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CAB Reviews 2020 15, No. 046
Emotional contagion and its implications for animal welfare
Sandra Düpjan*, Annika Krause*, Liza R. Moscovice* and Christian Nawroth*
Address: Institute of Behavioural Physiology, Leibniz Institute for Farm Animal Biology (FBN), 18196 Dummerstorf, Germany.
Correspondence: Christian Nawroth. Email: nawroth.christian@gmail.com
*These authors contributed equally to this work and appear in alphabetical order.
ORCID information: Christian Nawroth (orcid: 0000-0003-4582-4057); Liza R. Moscovice (orcid: 0000-0002-1823-7757)
Received: 03 April 2020
Accepted: 02 July 2020
Abstract
Altering one’s emotional state in response to the emotional expressions of others, called emotional
contagion, is a well-studied phenomenon in humans and many nonhuman animals. Here we describe
the methods that are typically used to assess changes in the emotional state in demonstrators and
the transmission of emotions to naïve observers. We then review the evidence for the transmission
of positive and negative emotions in farm animals. We conclude by highlighting examples of how a
better understanding of emotional contagion in farm animals can lead to novel and innovative
interventions to improve their welfare.
Keywords: affective state, arousal, cognition, emotions, empathy, farm animals, livestock, mood, valence
Review Methodology:
Definition and descriptions
Affective states, referring to short-term emotions and
long-term moods, are inherently ‘personal’ experiences of
individuals. However, individuals often live in social groups,
and there is increasing evidence that social partners are
highly sensitive to indicators of affective states in others,
whether these are expressed as signals in a voluntary act
of communication or as involuntary cues. This sensitivity to
others’ emotional states can lead to emotional contagion,
which is dened as the tendency to alter one’s behavioral
(e.g., postures, vocalizations) and physiological (e.g., heart
rate, hormone levels) states in response to the emotional
expressions of others (reviewed by [1]), reecting changes
in the observer’s affective state. Emotional contagion is
suggested to have its evolutionary origins in the subco nscious,
automatic mimicry of behavioral expressions, including
emotional ones, and has been described by two conceptually
distinct and empirically separable components, namely
socially-mediated arousal, referring to an observer’s
heightened sensitivity in response to changes in a
demonstrator, and behavioral/physiological contagion,
referring to the matching of the demonstrator’s behavioral
or physiological state [2]. It is a highly efcient way for
tness-relevant information to spread through a social
group, and is widely considered the most basic form of
empathic responses [3]. While emotional contagion does
not involve all of the cognitive and emotional systems that
we associate with human empathy, it is highly relevant given
that it is widespread in animals [4] and has applied value
for animal welfare, especially under captive conditions [5].
Emotional contagion implies that it is not only important to
consider the effect of a treatment on an individual, but also
the extent to which its group members may be affected
by its response, even if they were not subjected to the
treatment themselves.
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State of the art
Research into emotional contagion in animals integrates
multiple behavioral, autonomic, and/or physiological measures
to provide evidence for the transmission not only of arousal
but also of valence (i.e., the positive or negative perception of
a situation [6]). In typical paradigms, a naïve individual directly
observes a conspecic demonstrator during a situation that
induces a change in the demonstrator’s emotional state. The
observer has access to visual, olfactory, and/or auditory cues,
but usually is not allowed to directly interact with the
demonstrator [7]. Measuring the transmission of emotions
requires methods to assess changes in emotional states in
demonstrators, as well as evaluating whether observers
exhibit corresponding changes that indicate a similarly
valenced (e.g., pleasant vs. unpleasant) emotional response.
Indicators of emotions that have been studied in the context
of emotional contagion include functionally relevant behaviors
that accompany emotional states, such as approach and
avoidance, freezing, vocalizations, tail wagging, ear postures, or
facial expressions [7, 8]. Autonomic indicators such as changes
in heart rate (HR) and its variability (HRV) and surface eye
temperature are also commonly used [2, 9]. In addition,
concentrations of neuroendocrine hormones such as cortisol
and oxytocin can change rapidly in blood, saliva, or urine in
response to positive or negative stimuli (e.g., [10]). The
integration of multiple behavioral and physiological measures
can provide insights into both the arousal and valence aspects
of emotional contagion.
Evidence for emotional contagion is widespread across
animal taxa, but primarily restricted to the transmission of
negative emotional states such as fear, pain, or distress ([2],
see Table 1 [7, 9]). This may be in part because negative
emotional states are easier to detect, due to their more
direct link to survival and tness, but it also may reect the
more well-developed methods for identifying negative
emotional states in animals (reviewed in [5]). While studies
of emotional contagion in farm animals have lagged behind
other species (see Fig. 1), the available evidence suggests
that farm animals may also transmit both negative and
positive emotions ([8, 11], see also Table 1). Modications
to standard paradigms suggest that emotions can even be
transmitted to naïve individuals who do not directly
observe demonstrators receiving a positive or negative
treatment, but merely interact with them beforehand when
they are anticipating the stimulus [11, 12], or afterward when
they are returned to their social groups [8, 13]. For example,
naïve pigs responded differently to being reunited with group
mates who had experienced a negative or positive treatment.
They exhibited decreased activity and exploration when
group mates received a negative treatment, and increased
social contact and exploration when group mates received a
positive treatment ([8], see also Table 1). This suggests that
the impact of a specic treatment on an individuals’ emotional
state can last well beyond the treatment itself, and can also
affect the emotional state of group members.
Implications for farm animals and outlook for
future studies
Emotions, both positive and negative, have the potential to
spread across a group of individuals via emotional
contagion. This phenomenon is especially important from a
farm animal welfare perspective, since it suggests that even
brief husbandry interventions can have positive or negative
impacts on the affective states of individuals who anticipate
and experience them, as well as on the rest of their social
group. Although research on transmission of emotions in
applied ethology is still in its infancy (see Fig. 1), the available
Figure 1. Number of publications covering emotional contagion in humans and animal species other than farm animals
Sandra Düpjan et al. 3
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Table 1. Overview of behavioral and physiological responses* of demonstrators and observers in different testing paradigms for emotional contagion in farm animals.
Reference Test paradigm Treatments Measures Test
(effect of...)
Reaction of the
treated individual
Reaction of the
individual
Edgar
et al. [9]
Chicken During
experience
of a negative
treatment
Negative:
aversive air puff
Control: no
treatment
Control with
noise
Eye temperature,
comb temperature,
heart rate, heart rate
variability, behavior:
standing alert,
preening, vocaliza-
tions, maternal
clucking
During a negative
treatment: air puff
to hen itself (vs.
pre-treatment)
Interaction of
treatment*
period
Data not shown
During a negative
treatment: air puff
to chicks (vs.
pre-treatment)
Interaction of
treatment*
period
No interaction effect
between treatment
and period
concerning chick
distress vocalization
Edgar
et al. [2]
Chicken During
experience
of a negative
treatment
Negative:
aversive air puff
Control: air puff
was directed
away
Eye temperature,
behavior: ground
pecking, standing,
sitting, preening,
freezing, walking
During a negative
treatment (vs.
pre-treatment)
Interaction of
treatment*
period
-
During control
treatment (vs.
pre-treatment)
Interaction of
treatment*
period
No statistical
differences
No statistical
differences
During a negative
treatment (vs.
control)
correlation
Highly correlated demonstrator-observer
behavior (ground pecking, standing,
freezing) and eye temperature
Goumon
and
[7]
During
experience
of a negative
treatment
Negative:
restrained behind
a movable wall
Control: wall
moves, but no
restraint
Heart rate, heart rate
variability, behavior:
locomotion, proxim-
ity, escape attempts,
freezing, defecating,
urinating, lying,
pair mate, ears
vocalization
Phase 1: naïve observers
During a negative
treatment
(vs. control)
Treatment
(negative vs.
control)
proximity to pen mate
Phase 2: experienced observers
During a negative
treatment (vs.
control)
Treatment
(negative vs.
control)
differences
Reimert
et al. [12]
During
anticipation
and experience
positive
treatment
Negative:
social isolation
with negative
handling
Positive:
access to a
compartment with
straw and food
reward
Cortisol, behavior:
freezing, escape
attempts, play,
defecating, urinating,
ears back, ear
posture changes, tail
vocalization
During anticipation
of a negative (vs.
positive) treatment
Treatment
(negative
vs. positive)
orienting head
No statistical
differences
During a negative
(vs. positive)
treatment
Treatment
(negative
vs. positive)
Nosing aversive door
-
Continued
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Reimert
et al. [11]
During anticipa-
tion and
experience of
positive
treatment
Effect of
intranasal
administration
of Oxytocin in
observers
Negative: social
isolation with
negative handling
Positive: access
to a compartment
with straw and
food reward
alert, escape
attempts, play,
urinating, defecating,
exploring doors, ear
postures, head
postures, head
orientation,
vocalization
During anticipation
of a negative (vs.
positive) treatment
Treatment
(negative
vs. positive)
No statistical
analysis, descrip-
tive reporting only
No statistical analysis,
descriptive reporting
only
Without intranasal administration of oxytocin:
During a negative
(vs. positive)
treatment
Treatment
(negative
vs. positive)
high-pitched vocaliza-
Negative treatment vs.
positive treatment vs.
without pen mates
present: standing
to positive compart-
During a treatment
with (vs. without)
pen mates present
positive treatment
mates present
Interaction of
treatment*
situation
With intranasal administration of oxytocin or placebo in observer/naïve individuals:
During a negative
(vs. positive)
treatment
Treatment
(negative vs.
positive)
low-pitched
exploring door to
positive treatment
with admin. of
oxytocin (vs. placebo)
Intranasal
administration
Low-pitched vocaliza-
positive Treatment
with admin. of
Interaction of
treatment*
administration
Defecating, exploring
treatment door, tail low
Exploring neutral door
Reference Test paradigm Treatments Measures Test
(effect of...)
Reaction of the
treated individual
Reaction of the
individual
Table 1. Continued
Sandra Düpjan et al. 5
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Reimert
et al. [8]
During reunion
after exposure
positive
treatment
Negative: social
isolation with
negative handling
Positive: access
to a compartment
with straw and
food reward
standing alert,
sitting, lying, walking,
play, drinking, eating,
comfort behavior,
pen mate), manipu-
late pen mate,
aggressive behavior,
postures (in curl,
wagging, low,
between legs),
social interaction
behaviors (nosing
mate)
Day 2 (at the beginning of the experiment)
After a negative
(vs. positive)
treatment
Treatment
(negative vs.
positive)
nosing the nose of
behavior (nose-nose,
After a treatment
being the observ-
er (vs.
demonstrator)
Type (only in
the context
of social
behaviors)
Nosing the nose of
Day 18 (at the end of the experiment)
After a negative
(vs. positive)
treatment
Treatment
(negative vs.
positive)
nose and body of
behavior (nose-nose,
After a treatment
being the observ-
er (vs.
demonstrator)
Type (only in
the context
of social
behaviors)
Nosing the nose and
body of the
Colditz
et al. [12]
After the
experience of
a negative
treatment
Negative:
knife castration
Control: sham
castration
Cortisol, rectal
temperature, pain
avoidance behavior:
foot stamping, rolling,
jumping, licking
wound, easing
quarters, teat seeking,
postural behavior:
normal ventral lying,
abnormal ventral
lying, ventral lying
other, lateral lying,
abnormal lying, total
lying, normal standing,
statue standing,
abnormal standing,
standing other, normal
walking, abnormal
walking, walking
other, total standing,
total abnormal
behaviors, synchrony
of behavior
After a negative
(knife castration)
treatment vs. ring
vs. sham
castration
Treatment
(negative1
vs. negative2
vs. control)
-
After a negative
treatment in
homogenous (vs.
heterogeneous)
social groupings
grouping
control treatment
heterogeneous
social groupings
Interaction of
treatment*
social
grouping
Lateral lying
At three different
time periods after
treatment
Interaction of
treatment*
period
After a treatment in
homogenous (vs.
heterogeneous)
social groupings
synchrony (K
synchroniza-
tion)
Heterogeneous groups: synchronization of
walking
homogeneous groups: synchronization of
feeding at the trough (sham + ring
castration)
negative synchronization of lying and
standing (ring + knife castration)
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literature is a promising indicator of what we might expect
to nd across a range of farm animals [5].
Future research should aim at increasing our knowledge
of emotional contagion in farm animals to design husbandry
environments that improve their welfare, that is, by
decreasing the spread of negative emotions or promoting
the spread of positive ones [5]. This could be achieved
through modications to the husbandry and management
environment. For example, selective noise-canceling of
high-pitched distress calls, while allowing low-pitched
non-distress calls that might provide social support, is one
possibility to reduce the spread of negative emotions through
groups. In addition to noise-canceling speaker systems,
technical innovations such as visual or acoustic displays of
demonstrators in positive states also have potential. To this
end, we need to investigate the sensory modalities (including
visual, acoustic, or olfactory cues) that make individuals of
a specic species most susceptible to emotional contagion.
Several studies have also shown that previous experience
of the observer with the same positive or negative event as
the demonstrator [7], or the strength of social relationships
between the observer and demonstrator [9] can inuence
the likelihood of emotional contagion and these areas
deserve further research. The development and integration
of a broader range of indicators, including non-invasive
physiological parameters, to validate emotional states in
demonstrators and track changes in emotional states
in observers, are also needed. Lastly, future research should
take into account that emotional contagion does not require
exact matching of every aspect of the demonstrator’s respon se.
It can also lead to a more generalized synchronization of
behavioral and physiological parameters resulting in varied
responses that still match the valence aspect of the
observed emotional state.
In the long term, an increased understanding of when
and how emotional contagion occurs will provide novel
insights into the emotional experiences of animals, and is
thus key to improving their welfare.
Acknowledgments
This work was supported by a grant from the Deutsche
Forschungsgemeinschaft (DFG, LA 1187/6-1) to CN. The
publication of this article was funded by the Open Access
Fund of the Leibniz Association and the Open Access Fund
of the Leibniz Institute for Farm Animal Biology (FBN).
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