Consequently, the feeding ecology of both species became characterized by human refuse scavenging, both became highly dependent on humans—as a food source—for survival. As opposed to the intensive usage of dogs for various work-related purposes throughout history e. They are able to flexibly use various forms of the pointing gesture to locate hidden food reward; they are successful in following proximal and distal pointing with arms, legs, even in complex situations for a review, see Kaminski and Nitzschner or even following gaze direction Met et al.
They also readily initiate and use eye contact as a form of social interaction when previously provided food reward is withheld e. Furthermore, dogs tend to exhibit the above-listed socio-communicative behaviours without any special training and already from a very early age on e.
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Differences between dogs and their wolf ancestor related to the display of these behaviours show that dogs acquired their skills through the process of domestication Hare et al. On the other hand, scientific interest to date had predominantly focused on the intraspecific social interactions of pigs kept together either under farm or laboratory conditions Gieling et al. Although recent studies have already investigated several aspects of pig—human interactions as well e.
Nawroth et al. In spite of the fact that in one study farm pigs did not prove to be sensitive to human-given referential signals i. With the increasing recognition of the pig as a model species for biomedical research Conrad et al. Due to their reduced size and the sophisticated socio-cognitive capacities of pigs in general, the number of miniature pigs kept as companion animals has increased considerably in the last several years Marino and Colvin When kept as companion animals, dogs and pigs occupy a similar ecological niche; they live among humans from an early age in a highly similar environment enriched in human social stimuli and contact.
In addition, collecting data already at a young age is also important, since it allows for later follow-up comparisons to see whether and how specific behaviours might change throughout ontogeny. Both studies relied on paradigms that have already been well established for studying the interspecific social skills of dogs. In Study 1, we investigated the appearance of spontaneous human-oriented behaviours without the presence of food as well as when previously provided food reward was withheld.
We chose the feeding situation for testing, because humans feed their animals day by day, during which they supposedly behave similarly with both species, and thus, we consider that to be a fairly comparable context. Based on the similarities in their species-specific socio-communicative and learning abilities, as well as the fact that they have been able to successfully adapt to the human social environment, we hypothesized that the two species—given the similar rearing environments—communicate with humans and react to human cues in a similar manner.
Animal owners volunteered to participate in the studies, which were non-invasive, not causing any pain or suffering to the animals. According to this statement and the corresponding definition by law in our country, the current non-invasive observational studies are not considered to be animal experiments.
Both studies were carried out in the laboratory 4. None of the subjects showed any species-specific behaviours indicative of excessive fear or frustration including aggression throughout the experiments. All subjects were mother-reared, living with their mother and littermates before weaning, where they were exposed to regular human contact.
The pigs were from different litters with at least one parent different, and they were acquired from six different breeders in Hungary after all the necessary veterinary screening examinations. We partly based our method on the work done by Bensoussan et al. The test room was equipped with a table positioned next to the wall holding a camera tripod and a plastic container with or without food , as well as a chair for the owner at 1. We followed the method by Bensoussan et al. She followed S with her gaze and tried to establish eye contact. The E behaved the same way as described above in the Control condition, the only difference from the Control condition was the presence of food; during both the pre-test and test phases , E, instead of imitating the action, actually took treats out of the plastic container and delivered them on the floor.
Body-orientation duration, s : S is close to the E within a max. Body-touch duration, s : S establishes physical contact with the E e. Face-orientation duration, s : S is close to the E within a max. Due to species-specific anatomical characteristics e. That is the reason why we chose to measure the face-oriented behaviour i. Orientation to E duration, s : S is close to the E within a max. E-oriented vocalization duration, s : concurrence of Vocalization and Orientation to E.
The vocalization durations could be determined obviously based on the sonograms belonging to the video recordings; thus, we did not calculate interrater agreement for that variable. We used the R statistical environment v. R Development Core Team for data analysis. The continuous variables did not follow normal distributions, as indicated by Shapiro—Wilk tests. Using square root transformation, the variable Body-orientation fulfilled the assumptions of normality.
For Face-orientation and Body-touch, a similar transformation did not result in normal distributions, so we used the corresponding frequency-count unit that followed a Poisson distribution during the analysis. We obtained pairwise post-hoc comparisons for the fixed factors. Since four of the dog subjects did not produce any vocalizations in neither conditions and additional two of them vocalized only in one condition for a max. The data sets generated and analysed during the current study are available in the form of electronic supplementary material Online Resource 2. Bold lines stand for the median, boxes indicate the interquartile range and whiskers extend until the smallest and largest values excluding outliers and extremities.
The dots represent the individual data points.
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Bold lines stand for the median, boxes indicate the interquartile range, and whiskers extend until the smallest and largest values excluding outliers and extremities. As a human cue, we applied two forms of the distal pointing differing in their temporal parameters i. All the pigs had participated in Study 1 previously, while the dogs were a new group of randomly selected subjects. The apparatus consisted of two identical, opaque red plastic containers Experimental setup for Study 2.
D1, D2 and D3 indicate doors of which D1 was used during the experiment. The test trials immediately followed the training trials. O was holding the animal and E was at a kneeling position facing them at approx. Before the trials, the kneeling E was holding both containers in front of her body and placed one piece of food into one of them, kept exchanging them in her hands two times to prevent S from knowing, where the food was and then placed them on the floor 2. E was positioned equidistant from the two containers and approx.
Before the pointing gesture, E with her arms bent in front of her chest gave an attention-getting signal making short, clapping sounds with her mouth and tried to establish eye-contact with S.
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The pointing gestures immediately followed the attention-getting signal and were presented when S was standing still facing E. In the DDS condition, E was pointing with one extended arm towards the baited container while looking at S until S made its choice. The distance between the tip of the index finger and the container was approx. S was released to choose immediately after the pointing gesture. After choosing the baited container, S was allowed to eat the food and was praised verbally by its owner. If the animal stopped choosing any of the containers during the test, then one training trial was introduced.
After each break and before the new session, one training trial was introduced. Reward side and gesture type were semi-randomized and the first trial was counterbalanced across subjects with no side and gesture type being presented more than two times in a row, and the first two trials were always different. The control trials differed from the other test trials in a way that E did not produce any gestures to indicate the baited container.
She was kneeling with her arms resting besides her body looking straight at S after placing the two bowls on the floor, and S was allowed to choose from the two containers in approx. All sessions were videotaped and later coded. To check for the effects of the two conditions and species on performance i.
Mean number of correct choices of dogs and pigs in the two conditions. Numbers in the bars indicate the amount of subjects performing above chance on individual-level versus the total number of subjects. DDS distal dynamic-sustained pointing, DM distal momentary pointing. The dashed line represents the chance level, the error bars show standard deviations.
Number of individual choices to left and right sides in the test trials. The y axis represents individual subjects; D dog, P pig. To sum up, in the present two-way choice task, neither of the two species followed the distal momentary pointing gesture above the chance level, and only dogs relied spontaneously on the distal dynamic-sustained version of the same gesture. Regardless of gesture type, all pigs—while only less than half of the dogs—developed a clear lateralized behaviour i.
Furthermore, our results also point out that the experience of being fed by the human plays a major role in triggering the display of face-orientation only in pigs but not in dogs. In our second study, only dogs but not pigs showed evidence of spontaneously relying on a human distal dynamic-sustained pointing as directional signal for locating a hidden food reward in a two-way object choice test. As a group, neither of the two species was successful in following the momentary version of the pointing gesture, whereas all pigs while only some of the dogs showed a clear lateralized behaviour i.
The observation that both species were performing a considerable amount of explorative behaviour in the Control condition—besides the explicitly coded ones—gives further support to the above argument. All this is important, since multiple works with farm pigs pointed out the appearance of fearful or aggressive behaviours at the onset of the experimental procedures that made it necessary to include several occasions of familiarization procedures before the start of the data collection e.
This behaviour and more specifically the establishment of eye contact is widely reported in dogs; it typically appears spontaneously without special training and is regarded as an interspecific communication skill that domestication seems to have uniquely strengthened in them e.
Such evolutionary differences hold true for dogs and pigs as well. Along with these, it is also important to note here that all experimenter-oriented behaviours were scored from within a max. Due to anatomical differences between the two species, however, it might be more difficult for a pig than for a dog to raise the head at the necessary angle to perform face-orientation for a longer period while body-orientation can be performed even with a more neutral head position.
Consequently, we cannot rule out the possible influence of this anatomical factor on the above outlined findings. The two species might also differ in their persistence to anticipate food that they had just experienced to get, which might as well relate to general motivational differences.
Pigs and Humans: 10,000 Years of Interaction
Furthermore, considering the apparent intensification of all the measured experimenter-oriented behaviours in the presence of food, we can assume an underlying role of simple associative learning mechanisms, i. These can be related to our finding that young pigs display face orientation almost exclusively in the feeding context, which also suggests the necessity of previous learning processes for this behaviour to appear apparently in this species, whereas it seems to be displayed more unconditionally in young dogs.
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