Recent studies purported to demonstrate that chimpanzees, monkeys and corvids possess a basic Theory of Mind, the ability to attribute mental states like seeing to others. However, these studies remain controversial because they share a common confound: the conspecific's line of gaze, which could serve as an associative cue. Here, we show that ravens Corvus corax take into account the visual ac...

Cooperative decision rules have so far been shown experimentally mainly in mammal species that have variable and complex social networks. However, these traits should not necessarily be restricted to mammals. Therefore, we tested cooperative problem solving in ravens. We showed that, without training, nine ravens spontaneously cooperated in a loose-string task. Corroborating findings in several...

Behavioral and physiological characteristics of individuals within the same species have been found to be stable across time and contexts. In this study, we investigated individual differences in learning abilities and object and social manipulation to test for consistency within individuals across different tasks. Individual ravens (Corvus corax) were tested in simple color and position discri...

Reasoning The abstract reasoning was assessed using Ravens Advanced Progressive Matrices (Raven, Court, & Raven, 1994) Set I and Set II. Also, this test gives us a measure of the general Intelligence quotient (IQ) of the participants in the study. The number of correct respons-

A core feature of social intelligence is the understanding of third-party relations, which has been experimentally demonstrated in primates. Whether other social animals also have this capacity, and whether they can use this capacity flexibly to, for example, also assess the relations of neighbouring conspecifics, remains unknown. Here we show that ravens react differently to playbacks of domin...

What man is so mad as wil say the swan is black: or that the raven is in couloure white, when the matter is otherwise to be judged by commonsense? {Cardanus ca. 1576 Abstract. What sorts of observations could connrm the universal hypothesis that all ravens are black? Carl Hempel proposed a number of simple and plausible principles which had the odd (\paradoxical") result that not only do observ...

The Brucella abortus vaccine strain RB51 (SRB51) is being considered for use in the management of bnucellosis in wild bison (Bison bison) and elk (Cervus elaphus) populations in the Greater Yellowstone Area (USA). Evaluation of the vaccines safety in non-target species was considered necessary prior to field use. Between June 1998 and December 1999, ground squirrels (Spermophilus richardsonii, ...

Choice by exclusion, that is, the ability to base the choice of a target on the rejection of potential alternatives, is becoming increasingly interesting for comparative cognition research. Recently, ravens have been shown to solve an exclusion task and it had been suggested that this ability might benefit ravens in a food-caching context. To investigate this possibility, the raven study was re...

What man is so mad as wil say the swan is black: or that the raven is in couloure white, when the matter is otherwise to be judged by commonsense? {Cardanus ca. 1576 Abstract. What sorts of observations could connrm the universal hypothesis that all ravens are black? Carl Hempel proposed a number of simple and plausible principles which had the odd (\paradoxical") result that not only do observ...

Group-foraging ravens scatter-hoard when they are competing for food and, to some extent, also raid the caches made by others. We investigated the effects of observational spatial memory on individual caching and raiding tactics. With captive ravens, we found visual observation was essential for locating and raiding the caches of conspecifics. Both captive and free-ranging ravens, food cachers ...