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Research
Cite this article: Albuquerque N, Guo K,
Wilkinson A, Savalli C, Otta E, Mills D. 2016
Dogs recognize dog and human emotions. Biol.
Lett. 12: 20150883.
http://dx.doi.org/10.1098/rsbl.2015.0883
Received: 20 October 2015
Accepted: 22 December 2015
Subject Areas:
behaviour, cognition
Keywords:
Canis familiaris, cross-modal sensory
integration, emotion recognition,
social cognition
Author for correspondence:
Kun Guo
e-mail: kguo@lincoln.ac.uk
Electronic supplementary material is available
at http://dx.doi.org/10.1098/rsbl.2015.0883 or
via http://rsbl.royalsocietypublishing.org.
Animal behaviour
Dogs recognize dog and human emotions
Natalia Albuquerque1,3, Kun Guo2, Anna Wilkinson1, Carine Savalli4,
Emma Otta3and Daniel Mills1
1
School of Life Sciences, and
2
School of Psychology, University of Lincoln, Lincoln LN6 7DL, UK
3
Department of Experimental Psychology, Institute of Psychology, University of Sa
˜o Paulo, Sa
˜o Paulo 05508-030,
Brazil
4
Department of Public Politics and Public Health, Federal University of Sa
˜o Paulo, Santos 11015-020, Brazil
KG, 0000-0001-6765-1957
The perception of emotional expressions allows animals to evaluate the
social intentions and motivations of each other. This usually takes place
within species; however, in the case of domestic dogs, it might be advan-
tageous to recognize the emotions of humans as well as other dogs. In
this sense, the combination of visual and auditory cues to categorize
others’ emotions facilitates the information processing and indicates high-
level cognitive representations. Using a cross-modal preferential looking
paradigm, we presented dogs with either human or dog faces with different
emotional valences (happy/playful versus angry/aggressive) paired with a
single vocalization from the same individual with either a positive or nega-
tive valence or Brownian noise. Dogs looked significantly longer at the face
whose expression was congruent to the valence of vocalization, for both con-
specifics and heterospecifics, an ability previously known only in humans.
These results demonstrate that dogs can extract and integrate bimodal sen-
sory emotional information, and discriminate between positive and
negative emotions from both humans and dogs.
1. Introduction
The recognition of emotional expressions allows animals to evaluate the social
intentions and motivations of others [1]. This provides crucial information
about how to behave in different situations involving the establishment and
maintenance of long-term relationships [2]. Therefore, reading the emotions
of others has enormous adaptive value. The ability to recognize and respond
appropriately to these cues has biological fitness benefits for both signaller
and the receiver [1].
During social interactions, individuals use a range of sensory modalities,
such as visual and auditory cues, to express emotion with characteristic changes
in both face and vocalization, which together produce a more robust percept
[3]. Although facial expressions are recognized as a primary channel for the
transmission of affective information in a range of species [2], the perception
of emotion through cross-modal sensory integration enables faster, more accu-
rate and more reliable recognition [4]. Cross-modal integration of emotional
cues has been observed in some primate species with conspecific stimuli,
such as matching a specific facial expression with the corresponding vocaliza-
tion or call [5 –7]. However, there is currently no evidence of emotional
recognition of heterospecifics in non-human animals. Understanding heterospe-
cific emotions is of particular importance for animals such as domestic dogs,
who live most of their lives in mixed species groups and have developed mech-
anisms to interact with humans (e.g. [8]). Some work has shown cross-modal
capacity in dogs relating to the perception of specific activities (e.g. food-guard-
ing) [9] or individual features (e.g. body size) [10], yet it remains unclear
whether this ability extends to the processing of emotional cues, which
inform individuals about the internal state of others.
&2016 The Author(s) Published by the Royal Society. All rights reserved.
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Dogs can discriminate human facial expressions and
emotional sounds (e.g. [11–18]); however, there is still no evi-
dence of multimodal emotional integration and these results
relating to discrimination could be explained through simple
associative processes. They do not demonstrate emotional
recognition, which requires the demonstration of categoriz-
ation rather than differentiation. The integration of
congruent signals across sensory inputs requires internal cat-
egorical representation [19– 22] and so provides a means to
demonstrate the representation of emotion.
In this study, we used a cross-modal preferential looking
paradigm without familiarization phase to test the hypoth-
esis that dogs can extract and integrate emotional
information from visual (facial) and auditory (vocal)
inputs. If dogs can cross-modally recognize emotions, they
should look longer at facial expressions matching the
emotional valence of simultaneously presented vocalizations,
as demonstrated by other mammals (e.g. [5 –7,21,22]). Owing
to previous findings of valence [5], side [22], sex [11,22] and
species [12,23] biases in perception studies, we also investi-
gated whether these four main factors would influence the
dogs’ response.
2. Material and methods
Seventeen healthy socialized family adult dogs of various breeds
were presented simultaneously with two sources of emotional
information. Pairs of grey-scale gamma-corrected human or
dog face images from the same individual but depicting different
expressions (happy/playful versus angry/aggressive) were pro-
jected onto two screens at the same time as a sound was
played (figure 1a). The sound was a single vocalization (dog
barks or human voice in an unfamiliar language) of either
positive or negative valence from the same individual, or a neu-
tral sound (Brownian noise). Stimuli (figure 1b) featured one
female and one male of both species. Unfamiliar individuals
and an unfamiliar language (Brazilian Portuguese) were used
to rule out the potential influence of previous experience with
model identity and human language.
Experiments took place in a quiet, dimly-lit test room and
each dog received two 10-trial sessions, separated by two
weeks. Dogs stood in front of two screens and a video camera
recorded their spontaneous looking behaviour. A trial consisted
of the presentation of a combination of the acoustic and visual
stimuli and lasted 5 s (see electronic supplementary material
for details). Each trial was considered valid for analyses when
the dog looked at the images for at least 2.5 s. The 20 trials pre-
sented different stimulus combinations: 4 face-pairs (2 human
and 2 dog models) 2 vocalizations (positive and negative
valence) 2 face positions (left and right), in addition to 4 con-
trol trials (4 face-pairs with neutral auditory stimulus).
Therefore, each subject saw each possible combination once.
We calculated a congruence index ¼(C2I)/T, where Cand
Irepresent the amount of time the dog looked at the congruent
(facial expression matching emotional vocalization, C) and
incongruent faces (I), and Trepresents total looking time (look-
ing left þlooking right þlooking at the centre) for the given
trial, to measure the dog’s sensitivity to audio-visual emotional
cues delivered simultaneously. We analysed the congruence
index across all trials using a general linear mixed model
(GLMM) with individual dog included in the model as a
random effect. Only emotion valence, stimulus sex, stimulus
species and presentation position (left versus right) were
included as the fixed effects in the final analysis because first-
and second-order interactions were not significant. The means
were compared to zero and confidence intervals were presented
for all the main factors in this model. A backward selection pro-
cedure was applied to identify the significant factors. The
normality assumption was verified by visually inspecting plots
of residuals with no important deviation from normality ident-
ified. To verify a possible interaction between the sex of
subjects and stimuli, we used a separate GLMM taking into
account these factors. We also tested whether dogs preferentially
looked at a particular valence throughout trials and at a particu-
lar face in the control trials (see the electronic supplementary
material for details of index calculation).
3. Results
Dogs showed a clear preference for the congruent face in
67% of the trials (n¼188). The mean congruence index
was 0.19 +0.03 across all test trials and was significantly
greater than zero (t
16
¼5.53; p,0.0001), indicating dogs
looked significantly longer at the face whose expression
matched the valence of vocalization. Moreover, we found a
consistent congruent looking preference regardless of the
stimulus species (dog: t
167
¼5.39, p,0.0001; human:
t
167
¼2.48, p¼0.01; figure 2a), emotional valence (negative:
t
167
¼5.01, p,0.0001; positive: t
167
¼2.88, p¼0.005;
figure 2b), stimulus gender ( female: t
167
¼4.42, p,0.0001;
male: t
167
¼3.45, p,0.001; figure 2c) and stimulus
position (left side: t
167
¼2.74, p,0.01; right side: t
167
¼
5.14, p,0.0001; figure 2d). When a backwards selection pro-
cedure was applied to the model with the four main factors,
the final model included only stimulus species. The congru-
ence index for this model was significantly higher for
viewing dog rather than human faces (dog: 0.26 +0.05,
human: 0.12 +0.05, F
1,170
¼4.42; p¼0.04, figure 2a), indicat-
ing that dogs demonstrated greater sensitivity towards
conspecific cues. In a separate model, we observed no signifi-
cant interaction between subject sex and stimulus sex
(F
1,169
¼1.33, p¼0.25) or main effects (subject sex: F
1,169
¼
0.17, p¼0.68; subject stimulus: F
1,169
¼0.56, p¼0.45).
Dogs did not preferentially look at either of the facial
expressions in control conditions when the vocalization was
the neutral sound (mean: 0.04 +0.07; t
16
¼0.56; p¼0.58).
The mean preferential looking index was 20.05 +0.03,
which was not significantly different from zero (t
16
¼21.6,
p¼0.13), indicating that there was no difference in the pro-
portion of viewing time between positive and negative
facial expressions across trials.
4. Discussion
The findings are, we believe, the first evidence of the inte-
gration of heterospecific emotional expressions in a species
other than humans, and extend beyond primates the
demonstration of cross-modal integration of conspecific
emotional expressions. These results show that domestic
dogs can obtain dog and human emotional information
from both auditory and visual inputs, and integrate them
into a coherent perception of emotion [21]. Therefore, it
is likely that dogs possess at least the mental prototypes
for emotional categorization (positive versus negative
affect) and can recognize the emotional content of these
expressions. Moreover, dogs performed in this way without
any training or familiarization with the models, suggesting
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that these emotional signals are intrinsically important. This
is consistent with this ability conferring important adaptive
advantages [24].
Our study shows that dogs possess a similar ability to
some non-human primates in being able to match auditory
and visual emotional information [5], but also demonstrates
an important advance. In our study, there was not a strict tem-
poral correlation between the recording of visual and auditory
cues (e.g. relaxed dog face with open mouth paired with play-
ful bark), unlike the earlier research on primates (e.g. [5]). Thus
the relationship between the modalities was not temporally
contiguous, reducing the likelihood of learned associations
accounting for the results. This suggests the existence of a
robust categorical emotion representation.
Although dogs showed the ability to recognize both con-
specific and heterospecific emotional cues, we found that
they responded significantly more strongly towards dog
stimuli. This could be explained by a more refined mechanism
for the categorization of emotional information from conspeci-
fics, which is corroborated by the recent findings of dogs
showing a greater sensitivity to conspecifics’ facial expressions
[12] and a preference for dog over human images [23]. The
ability to recognize emotions through visual and auditory
cues may be a particularly advantageous social tool in a
highly social species such as dogs and might have been
exapted for the establishment and maintenance of long-term
relationships with humans. It is possible that during domesti-
cation, such features could have been retained and potentially
selected for, albeit unconsciously. Nonetheless, the communi-
cative value of emotion is one of the core components of the
process and even less-social domestic species, such as cats,
express affective states such as pain in their faces [25].
test space(a)
(b)
220 cm
0 0.5 1.0 1.5 2.0 2.5
time (s)
23
17
11
5
0
3.0 3.5 4.0 4.5 0 0.5 1.0 1.5 2.0 2.5
time (s)
frequency (kHz)
23
17
11
5
0
3.0 3.5 4.0 4.5
0 0.5 1.0 1.5 2.0 2.5
time (s)
23
17
11
5
0
3.0 3.5 4.0 4.5 0 0.5 1.0 1.5 2.0 2.5
time (s)
frequency (kHz)
23
17
11
5
0
3.0 3.5 4.0 4.5
140 cm
S
CLP
R1
R2
167 cm
Figure 1. (a) Schematic apparatus. R2: researcher, C: camera, S: screens, L: loudspeakers, P: projectors, R1: researcher. (b) Examples of stimuli used in the study:
faces (human happy versus angry, dog playful versus aggressive) and their correspondent vocalizations.
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There has been a long-standing debate as to whether dogs
can recognize human emotions. Studies using either visual or
auditory stimuli have observed that dogs can show differen-
tial behavioural responses to single modality sensory inputs
with different emotional valences (e.g. [12,16]). For example,
Mu
¨ller et al. [13] found that dogs could selectively respond to
happy or angry human facial expressions; when trained with
only the top (or bottom) half of unfamiliar faces they gener-
alized the learned discrimination to the other half of the
face. However, these human-expression-modulated behav-
ioural responses could be attributed solely to learning of
contiguous visual features. In this sense, dogs could be discri-
minating human facial expressions without recognizing the
information being transmitted.
Our subjects needed to be able to extract the emotional
information from one modality and activate the correspond-
ing emotion category template for the other modality. This
indicates that domestic dogs interpret faces and vocalizations
using more than simple discriminative processes; they obtain
emotionally significant semantic content from relevant audio
and visual stimuli that may aid communication and social
interaction. Moreover, the use of unfamiliar Portuguese
words controlled for potential artefacts induced by a dog’s
previous experience with specific words. The ability to form
emotional representations that include more than one sensory
modality suggests cognitive capacities not previously demon-
strated outside of primates. Further, the ability of dogs to
extract and integrate such information from an unfamiliar
human stimulus demonstrates cognitive abilities not known
to exist beyond humans. These abilities may be fundamental
to a functional relationship within the mixed species social
groups in which dogs often live. Moreover, our results
may indicate a more widespread distribution of the ability
to spontaneously integrate multimodal cues among non-
human mammals, which may be key to understanding the
evolution of social cognition.
Ethics. Ethical approval was granted by the ethics committee in the
School of Life Sciences, University of Lincoln. Prior to the study, writ-
ten informed consent was obtained from the dogs’ owners and human
models whose face images and vocalizations were sampled as the
stimuli. We can confirm that both the human models have agreed
that their face images and vocalizations can be used for research and
related publications, and we have received their written consent.
Data accessibility. The data underlying this study are available from
Dryad: http://dx.doi.org/10.5061/dryad.tn888.
Authors’ contribution. N.A., K.G., A.W. and D.M. conceived/designed the
study and wrote the paper. E.O. conceived the study. N.A. performed
the experiments. N.A. and C.S. analysed and interpreted the data.
N.A. prepared the figures. All authors gave final approval for publi-
cation and agree to be held accountable for the work performed.
Competing interests. We declare we have no competing interests.
Funding. Financial support for N.A. from Brazil Coordination for the
Improvement of Higher Education Personnel is acknowledged.
Acknowledgements. We thank Fiona Williams and Lucas Albuquerque for
assisting with data collection/double coding and figures preparation.
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