Jealousy in Dogs
Christine R. Harris*, Caroline Prouvost
University of California San Diego, La Jolla, California, United States of America
It is commonly assumed that jealousy is unique to humans, partially because of the complex cognitions often involved in
this emotion. However, from a functional perspective, one might expect that an emotion that evolved to protect social
bonds from interlopers might exist in other social species, particularly one as cognitively sophisticated as the dog. The
current experiment adapted a paradigm from human infant studies to examine jealousy in domestic dogs. We found that
dogs exhibited significantly more jealous behaviors (e.g., snapping, getting between the owner and object, pushing/
touching the object/owner) when their owners displayed affectionate behaviors towards what appeared to be another dog
as compared to nonsocial objects. These results lend support to the hypothesis that jealousy has some ‘‘primordial’’ form
that exists in human infants and in at least one other social species besides humans.
Citation: Harris CR, Prouvost C (2014) Jealousy in Dogs. PLoS ONE 9(7): e94597. doi:10.1371/journal .pone.0094597
Editor: Elissa Z. Cameron, University of Tasmania, Australia
Received September 12, 2012; Accepted March 19, 2014; Published July 23, 2014
Copyright: ß 2014 Harris, Prouvost. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: This research was not supported by any funding agency. It was performed in CH’s position as a professor at UCSD with volunteer subjects.
Competing Interests: The authors have declared that no competing interests exist.
* Email: firstname.lastname@example.org
In humans, jealousy is an emotion with far-reaching psycho-
logical and social consequences. For example, it typically emerges
as the third leading cause of non-accidental homicide across
cultures . While the origins and possible function of jealousy
have been debated, most theorists agree on one defining feature: It
requires a social triangle, arising when an interloper threatens an
important relationship. A common assumption has been that the
elicitation of jealousy involves, and perhaps requires, complex
cognitive abilities [2–3], including appraisals about the meaning of
the rival threat to one’s self (e.g., self-esteem) and to one’s
relationship. For example, Lewis  has proposed that the
emergence of jealousy requires the cognitive ability to reflect on
the self and to understand conscious intentions.
The vast majority of research in this area has concentrated on
jealousy within romantic relationships particularly over potential
or actual infidelity. Hence, functional or evolutionary analysis of
jealousy has focused on the fitness consequences of loss of a
romantic or sexual relationship (e.g., cuckoldry, loss of resources)
and on the psychological and behavioral effects of protecting such
relationships [5–7]. A broader functional view, however, would
argue that jealousy evolved to secure resources not just in the
context of sexual relationships, but also in any of a wide-range of
valued relationships [1,8]. Accordingly, the same underlying
emotional process that gives rise to jealousy in sexual relationships
also produces jealousy in other types of bonds (e.g., friendships).
One possibility is that jealousy first evolved in the context of
sibling-parent relationships where dependent offspring compete
for parental resources. An implication of this hypothesis is that
jealousy may have a primordial or core form that can be triggered
without complex cognition about the self or about the meaning of
the social interaction [1,9]. This primordial form of jealousy may
be elicited by the relatively simple perception that an attachment
figure or loved one’s attention has been captured by a potential
usurper, which suffices to elicit a motive to regain the loved one’s
attention and block the liaison. Primordial jealousy may serve as
the building block for jealousy elicited by more complex cognitive
processes. For example, in adult human relationships, the
experience of jealousy is greatly impacted by additional appraisals
about the meaning of the interaction (e.g., does this mean my mate
will leave me? Am I unloveable?). In both primordial and complex
cases of jealousy, there is a motivation to restore the relationship
and remove the usurper. However, in the latter case, interpreta-
tions of the situation play a large role in the elicitation and
experience of the emotion.
The theory that jealousy can take a primordial form finds
support from the small but emerging body of research on human
infant jealousy. Several studies [10–12] found that infants as young
as 6-months of age show behaviors indicative of jealousy, for
example, when their mothers interacted with what appeared to be
another infant (but was actually a realistic looking doll). The
infants did not display the same behaviors when their mothers
attend to a nonsocial item (a book).
The functional account we are proposing would further predict
that jealousy should occur not only in humans, but also in other
social species in which emotional bonds between individuals
develop and can be threatened by third parties. Interestingly,
several observers of animal behavior, including Charles Darwin
, have suggested that jealousy may exist in other species,
particularly in dogs. This possibility has also been underscored in a
recent paper that had owners recount specific cases of their
animals displaying emotions . Descriptions of dog jealousy
were fairly consistent across owners and always involved a social
triangle. When the owners gave attention and affection to another
person or animal, the dogs seemed to engage in attention-seeking
behaviors (pushing against the owner or in between the owner and
the rival, barking/growling/whining) and some showed aggres-
sion. Reports of the occurrence of jealousy in dogs was at least as
common, if not more so, than some other emotions that are often
considered more primary (anxiety and anger). However, despite
such reports, experimental evidence demonstrating behavioral
PLOS ONE | www.plosone.org 1 July 2014 | Volume 9 | Issue 7 | e94597
indices of jealousy in dogs does not exist. This type of empirical
research seems particularly important, given that dog owners also
report that their animals experience guilt but experimental work
raises some doubt about whether dogs do show guilt .
The idea that dogs are capable of jealousy is congenial to the
burgeoning body of research on animal social cognition that
reveals that dogs have sophisticated social-cognitive abilities. For
example, dogs can use a variety of human communicative signals
(e.g., pointing, eye gaze) to determine the location of hidden food
, are better at using social cues than chimpanzees , show
some sensitivity to reward inequity when a partner is rewarded
and they are not  and appear aware of, and actively attempt to
manipulate, the visual attention of their play partners .
The Present Research
Although there are several reasons to predict that jealousy
should lie within a dog’s emotional repertoire, empirical evidence
is lacking. The purpose of the present study was to construct a
social situation and determine whether dogs, whose owners show
affection to a potential interloper, engage in behaviors indicative of
To evaluate dogs’ jealous behaviors, we modified a paradigm
used to assess jealousy in 6-month-old infants [10–12]. Thirty-six
dogs were individually tested and videotaped while their owners
ignored them and interacted with a series of three different objects.
In the jealousy condition, the owner treated a stuffed dog, which
briefly barked and wagged its tail, as if it were a real dog (e.g.,
petting, talking sweetly). In another condition, owners engaged in
these same behaviors but did so towards a novel object (jack-o-
lantern pail). This enabled us to test whether the elicitation of
jealousy required that the owner show affection to an appropriate
stimulus (what appeared to be a conspecific) or whether
affectionate behaviors directed to a nonsocial stimulus would be
enough to arouse jealous behaviors. In the third condition, the
owner read aloud a children’s book, which had pop-up pages and
played melodies. This condition allowed us to test whether dogs’
behaviors in the other conditions were indicative of jealousy per se
(arising over the loss of affection and attention towards an
interloper) or more general negative affect due to the loss of the
As discussed earlier, the proposed function of jealousy is to
break-up a potentially threatening liaison and protect the primary
relationship. This motivates several types of behaviors including
approach actions such as attempts to get physically or psycholog-
ically between the attachment 3ure and the interloper, attending
to the threatening interaction, seeking attention from the
attachment figure, as well as indicators of negative emotion such
as aggression, particularly toward the interloper [1–2,8,10–12,19].
Across social species, we would expect to see similar types of
behaviors that serve the function of this motivational state.
Therefore, the specific behaviors assessed in our experiment were
based on studies of jealousy in non-verbal human infants and
adults as well as behaviors described by dog owners and experts as
indicative of jealousy.
This research was approved by the University of California San
Diego Institutional Animal Care and Use Committee and by the
University of California at San Diego Human Research Protec-
tions Program. Owners and pet dogs were recruited from the
University of California, San Diego subject pool. Owners received
partial course credit in psychology class for participation.
Dogs were tested individually at their homes and had to be less
than 35 pounds or shorter than 15 inches. A size criterion was used
because of the possibility that the jealousy manipulation would
result in aggression and small dogs could be more easily controlled
in such circumstances. Upon arrival at the subjects’ homes, the
experimenter obtained written consent from the dog owners for
participation. The experimenter also gave a brief overview of the
study stating, ‘‘For this experiment, we are examining individual
differences in dog behavior across various situations. Thus, we’ll be
asking you to act out various situations in front of your dog, while
ignoring him or her, while we film his or her reaction." The
experimenter also said, "If you think that your dog will act
aggressively in this situation, we ask that you and your dog don’t
participate, but you’ll still receive your Experimetrix [course]
credit." All owners chose to continue with the experiment.
The initial sample size was n = 37. However, one male dog was
excluded from all analyses due to a miscommunication between
the owner and experimenter resulting in one condition ending
prematurely. Therefore, the final sample size was n = 36. The
mean age of the dogs was 32.2 months (range = 4–135). Equal
numbers of male and female dogs participated. The sample
consisted of a variety of dog breeds as can be seen in Table 1.
Owners (31 females and 5 males) had owned their dogs an average
of 25.4 months (range = 1–134).
Owners were not aware of the hypotheses of the experiment. A
within-subjects design was employed with order counter-balanced
across participants. Each experimental condition was videotaped
and lasted for 1 minute, followed by a 30 sec post-condition phase
in which the owner set the object down within reach of the dog.
The owner completed a questionnaire after each condition and
then the dog and owner were given one minute to freely interact in
order to reduce any potential carryover effects from the previous
Stuffed Dog. Owners were instructed to interact with a
realistic-looking stuffed dog that barked, whined, and wagged its
tail (which lasted for a total of approximately 8 secs) when a button
on the top of its head was pressed. The owners were asked to press
the button only once and to interact with the stuffed dog as if they
were playing with a real dog. They were also instructed to
completely ignore their dog, which was present in the room for the
duration of the interaction.
Jack-o-lantern. In the novel object condition (jack-o-lantern),
owners were given the same instructions as in the stuffed dog
condition: to interact with a jack-o-lantern as if they were playing
with a real dog.
Book. In the book control condition, owners were instructed
to read aloud a children’s book, which popped up and played
melodies, as if they were reading to a young child. Total amount of
time the object made a noise was closely matched to that of the
dog condition (approximately 8 secs).
Two raters, blind to the study’s purpose, coded the videos.
Unless otherwise noted, behaviors were coded as present or absent
and are reported as percent of dogs showing such behaviors per
condition. To compute interrater reliability, 29 dogs were coded
by both raters. Behaviors in which interrater reliability was lower
than .7 were not included in the analyses. For analyses that
required whole numbers (i.e., Cochran’s Test for presence/
absence of a behavior), we used one rater’s codes for half the dogs
Jealousy in Dogs
PLOS ONE | www.plosone.org 2 July 2014 | Volume 9 | Issue 7 | e94597
and the other rater’s codes for the other half. Behaviors coded
during the interaction of the owner with the object are described
first, followed by the behaviors coded post-interaction.
Aggression. We coded for aggression given its link to jealousy
in human adults  and in owners’ reports of dog jealousy .
Our primary measure of aggression was whether the dog
attempted to bite/snap at the object. Coders also attempted to
code more subtle signs of aggression that include lip curling (lips
being held open with force in order to expose teeth), raised tail–
holding the tail up between the horizontal and vertical positions
(an aggressive posture in wolves), and keeping the ears forward.
Interrater reliability was low for ears forward (.57) and so this
behavior was not analyzed. Our coders also reported difficulty
assessing the raised tail in many dogs due to their physical
characteristics (e.g., a clipped tail); however, interrater reliability
was acceptable, so these analyses are reported in the results
section. Lip curling was not seen across any condition.
Attention Seeking/Disruption of Interaction. The most
common category of behavior in owner descriptions of their dogs’
jealousy was attention seeking . These behaviors often took the
form of pushing the owner or attempting to get between the owner
and the rival. We coded for both of these behaviors. Some owners
also reported attempts by their dogs to shoo the rival away. In our
coding scheme, we operationalized this as the dog pushing against
the rival object. Another class of behaviors categorized as attention
seeking by Morris et al.  was vocalizations (described as
barking, growling, and whining), which we assessed. (Growling
interrater reliability was lower than our .7 cutoff so was excluded
from our analyses.)
Interest/Attention. The preverbal human infant literature
(e.g., by Hart and colleagues) suggests that jealousy produces
increased interest and attention toward the mother. We assessed
several behaviors pertaining to attention, which included 1)
looking at the owner, 2) looking at the rival object, 3) orienting
away from the owner, and 4) orienting away from the object. The
first two categories were operationally defined as having the head
turned and gaze directed toward the owner/object; the later two
were operationally defined as having the head and body turned
away from the owner/object. Due to their frequency across
conditions, a simple present/absent code for the entire interaction
period did not adequately capture these behaviors. Therefore, we
performed more fined grained coding that consisted of denoting
whether the behavior was present or absent every 5 seconds,
resulting in total score that ranged from 0–12. Total scores were
then transformed into proportion of time behavior was present. (In
the cases where both raters coded the same dog’s behavior, the
average of the two coders’ scores was used for these measures.)
Behaviors coded during the 30-second post interaction
During the post-interaction period, the owner put the
object down and walked away. We coded four behaviors during
this phase: 1) aggression/snapping directed at the object; 2)
following the owner; 3) observing the object; and 4) ignoring the
object. Due to the laborious nature of coding, we only coded for
presence/absence of attention behaviors (observing/ignoring
object) in this phase rather than assessing attention every 5
seconds as done in the condition phase. Additionally, in the dog
condition, we noted if the dog sniffed the rear end of the toy dog.
This was included as a measure of whether the dog perceived the
stuffed dog as a real dog.
Additional exploratory measures. In addition to assessing
jealousy, we used this opportunity to explore attachment style in
dogs (and its possible interaction with our conditions), which we
mention here for the sake of completeness. We created a scale for
owners to complete regarding their dog’s attachment style and
coded for behaviors that might be linked to different attachment
styles. These included behaviors that might be indicative of anxiety
(paw slightly raised; yawning) and of submission (ears back, tail
down, and licking). We also attempted to code tail wagging to the
left vs. the right because work by Quaranta, Siniscalchi, and
Vallortigara  suggested that the former is associated with
withdrawal and the latter with approach. However, our coders
found this too difficult to assess via video. Analyses pertaining to
attachment style are not reported here given their exploratory
nature and the difficulty of measuring some of these behaviors.
Table 1. Dog Breeds.
Boston Terrier 1 (2.7)
Chihuahua 2 (5.4)
Dachshund 1 (2.7)
Havanese 1 (2.7)
Malinois 1 (2.7)
Maltese 3 (8.1)
Miniature Pincher 1 (2.7)
Miniature Schnauzer 1 (2.7)
Pomeranian 2 (5.4)
Pug 1 (2.7)
Shetland Sheepdog 1 (2.7)
Shih-tzu 2 (5.4)
Welsh Corgi 1 (2.7)
Yorkshire Terrier 3 (8.1)
Mix 14 (37.8)
Jealousy in Dogs
PLOS ONE | www.plosone.org 3 July 2014 | Volume 9 | Issue 7 | e94597
Results & Discussion
Figure 1 shows the proportion of dogs that engaged in the
various behaviors during the interactions with the objects in each
condition. Our analyses showed significantly greater aggression in
the jealousy condition, Cochran’s Q, x
(2) = 12.80, p, .002. One
fourth of the dogs snapped at the object in the jealousy condition
but only 1 dog did so in the other two conditions. (Results from
follow up McNemar nonparametric tests are presented in Figure 1.)
We, however, did not see a difference across conditions in the
number of dogs that placed their tails between the vertical and
horizontal positions (Cochran’s Q, x
(2) = .67, ns). This may be
due to our coders having difficulty accurately assessing tail
movement (e.g., in dogs with snipped tails). In the post-interaction
phase (when the owner had put the object down), 36% of the dogs
snapped at the stuffed dog while snapping behavior in the other
conditions was confined to one dog (Cochran’s Q, x
(2) = 20.57,
p, .001). The aggression in the jealousy condition is particularly
impressive given that we only tested dogs whose owners believed
that their dogs would not behave aggressively in novel situations.
The next series of analyses examined attention seeking and
specifically focused on the behaviors most commonly noted by
owners when describing their animals’ jealous behaviors .
Dogs were significantly more likely to push or touch their owners
(Cochran’s Q, x
(2) = 26.87, p, .001) and the object (Cochran’s
(2) = 24.07, p, .001) in the jealousy condition relative to
either the jack-o-lantern or book conditions. Results for follow up
McNemar nonparametric tests are presented in Figure 1. Of
particular interest, dogs specifically tried to get between the owner
and the object more often in the jealousy condition (Cochran’s Q,
(2) = 6.53, p, .04). Such behaviors aimed at preventing or
breaking up a liaison have been hypothesized to be the primary
motivational state that accompanies jealousy and that distinguishes
jealousy from other emotions such as anger [1,19]. Although
vocalizations during the experiment were relatively infrequent,
whining occurred significantly more in the jealousy condition than
in the book condition. Barking did not significantly differ across
At the suggestion of a reviewer, we summed the behaviors
presented in Figure 1 for each condition in order to get a sense of
the effect size of the jealousy condition and performed within-
subjects ANOVA with partial eta-squared tests. Partial eta-
squared for the dog vs. jack-o-lantern conditions was .41 and for
dog vs. book was .58.
In the preverbal human infant literature, jealousy is accompa-
nied not only by negative affect but also by heightened interest and
attention toward the mother while she is interacting with what
appears to be another infant [10–12]. We found similar effects in
dogs. Results for within-subject ANOVAs are presented in the text
while results for follow up paired t-tests are displayed in Figure 2.
As shown in Figure 2, dogs gazed significantly more at their
owners (F(2, 70) = 7.47, p, .001, g
= .18) and the objects (F(2,
70) = 56.39, p, .001, g
= .62) in the conditions in which the
owner was displaying affection towards an object relative to the
control condition of reading aloud. Furthermore, when the object
of affection appeared to be a conspecific, dogs looked more at the
object relative to when it was a novel item (jack-o-lantern). This
pattern is furthered supported by the inversely related measures of
disinterest, operationally defined by orienting the body away from
the owner and object (Figure 2). Dogs spent significantly more
time ignoring the owner and object in the book condition relative
to the conditions that involved displays of affection: F(2,
70) = 30.62, p, .001, g
= .47 for owner; F(2, 70) = 87.27, p,
= .71 for object.
Behaviors during the post-task period were similar to those seen
during the actual interaction (although less informative given that
behavior was merely coded as present/absent). More dogs ignored
the object in the jack-o-lantern (94.4%) and book (91.7%)
conditions than in the dog condition (52.8%); Cochran’s Q, x
(2) = 20.01, p, .001. There was also a significant difference in the
number of dogs who observed the object across conditions (72.2%
in dog condition; 63.9% in jack-o-lantern condition; and 44.4% in
book condition): Cochran’s Q, x
(2) = 6.58, p, .04. There was
not a significant difference in the number of dogs who followed
their owner after each condition, x
(2) = 4.67, p = .10.
Figure 1. Comparisons of the proportion of dogs exhibiting each type of behavior in each of the three experimental conditions.
Jealousy in Dogs
PLOS ONE | www.plosone.org 4 July 2014 | Volume 9 | Issue 7 | e94597
Was the stuffed dog perceived as real?
One might wonder whether the subject dogs believed that the
stuffed animal was a real dog. The data discussed previously,
particularly the aggressive behaviors aimed at the stuffed animal,
would seem to suggest that they did. Perhaps even more
compellingly, 86% of the dogs sniffed the anal region of the toy
dog during the experiment or post-experiment phases. Having a
faux rival dog enabled us to maximize the amount of control we
had in the experiment. That jealousy behaviors were seen under
these somewhat impoverished social conditions leads us to predict
that such behaviors would be even more enhanced in the present
of an actual rival dog who responded to the owner’s affectionate
In the present work any single behavior might not be indicative
of jealousy per se. However, the pattern of behaviors, particularly
when dogs were confronted with their owners displaying affection
to what appeared to be another dog, is similar to the constellation
of behaviors seen in humans. These data thus present a strong case
that domestic dogs have a form of jealousy.
An anonymous reviewer suggested that our data might reflect
individual differences in dog cognition and/or jealousy. One
possibility is that only some dogs perceived the stuffed dog as real
and that this difference in cognitive ability resulted in jealousy in
some dogs but not others. To the reviewer’s mind, only those dogs
that aggressed against the ‘‘rival’’ dog can be shown to definitively
consider the fake dog stimulus as real. We believe that the fact that
the vast majority of the dogs sniffed the anal region of the stuffed
dog (including all of the aggressive dogs) suggests that most of the
dogs conceptualized the dog as real, but we cannot rule out the
However, even if most dogs perceived the stimulus as real, it is
still possible that only some of them reacted with jealousy to it. The
reviewer suggested some additional analyses to explore possible
individual differences. One question is whether the snapping dogs
were the only ones to show additional jealous behaviors. As
described below, our data suggest that they were not, although
their jealousy might be argued to be more intense in some respects
than their nonsnapping peers. In total, 41.7% of dogs snapped
during or after their owner interacted with the stuffed dog. We
found that these aggressive dogs did display many other jealous
behaviors: All of them pushed at the owner and 86.7% pushed at
the fake dog during the jealousy interaction. There was also some
tendency for these dogs to spend more time (although not
significantly so) attending to the owner and the fake dog (and
conversely less time ignoring the owner and rival) than nonsnap-
ping dogs. However, not all jealous behaviors were more common
in the snapping dogs. Whining was similar across the two types of
dogs and while 26.7% of the snapping dogs attempted to get
between their owner and the rival dog, 33.3% of the nonaggressive
dogs did so. Moreover, many of the nonsnapping dogs also
displayed other jealousy indicators. For example, 61.9% pushed at
the owner and 57.1% pushed at the stuffed dog. These percents
are higher if the dogs that did not sniff the rear end are excluded
(who likely did not perceive the stuffed dog as a threat). Thus,
these exploratory analyses would argue against the suggestion that
only aggressive dogs displayed jealous behaviors, although their
jealousy may be viewed as more extreme. These data raise the
possibility that dogs, like humans, show individual differences in
how jealousy is exhibited, which ranges from attention seeking and
restorative behaviors to aggressive acts.
The fact some dogs (13.8%) failed to sniff the rear end of the
fake dog raises stimulating questions for future studies. Jealous
behaviors were infrequent among these animals, suggesting that
they were not in an emotional state (e.g., none pushed on the
owner or the stuffed dog and only one got between them). One
interesting possible avenue for future work is to examine the
cognitive abilities that are associated with not believing the stuffed
dog is real. It might be that such dogs are less cognitively
sophisticated (they do not perceive the toy as representation of a
real dog.). However, it is also possible that they are more
sophisticated, (i.e., were not fooled into believing that the stuffed
dog was genuine, and hence it was not a threat).
In sum, it may be that while all dogs have the neurobiological
cognitive capacity for jealousy, the current situation may have
failed to induce the emotional state in some dogs. Understanding
what factors (cognition or social dynamics) contribute to individual
differences in dog jealousy would seem a ripe area for future work.
Figure 2. Proportion of time dogs spent attending to and orienting away from their owner and the object in each of the three
Jealousy in Dogs
PLOS ONE | www.plosone.org 5 July 2014 | Volume 9 | Issue 7 | e94597
The current findings add support to the emerging view [1,9]
that there is a primordial form of jealousy. This emotional state
does not presuppose complex interpretations of the behavior of the
rival and the attachment figure and its meaning to the self,
(although such cognitions clearly can impact jealousy in adult
interpersonal relationships). Primordial jealousy appears not only
ontogenetically early in humans but may also have emerged
phylogenetically early. We use the term ‘primordial’ to reflect a
state that motivates jealous action tendencies that are similar
across dogs and humans (of course, these findings do not speak to
whether the subjective experience of the emotional state is similar).
If jealousy is phylogenetically old, then one might expect to see
some form of it in other animal species that form emotional bonds
that can be threatened by rivals, whether that rival be a sibling, or
a mate, or another group member. Here we tentatively suggest
some possibilities about features that might have given rise to
jealousy, which could be explored in further work.
One possibility is that jealousy evolved in species that have
multiple dependent young that concurrently compete for parental
resources such as food, attention, care, and affection. It is easy to
imagine the advantages that might be gained by a young animal
that is not only alert to interactions between siblings and parents,
but also motivated to interpose itself in such interactions. Several
of the behaviors assessed in the current work (e.g., pushing on the
owner, getting between the owner and ‘‘rival’’ dog) would seem to
serve that goal. Future work might look at how effective these
behaviors are in natural triadic interactions (e.g., does pushing on
one’s mother divert her attention from a sibling?). Another
possibility is that jealousy behaviors emerged to protect pair-
bonded sexual relationships from interlopers. If so, then jealousy
might not exist in species that do not pair-bond, regardless of the
number of offspring reared simultaneously. (To date, little is
known about the relationship between romantic and nonromantic
jealousy.) Finally, it is possible that jealousy evolved in animals that
require cooperation from other group members for survival and in
which alliances are formed (and therefore, can be threatened by
rivals). These possibilities are difficult to tease apart by studying
dogs given that they are litter born, have the potential for pair-
bonding (see Bradshaw  for discussion), and hunt coopera-
tively. It would be informative to examine jealousy in species that
differ on these factors (e.g., domestic cats, which bear litters but are
Finally, it is also possible that the long co-evolution and
domestication of dogs, which likely gave rise to many of their
remarkable social-communicative skills [16,22], created their
capacity for jealousy. (Perhaps this is a function of their emotional
bonding with humans along with their motivation and ability to
track human gaze/attention. Humans, afterall, have been rich
resource providers over our coevolution.) One might speculate
that even if several social species have the capacity for jealousy,
dogs may be the only species besides humans in which the emotion
can be evoked in connection with a member of a different species.
Future studies that examine the affective and cognitive abilities of
a variety of animal species could help tease apart these various
intriguing possibilities. Such work is particularly warranted given
that a large percentage of owners of some other types of domestic
animals such as horses, birds, and cats also report signs of jealousy
in their animals . Moreover, some of these species such as
horses have been shown to be highly sensitive to human
attentional cues . Further research on the neurobiological
components of and influences on emotions in both humans and
other animals may also help disentangle the similarities and
differences of emotion and social behavior across species [24–25].
In closing, these findings add additional support to the view that
jealousy can arise in the absence of complex interpretations of the
meaning of the rival and loved one’s interaction and occurs in
another species besides humans. We hope the current work will
inspire further research into the social emotions of animals.
We thank Alison Yee and Wanting Tan for coding the videos and Noriko
Coburn for her assistance with various aspects of the study.
Conceived and designed the experiments: CH CP. Performed the
experiments: CP. Analyzed the data: CH CP. Contributed reagents/
materials/analysis tools: CH CP. Wrote the paper: CH CP.
1. Harris CR (2003) A review of sex differences in sexual jealousy, including self-
report data, psychophysiological responses, interpersonal violence, and morbid
jealousy. Pers Soc Psychol Rev 7: 102–128.
2. Hart SL, Legerstee M (2010) Handbook of jealousy: Theory, research, and
multidisciplinary approaches. Malden: Wiley-Blackwell.
3. White GL, Mullen PE (1989) Jealousy: Theory, research, and clinical strategies.
New York: Guilford Press.
4. Lewis M (2010) Loss, protest, and emotional development. In: Hart SL,
Legerstee M, editors. Handbook of jealousy, theory, research, and multidisci-
plinary approaches. Malden: Wiley-Blackwell. pp. 27–39.
5. Buss DM (2000) The dangerous passion: Why jealousy is as necessary as love
and sex. New York: Free Press.
6. Harris CR (2002) Sexual and romantic jealousy in heterosexual and homosexual
adults. Psychol Sci 13: 7–12.
7. Symons D (1979) The evolution of human sexuality. New York: Oxford
8. DeSteno D, Valdesolo P, Bartlett MY (2006) Jealousy and the threatened self:
getting to the heart of the green-eyed monster. J Pers Soc Psychol 91: 626–641.
9. Hobson RP (2010) Is jealousy a complex emotion? In: Hart SL, Legerstee M,
editors. Handbook of jealousy, theory, research, and multidisciplinary
approaches. Malden: Wiley-Blackwell. pp. 293–311.
10. Hart S, Carrington HA (2002) Jealousy in six-month-old infants. Infancy 3: 395–
11. Hart S, Field T, Del Valle C, Letourneau M (1998) Infants Protest Their
Mothers’ Attending to an Infant-Size Doll. Soc Dev 7: 54–61.
12. Hart SL, Carrington HA, Tronick E, Carroll SR (2004) When infants lose
exclusive maternal attention: Is it jealousy? Infancy 6: 57–78.
13. Darwin C (1871) The descent of man. London: John Murray.
14. Morris PH, Doe C, Godsell E (2008) Secondary emotions in non-primate
species? Behavioural reports and subjective claims by animal owners. Cogn
Emot 22: 3–20.
15. Horowitz A (2009) Disambiguating the ‘‘guilty look’’: Salient prompts to a
familiar dog behaviour. Behav Processes 81: 447–452.
16. Hare B, Brown M, Williamson C, Tomasello M (2002) The domestication of
social cognition in dogs. Science 298: 1634–1636.
17. Range F, Horn L, Viranyi Z, Huber L (2009) The absence of reward induces
inequity aversion in dogs. Proc Natl Acad Sci U S A 106: 340–345.
18. Horowitz A (2009) Attention to attention in domestic dog (Canis familiaris)
dyadic play. Anim Cogn 12: 107–118.
19. Harmon-Jones E, Peterson CK, Harris CR (2009) Jealousy: Novel methods and
neural correlates. Emotion 9: 113–117.
20. Quaranta A, Siniscalchi M, Vallortigara G (2007) Asymmetric tail-wagging
responses by dogs to different emotive stimuli. Curr Biol 17: R199–R201.
21. Bradshaw J (2011) Dog sense: How the new science of dog behavior can make
you a better friend to your pet. New York: Basic Books.
22. Topa´l J, Gergely G, Erdo˝hegyi A
, Csibra G, Miklo´si A
sensitivity to human communication in dogs, wolves, and human infants. Science
23. Proops L, McComb K (2010) Attributing attention: the use of human-given cues
by domestic horses (Equus caballus). Anim Cogn 13: 197–205.
24. Griffin DR, Speck GB (2004) New evidence of animal consciousness. Anim
Cogn 7: 5–18.
25. O’Connell LA, Hofmann HA (2011) Genes, hormones, and circuits: an
integrative approach to study the evolution of social behavior. Front
Neuroendocrinol 32: 320–335.
Jealousy in Dogs
PLOS ONE | www.plosone.org 6 July 2014 | Volume 9 | Issue 7 | e94597