evolutionary history, potentially reducing enemy pressure by insect herbivores. However, it is not known how the evolutionary isolation of a plant affects the fitness of an insect herbivore living on such a plant, especially the herbivore's enemy pressure. Here, we suggest that evolutionary isolation of host plants may operate similarly as spatial isolation and reduce the enemy pressure per insect herbivore. We investigated the effect of the phylogenetic isolation of host trees on the pressure exerted by specialist and generalist enemies (parasitoids and birds) on ectophagous Lepidoptera and galling Hymenoptera. We found that the phylogenetic isolation of host trees decreases pressure by specialist enemies on these insect herbivores. In Lepidoptera, decreasing enemy pressure resulted from the density dependence of enemy attack, a mechanism often observed in herbivores. In contrast, in galling Hymenoptera, enemy pressure declined with the phylogenetic isolation of host trees per se, as well as with the parallel decline in leaf damage by non-galling insects. Our results suggest that plants that leave their phylogenetic ancestral neighborhood can trigger, partly through simple density-dependency, an enemy release and fitness increase of the few insect herbivores that succeed in tracking these plants