Representation of rewards differing in their hedonic valence in the caudate nucleus correlates with the performance in a problem-solving task in dogs (Canis familiaris).

We have investigated dogs' (Canis familiaris) abilities in associating different sounds with appetitive stimuli of different incentive values. The association's establishment was first tested on family dogs (n = 20) in a problem-solving behavioural paradigm (experiment 1), then in a problem-solving behavioural paradigm as well as an fMRI study on specially trained family dogs (n = 20) (experiment 2). The aim was to show behavioural and parallel neural effects of the association formed between the two sounds and two different associated appetitive stimuli. The latency of solving the problem was considered an indicator of the motivational state. In our first experiment, where only behaviour was studied, we found that dogs were quicker in solving a problem upon hearing the sound associated with food higher in reward value, suggesting that they have successfully associated the sounds with the corresponding food value. In our second experiment, this behaviour difference was not significant. In the fMRI study, the cerebral response to the two sounds was compared both before and after the associative training. Two bilateral regions of interest were explored: the caudate nucleus and the amygdala. After the associative training, the response in the caudate nucleus was higher to the sound related to a higher reward value food than to the sound related to a lower reward value food, which difference was not present before the associative training. We found an increase in the amygdala response to both sounds after the training. In a whole-brain representational similarity analysis, we found that cerebral patterns in the caudate nucleus to the two sounds were different only after the training. Moreover, we found a positive correlation between the dissimilarity index in the caudate nucleus for activation responses to the two sounds and the difference in latencies (i.e. high reward value associated sound condition latency-low reward value associated sound condition latency) to solve the behavioural task: the bigger the difference between the conditions in latency to solve the task, the greater the difference in the neural representation of the two sounds was. In summary, family dogs' brain activation patterns reflected their expectations based on what they learned about the relationship between two sounds and their associated appetitive stimuli.

The difference between two brachycephalic and one mesocephalic dog breeds' problem-solving performance suggests evidence for paedomorphism in behaviour.

Despite serious health and longevity problems, small brachycephalic breeds are becoming increasingly popular among pet owners. Motivations for choosing short-nosed breeds have been extensively investigated in recent years; however, this issue has been addressed mainly by relying on owner reports, resulting in explanations of "cute looks", referring to the baby-schema phenomenon and "behaviour well suited for companionship". We aimed to compare the behaviour of two brachycephalic (English and French bulldogs) and one mesocephalic (Mudi) breed in a problem-solving context. The dogs were given the task of opening boxes containing food rewards. We investigated human-directed behaviour elements over success and latency (indicators of motivation and ability). We found that both English and French bulldogs were significantly less successful in solving the problem than mudis. Both brachycephalic breeds had longer opening latencies than the mesocephalic breed. Brachycephalic breeds oriented less at the problem box and more at humans present. In summary, the short-headed breeds were less successful but oriented much more toward humans than mesocephalic dogs. Owners might interpret these behaviours as "helplessness" and dependence. The results support the hypothesis that infant-like traits may be present not only in appearance but also in behaviour in brachycephalic breeds, eliciting caring behaviour in owners.

Comparing the tractability of young hand-raised wolves (Canis lupus) and dogs (Canis familiaris).

Dogs live in 45% of households, integrated into various human groups in various societies. This is certainly not true for wolves. We suggest that dogs' increased tractability (meant as individual dogs being easier to control, handle and direct by humans, in contrast to trainability defined as performance increase due to training) makes a crucial contribution to this fundamental difference. In this study, we assessed the development of tractability in hand-raised wolves and similarly raised dogs. We combined a variety of behavioural tests: fetching, calling, obeying a sit signal, hair brushing and walking in a muzzle. Wolf (N = 16) and dog (N = 11) pups were tested repeatedly, between the ages of 3-24 weeks. In addition to hand-raised wolves and dogs, we also tested mother-raised family dogs (N = 12) for fetching and calling. Our results show that despite intensive socialization, wolves remained less tractable than dogs, especially in contexts involving access to a resource. Dogs' tractability appeared to be less context dependent, as they followed human initiation of action in more contexts than wolves. We found no evidence that different rearing conditions (i.e. intensive socialization vs. mother rearing) would affect tractability in dogs. This suggests that during domestication dogs might have been selected for increased tractability, although based on the current data we cannot exclude that the differential speed of development of dogs and wolves or the earlier relocation of wolves to live as a group explains some of the differences we found.

Differences in greeting behaviour towards humans with varying levels of familiarity in hand-reared wolves (Canis lupus).

Socialized wolves' relationship with humans is a much debated, but important question in light of dog domestication. Earlier findings reported no attachment to the caretaker at four months of age in a Strange Situation Test, while recently attachment to the caretaker was reported at a few weeks of age in a similar paradigm. To explore wolf-human relationship, we analysed behaviours of hand reared, extensively socialized wolves towards four visitor types: foster-parents, close acquaintances, persons met once before, and complete strangers during a greeting episode. As hypothesized, in the greeting context subjects showed more intense and friendly behaviour towards foster-parents, than other visitor types, which may reflect familiarity and affinity. However, differences were more pronounced in the group situation (at six months of age) than in the individual situation (at 12 and 24 months), suggesting that unique status of foster parents may become less distinct as wolves get older, while exploration of novel social agents is expressed more with older age. Fear related behaviour patterns were only found in the individual situation, mainly displayed towards strangers. We showed that, in case of extensively socialized wolves, distinctive affiliation and affinity towards the foster parent prevails into adulthood.

Role of mental representations in quantity judgments by jackdaws (Corvus monedula).

The representation of quantity by the preverbal or nonverbal mind is a question of considerable interest in the study of cognition, as it should be generally adaptive to most animals to be able to distinguish quantity. We already know that some primate species and human infants represent and enumerate objects in similar ways. Considerable data also exist concerning such abilities in birds. Our aim in this study has been to find out whether jackdaws (Corvus monedula) are capable of performing relative quantity judgments based on mental representations, and if so, what are the limiting factors to their abilities. In our setting the birds were required to make a choice between two visibly and sequentially placed set of food items which, at the moment of choice were not visible to the subjects. We investigated all the number combinations between 1 and 5. Our results show that jackdaws are able to perform relative quantity judgments successfully, even when temporal cues are controlled for, whereas their performance declines in the direction of larger set size (numerical size effect), and when the difference between the two arrays decreases (numerical distance and ratio effect). These signatures are usually interpreted as evidence for the "accumulator" model of mental representation of quantity. Our control results suggest that jackdaws do not use temporal cues, but may well use total volume as basis for discrimination, perhaps among other attributes (choice may be based on multiple cues).

Ontogeny of object permanence in a non-storing corvid species, the jackdaw (Corvus monedula).

The aim of the present study was to investigate the ontogeny of object permanence in a non-caching corvid species, the jackdaw (Corvus monedula). Jackdaws are often presented as typical examples of non-storing corvids, as they cache either very little or not at all. We used Uzgiris and Hunt's Scale 1 tasks to determine the age at which the certain stages set in and the final stage of this capacity that is reached. Our results show that the lack of food-storing behaviour is not associated with inferior object permanence abilities in the jackdaw, as our subjects (N = 19) have reached stage 5 competence (to follow successive visible displacements) at the average age of 61 days post-hatch and showed some evidence of stage 6 competence (to follow advanced invisible displacements) at 81 days post-hatch and thereafter. As we appreciate that object permanence abilities have a very wide ecological significance, our positive results are probably the consequence of other, more fundamental ecological pressures, such as nest-hole reproduction or prey-predator interactions.