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Animal Cognition (2021) 24:33–40
https://doi.org/10.1007/s10071-020-01410-2
ORIGINAL PAPER
Who turns tothehuman? Companion pigs’ anddogs’ behaviour
intheunsolvable task paradigm
PaulaPérezFraga1 · LindaGerencsér1,2· MelindaLovas1· DóraÚjváry1· AttilaAndics1,2
Received: 16 March 2020 / Revised: 23 June 2020 / Accepted: 29 June 2020 / Published online: 17 July 2020
© The Author(s) 2020
Abstract
When facing an unsolvable problem, dogs exhibit spontaneous human-oriented behaviours (e.g. looking at the human part-
ner, gaze alternations between the human and the target) sooner and for longer than domestic cats and hand-raised wolves.
These behaviours have been interpreted as interspecific communicative acts aimed to initiate interaction. Here, we compare
the emergence of human-oriented behaviours (e.g. orientation towards humans, orientation alternations, vocalizations) in
similarly raised family dogs and miniature pigs utilising an unsolvable task paradigm which consists of Baseline (no task),
Solvable and Unsolvable phases. Relative to the Baseline phase in which both species showed human-oriented behaviours to a
similar extent, during the Unsolvable phase dogs showed more and pigs showed less such behaviours. Species-predispositions
in communicative behaviour may explain why dogs have a higher inclination than pigs to initiate interspecific interactions
with humans in problem-solving contexts.
Keywords Comparative· Dog· Human–animal interaction· Interspecific communication· Pig· Unsolvable task
Introduction
Various domestic (Malavasi and Huber 2016; Miklósi etal.
2000; Nawroth etal. 2016; Turner 2017) and wild (Can-
teloup etal. 2015; Roberts etal. 2014; Xitco etal. 2004,
2001) mammals engage in communicative interactions with
humans. Family dogs (Canis familiaris) may be unique in
performing a variety of human-directed communicative
behaviours (Kaminski and Nitzschner 2013; Udell and
Wynne 2008; Udell etal. 2010) already from an early age
(Passalacqua etal. 2011; Riedel etal. 2008). Dogs look at
humans to establish joint attention (Bentosela etal. 2016;
Miklósi etal. 2003) and they use gaze alternations for ref-
erential communication, analogously to human infants
(Marshall-Pescini etal. 2013). Genetic changes during
domestication may have predisposed dogs to communicate
with humans more than other species (Hare etal. 2002;
Sommese etal. 2019), although experience with humans
during development also plays a role (Barrera etal. 2011;
Marshall-Pescini etal. 2009).
When facing an unsolvable task, dogs looked at the
human partner earlier and for longer periods than similarly
socialized wolves (Marshall-Pescini etal. 2017a; Miklósi
etal. 2003) and cats (Miklósi etal. 2005). Wolves and cats
were more persistent in trying to solve the task indepen-
dently (Marshall-Pescini etal. 2017a, b; Miklósi etal. 2005).
Single-species studies also reported human-directed commu-
nicative behaviours in domestic farm animals (goats, horses)
in similar contexts (Malavasi and Huber 2016; Nawroth etal.
2016). However, no direct comparisons have been made
between the dog and another social domestic species kept
in similar rearing conditions.
Like dogs, pigs (Sus scrofa domesticus) are also group-
living, highly social animals (Marino and Christina 2015),
performing a variety of intraspecific communicative sig-
nals (Bensoussan etal. 2019; Gieling etal. 2011). Simi-
larly to dogs, pigs’ domestication, while clearly different
in trajectory - dogs were used mainly for working pur-
poses and pigs mainly as meat stock (Frantz etal. 2016),
Electronic supplementary material The online version of this
article (https ://doi.org/10.1007/s1007 1-020-01410 -2) contains
supplementary material, which is available to authorized users.
* Paula Pérez Fraga
pauliperezfraga@gmail.com
1 Department ofEthology, Eötvös Loránd University (ELTE),
Pázmány P. s. 1/C, Budapest1117, Hungary
2 MTA-ELTE ‘Lendület’ Neuroethology ofCommunication
Research Group, Hungarian Academy ofSciences, Eötvös
Loránd University, Budapest, Hungary
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34 Animal Cognition (2021) 24:33–40
1 3
was also characterized by a relatively close human contact
(Hongo 1998; Piper 2008) and occasionally, pigs were also
used for work or treated as pets (Robbins and Rappaport
2006). Also today, miniature pigs are becoming popu-
lar as companion animals (Marino and Christina 2015),
occupying a similar ‘social niche’ in human families as
the family dog (Gerencsér etal. 2019). There has been
growing interest in studying farm pigs’ interspecific social
skills, focusing on their sensitivity to human communica-
tive cues and attentive states (Albiach-Serrano etal. 2012;
Bensoussan etal. 2019; Nawroth etal. 2013, 2014). Still,
little is known about how pigs use communicative behav-
iours towards humans. Recently, we showed that even if
kept as companion animals, pigs differ from dogs in their
responses to human communicative cues (Gerencsér etal.
2019) and in exhibiting spontaneous human-oriented com-
municative behaviours. The two species differed in the
readiness to look at the human face, a behaviour that dogs
often performed in a neutral context but that was almost
exclusively triggered in pigs in the presence of food. Pigs
also vocalized more, and these results altogether indicated
a strong influence of species-predispositions.
Here we compared human-directed communicative
behaviours of ~ 7months old dogs and miniature pigs—
both kept as companion animals from an early age—in
an unsolvable task paradigm. We hypothesized that both
species would exhibit spontaneous human-oriented behav-
iours, and an increase of thosebehaviours during the
unsolvable phase in comparison with a baselinephase,
especially in dogs. We also expected more orientation
alternations from dogs and more vocalizations from pigs,
reflecting differential species-predispositions.
Methods
Subjects
Our subjects were juvenile pigs (N = 10, 6 males and 4
females, Xage ± SD = 7.0 ± 1.24 months, Minnesota and
mixed miniature variants) and dogs (N = 12 family dogs
passed the criteria out of 19 tested, see below), 7 males
and 5 females, Xage ± SD = 6.91 ± 1.92months, from 8 dif-
ferent breeds). All animals were living in human families
from ~ 8 weeks of age (more details in Supplementary
TableS1). Subjects from both species were tested inter-
mixed, there was no fixed species order.
Procedure
The study was carried out in the laboratory (4.45 × 3.86m
room) of the Department of Ethology (Eötvös Loránd Uni-
versity, Budapest). A transparent plastic container (the
apparatus, 15 × 15cm) was placed equidistant from the two
longer sides of the test room (Fig.1), upside down (over
a few titbits of sausages for dogs and apple/dog food for
pigs—based on preparatory owner reports and pilot trials
we assumed that these food types were of similarly high
value for the individuals, since all of them willingly ate the
offered titbits) on a wooden platform (40 × 60cm), with the
base permanently fixed to the platform. The upper cover
part—with holes on it—could be moved off the platform
easily by manipulation (solvable phase), but it could also
be securely attached so the food was still visible but not
accessible (unsolvable phase, adapted from Passalacqua
etal. 2013).
Fig. 1 Experimental setup. S
subject, O owner, E experi-
menter, A apparatus
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35Animal Cognition (2021) 24:33–40
1 3
Each individual test was done in the same day. We fol-
lowed the method applied by Passalacqua etal. (2013) with
some modifications; we increased the time of the unsolvable
phase by 30s to allow more time for the investigated behav-
iours to evolve, and we added an additional Baseline phase
as well for observing any human- or apparatus-oriented
behaviour in the absence of food, and familiarizingthe sub-
ject (S) with the apparatus. The whole procedure consisted
of a baseline phase (60s), a solvable phase (5 solvable trials)
and an unsolvable phase (90s) in fixed order. Before the test
session began, the S, the owner (O) and the experimenter (E)
entered the test room andthe S was allowed to walk around
off leash and explore the room for 60s.
During all phases O and E kneeled down by two different
sides of the apparatus at 50cm distance facing towards it.
In the beginning of each phase O kept S in between his/her
legs with S facing the apparatus. In the baseline phase, E
manipulated the apparatus without covering it, placing the
upper part next to the fixed bottom part. O let S free when
E signalled with her hand. E and O, with the hands behind
their backs stayed passive, following S with their gaze.
After a short (− 30s) break, the test continued with the
solvable phase. E showed a piece of food to S, placed it on
the bottom of the apparatus without covering and O let S
free. This served for testing S’s motivation for eating and
informing the S where the food would be placed. E then
showed another piece of food to S, placed it on the bottom
of the apparatus and covered it with the upper part with-
out closing it securely. O let S free. E and O did not move.
The trial ended when S obtained the food or aftera maxi-
mum 60s. Only subjects succeeding (accessing the food)a
minimum 3 out of 5 times (10/10 pigs, 12/19 dogs) were
tested in the unsolvable phase that followed immediately,
and included in analyses.
The unsolvable phase was identical to the solvable phase,
except that the cover part of the apparatus was securely
closed (i.e. food inaccessible for S).
Behaviour coding
All tests were video recorded for behavioural analysis by
Solomon Coder (v. 090913; © András Péter https ://solom
oncod er.com). Starting from O releasing S, during the
baseline and unsolvable phases we measured latency and
duration of orientation to humans, frequency of orientation-
alternation between the apparatus and the humans, and dura-
tions of vocalization, human-oriented vocalization and appa-
ratus-interaction. During the solvable phase we measured
the latency to success (i.e. solving the task), and apparatus-
interaction and human-orientation in the first trial (see Sup-
plementary TableS2 for behavioural variables definitions).
The recordings were coded by one main coder, and
twenty percent of them was also coded by a secondary
coder. Interrater agreement was near perfect for ‘Success
latency’ (ICC = 0.99 for both species). We used the raw cod-
ing sheets to calculate the agreement between the two raters
for ‘orientation to human and to apparatus’ and ‘apparatus-
interaction’, where the occurrence (yes/no) of any of these
behaviours was marked every 0.2s. The agreement was
near perfect for ‘orientation’ (Cohen’s Kappa, ĸpigs = 0.89,
ĸdogs = 0.97, Ps < 0.001) and also for ‘apparatus-interaction’
(ĸpigs = 0.93, ĸdogs = 0.98, Ps < 0.001). We therefore used the
coding of the main coder only to extract the variables of
interest.
Data analysis
We used the R statistical environment (v.3.5.0. R Devel-
opment Core Team) with the following packages: lme4,
emmeans and ggplot2. We used Shapiro–Wilk test and data
visualization (normal Q-Q plots) to check for the distribution
of the response variables and residuals, and applied Box-
Cox power transformations with optimal lambda parameters
where it was necessary to fulfil normality criteria. We used
non-parametric tests where neither transformation method
resulted ina normal distribution. We built a linear mixed-
effects model (LMM) with ‘Success latency’ asthe response
variable, trial (within-subject) and species (between-subject)
as explanatory factors and individual subjects as a random
factor for the solvable phase analysis. We used Mann–Whit-
ney–Wilcoxon tests to compare the total times pigs and dogs
spent orienting at the two humans and manipulating the
apparatus in the first trial of the solvable phase—to test for
factors that could possibly explain success latency differ-
ences between the two species (see “Results”).
Since we did not aim to test for the familiarity effect of
the humans on the subjects’ interspecific behaviour and the
owner-experimenter contrast was not well controlled to make
it clearly interpretable, we did not consider orientation to
owner and experimenter as separate measures throughout the
main analyses, but used a combined ‘orientation to human’
variable instead. To test for main effects of phase (baseline
vs. unsolvable, within-subject factor) and species, as well as
for their interaction, we built LMMs with either ‘orientation
to human’ (duration, s), ‘latency of orientation to human’ (s),
and ‘apparatus-interaction’ (duration, s) as response vari-
ables. For testing the same main and interaction effects on
‘orientation-alternation’ (Poisson-distributed count data)
we built a generalized mixed-effects model (GLMM) fit
by maximum likelihood using Laplace approximation. We
included individual subjects as a random factor in all the
models and obtained corrected multiple post-hoc compari-
sons for the fixed factors. In all the above models we used
the data from the first 60s of the unsolvable phase (and all
data from the 60s long baseline phase) to make a fair com-
parison between the two phases. However, to further explore
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36 Animal Cognition (2021) 24:33–40
1 3
species differences during the total duration of the unsolv-
able phase in the above mentioned response variables, we
used Mann–Whitney–Wilcoxon tests and two-sample t test
(according to data distribution). To show how the human-
oriented behaviours in the unsolvable phase were divided
across the experimenter and the owner, we built LMMs for
‘orientation’, ‘latency of orientation’, a GLMM for ‘orien-
tation-alternation’, and tested for main effects of orientation
target (experimenter and owner), species and their interac-
tion (see Supplementary material).
We compared the number of pigs and dogs that vocalized
in the baseline and unsolvable phase by Chi-square test (with
Yates’ continuity correction), and used Mann–Whitney–Wil-
coxon test to compare the duration of their vocalization.
Because of dogs’ overall less vocalization (see “Results”)
we further analysed pigs’ vocal behaviour only. To see
whether there was any difference between the proportions
of time pigs vocalized while exhibiting different orienta-
tion behaviours, we calculated the ratios of ‘human- and
apparatus-oriented vocalization’ and ‘orientation to human
or apparatus’ in both conditions (to make a fair comparison
between the proportions of times—expressed as the ratio of
the total duration of the session—pigs spent vocalizing while
being oriented either to the humans or to the apparatus), and
compared them by Wilcoxon signed-rank tests.
Results
In the solvable phase, animals’ performance improved sig-
nificantly across the five trials (LMM, main effect of trial
on ‘success latency’: F4,84 = 6.302, P < 0.001). Pigs proved
to be overall faster than dogs (Xdogs ± SD = 12.8 ± 17.9s
and Xpigs ± SD = 6.5 ± 10.5 s; LMM, main effect of spe-
cies on ‘success latency’: F1,20 = 5.188, P = 0.034). Dur-
ing the first solvable trial, a low proportion of the subjects
showed any human-orientation (N = 2/10 pigs and N = 5/12
dogs)—measured from the moment they started manipulat-
ing the apparatus. The duration of human-orientation did
not differ between the two species (XPigs ± SD = 1.0 ± 2.5s,
XDogs ± SD = 6.3 ± 12.2 s, W = 74, P = 0.282—although
note the low subject number), while pigs spent signifi-
cantly less time in total (XPigs ± SD = 4.1 ± 1.9 s) than
dogs (XDogs ± SD = 9.9 ± 5.4s) manipulating the apparatus
(W = 103.5, P = 0.005) (note t hat N = 9/10 pigs and 9/12
dogssuccessfully opened the apparatus in the first trial,
although all subjects attempted to).
The joint analysis of the baseline and unsolvable phases
revealed that the interaction between species and phase
had a significant effect on several variables. Pigs in the
unsolvable phase exhibited less human-orientation than in
the baseline phase (interaction effect, LMM, F1,20 = 9.779,
P = 0.005, Fig.2a). Pigs oriented later to a social partner
(either the owner or the experimenter) in the unsolvable
than in the baseline phase, while dogs oriented sooner to
a human than pigs in the unsolvable phase (interaction
effect, LMM, F1,20 = 9.203, P = 0.007, Fig. 2b). Dogs in
the unsolvable phase alternated their orientation more fre-
quently between the apparatus and a human partner than
in the baseline phase, and also more frequently than pigs
(interaction effect, GLMM, Z = − 4.601, P < 0.001, Fig.2c).
Both species spent more time interacting with the apparatus
in the unsolvable phase, and in this phase pigs interacted
with the apparatus for longer than dogs (LMM, F1,20 = 4.426,
P = 0.048, Fig.2d). See Supplementary Tables S3–S10 for
all corresponding post-hoc comparisons and further model
parameters.
During the total duration of the unsolvable phase,
dogs, as compared to pigs, spent more time orienting at
humans (Xdogs ± SD = 14.4 ± 10.4s, Xpigs ± SD = 5.8 ± 6.4s;
Mann–Whitney–Wilcoxon test, W = 92, P = 0.038),
they also looked sooner (Xdogs ± SD = 21.9 ± 23.4 s,
Xpigs ± SD = 57.8 ± 25.2 s; two-samples t test,
T18.68 = − 3.429, P = 0.003) and exhibited more ‘orientation-
alternations’ (Xdogs ± SD = 9.8 ± 7.4, Xpigs ± SD = 2.3 ± 2.3;
Mann–Whitney–Wilcoxon test, W = 107, P = 0.002). Pigs
spent more time than dogs interacting with the apparatus
(Xpigs ± SD = 51.44 ± 17.9 s, Xdogs ± SD = 24.9 ± 20.9 s,
W = 88, P < 0.001). The follow-up analysis comparing
experimenter- and owner-oriented behaviours showed ear-
lier and longer orientation towards the experimenter in both
species and more frequent orientation alternations with the
experimenter in pigs, but did not reveal effects that biased
the above species differences (see Supplementary Fig. S1
and Tables S11–13).
3/12 dogs vs. 7/10 pigs vocalized in the baseline
phase (χ2 = 2.825, P = 0.093), and 2/12 dogs vs. 7/10 pigs
in the entire unsolvable phase (χ2 = 4.402, P = 0.036).
Pigs also spent more time vocalizing in both phases
(Mann–Whitney–Wilcoxon tests, WBaseline = 31.5, P = 0.043
and WUnsolv = 25.5, P = 0.012). Because dog vocalizations
were rare, we further analysed pigs’ vocal behaviour only.
Pigs vocalized more during the baseline than the unsolvable
phase (XBaseline ± SD = 9.2 ± 8.9s, XUnsolv ± SD = 1.2 ± 1.3s;
Wilcoxon signed-rank test, W = 40, P = 0.044), but there
was no difference between the two conditions in the relative
duration of neither human-oriented nor apparatus-oriented
vocalizations (Wilcoxon signed-rank tests, WHuman = 6,
P = 0.205 and WApparatus = 14, P = 0.529).
Discussion
To the authors’ present knowledge this is the first study
comparing human-directed communicative behaviour of
two social domestic species kept as companion animals,
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37Animal Cognition (2021) 24:33–40
1 3
in an unsolvable task paradigm; and the first research on
pigs’ referential communicative abilities towards humans. In
line with our hypothesis, the two species exhibited human-
oriented behaviours to a similar extent during the initial
baseline phase, indicating that the spontaneous display of
thesebehaviours is not unique to dogs. Differences became
apparent in the problem-solving context only. As we pre-
dicted, dogs performed more human-oriented behaviours
than pigs; they oriented for longer and earlier to the humans,
and also alternated their orientation between the human
partners and the apparatus more frequently, corroborating
previous research (Miklósi etal. 2005, 2003). Interestingly,
the expected increase of referential communicative signals
during the unsolvable phase in comparison with the base-
line phase was only observed in dogs but not in pigs. Pigs,
in contrast, interacted more with the apparatus than dogs.
Dogs thus may be predisposed to use orientation alternations
to communicate referentially towards humans for problem
solving, even at an early age. This is supported by previous
observations including dogs’ tendency to reduce their inde-
pendent problem-solving behaviours in humans’ presence
(Brubaker etal. 2017; Udell 2015), and dogs’ ability to use
similar communicative signals towards both conspecifics
and humans (Hare and Tomasello, 1999)—analogue to those
used among, and thus easy to recognize by humans (review
Marshall-Pescini etal. 2013; Udell and Wynne 2008).
One could argue that pigs may use not less but different,
perhaps less easily recognizable communicative signals.
Pigs indeed tended to use more vocalizations, and earlier we
showed that pigs make more physical contact with humans
in a similar food-requesting context than in a neutral condi-
tion (Gerencsér etal. 2019). Nevertheless, as neither the
total duration of vocalizations or human-oriented behaviours
(including touch), nor human-oriented or apparatus-oriented
vocalizations increased in the unsolvable vs. the baseline
phase, we cannot claim that that pigs used these for ref-
erential signalling (i.e. to direct the human’s attention to
the apparatus). Furthermore, pigs not only performed less
human-oriented behaviours in the unsolvable phase than
dogs, but also interacted more with the apparatus, which
might have contributed to their decreased readiness to inter-
act with humans compared to dogs.
Another potential reason for species differences in
human-oriented behaviours in the unsolvable phase may
be that pigs’ laterally positioned eyes, wider viewing angle
(Zonderland etal. 2008) and less flexible neck (Sack 1982)
make them anatomically less predisposed to orient towards
a human and to perform orientation alternations, and they
Fig. 2 Pigs’ and dogs’ performance in the baseline and unsolvable
(first 60 s) phases. Bold lines stand for the median, boxes indicate
the interquartile range and whiskers extend until the smallest and
largest values (excluding outliers and extremities). Dots represent
individual data points. Significance codes of post-hoc comparisons:
***P < 0.001; **P < 0.01; *P < 0.05; ·P < 0.1 (see also Supplemen-
tary Tables S3–S10)
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38 Animal Cognition (2021) 24:33–40
1 3
also need to do it less than dogs for a comparable visual
input. In support, short-headed dogs (with less lateral eyes)
were found to gaze more at humans than long-headed dogs
(Bognár etal. 2018). However, both wolves (with similar
anatomy) and cats (with a flexible neck Graf etal. 1995;
Zhang etal. 2014) were shown to perform less human-ori-
ented behaviours in a problem-solving context than dogs
(Brubaker etal. 2017; Miklósi etal. 2005). Furthermore, we
showed earlier that pigs easily orient towards a human face
in food-related task settings (Gerencsér etal. 2019). Horses
and goats, with similarly lateral eyes (Broadwater etal.
2007; Hanggi and Ingersoll 2012), have also been reported
to perform orientation alternations (Langbein etal. 2018;
Malavasi and Huber 2016; Nawroth etal. 2016). So while
pigs’ anatomical and sensory capacities may have influenced
their human-oriented behaviours, it is improbable that these
account for much of the species differences.
Pigs’ greater manipulative persistence may reflect their
predisposition to solve problems independently (Gieling
etal. 2011) as argued for other species (Brubaker etal. 2017;
Marshall-Pescini etal. 2017a). However, we cannot exclude
that the difference in persistence here is partly caused by
specific task features. First, the box-opening problem may
have been more natural to pigs who routinely use their snout
for rooting (Studnitz etal. 2007; Tynes 2001). Consequently,
pigs may have perceived the task as one that is solvable inde-
pendently, without communicating with humans. Pigs were
indeed faster than dogs in their box-opening speed during
the Solvable trials with also spending less time in total than
dogs manipulating the apparatus in the first trial already.
Thus, even though we cannot exclude that human-oriented
behaviours could have also influenced success latency here,
total manipulation time alone sufficiently accounts for the
species differences behind the time taken to open the appa-
ratus. Future comparative studies should attempt to con-
trol for species differences in task naturalness (Kamil and
Mauldin 1988). Second, species differences in persistence
may have been influenced by pigs’ greater food motivation
(Marino and Christina 2015). We cannot exclude this, but
dogs also attempted to solve the problem in all cases, and
also improved across trials, suggesting that motivation alone
does not account for the behavioural difference.
A few factors may limit the interpretation of our results.
Even though we supervised pigs’ daily home routines to
ensure similar rearing conditions to the two species, pigs’
and dogs’ interactions and experiences with humans may
have differed. Additionally, we had no control over the first
8weeks’ socialization events and how they affected the
appearance of human-directed communicative propensi-
ties—especially in pigs, where the lack of breed variability
(see Supplementary TableS1) may as well restrict the gen-
eralizability of the present results. Furthermore, we cannot
completely exclude that the reported changes in behaviour
between the baseline and the unsolvable phase are not due
to the necessarily fixed order of the conditions (to confront
the subject with a novel apparatus and measure sponta-
neous human-oriented behaviours without any possible
expectations of food reward). However, we believe that
the fact that expressed species differences emerged in the
unsolvable phase only makes it unlikely that those would
be due to an order effect, but rather due to the introduction
of a new salient stimulus (i.e. food reward, clearly attrac-
tive for both species). Finally, since it was not our aim
to test for the effect of familiarity with the humans, the
study was not well controlled for contrasting owner- ver-
sus experimenter-oriented behaviours. Collapsing across
the two humans in the analysis could possibly mask exist-
ing species differences, butthe fact that the main results
were not biased by the split follow-up analysis makes this
improbable. We speculate that no bias in the unsolvable
phase towards owner-oriented behaviours (similarly to
Aniello and Scandurra 2016; Scandurra etal. 2015), and
bias towards experimenter-oriented behaviours in both
species may be explained bythe fact that the experimenter
was the one manipulating the food and showing it to the
subject during the solvable trials, thus the animals may
have expected food/instructions from her rather than from
the owner.
To sum up, we used the unsolvable task paradigm frame-
work to shed more light on the factors that influence the
human-directed communicative abilities of domestic ani-
mals. The found parallels between dogs’ and highly social-
ized miniature pigs’ human-oriented behaviour in a neutral
context point to similar propensities for interspecific interac-
tion, given a similar socialization background. However, the
differences between the two species in the problem-solving
context suggest an influence of species-predispositions in
communicative behaviours on why dogs are more successful
than other species in engaging in interspecific interactions
with humans.
Acknowledgements Open access funding provided by Eötvös Loránd
University. This project was funded by the National Research, Develop-
ment and Innovation Office (NKFI KH125527 to AA), the Hungarian
Academy of Sciences [a Grant to the MTA-ELTE’Lendület’ Neuro-
ethology of Communication Research Group (LP2017-13/2017)] and
by Eötvös Loránd University. All pigs, dogs, and their owners for their
participation.
Author contributions PPF conceptualization, methodology, inves-
tigation, writing—original draft, writing—review and editing. LG:
conceptualization, methodology, formal analysis, visualization, writ-
ing—review and editing, supervision. ML methodology, investigation,
writing—editing, project administration. DÚ investigation, writing—
editing, project administration. AA conceptualization, methodology,
writing—review and editing, supervision, funding acquisition.
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39Animal Cognition (2021) 24:33–40
1 3
Data availability All data generated and analysed during this study are
included in this published article and its Supplementary Information
file (see Supplementary Data).
Compliance with ethical standards
Conflict of interest The authors declare that they have no conflict of
interest.
Ethical approval All applicable international, national, and institutional
guidelines for the care and use of animals were followed. All proce-
dures performed in both animal studies were in accordance with the
ethical standards of the institution at which the studies were conducted.
Open Access This article is licensed under a Creative Commons Attri-
bution 4.0 International License, which permits use, sharing, adapta-
tion, distribution and reproduction in any medium or format, as long
as you give appropriate credit to the original author(s) and the source,
provide a link to the Creative Commons licence, and indicate if changes
were made. The images or other third party material in this article are
included in the article’s Creative Commons licence, unless indicated
otherwise in a credit line to the material. If material is not included in
the article’s Creative Commons licence and your intended use is not
permitted by statutory regulation or exceeds the permitted use, you will
need to obtain permission directly from the copyright holder. To view a
copy of this licence, visit http://creat iveco mmons .org/licen ses/by/4.0/.
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