Does pet arrival trigger prosocial behaviors in individuals with autism?

Abstract

Alteration of social interactions especially prosocial behaviors--an important aspect of development--is one of the characteristics of autistic disorders. Numerous strategies or therapies are used to improve communication skills or at least to reduce social impairments. Animal-assisted therapies are used widely but their relevant benefits have never been scientifically evaluated. In the present study, we evaluated the association between the presence or the arrival of pets in families with an individual with autism and the changes in his or her prosocial behaviors. Of 260 individuals with autism--on the basis of presence or absence of pets--two groups of 12 individuals and two groups of 8 individuals were assigned to: study 1 (pet arrival after age of 5 versus no pet) and study 2 (pet versus no pet), respectively. Evaluation of social impairment was assessed at two time periods using the 36-items ADI-R algorithm and a parental questionnaire about their child-pet relationships. The results showed that 2 of the 36 items changed positively between the age of 4 to 5 (t(0)) and time of assessment (t(1)) in the pet arrival group (study 1): "offering to share" and "offering comfort". Interestingly, these two items reflect prosocial behaviors. There seemed to be no significant changes in any item for the three other groups. The interactions between individuals with autism and their pets were more--qualitatively and quantitatively--reported in the situation of pet arrival than pet presence since birth. These findings open further lines of research on the impact of pet's presence or arrival in families with an individual with autism. Given the potential ability of individuals with autism to develop prosocial behaviors, related studies are needed to better understand the mechanisms involved in the development of such child-pet relationship.

Full text

Page 1

Does Pet Arrival Trigger Prosocial Behaviors in
Individuals with Autism?
Marine Grandgeorge1,2*, Sylvie Tordjman3, Alain Lazartigues1, Eric Lemonnier1, Michel Deleau4,
Martine Hausberger2
1CHRU de Brest, Ho ˆpital de Bohars, Centre de Ressources Autisme, Bohars, France, 2UMR-CNRS 6552, Laboratoire Ethologie Animale et Humaine, Rennes, France, 3CHRU
Guillaume Re ´gnier, Rennes, France, 4Centre de recherches en psychologie, cognition et communication, Rennes, France
Abstract
Alteration of social interactions especially prosocial behaviors – an important aspect of development – is one of the
characteristics of autistic disorders. Numerous strategies or therapies are used to improve communication skills or at least to
reduce social impairments. Animal-assisted therapies are used widely but their relevant benefits have never been
scientifically evaluated. In the present study, we evaluated the association between the presence or the arrival of pets in
families with an individual with autism and the changes in his or her prosocial behaviors. Of 260 individuals with autism - on
the basis of presence or absence of pets - two groups of 12 individuals and two groups of 8 individuals were assigned to:
study 1 (pet arrival after age of 5 versus no pet) and study 2 (pet versus no pet), respectively. Evaluation of social impairment
was assessed at two time periods using the 36-items ADI-R algorithm and a parental questionnaire about their child-pet
relationships. The results showed that 2 of the 36 items changed positively between the age of 4 to 5 (t0) and time of
assessment (t1) in the pet arrival group (study 1): ‘‘offering to share’’ and ‘‘offering comfort’’. Interestingly, these two items
reflect prosocial behaviors. There seemed to be no significant changes in any item for the three other groups. The
interactions between individuals with autism and their pets were more – qualitatively and quantitatively - reported in the
situation of pet arrival than pet presence since birth. These findings open further lines of research on the impact of pet’s
presence or arrival in families with an individual with autism. Given the potential ability of individuals with autism to
develop prosocial behaviors, related studies are needed to better understand the mechanisms involved in the development
of such child-pet relationship.
Citation: Grandgeorge M, Tordjman S, Lazartigues A, Lemonnier E, Deleau M, et al. (2012) Does Pet Arrival Trigger Prosocial Behaviors in Individuals with
Autism? PLoS ONE 7(8): e41739. doi:10.1371/journal.pone.0041739
Editor: Liane Young, Boston College, United States of America
Received October 12, 2011; Accepted June 28, 2012; Published August 1, 2012
Copyright: ? 2012 Grandgeorge et al. 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: The Adrienne and Pierre Sommer Foundation gave the financial support for this study. The funders had no role in study design, data collection and
analysis, decision to publish, or preparation of the manuscript. The authors declare that they have no financial interests.
Competing Interests: The authors have declared that no competing interests exist.
* E-mail: marine.grandgeorge@chu-brest.fr
Introduction
Impairments of social development associated with communi-
cation deficits, restricted interests and repetitive behaviors
constitute the triad of autistic disorders [1,2]. Individuals with
autism have difficulty interacting with others as well as using and
interpreting nonverbal communication. Social impairments have
been regarded as primary deficits by several authors [3,4] since
they are among the first symptoms of autistic disorders (e.g.
difficulty in participating in imitative or pretend play [5,6]).
Individuals with autism appear to have problems recognizing,
understanding and expressing both feelings and intentions, which
may be due to a lack of ‘‘theory of mind’’ [7]. These individuals
fail to infer mental states and display impairment of abilities to
understand and manage emotions (i.e. understand the other’s
feelings and display appropriate behavior or response [4,8]).
Many strategies, supports or therapies have been aimed at
improving the everyday lives and social interactions of individuals
with autism [9,10] For example, peer-mediated interventions have
proved to be useful through increasing the communicative
interactions and stimulating the development of joint attention
[11]. Complementary and alternative interventions are also
proposed: relaxation, music or activities with animals [12]. Indeed,
since early findings by Levinson’s reporting that a dog could help
in therapy [13], animal assisted therapies (AAT) have been used
largely. Sessions with dogs, horses or dolphins are proposed, and
considered overall as beneficial to improve prosocial behaviors
[14–17]. However, to date, there is no scientific evaluation of their
relevant benefit [18,19]. Moreover, the context in which AAT
occur must be accounted for. The impact of having a pet in
a therapeutic or home setting seems to be different when
encountering humans [20].
More broadly, beneficial effects of having a pet at home have
been reported for improvement of health or well-being of elderly,
isolated women, adults and children [21–26]. It is considered as
a source of non judgmental and positive affection [27,28]. Several
studies suggest that children learn prosocial behaviors through
their interactions with pets [29–31]. These prosocial behaviors
constitute an important aspect of a child’s development. They are
triggered by pet’s presence under certain circumstances (e.g. if
a strong bond is formed, if the pet lives at home or if the human
partner is younger than 6 years old [32–34]). Thus, bonding with
a pet may help with developing some prosocial behaviors. This
hypothesis seems to be consistent with the results of other studies
about the reciprocal behavior that leads an animal to exceptional
PLoS ONE | www.plosone.org1August 2012 | Volume 7 | Issue 8 | e41739

Page 2

learning (e.g. Alex the parrot [35], Hoover the seal [36], Kanzi the
chimpanzee [37]).
In the present study, we hypothesized that a pet at home might
help individuals with autism to develop some prosocial behaviors.
For this, we compared three situations: never owned a pet, owned
a pet since birth (i.e. pet has been part of the individual’s
environment) or owned a pet after the age of 5. The age of 4 to 5 is
considered as a ‘‘key age’’ in autistic disorders [38] because it
seems to be representative of the period when the severity of
autism is the most important. Indeed, older subjects might
outgrow some of the major impairments. Accordingly, there is
a need to avoid focusing on the basis of behavior in childhood.
Consequently, the Autism Diagnostic Interview-Revised (ADI-R)
explains that the most satisfactory compromise is to consider the
age of 4 to 5 as the key age to evaluate the individual’s behavior.
The arrival of a pet in a family has been shown to increase the
level of interactions between family members: they spend more
time together and share joint attention on the new family member
[39]. The new arrival of a pet potentially elicits more attention in
individuals with autism thus leading to a greater chance of
bonding with the pet. We further hypothesized that the arrival of
a pet when the human partner was old enough to ‘‘realize this
change’’ would increase the chances of improving the human’s
prosocial behaviors. For this, we evaluated the individual’s
impairments using the ADI-R [38], to compare two time periods
(i.e. t0at the age of 4 to 5 and t1at the time of assessment), and
a parental questionnaire about the child-pet relationship. Since
direct questioning of individuals with autism can be complicated,
we only used parental reports in this study. According to the
literature, individuals with autism display delays and deficits in the
acquisition of language (e.g. complete absence of functional
communication, impairments in conversation) [40,41]. Parents
are a reliable source of information in regard to the evaluation of
their child’s developmental problems [42,43]. For example, in
a previous study, Siegel et al. [44] found that parental reports
about typical daily behaviors of their children with autism
confirmed observations made during diagnostic play sessions by
trained professionals. In addition, parental reports concerning
both their pets and their child’s behaviors are more reliable than
children’s interviews [45].
Methods
Participants
All the individuals with autism (n=260; 59R/191=; mean age,
1567.5 years old, range from 6 to 34 years old) in this study, came
from the ‘‘Centre de Ressources sur l’Autisme de Bretagne’’ (Bohars,
France) or the child day-care facilities controlled by the Bice ˆtre
and Reims University Hospitals (France). The cognitive and
behavioral assessments were approved by the ethics committee of
Bice ˆtre hospital (the committee was not specific to this study). It is
worth mentioning that the present research was non-invasive and
did not involve pharmacological interventions. Hence, in accor-
dance to the ethics committee, parents (or guardians) gave a simple
verbal consent. All individuals met DSM-IV criteria for autistic
disorders [1]. As part of a routine follow-up of individuals with
autism, the same psychiatrists did the diagnosis and the ADI-R
[38] assessment to confirm the diagnosis.
Cognitive and Behavioral Assessments
The cognitive functioning of individuals with autism from child
day-care facilities of the University Hospitals of Bice ˆtre and Reims
(n=70) was assessed by two psychologists using the age-
appropriate Weschler intelligence scale and the Kaufman K-
ABC [46]. All assessed individuals with autism were cognitively
impaired (mean full scale IQ 6 S.D: 42.163.4, with a range of
40–58; mean verbal IQ 6 S.D: 45.262.3, with a range of 45–57;
mean performance IQ 6 S.D: 45.264.4, with a range of 45–80).
ADI-R was used to assess the behavior of 260 participants with
autism [38]. ADI-R, an extensive, semi-structured parental
interview, was conducted by trained psychiatrists (EL, ST). The
structuring lies in the details of the predetermined codings for each
behavioral item. The interview schedule specifies a variety of
screening questions, the purpose of which is to guide the
interviewer on the content of the response (yes or no responses
from the informant, i.e. parents or guardians, were inadequate).
Behavioral descriptions are coded. The codings have been devised
with the aim of differentiating developmental delay from deviance.
Thus, for each section of the interview, there is an initial
compulsory probe printing. The interviewer should then continue
to ask further questions until he/she is able to make the coding for
each item, for example, using different supplementary probes
proposed in the ADI-R. The ADI-R scale assessed the three major
domains of autistic impairments: (1) reciprocal social interactions,
(2) verbal and non-verbal communication and (3) stereotyped
behavior and restricted interests. The presence of verbal language
is defined as daily, functional and comprehensible use of
spontaneous phrases of at least three words, including at least
sometimes, a verb [38].
The ADI-R algorithm is validated to assess the behavior and is
based on the 4-to-5-year-old period of life. To reveal possible
variations, we compared the ratings at the current period (t1) of the
subset of ADI-R to those at the age of 4 to 5 (t0) [47]. The severity
of behavioral impairments was scored using the subset of ADI-R
items included in the ADI-R algorithm, following the procedure
previously described [48]. We give below the mean score for each
main domain: (1) total reciprocal social interaction (15 items), (2)
total verbal communication and total non-verbal communication
(13 items for non verbal patients, the score was based on 9 items),
(3) total stereotypies (8 items). A score for the combined domain
(social/communication/stereotypies) was calculated and regarded
as a global score of autism severity (Table 1).
Based on direct clinical observation for each participant by an
independent psychiatrist, a diagnosis of autistic disorder was made
according to DSM-IV [1] and ICD-10 [49] criteria and was
confirmed by the ADI-R ratings. We didn’t perform an Autistic
Diagnostic Observation Schedule [50] assessment. It has not been
a routine practice in France before 2008 [51].
Questionnaires on Human-pet Relationships
Parents were interviewed by phone by one of the investigators
(MG) not involved in the ADI-R scoring (i.e. was not aware of the
data values). They were asked to answer a short standardised
questionnaire about the child-pet relationship. No further in-
formation was given before the beginning of the questionnaire.
Verbal informed consent was given by the parents (or guardians)
when the questionnaire on human-pet relationships was filled in.
The consent form explained that the questionnaire and ADI-R
data will be used together. ADI-R evaluation was performed by
the psychiatrist who was not aware of our project. Therefore,
neither parents nor evaluators were influenced by the potential
expectations of the pet’s impact. The interval between the ADI-R
assessment and the questionnaire phase was less than one year.
The data from parental questionnaire were collected between
winter 2006 and winter 2007.
The questionnaire was about the presence (or absence) of pets in
the family at t0(i.e. at the individual’s age of 4 to 5) and at t1(i.e. at
the time of ADI-R assessment). If one or more pets were present,
Pet, Autism and Prosocial Behavior
PLoS ONE | www.plosone.org2August 2012 | Volume 7 | Issue 8 | e41739

Page 3

parents gave information on the species and the pet ownership
duration, as well as their child-pet relationship. The following data
were gathered (yes or no answers): tactile interactions, visual
interactions, play, care (e.g. feeding, walking with the pet, brushing
the pet), time spent with and any privileged relationship. The
above data helped us to evaluate the individual-pet bond.
Moreover, parents specified whether the pet was specially acquired
for their child with autism. Pets were dogs, cats and/or little furry
animals. Half of the pets were acquired for the individuals with
autism.
Study 1: Arrival of a Pet between the Age of 4 to 5 and
the Time of ADI-R Assessment
From the initial pool of 260 participants, we selected two
groups. The first group, Gpet,did not own a pet before t0but
owned at least one afterwards (n=12; pets were dogs, cats and one
hamster). The Gpet individuals were matched with control
individuals – who never owned a pet (G0A, n=12) - for sex, age,
overall level of language (absence/presence of verbal language as
defined by ADI-R criteria in the following section) and history of
epilepsy (Table 1; all chi-square tests and Mann Whitney U-tests
p.0.05). Both the total score and the sub-scores of the ADI-R
were not significantly different (all Mann-Whitney U-tests,
p.0.05; Table 1). The Gpetand G0Amean age was 10.862.3
years old at t1. On the average, we obtained the Gpetparents
responses to the questionnaire 79629 months after the pet’s
arrival.
Study 2: Owned a Pet since Birth
We investigated whether the arrival (or presence) per se of pets
was associated with changes in any of the ADI-R social items. We
selected two groups from the initial pool of 260 participants. The
first group, Galw,owned at least one pet at home since birth (n=8;
pets were dogs, cats and one rabbit). Among the Galwindividuals,
three owned two pets. These Galwindividuals were matched with
control individuals - who never owned a pet (G0B, n=8) - for the
same individual’s characteristics as in study 1 (all chi-square and
Mann Whitney U-tests p.0.05; Table 1). Both the total score and
the sub-scores of the ADI-R were not significantly different (all
Mann-Whitney U-tests, p.0.05; Table 1). The Galwand G0B
mean age was 11.161.9 years old at t1.
Statistical Analyses
Changes between item scores at t0and at t1in each group (Gpet,
Galw, G0Aand G0B) were evaluated using Wilcoxon’s matched-
pairs signed rank test. When a significant effect was observed,
Mann-Whitney test was then applied to evaluate whether or not
the change could be associated with the following variables:
N individual’s gender
N reasons for obtaining the pet(s)
Table 1. Demographic and behavioral characteristics of study groups (G0Aand G0Bnever owned pet; Galwalways owned a pet;
Gpetdidn’t own a pet before the age of 5, but owned at least one at the time of assessment).
GOA(n=12)Gpet(n=12)GOB(n=8)Galw(n=8)
Gender (M/F) 9/39/34/44/4
Age (months; mean 6 SD; range)122.8652.3 (87–180)137.1660.6 (80–185)137.2642.7 (73–201)128.6644.4 (75–200)
Overall level of language1
9/3 9/3 2/62/6
Epilepsy (yes/no)8/08/0 1/110/12
ADI-R at t0(mean 6 SD)
Total 44.565.344.664.545.861.743.163.0
Reciprocal social interactions23.263.122.163.6 25.061.921.962.1
Non verbal Communication10.362.2 11.061.710.960.69.961.5
Verbal Communication2
15.962.616.961.017.360.613.561.8
Restricted and repetitive behaviors5.461.15.660.97.861.39.961.0
ADI-R at t1(mean 6 SD)
Total38.764.538.665.039.867.038.865.9
Reciprocal social interactions22.163.618.863.518.664.519.163.6
Non verbal Communication 7.162.010.361.910.362.97.562.8
Verbal Communication2
11.561.914.961.5 14.562.010.462.2
Restricted and repetitive behaviors5.161.2 4.860.9 6.661.4 9.361.5
Mann Whitney U-test at t0
U p-valueU p-value
Total 1520.93181.50.170
Reciprocal social interactions 1570.70781 0.189
Non verbal Communication138.5 0.52174 0.564
Verbal Communication2
133.50.353 720.554
Restricted and repetitive behaviors1480.931 740.560
1Absence/presence of verbal language as defined according to the ADI-R criteria.
2Scores corresponded to children who had a verbal language according to the ADI-R criteria.
doi:10.1371/journal.pone.0041739.t001
Pet, Autism and Prosocial Behavior
PLoS ONE | www.plosone.org3August 2012 | Volume 7 | Issue 8 | e41739

Page 4

N presence of different pets
N type of human-pet interactions (including privileged relationship)
N life setting (i.e. urban or rural)
Spearman’s rank order correlation assessed the correlation
between the individual’s age or IQ score and his or her ADI-R
item score. Since 36 tests were performed at both t0and t1, in
order to avoid false positive due to chance, Bonferroni correction
for multiple comparison was applied systematically (p,0.0014).
Results
Study 1
Comparison of ADI-R assessment between t0and t1revealed
significant changes in two of the 36 items in the Gpet. Thus, Gpet
had a lower deficit score for the items ‘‘offering to share’’, e.g.
sharing food or toys with parents or other children (Wilcoxon test:
ZGpet=21 p,0.0014; Fig. 1) and ‘‘offering comfort’’, e.g. reassur-
ing parents or peers who were sad or hurt (Wilcoxon test:
ZGpet=21 p,0.0014; Fig. 2). No changes were observed for the
control individuals (Wilcoxon tests: ZG0A=3, ZG0A=6 p.0.05 in
both cases; Fig. 1, Fig. 2). In Gpetand G0A, neither the total scores
of ADI-R at t0 and t1 (Wilcoxon tests: ZGpet=4 p=0.011;
ZG0A=15 p=0.065) nor the sub-scores in the main domains (all
Wilcoxon tests: p.0.0014) were statistically different at p,0.0014.
Score differences between t0and t1were neither correlated with
individual’s age (all Spearman’s rank order correlation p.0.05)
nor affected by gender, life setting, presence of different pets, and
type of human-pet interaction (all Mann Whitney U-tests p.0.05).
Interestingly, whether the parents had acquired the animal for
their child or for the family revealed no significant difference in
ADI-R scores (Mann Whitney U-test=53.5 p.0.05), indicating
that the results were not influenced by the parents expectations on
the pet’s impact. In addition, communication and non-social
aspects (e.g. scores for repetitive behavior and stereotyped patterns)
were not affected by the pet’s arrival (all Wilcoxon tests p.0.05).
No significant correlation (Spearman’s rank order correlation,
p.0.05) between the items ‘‘offering comfort’’ or ‘‘offering to
share’’ and IQ scores (verbal IQ, performance IQ and full IQ) was
observed.
Parental questionnaire offered some information about the
interaction type Gpetindividual had with his or her pet (Table 2).
Tactile interactions were the most reported (i.e. 75%; n=9),
followed by time spent with the pet (n=8), play (n=7) and visual
interactions (n=7). Care was the least reported item (n=6). Thus,
seven Gpetindividuals were considered by their parents as having
a privileged relationship with their pets. Among the five remaining
individuals, three owned a cat and two owned a dog.
Study 2
No significant change was observed for individuals with autism
who owned a pet since birth or for control individuals (Galwand
GOB; all Wilcoxon test p.0.05; Fig. 1, Fig. 2). In Galwand GOB,
neither the total scores of ADI-R at t0and t1(Wilcoxon tests:
ZGalw=9 p=0.447; ZG0B=11 p=0.363) nor the sub-scores in
the four domains (all Wilcoxon tests: p.0.05) were statistically
different at p,0.0014.
Here again, an exploration of the parental questionnaire offered
some information about the interaction type Galwindividual had
with his or her pet. Few individuals were reported as interacting
with their pets (Table 2). Care and play were not mentioned. Two
individuals spent time with their pet, four had tactile interactions
and five had visual interactions. Only three Galwindividuals were
considered by their parents as having privileged relationships with
their pets (i.e. three dogs). However, two of the three individuals
who owned the same pet since birth, neither interacted nor
bonded with it (i.e. all items were reported as absent).
Discussion
Comparison of ADI-R assessment between Gpetand Galwat two
different time periods revealed significant changes in ADI-R scores
only in the group experiencing the pet arrival in their homes.
However, these changes were limited to two ADI-R items,
‘‘offering to share’’ and ‘‘offering comfort’’. These findings suggest
an improvement in prosocial behaviors of the individuals with
autism. These prosocial behaviors are mainly impaired in
individuals with autism [1,52]. The absence of a significant
correlation with IQ scores might imply that these changes were
not related to the level of cognitive functioning. Interestingly, the
individual-pet interactions (i.e. bonding) were more - qualitatively
and quantitatively - reported in the case of pet arrival than pet
presence since birth. To our knowledge, this is the first study
showing an association between pet arrival and changes in
prosocial behaviors. Our study follows the footsteps of the human-
pet reports on the improvement of prosocial behaviors in
individuals with typical development [53,54].
On the Significance of Changes
On the one hand, two main possible explanations could account
for these findings.
First, parents may have acquired a pet because they believed
that it would improve the prosocial behaviors of their children
with autism. In this case, their responses to the ADI-R could be
biased. The following findings strongly suggest that this was not
the case:
1. Only 6 pets (of the 15 pets in Gpet) were acquired especially
for the individuals with autism; the others were acquired for
another family member. Changes in the prosocial behaviors
were observed in both cases. Thus, these changes were not
related to parental expectations.
2. This ‘‘pet study’’ (and its related questionnaire) began after the
ADI-R completion. This suggests that the parents were not
aware of the possible pet impact at t1.
3. Improvement was found only for two of the 36 items, further
indicating the non-bias character of parent’s responses.
The second explanation is that the arrival of a pet may have
triggered a change in the individuals’ ‘‘perception of the social
world’’. Pets are supposed to enhance different skills in children
with typical development such as self-esteem, socio-emotional
development and empathy [32,33,54]. According to several
authors, children with typical development seem to learn prosocial
behaviors through their interactions with pets (e.g. sharing with
and stroking the pet) [30,55]. Could this also be the case for
individuals with autism? Only observational studies can reveal how
individuals with autism interact with their pet and whether
somehow they develop skills to understand pet’s behaviors or
needs [56].
On the other hand, it is not very surprising that other ADI-R
items did not change, not even those related to the prosocial
behaviors. Since verbal exchanges with pets are excluded, we
would expect no changes in language skills whereas parents can
indeed influence such skills [57]. Moreover, other studies confirm
that animals neither influence motor skills nor reduce restricted
behaviors in children with autism [16].
Pet, Autism and Prosocial Behavior
PLoS ONE | www.plosone.org4August 2012 | Volume 7 | Issue 8 | e41739

Page 5

Potential Mechanisms
Numerous theories have been proposed to explain the pet’s
influence on human life (for a review, see [58]). Animals are
animates, thus differ from inanimates in regard to many biological
characteristics such as motion or sensory properties. Specifically,
animates are beings that know, perceive, learn and think. These
abilities make them appealing ([59] in [60]).
Friedman et al. [61] proposed the bio-psycho-social model that
considers pets could reduce loneliness and thus could also be
considered as ‘‘transitional objects’’ especially for the children
[31,62]. Pets may also be considered as ‘‘distracters’’. Brickel [63]
and more recently Odendaal [64] proposed to explain this
phenomenon by the attention-shift theory. They stated that when
a human is in a stressful situation, a pet seems to distract him/her
from the anxiogenic stimulus (e.g. unknown situations in the case
of people with autism). Animal’s presence triggers human’s
attention-shift. Attention-shift offered by a pet under repeated
exposure to a stressful situation, leads to a decrease in anxiety.
Therefore, a family pet may also become a source and a center of
attention that could be useful in individual’s learning.
On the one hand, the presence of a pet can have a direct
influence. When a human and a pet are interacting, each partner
uses signals emitted by the other to adjust their behavior: the
behavior of one influences the response of the other (e.g. between
a dog and a child [65–67]). A bond or a relationship emerges from
these series of interactions where both partners have expectations
on the next interaction on the basis of the previous ones [68].
Thus, as stated by Filiatre et al. [65] the pet’s behavior ‘‘could
contribute to the acquisition by the child of a more structured and
more socially efficient behavioral repertoire’’. Moreover, the
attitudes that children display towards pets have an impact on
their prosocial and social behaviors [34,69]. On the other hand,
a pet can have an indirect influence on children through the
family. Indeed numerous parents state that pets can be precious
tools with which they educate their children [29,70,71]. For
example, Beck et al [72] showed that an increased knowledge
about wild birds after a ten-week educational home-based
program for feeding was associated with parental involvement.
People with autism have been shown to be less sensitive to
human voices [73] or faces [74] than to other environmental
stimuli. To our knowledge, little is known about how they perceive
animals’ characteristics, but they are quite able to classify their
animal preferences based on pictures [75]. Using a task based on
sorting by preference, Celani [76] showed that children with
Figure 1. Item scores of ‘‘offering to share’’ at t0(4-to-5-years old; in grey) and t1(current period; mean age: 129.9655.8 months
old; in black) for G0A(group with no pet in the family), Gpet(group with a pet arriving after the child’s 5thbirthday), G0B(group with
no pet in the family) and Galw(group always with at least one pet at home since birth). Higher the score, more significant was the
‘‘offering to share’’ (e.g. sharing food or toys with parents or other children).
doi:10.1371/journal.pone.0041739.g001
Pet, Autism and Prosocial Behavior
PLoS ONE | www.plosone.org5August 2012 | Volume 7 | Issue 8 | e41739

Page 6

autism chose pictures with an animal (e.g. dog, cat) rather than the
ones with objects. At last, some authors explained that the affinity
of people with autism for pets comes from animal’s multisensory
characteristic. In addition, according to these authors, an animal’s
behavior seems to be easier to decode and to predict than that of
a human partner [14,17].
Pet Presence versus Arrival
One intriguing finding was that similar results were observed for
the individuals who were in the presence of a pet from birth and
those who never owned a pet. Changes were only observed in the
group where the pet arrived after the age of 5. Different
hypotheses are possible and are explored below.
When the pet was reported to be present since the individual’s
birth, one would expect a cumulative effect of its presence. We
cannot exclude this effect even if the ADI-R did not clearly explore
it here (e.g. neither a too low nor a specific effect was explored by
ADI-R items). However, we proposed an alternative explanation.
Individuals with autism may usually avoid unfamiliar social
partners and display diminished interest in novelty [1]. But under
certain circumstances, children with autism prefer new stimuli
rather than familiar ones [77]. The presence of a pet may be
a mere ‘‘additional’’ element of the environment, therefore not
attracting special attention. This is consistent with our parental
Figure 2. Item scores of ‘‘offering comfort’’ at t0(4-to-5-years old; in grey) and t1(current period, mean age: 129.9655.8 months
old; in black) for G0A(group with no pet in the family), Gpet(group with a pet arriving after the child’s 5thbirthday), G0B(group with
no pet in the family) and Galw(group always with at least one pet at home since birth). Higher the score, more significant was the
impairment ‘‘offering comfort’’ (e.g. reassuring parents or peers who were sad or hurt). Comparisons were performed using Wilcoxon’s matched-pairs
signed ranks tests (Significant threshold: p,0.0014).
doi:10.1371/journal.pone.0041739.g002
Table 2. Number of individuals with autism who display
different types of relationships with their pet according to
parents.
Presence of each itemGpet(n=12)Galw(n=8)
Tactile interactions92 [4]
Visual interactions73 [5]
Play7 0 [2]
Care60 [0]
Time spent with pet83 [3]
Privileged relationship72 [2]
As three individuals of Galwowned two pets, the first number showed the first
pet’s answer and the second number in brackets showed the second pet’s
answer.
doi:10.1371/journal.pone.0041739.t002
Pet, Autism and Prosocial Behavior
PLoS ONE | www.plosone.org6 August 2012 | Volume 7 | Issue 8 | e41739

Page 7

questionnaire revealing that few of these individuals (Galw)
developed a real bond with the pet in comparison to the other
group (i.e. Gpet, pet arrival). For example, only a quarter of Galw
individuals had a privileged relationship with their pet. The sole
presence of the pet did not confer benefit for the individuals with
autism. Such situation was previously reported in the children with
typical development : the quality of relationship with their own pet
appears to be a direct determinant of their socio-emotional
development [33] and ‘‘pet bonding’’ is a stronger determinant of
pet-associated benefits than the sole pet ownership [78]. If we take
a look at the other side, the pet may also have formed a preferential
bond with another member of the family and therefore been less
demanding on the individual with autism.
The other non-exclusive possibility is that the arrival of a pet
strengthens the cohesion of the family and increases the levels of
interactions between their members. Pet’s arrival plays an even
more important role in the lives of children who have inadequate
or destructive family and social environments [79]. Most families
acquiring a pet experienced an increase in quantity and quality of
time spent together and felt happier after pet’s arrival [39]. This
situation might be due to the collective attention on the new pet.
This new pet arrival might induce an increased interest of the
individuals towards the pet and/or their involvement in the
family’s interactions. Cain [39] talked about the ‘‘triangling’’
process initiated by the pet (i.e. structuring and promoting
interactions between two humans).
In our study, playing with the pet was reported by seven of the
parents in Gpetwhereas only two of the parents in Galwnoticed it.
This behavior is a powerful means by which children master skills
that are important for their development [80]. Playing with a pet is
a complex behavior, sometimes involving object manipulation as
a means for practice and mastery of action schemas (i.e.
sensorimotor play) or child’s ability for mental representation.
Thus, it provides a child with means of practicing and un-
derstanding the events of his or her social world (i.e. pretend play)
[81]. These behaviors are not only observed in humans but also in
human-pet interactions [55,82]. Such interactions may have some
positive outcome: playing with a dog during pet therapy had
beneficial impact on hospitalized children [83]. This implies that
playing with a pet may be beneficial to individuals with autism.
Interestingly, in our study, taking care of the pet was reported
by half of the parents in Gpetwhereas none of the parents in Galw
noticed it. Our finding infers the positive influence of pet arrival on
parental support in the development of individuals with autism.
Previous studies have shown that parents use pets to teach their
children how to take care of pets by giving them age-appropriate
tasks [29]. With parental support, the child involvement towards
a pet may influence his/her socio-emotional development [84].
Finally individuals with autism may be sensitive to an overall
change in their social sphere. Therefore the changes may be
related merely to the overall family functioning rather than the
sole pet arrival. This however would not explain why only two
precise items were affected and not the others.
Conclusion
This study reveals that in individuals with autism, pet arrival in
the family setting may bring about changes in specific aspects of
their socio-emotional development. It suggests the improvement of
some prosocial behaviors in such individuals under certain
circumstances. Thus, it offers a ‘‘window of opportunity’’ to
future longitudinal developmental studies to further confirm these
findings and explain their underlying mechanisms. Given the
current state of knowledge, we suggest further research exploring
our hypothesis on the association between the arrival of a new pet
and the change in a family dynamic to evaluate the impact of
another child’s arrival.
Our study has limitations that need to be noted. Both our study
design and its lack of power (40 individuals from an initial cohort
of 260 participants) didn’t allow us to clarify the exact role of pets
in the families who already owned pets. Nevertheless these first
results open interesting lines of research exploring the efficacy of
animals employed in AAT settings. Further studies with larger
sample sizes (e.g. including more control groups) are needed to
clarify the exact role of pets in this context.
Acknowledgments
We are thankful to Dr. Ann Cloarec, researcher, Ethos laboratory and
Zarrin Alavi, (for her pertinent advice) medical writer and translator, Brest
University Hospital, Department of Internal Medicine and Chest Diseases;
INSERM CIC 0502, to Pr Michel Botbol, CHRU Brest, to families for
their participation, to the Fondation Sommer for their support and the
French GIS CCS (Groupe d’Inte ´re ˆt Scientifique - Comportement Cerveau
et Socie ´te ´)
Author Contributions
Conceived and designed the experiments: MG MH AL ST MD EL.
Performed the experiments: MG MH EL. Analyzed the data: MG MH EL.
Contributed reagents/materials/analysis tools: MG MH EL. Wrote the
paper: MG MH ST EL.
References
1. American Psychiatric Association (1994) Diagnostic and Statistical Manual of
Mental Disorders. Washington.
2. Wing L, Gould J (1979) Severe impairements of social interaction and associated
abnormalities in children: Epidemiology and classication. Journal of Autism and
Developmental Disorders 9: 11–29.
3. Baron-Cohen S (1995) Mindblindness: An Essay on Autism and Theory of
Mind. Cambridge: MIT Press. 197 p.
4. Mundy P (1995) Joint attention and social-emotional approach behavior in
children with autism. Development and Psychopathology 7: 63–82.
5. Osterling JA, Dawson G, Munson JA (2002) Early recognition of 1-year-old
infants with autism spectrum disorder versus mental retardation. Development
and Psychopathology 14: 239–251.
6. Baranek GT (1999) Autism during infancy: A retrospective video analysis of
sensory-motor and social behaviors at 9–12 months of age. Journal of Autism
and Developmental Disorders 29: 213–224.
7. Baron-Cohen S, Leslie AM, Frith U (1985) Does the autistic-child have a theory
of mind. Cognition 21: 37–46.
8. Kasari C, Sigman M, Mundy P, Yirmiya N (1990) Affective sharing in the
context of joint attention interactions of normal, autistic, and mentally-retarded
children. Journal of Autism and Developmental Disorders 20: 87–100.
9. McConnell SR (2002) Interventions to facilitate social interaction for young
children with autism: Review of available research and recommendations for
educational intervention and future research. Journal of Autism and De-
velopmental Disorders 32: 351–372.
10. Wong HHL, Smith RG (2006) Patterns of complementary and alternative
medical therapy use in children diagnosed with autism spectrum disorders.
Journal of Autism and Developmental Disorders 36: 901–909.
11. Pierce K, Schreibman L (1997) Multiple peer use of pivotal response training to
increase social behaviors of classmates with autism: Results from trained and
untrained peers. Journal of Applied Behavior Analysis 30: 157–160.
12. Gasalberti D (2006) Alternative Therapies for Children and Youth With Special
Health Care Needs. Journal of Pediatric Health Care 20: 133–136.
13. Levinson BM (1962) The dog as a ‘‘co-therapist’’. Mental Hygiene 179: 46–59.
14. Redefer LA, Goodman JF (1989) Pet-facilitated therapy with autistic children.
Journal of Autism and Developmental Disorders 19: 461–467.
15. Nathanson DE, DeFaria S (1993) Cognitive improvement of children in water
with and without dolphins. Anthrozoo ¨s 65: 17–29.
16. Bass M, Duchowny C, Llabre M (2009) The Effect of Therapeutic Horseback
Riding on Social Functioning in Children with Autism. Journal of Autism and
Developmental Disorders 39: 1261–1267.
17. Martin F, Farnum J (2002) Animal-assisted therapy for children with pervasive
developmental disorders. Western Journal of Nursing Research 24: 657–670.
Pet, Autism and Prosocial Behavior
PLoS ONE | www.plosone.org7 August 2012 | Volume 7 | Issue 8 | e41739

Page 8

18. Barker SB, Wolen AR (2008) The Benefits of Human-Companion Animal
Interaction: A Review. West Lafayette, IN. Univ Toronto Press Inc. pp.487–
495.
19. Katcher A (2000) The future of education and research on the human-animal
bond and animal-assisted therapy Part B: Animal-assisted therapy and the study
of human-animal relationships: Discipline or bondage? Context or transitional
object? In: A F, editor. Handbook on animal-assisted therapy: Theoretical
foundations for guidelines and practice. San Diego: Academic Press. pp.461–
473.
20. Burrows KE, Adams CL, Spiers J (2008) Sentinels of Safety: Service Dogs
Ensure Safety and Enhance Freedom and Well-Being for Families With Autistic
Children. Qualitative Health Research 18: 1642–1649.
21. Anderson WP, Reid CM, Jennings GL (1992) Pet Ownership And Risk-Factors
For Cardiovascular-Disease. Medical Journal of Australia 157: 298–301.
22. Friedmann E, Katcher AH, Lynch JJ, Thomas SA (1980) Animal companions
and one-year survival after discharge from a coronary-care unit. Public Health
Reports 95: 307–312.
23. Turner DC, Rieger G, Gygax L (2003) Spouses and cats and their effects on
human mood. Anthrozoos 16: 213–228.
24. Beck AM, Meyers NM (1996) Health enhancement and companion animal
ownership. Annual Review of Public Health 17: 247–257.
25. Serpell JA (1991) Beneficial-effects of pet ownership on some aspects of human
health and behavior. Journal of the Royal Society of Medicine 84: 717–720.
26. Paul ES, Serpell JA (1996) Obtaining a new pet dog: Effects on middle childhood
children and their families. Applied Animal Behaviour Science 47: 17–29.
27. Beck AM, Katcher AH (1984) A new look at pet-facilitated therapy. Journal of
the American Veterinary Medical Association 184: 414–421.
28. Bryant BK (1990) The richness of the child pet relationship: A consideration of
both benefits and costs of pets to children. Anthrozoos 3: 253–261.
29. Endenburg N, Baarda B (1996) The Role of Pets in Enhancing Human Well-
being: Effects on Child Development. In: Robinson I, editor. The Waltham
Book of Human-Animal Interactions: Benefits and Responsibilities of Pet
Ownership. pp.7–17.
30. Filiatre JC, Millot JL, Montagner H., Eckerlin A, Gagnon AC (1988) Advances
in the study of the relationship between children and their pet dogs. Anthrozo ¨os
2: 22–32.
31. George H (1988) Child therapy and animals. In: CE S, editor. Innovative
interventions in child and adolescent therapy. New York: John Wiley. pp.400–
418.
32. Kidd AH, Kidd RM (1985) Children’s attitudes toward their pets. Psychological
Reports 57: 15–31.
33. Melson GF (1991) Children’s attachment to their pets: Links to socio-emotional
development. Children’s Environments Quarterly 82: 55–65.
34. Bailey C (1988) Exposure of Preschool Children to Companion Animals: Impact
on Role Taking Skills. Dissertation Abstracts International 48: 1976.
35. epperberg IM, Brezinsky MV (1991) Acquisition of a relative class concept by an
african grey parrot (Psittacus erithacus) - Discriminations based on relative size.
Journal of Comparative Psychology 105: 286–294.
36. Ralls K, Fiorelli P, Gish S (1985) Vocalizations and vocal mimicry in captive
harbor seals, Phoca vitulina. Canadian Journal of Zoology 63: 1050–1056.
37. Savage-Rumbaugh S, Lewin R (1994) Kanzi: The Ape at the Brink of the
Human Mind: John Wiley & Sons Inc. 299 pages p.
38. Lord C, Rutter M, Le Couteur A (1994) Autism Diagnostic Interview-Revised:
a revised version of a diagnostic interview for caregivers of individuals with
possible pervasive developmental disorders. J Autism Dev Disord 24: 659–685.
39. Cain AO (1985) Pets as family members. Marriage & Family Review 8: 5–10.
40. Tager-Flusberg H (2000) Understanding the Language and Communicative
Impairments in Autism. New York: Academic Press.
41. Tager-Flusberg H, Caronna E (2007) Language disorders: Autism and other
pervasive developmental disorders. Pediatric Clinics of North America 54: 469–
+.
42. Glascoe FP, Foster M, Wolraich ML (1997) An economic analysis of
developmental detection methods. Pediatrics 99: 830–837.
43. Glascoe FP (2005) Screening for developmental and behavioral problems.
Mental Retardation and Developmental Disabilities Research Reviews 11: 173–
179.
44. Siegel B, Anders TF, Ciaranello RD, Bienenstock B, Kraemer HC (1986)
Empirically derived subclassification of the autistic syndrome. Journal of Autism
and Developmental Disorders 16: 275–293.
45. Bryant B (1986) The relevance of family and neighborhood animals to social-
emotional development in middle childhood. Boston.
46. Anastasi A (1988) Psychological Testing. New York: Macmillan. 818 p.
47. Lord C, Pickles A, McLennan J, Rutter M, Bregman J, et al. (1997) Diagnosing
autism: Analyses of data from the autism diagnostic interview. Journal of Autism
and Developmental Disorders 27: 501–517.
48. Tordjman S, Gutknecht L, Carlier M, Spitz E, Antoine C, et al. (2001) Role of
the serotonin transporter gene in the behavioral expression of autism. Molecular
Psychiatry 6: 434–439.
49. World Health Organization (1994) The composite international diagnostic
interview, Version 1.1. Geneva: Researcher’s manual.
50. Lord C, Rutter M, Goode S, Heemsbergen J, Jordan H, et al. (1989) Autism
diagnostic observation schedule: a standardized observation of communicative
and social behavior. Journal of Autism and Developmental Disorders 19: 185–
212.
51. Roge ´ B, Fombonne E, Fremolle J, Arti E (2009) Adaptation franc ¸aise de
l’ADOS: Echelle d’observation pour le diagnostic de l’autisme: Editions Hogrefe.
52. Travis LL, Sigman M (1998) Social deficits and interpersonal relationships in
autism. Mental Retardation and Developmental Disabilities Research Reviews
4: 65–72.
53. Furman W (1989) The development of children’s social networks. In: Belle D,
editor. Children’s Social Networks and Social Support. New-York: Wiley. 151–
172.
54. Hills A (1995) Empathy and belief in the mental experience of animals.
Anthrozoo ¨s 8: 132–142.
55. Melson GF (2005) Why the wild things are; animals in the lives of children:
Harvard University Press. 236p.
56. Grandgeorge M (2010) Could the bond to an animal allow social and cognitive
recovery in children with autism? Rennes: University Rennes 2. 357p.
57. Grandgeorge M, Hausberger M, Tordjman S, Deleau M, Lazartigues A, et al.
(2009) Environmental Factors Influence Language Development in Children
with Autism Spectrum Disorders. PLoS ONE 4: e4683.
58. Maurer M, Delfour F, Trudel M, Adrien JL (2011) L’enfant avec un autisme et
l’animal dans un lien signifiant : des possibilite ´s d’interventions the ´rapeutiques.
La psychiatrie de l’enfant 54: 575–609.
59. Gelman R, Spelke ES (1981) The development of thoughts about animate and
inanimate objects: Implications for research on social cognition. In: JH Flavell, L
Ross, editors. Social cognition. New York: Academic. pp.43–66.
60. Poulin-Dubois D, Frenkiel-Fishman S, Nayer S, Johnson S (2006) Infants’
Inductive Generalization of Bodily, Motion, and Sensory Properties to Animals
and People. Journal of cognition and development 7: 431–453.
61. Friedmann E, Katcher AH, Thomas SA, Lynch JJ, Messent PR (1983) Social-
Interaction And Blood-Pressure - Influence Of Animal Companions. Journal of
Nervous and Mental Disease 171: 461–465.
62. Triebenbacher SL (1998) Pets as transitional objects: Their role in children’s
emotional development. Psychological Reports 82: 191–200.
63. Brickel CM (1982) Pet-Facilitated Psychotherapy - A Theoretical Explanation
Via Attention Shifts. Psychological Reports 50: 71–74.
64. Odendaal JSJ (2000) Animal-assisted therapy - magic or medicine? Journal of
Psychosomatic Research 49: 275–280.
65. Filiatre JC, Millot JL, Montagner H (1986) New data on communication
behavior between the young-child and his pet dog. Behavioural Processes 12:
33–44.
66. Millot JL, Filiatre JC (1986) The behavioral sequences in the communication-
system between the child and his pet dog. Applied Animal Behaviour Science 16:
383–390.
67. Millot JL, Filiatre JC, Gagnon AC, Eckerlin A, Montagner H (1988) Children
and their pet dogs: how they communicate. Behavioural Processes 17: 1–15.
68. Hinde R (1979) Towards Understanding Relationships. London: Academic
Press.
69. Poresky RH (1996) Companion animals and others factors affecting young
children’s development. Anthrozoos 9: 159–168.
70. Salomon A (1981) Animals and children - The role of the pets. Canadas Mental
Health 29: 9–13.
71. Macdonald A (1981) The pet dog in a home: a study of interactions. In: Fogle B,
editor. Interrelations between people and pets. Springfield, Illinois: Charles C.
Thomas.
72. Beck AM, Melson GF, da Costa PL, Liu T (2001) The educational benefits of
a ten-week home-based wild bird feeding program for children. Anthrozoos 14:
19–28.
73. Gervais H, Belin P, Boddaert N, Leboyer M, Coez A, et al. (2004) Abnormal
cortical voice processing in autism. Nature Neuroscience 7: 801–802.
74. Osterling J, Dawson G (1994) Early recognition of children with autism - a study
of 1st birthday home videotapes. Journal of Autism and Developmental
Disorders 24: 247–257.
75. Maurer M, Delfour F, Wolff M, Adrien JL (2010) Dogs, Cats and Horses: Their
Different Representations in the Minds of Typical and Clinical Populations of
Children. Anthrozoos 23: 383–395.
76. Celani G (2002) Human beings, animals and inanimate objects - What do people
with autism like? Autism 6: 93–102.
77. Kenzer AL, Bishop MR (2011) Evaluating preference for familiar and novel
stimuli across a large group of children with autism. Research in Autism
Spectrum Disorders 5: 819–825.
78. Poresky RH, Hendrix C (1989) Companion animal bonding, children’s home
environments and young children’s social development. Kansas City.
79. Blue GF (1986) The value of pets in children’s lives. Childhood Education 63:
84–90.
80. Bruner JS (1972) Nature and uses of immaturity. American Psychologist 27: 687–
708.
81. Piaget J (1962) Play, dreams, and imitation in childhood. New York: Norton.
82. Montagner H (1995) L’enfant, l’animal et l’e ´cole: AFIRAC. 222 p.
83. Kaminski M, Pellino T, Wish J (2002) Play and Pets: The Physical and
Emotional Impact of Child-Life and Pet Therapy on Hospitalized Children.
Children’s health care 31: 321–335.
84. Haggerty Davis J, Gerace L, Summers J (1989) Pet-care management in child-
rearing families. Anthrozoos 2: 189–193.
Pet, Autism and Prosocial Behavior
PLoS ONE | www.plosone.org8 August 2012 | Volume 7 | Issue 8 | e41739