Ten-month-old infants persistently search for a hidden object at its initial hiding place even after observing it being hidden at another location. Recent evidence suggests that communicative cues from the experimenter contribute to the emergence of this perseverative search error. We replicated these results with dogs (Canis familiaris), who also commit more search errors in ostensive-communicative (in 75% of the total trials) than in noncommunicative (39%) or nonsocial (17%) hiding contexts. However, comparative investigations suggest that communicative signals serve different functions for dogs and infants, whereas human-reared wolves (Canis lupus) do not show doglike context-dependent differences of search errors. We propose that shared sensitivity to human communicative signals stems from convergent social evolution of the Homo and the Canis genera.

Having repeatedly retrieved an object from a location, human infants tend to search the same place even when they observe the object being hidden at another location. This perseverative error is usually explained by infants' inability to inhibit a previously rewarded search response or to recall the new location. We show that the tendency to commit this error is substantially reduced (from 81 to 41%) when the object is hidden in front of 10-month-old infants without the experimenter using the communicative cues that normally accompany object hiding in this task. We suggest that this improvement is due to an interpretive bias that normally helps infants learn from demonstrations but misleads them in the context of a hiding game. Our finding provides an alternative theoretical perspective on the nature of infants' perseverative search errors.

Three experiments were designed to test whether adult pet dogs are able to show inferential reasoning when searching for their toy in a series of two-way choice tasks. The experimenter placed a toy under one of two identical containers and then provided some information by manipulating the covers: either both containers were lifted or just the empty or baited one. There were other trials when the experimenter not only revealed the corresponding container but manipulated also the other one without showing its content. In the second experiment the same conditions were used except that the content of the containers was revealed by strings without any human manipulation. Results of the two studies show that dogs are able to use inferential reasoning by exclusion (i.e. they can find the hidden toy if they have seen where the toy was missing). However, dogs were able to solve the reasoning task only when they could not rely on social-communicative cues (directional gesture and gaze cues) or could not use any other simple discriminative stimuli (movement of a container) for making decisions. This suggests that dogs are often prevented from showing reasoning abilities by pre-existing biases for social or movement cues. Results of the third experiment also support the primary importance of social cueing because in another object-choice task, individuals preferred to choose the 'socially marked' container (touching, gaze alternation) to the remotely moved one when they had no visual information about the location of the toy. Keywords: cognition; decision by exclusion; deduction; dog; reasoning Despite the wide range of studies based on human and animal cognition published in the past decades, the evolutionary emergence of reasoning abilities including different types of logical reasoning in humans continues to be a puzzle for cognitive science (Wright 2001). The fundamental question is whether an observed problemsolving behaviour is a result of gradual development in performance due to learning processes or is a sudden solution emerging from mental reorganization of problem elements (i.e. insight: Köhler 1925). In distinguishing between learning and reasoning, many assume that even though the more parsimonious learning processes can never be fully excluded (Heyes 1993), reasoning can be presumed if the subject shows an 'insightful solution' immediately (i.e. shows adequate behaviour without explicit training) in the first few trials (Premack 1995).To test for reasoning one may present a problem and provide sufficient but indirect information to solve it. One way to study the reasoning abilities is the Piagetian object permanence paradigm. In the invisible displacement task, no direct cues specify that the desired reward has moved behind the screen (i.e. the subject does not witness the reward being dropped). The subject must infer, upon seeing the empty container, that the object has been transferred. Previous studies with several species showed that some primates (e.g. orang-utans, Pongo pygmaeus: de Blois et al. 1998; o...