ORIGINAL PAPER
Dogs demonstrate perspective taking based on geometrical gaze
following in a Guesser–Knower task
Ame
´
lie Catala
1
•
Britta Mang
1
•
Lisa Wallis
1
•
Ludwig Huber
1
Received: 9 November 2016 / Revised: 15 March 2017 / Accepted: 17 March 2017 / Published online: 24 March 2017
Ó The Author(s) 2017. This article is an open access publication
Abstract Currently, there is still no consensus about
whether animals can ascribe mental states (Theory of
Mind) to themselves and others. Showing animals can
respond to cues that indicate whether another has visual
access to a target or not, and that they are able to use this
information as a basis for whom to rely on as an informant,
is an important step forward in this direction. Domestic
dogs (Canis familiaris) with human informants are an ideal
model, because they show high sensitivity towards human
eye contact, they have proven able to assess the attentional
state of humans in food-stealing or food-begging contexts,
and they follow human gaze behind a barrier when
searching for food. With 16 dogs, we not only replicated
the main results of Maginnity and Grace (Anim Cogn
17(6):1375–1392, 2014) who recently found that dogs
preferred to follow the pointing of a human who witnessed
a food hiding event over a human who did not (the
Guesser–Knower task), but also extended this finding with
a further, critical control for behaviour-reading: two
informants showed identical looking behaviour, but due to
their different position in the room, only one had the
opportunity to see where the food was hidden by a third
person. Preference for the Knower in this critical test
provides solid evidence for geometrical gaze following and
perspective taking in dogs.
Keywords Dog Perspective taking Guesser–Knower
task Geometrical gaze following
Introduction
Whether non-human animals are able to take the perspec-
tive of another individual or are aware of another’s
knowledge state is an equally fascinating and contentious
question in comparative cognition research. However, after
nearly 40 years of research (Premack and Woodruff 1978),
there is still neither theoretical consensus nor solid
empirical evidence for this ability in non-human animals.
Particularly, contentious is the question of the existence of
mind-reading, mental state attribution or Theory of Mind in
non-human animals, all of which describe an ability to
infer the presence of mental states in others (Buckner 2014;
Heyes 2015;Lurz2011; Whiten 2013). An important and
enduring difficulty is to distinguish mind-reading from
cognitively simpler processes like behaviour-reading, i.e.,
the use of directly observable features of other animals’
situations and behaviour, and associative learning. In the
recent past, attempts have been made to reduce the possi-
bility for low-level explanations (Emery and Clayton
2016).
Following Shettleworth’s (2010) advise, sweeping
anthropomorphic questions such as ‘Do animals have a
Theory of Mind?’ are best answered by dissecting broad
abilities into elements, some of which are phylogenetically
widespread, others confined to species with specific
ecologies or evolutionary histories, and some perhaps
unique to humans. A highly investigated element of per-
spective taking and knowledge attribution is the under-
standing of what others can see from their perspective,
especially if this deviates from the individual’s own per-
spective, in order to determine the others’ access to rele-
vant information. Arguably, this requires the observer to
appreciate the difference between their own and another’s
line of sight (Povinelli and Eddy 1996a). For example, a
& Ludwig Huber
ludwig.huber@vetmeduni.ac.at
1
Comparative Cognition, Messerli Research Institute,
University of Veterinary Medicine Vienna, Medical
University of Vienna, University of Vienna, Vienna, Austria
123
Anim Cogn (2017) 20:581–589
DOI 10.1007/s10071-017-1082-x
subject understands that if another’s eyes are directed
towards a location behind a barrier, it must alter its own
position in order to see the object of its interest. This ability
has been called ‘geometrical gaze following’ (Tomasello
et al. 1999).
A species considered as especially skilled in responding
to human communicative cues, such as pointing and gaz-
ing, is the domestic dog (recent reviews in Bensky et al.
2013; Huber 2016; Kaminski and Marshall-Pescini 2014;
Wynne 2016). Indeed, dogs do not only follow the gaze of
humans into distant space (Wallis et al. 2015), but at least
some dogs (about a third of the tested sample) are capable
of following the gaze of humans around a barrier in a food
searching context (Met et al. 2014). Interestingly, when the
dogs had not been primed to forage before the test, they did
not follow the experimenter’s gaze behind a barrier (sim-
ilarly to an earlier study by Agnetta et al. (2000) who also
found negative results for gaze following in a non-foraging
context).
It is still not clear what cognitive mechanisms support
the ability of dogs to follow human gaze and to respond
adaptively to human attentional states. In particular, the
question of whether dogs understand if humans have visual
access to food, or if they simply respond, because of a
special sensitivity or as a result of associative learning, to
perceptual cues, like seeing the human’s body or parts of it
(Bra
¨
uer et al. 2004; Kaminski et al. 2009), remains to be
answered. Can dogs infer from indirect cues what humans
can or cannot see? Two recent studies, one framed in a
non-cooperative and the other in a cooperative setting,
came very close to answering these tricky questions. The
first revealed that the level of illumination around the food
affected whether dogs attempted to steal the food in the
presence of a human (Kaminski et al. 2013). Results sug-
gested dogs understand when the food (and therefore the
area around it) is illuminated, the human can see them
approaching and stealing the food.
That dogs may actually understand something about a
human’s perspective has been demonstrated in the second
study by using the famous ‘Guesser–Knower task’ (Povi-
nelli et al. 1990). Maginnity and Grace (2014) showed that
dogs’ choices between two human informants were not
only influenced by cues related to food handling (Experi-
ment 1), but also by cues related to the humans’ visual
access to the food. In Experiment 2, dogs followed a
human’s (the Knower) point to a food container after
watching the food hiding (where she covered her cheeks
with her hands), rather than another human’s (the Guesser)
point to a different food container (after she covered her
eyes with her hands during the food hiding). In Experiment
3, dogs avoided a human (the Guesser) who looked at the
ceiling during the hiding of the food, and again followed
the human (the Knower) who observed the hiding. Controls
in two further experiments ruled out responding on the
basis of unintentional cues provided by the owners, or
informants, or olfactory cues. This study confirmed that
dogs have a remarkable sensitivity to cues relating to
humans’ attentional state, in this case the location of the
experimenter’s hands on their faces, and their gaze
directions.
It is still an open question if dogs can use geometrical
gaze following as a perspective-taking mechanism, to
assess what a human can see and therefore know. Dogs
do follow the gaze of humans into distant space (Wallis
et al. 2015), but this orientation response may be based
on a relatively simple mechanism, to align their view
with that of another individual gazing towards something
(Povinelli and Eddy 1996a).Thiswouldonlyallowthem
to search for something of interest to themselves. Such
an egocentric perspective was shown in another stealing
task, which required dogs to infer that a human could
see them, although they could not see the human.
However, results showed dogs could not conceal their
act of stealing from the human in the visual domain by
hiding their approach when they could not see a human
present. Still, they could do so in the auditory domain by
preferring a silent approach to forbidden food (Bra
¨
uer
et al. 2013). Although dogs seem to understand how
barriers impair others’ perception (Bra
¨
uer et al. 2006),
they have so far not been tested formally for geometrical
gaze following.
The aim of the present study was twofold. First, on the
basis of the contentious issue of perspective taking in non-
human animals, especially when using the Guesser–
Knower paradigm, and because most dog studies are
underpowered (Arden et al. 2016), we aimed at replicating
the study of Maginnity and Grace (2014). Secondly, in
order to check whether the dogs’ assessment of a human’s
knowledge can go beyond directly observable differences
between the two informants, we conducted a variant of the
Guesser–Knower task in which both human informants
behaved identically: they both looked in the same direction
but differed in whether they could see the baiting process.
Importantly, the object of interest to the human was not
visible to the dogs; therefore, they could not simply use the
eye-object line (Heyes 1994; Udell and Wynne 2011), but
must infer from the humans’ gaze direction what they can
see or not, i.e., geometrical gaze following. In order to
prevent the dogs from using unintentional cues, like
pointing more confidently, to discriminate between the
informants, the experimenters exchanged roles (Knower vs
Guesser) repeatedly in each test, and both were always
informed about the food location. Finally, to rule out
associative learning, we analysed the first-trial data and
checked for possible changes in the dogs’ performance
across trials.
582 Anim Cogn (2017) 20:581–589
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Methods
Subjects
As in Maginnity and Grace (2014), 16 privately owned
dogs (eight males, eight females; mean age = 4.8 years;
various breeds) participated in this study. All subjects lived
as pet dogs with their owners, who volunteered to bring
their dogs to the Clever Dog Lab for this study. These dogs
were naı
¨
ve to any experiment involving perspective taking,
but some of them have participated in other types of
experiments at the Clever Dog Lab before, with only five in
a pointing task (see Table 1).
Apparatus
All tests were conducted in the same 6.05 9 3.33 m large
room at the Clever Dog Lab Vienna, which was equipped
with a three-camera video recording system (Fig. 1a). The
experimental set-up consisted of a removable screen
(chipboard; 220 cm 9 56 cm), placed at 1.2 m distance
from the dog’s release point, and four opaque containers
(12.5 cm high 9 10 cm in diameter) in a semicircle
arrangement, equidistant (1.4 m) from the dog and 45 cm
apart from each other. To prevent any noise during baiting,
each container was filled with eight layers of paper towel
(approximately 2 cm thick in total). The outside of all
containers was rubbed with sausage and therefore saturated
in smell before each testing session, so that all containers
smelled of food regardless of whether they were baited in
the respective trial or not. The food used to bait the con-
tainers consisted of small pieces of sausage (Frankfurter).
The treat supply was kept in an opaque box
(15 9 11 9 12 cm), placed behind the experimenters.
Procedure
All subjects went through pre-training and three tests of a
four-alternative object-choice task following the Guesser–
Knower paradigm (Povinelli et al. 1990). Importantly, the
pre-training and the first two tests (Guesser Absent and
Guesser Present) applied identical procedures as Maginnity
and Grace (2014). Each dog completed two sessions sep-
arated by approximately 1 week. In the first session, the
Table 1 Individual characteristics (sex, age, breed) of the subjects, their pre-experimental experience, the percentages of Knower choices and
the first-trial performances in the three tests
Dog Sex Age Breed Experience
a
GP GA GLA
Mean First
trial
NVT
b
Mean First
trial
NVT Mean First
trial
NVT
Clio F 1.5 Mix TS, II 0.58 K 24 0.88 K240.83 K24
Lola F 3 Mix Shepherd P, TS, II, Ps 0.61 K 23 0.62 G 21 0.63 K 24
Freyja F 2.5 Czechoslovakian
Wolfdog
0.52 G 23 0.88 K 24 0.58 G 24
Louise F 9 Mix 0.63 G 24 0.78 K 23 0.63 K 24
Hybie F 7 Labrador Retriever ET, TS, II, Ps 0.64 K 22 0.91 G 22 0.54 K 24
Tuukka F 2 Mix P, ET, TS, II,
Ps
0.57 G 23 0.71 K 24 0.67 K 24
Haly F 5 Jack Russell Terrier 0.50 K 24 0.67 K 24 0.71 K24
Izy F 4 Podenco 0.41 K 22 0.71 K 24 0.65 K 23
Mowgli M 3 Mix II 0.58 K 24 0.67 G 24 0.67 K 24
Benji M 6 Mix P, ET, II, Ps 0.50 K 24 0.65 K 23 0.63 K 24
Koda M 4.5 Mix German
Shepherd
0.42 G 24 0.87 G 23 0.58 K 24
Cameron M 3.5 Border Collie ET, II, Ps 0.79 K240.83 – 23 0.58 K 24
Bucksi M 7 Papillon 0.27 G 22 0.65 K 21 0.71 K24
Patrasch M 8.5 Mix Spitz TS 0.63 G 24 0.54 K 24 0.43 K 23
Charlie M 7 Bearded Collie P, II, Ps 0.67 K 24 0.67 K 24 0.58 G 24
Cookie M 4 Bearded Collie P, II 0.70 K 23 0.54 K 24 0.46 G 24
Bold typeface indicates performance significantly different from chance
GP Guesser Present, GA Guesser Absent, GLA Guesser Looking Away
a
Experience: TS Touch screen, II Inhibition control; Inequity aversion: P Pointing, Ps Pro-social behaviour
b
NVT, number of valid trials (trials the dog chose a pointed cup); K, dog chose the Knower; G, dog chose the Guesser; – dog did not chose
Anim Cogn (2017) 20:581–589 583
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dogs completed pre-training (ranging from 18 to 23 trials)
and, after a 10-min break, either the Guesser Absent or
Guesser Present test (24 trials each). In the second session,
the dogs completed the remaining two tests (of 24 trials
each). The order of presentation was randomized.
Pre-training
The goal of the pre-training phase was to accustom the
dogs in six consecutive steps to the testing situation and to
prevent side or informant preferences. Two informants (AC
and BM) were present, but only one at a time hid the treat
and subsequently pointed to the baited container. Thus,
during pre-training the dog never had to choose between
the two informants.
During the first step, just one container was presented to
the dog. One of the informants showed the treat (a piece of
sausage) to the dog which was sitting centrally in front of
the owner, and put the food visibly into the container. After
closing the lid, she pointed at the target container with an
out-stretched arm and her index finger touching the lid of
the container, accompanied by a fixed gaze towards the
container. After 2 s, the owner released the dog and it was
free to approach the container. When the dog chose the
indicated container, the informant opened it and gave the
treat to the dog. Then the owner called the dog back to the
start position. The identity of the informants and their
position (left-/right-hand side of the dog) were pseudo-
randomly changed between trials.
In three further steps, the number of containers was
increased to four, but only one was baited. In the fifth
step, the screen was introduced, which blocked the dog’s
view of the baiting process (the hands and the containers).
After the silent baiting process, the screen was lowered
and the pointing was performed as before. The final step
involved, in addition to the screen, the manipulation of all
four containers, whereby only one of them was actually
baited (but all were rubbed with sausage and smelled of
food). The criterion for proceeding to the next step
increased from two (steps 1–4) to four and six successful
trials in a row.
In the following three tests, the roles of the informants,
the baited containers and the pointing positions were
counterbalanced and pseudo-randomly determined for each
trial prior to the experiment, subject to the constraint that
either the Knower or the Guesser did not point to the same
container more than twice in a row. Although the owners,
like the dogs, could not see the baiting and Clever Hans
effects are very unlikely in this context (Hegedu
¨
s et al.
2013; Schmidjell et al. 2012), they were instructed to look
away from the informants during the baiting and the dog
made a choice.
Guesser present test
The first test applied the Guesser Present (GP) condition.
Two of the four containers were baited (instead of one),
and the dogs view was occluded by a screen. The screen
was removed and then both informants pointed each to a
different, baited container. As both pointers observed the
baiting, this test controlled for a preference for a certain
informant and any other bias of the dogs. For reasons of
consistency with Maginnity and Grace (2014), we called
the person who baited the containers the Knower and the
other person the Guesser (who actually also observed the
baiting in this test).
Fig. 1 a. Sketch of the testing room showing the position of the three
video cameras (V), the owner (O), the dog’s releasing point (D), the
screen (S), the four containers (1, 2, 3, 4), the two informants (I1 and
I2) and the baiter (B) in blue, who was only present in GLA condition.
b. Photograph of informants and baiter (centre) in the Guesser
Looking Away (GLA) test. Two female experimenters looked down
and to the side in identical ways, while the third, male experimenter
baited the containers behind the wooden screen and outside of the
dog’s and the Guesser’s (left experimenter) but inside the Knower’s
(right experimenter) view. Note that the looking side, the identity of
the Knower, the position of the Knower, the position of the baited
container and the container to be baited were changed pseudo-
randomly across trials (see text) (colour figure online)
584 Anim Cogn (2017) 20:581–589
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Guesser absent test
The second test applied the Guesser Absent (GA) condi-
tion. It tested for the spontaneous discrimination of the two
pointers according to their observation of the baiting
(Knower vs. Guesser). After the screen was lifted but
before the Knower baited one container, the Guesser left
the room, returned after the baiting event and, after low-
ering the screen, pointed to an empty (previously deter-
mined) container while the Knower pointed to the correct
one.
Guesser looking away test
The third, novel test (Guesser Looking Away, GLA)
involved a separate baiter in addition to the two informants.
Similarly as in Experiment 2 of Maginnity and Grace
(2014) the introduction of a third, unfamiliar person con-
trolled for the influence of food handling (both informants
now being passive during baiting). As this sudden change
in the testing environment had no effect in Maginnity and
Grace (2014), we did not consider it having an impact on
the dogs’ responses. The baiter knelt between the two
informants and, still behind the screen, baited one con-
tainer. The informants behaved identically during the
baiting but had different visual access to the baiter’s
actions. The two informants looked down (45° from the
horizontal eye line) and in a parallel manner to one, pre-
determined side (left or right) at an angle of 45° from the
line between dog and baiter (Fig. 1b). Importantly, the
Knower did not follow the baiter’s hand movement, but
looked straight to the side like the Guesser. Therefore, they
had differing visual access to the baiter’s actions. Only one
(the Knower) could possibly see the baiting, while the other
(the Guesser) could not.
Analysis
For each trial, we coded which of the four containers the
dog chose. A choice was defined as a direct approach
towards one container followed by touching or gazing from
a close distance (maximally 50 cm) for at least 2 s at this
container. If the dog did not make a choice within 60 s, the
trial was terminated and recorded as a ‘no response’. If the
dog approached a container that was not pointed at, the
response was counted as ‘other choice’. Such ‘no respon-
ses’ and ‘other choices’ happened only 24 times in all tests
of all subjects (1128 total trials) and were excluded from
further analyses. For determining Knower preference, we
only used choices of pointed containers, i.e., Knower and
Guesser choices, with the conservative assumption of
chance probability for the Knower’s container being 50%.
For each trial, we used the video recordings from three
cameras to code which of the four containers the dog
chose. Reliability of this coding was verified by a coder
who was unfamiliar with the goals of the study, who coded
a randomly chosen sample (13%) of video recordings. Due
to the high quality of the videos and the ease of deter-
mining which container a dog approached, inter-observer
agreement was 100% (j = 1).
As in Maginnity and Grace (2014), Knower preference
was calculated for each dog and pooled over blocks of 4
trials. We also investigated the occurrence of learning
across trials within each test separately by conducting
Prism’s linear regression analysis with the average per-
centage of choice responses made to the Knower in each
trial. Knower preferences for individual dogs were assessed
with binomial tests. In order to compare the whole sam-
ple’s (N = 16) performance to chance level, the average
preference across dogs for each test was assessed with
binomial tests. In order to compare the performance of the
dogs in the current study with those of Maginnity and
Grace (2014), an independent samples t test was performed
for the GA, GP, and GLA tests.
Ethical note
This study was approved in accordance with good scientific
practice guidelines and national legislation by the Ethical
Committee of the University of Veterinary Medicine
Vienna (Ref: ETK-10/02/2016). All experimental proce-
dures were performed in compliance with the Austrian
Federal Act on the Protection of Animals (Animal Pro-
tection Act–TSchG, BGBl. I Nr.118/2004). All tests were
completely non-invasive and therefore, according to the
Austrian Animal Experiments Act (§ 2, Federal Law
Gazette No. 501/1989), are not considered as animal
experiments and do not require obtaining special permis-
sion. All dog owners gave written consent to participate in
the study.
Results
Overall dogs responded to the location pointed at by the
Knower or the Guesser on 97.9% of trials (n = 1128). As
in Maginnity and Grace (2014), trials with no response
(N = 5) or in which the dog chose a container that was not
pointed at occurred rarely (N = 19), and were omitted
from subsequent analyses.
Figure 2 shows the percentage of choice responses made
for the Knower across successive blocks of four trials for
all three tests. On a group level, Knower preference was
significantly greater than chance (50%) in two tests (GA:
mean = 72.3%, t(15) = 7.46, p \ 0.0001; GLA:
mean = 61.7%, t(15) = 4.89, p = 0.0002) and
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