A crucial stage in hominin evolution was the development of metatool use -- the ability to use one tool on another [1, 2]. Although the great apes can solve metatool tasks [3, 4], monkeys have been less successful [5-7]. Here we provide experimental evidence that New Caledonian crows can spontaneously solve a demanding metatool task in which a short tool is used to extract a longer tool that ca...

Sensitivity to inequity is considered to be a crucial cognitive tool in the evolution of human cooperation. The ability has recently been shown also in primates and dogs, raising the question of an evolutionary basis of inequity aversion. We present first evidence that two bird species are sensitive to other individuals' efforts and payoffs. In a token exchange task we tested both behavioral re...

Individual specialization in the use of foraging tools occurs in hunter-gatherer societies but is absent in non-human primate tool use. 'Parallel tool industries' in hunter-gatherers are mainly based on strict sexual division of labour that is highly reliant on social conformity. Here, we show that 12 individuals in a population of New Caledonian crows on Maré Island had strong preferences for ...

Host defences against cuckoo parasitism and cuckoo trickeries to overcome them are a classic example of antagonistic coevolution. Recently it has been reported that this relationship may turn to be mutualistic in the case of the carrion crow (Corvus corone) and its brood parasite, the great spotted cuckoo (Clamator glandarius), given that experimentally and naturally parasitized nests were depr...

While personality-dependent dispersal is well studied, local space use has received surprisingly little attention in this context, despite the multiple consequences on survival and fitness. Regarding the coping style of individuals, recent studies on personality-dependent space use within a habitat indicate that 'proactive' individuals are wider ranging than 'reactive' ones. However, such studi...

Nicola Clayton is Professor of Comparative Cognition in the Department of Experimental Psychology at the University of Cambridge, and a Fellow of Clare College. Nicky studies the development and evolution of cognition, and the questions she address are informed by an understanding of biology and psychology. Her work has challenged many of the common-held assumptions that only humans can plan fo...

Crow and Kimura (1965) constructed a model to quantify the arguments originally due to Fisher (1930) and Muller (1932) that recombination accelerates evolution because it enables mutations originally occurring in distinct individuals to be combined in a single descendent. The model contained the assumption that even though the population be large, the mutation rate should be so small that the d...

The shadow of Kraepelin stands over psychosis nosology like a colossus. The reason is that Kraepelin made an attempt to systematize diagnosis in a rational, pathophysiological manner. But, to this day, no one has done better. The tragedy is that one can say of Kraepelin that the measure of his stature is the extent to which his infl uence has delayed progress since his death. With such a judgme...

Well placement optimization is considered a non-convex and highly multimodal problem. In this article, modified crow search algorithm proposed to tackle the well This article proposes modifications based on local niching techniques in (CSA). At first, suggested approach verified by experimenting with benchmark functions. For test functions, results of demonstrated higher convergence rate better...

The "cock-a-doodle-doo" crowing of roosters, which symbolizes the break of dawn in many cultures, is controlled by the circadian clock. When one rooster announces the break of dawn, others in the vicinity immediately follow. Chickens are highly social animals, and they develop a linear and fixed hierarchy in small groups. We found that when chickens were housed in small groups, the top-ranking ...