Animal Emotions—Do Animals Feel as We Do?

Abstract

Emotions are an essential part of how we experience our world. Humans can express emotions by telling others how we feel—but what about animals? How can we tell whether they experience emotions and, if they do, which ones? When we think about the animals under human care, it is not only scientifically interesting but also ethically important to understand how these animals experience their worlds. Over the last 20 years, researchers have made considerable progress by identifying ways to assess emotions in animals. For example, researchers can look at the facial expressions of animals, record their vocalisations, or measure body processes such as changes in the heartbeat or hormone concentrations in the blood. This information can tell us more about how animals feel, why and how emotions have evolved, and what we, as humans, share with animals in our emotional experience of the world around us.

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BIODIVERSITY
Published: 17 November 2021
doi: 10.3389/frym.2021.622811
ANIMAL EMOTIONS—DO ANIMALS FEEL AS WE DO?
Annika Krause *† and Christian Nawroth *†
Institute of Behavioural Physiology, Research Institute for Farm Animal Biology (FBN), Dummerstorf, Germany
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Emotions are an essential part of how we experience our world.
Humans can express emotions by telling others how we feel—but
what about animals? How can we tell whether they experience
emotions and, if they do, which ones? When we think about the
animals under human care, it is not only scientifically interesting
but also ethically important to understand how these animals
experience their worlds. Over the last 20 years, researchers have
made considerable progress by identifying ways to assess emotions in
animals. For example, researchers can look at the facial expressions of
animals, record their vocalisations, or measure body processes such
as changes in the heartbeat or hormone concentrations in the blood.
This information can tell us more about how animals feel, why and
how emotions have evolved, and what we, as humans, share with
animals in our emotional experience of the world around us.
WHAT ARE EMOTIONS AND WHY DO WE EXPERIENCE
THEM?
Emotions play a central role in our lives. But if we are asked, we might
find it hard to describe what an emotion actually is! It is dicult to
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Krause and Nawroth Do Animals Experience Emotions?
know how many dierent emotions there are, or whether everyone
experiences certain emotions in the same way. What we know for
sure is that emotions arise from the activity of nerve cells in several
parts of the brain. Emotions can be described as pleasant (positive) or
unpleasant (negative) and more arousing or less arousing, which refers
to the intensity of the emotion [1]. When we experience emotions,
they are often linked to changes in our behaviour and our physiology,
PHYSIOLOGY
Summary of all organic
processes and
phenomena of
an organism.
which means the functions of our bodies, such as changes in posture,
blood pressure, sweating, or heartbeat. For example, imagine you see
a bear approaching you in the forest. What would you feel? Probably
fear! The emotion of fear would probably be accompanied by a fearful
facial expression and a rising heart rate, and would probably result in
you running away.
But why do we experience emotions at all? While emotions are
intangible and hard to describe—even for scientists—they serve
important purposes. Emotions help us learn, initiate actions, and
survive by adapting to new and sudden changes in the environment.
Emotions change how we think, to prepare us to quickly select an
appropriate response, such as running away when you see a bear
approaching. Our behaviour can help us to avoid situations that evoke
negative emotions (harm or punishment), or to seek out situations
that generate positive emotions, such as joy. From an evolutionary
perspective, experiencing emotions increases our ability to survive
and reproduce.
DO ANIMALS EXPERIENCE EMOTIONS?
Since animals cannot tell us how they feel, how can we know whether
they experience emotions? Because animal emotions are dicult
to see, the question of whether animals experience emotions has
historically been a philosophical one. Researchers have only started to
investigate the emotional lives of animals in the past few decades. But
when we think about farm animals, or any other animal under human
care, it is not only scientifically interesting but also ethically important
to try to understand how these animals emotionally experience
their worlds. Farm animals are often kept in very large numbers
in rather barren environments. This might lead to sickness, stress,
and decreased well-being. If we could tell how animals emotionally
experience their situations, this could help us to improve animal
welfare. As we have already seen, emotional processes are complex
and include feelings, behaviours, and physiological changes. Feelings
are especially hard to assess in animals because they cannot tell us
how they feel. However, when emotional things happen (such as
when you see a bear approaching you), they cause changes in several
biological processes. Based on these changes, researchers developed
a wide set of methods to monitor emotions in animals, by measuring
changes on the behavioural or physical levels, often at the same time
(Figure 1) [2].
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Krause and Nawroth Do Animals Experience Emotions?
Figure 1
Figure 1
There are a variety of
behavioural and
physiological
parameters that
scientists can use to
assess emotions in
animals.
MEASURING THE BEHAVIOURAL COMPONENT OF ANIMAL
EMOTIONS
The most easily detectable reaction of an animal to an event is how
it changes its behaviour. Humans often change facial expressions and
gestures depending on whether we experience an event as pleasant or
not. If you look at your friends’ faces, you can often very quickly assess
if they are happy, fearful, angry, or disgusted. Animals show these
characteristic facial expressions as well! So called grimace scales for
GRIMACE SCALE
A methods of pain
assessment for
non-human animals
that is based on
changes in a number of
“facial action units” in
the animal, such as
narrowing of the eyes.
horses, pigs, sheep, rats, mice, and cats have already been developed.
For example, changes in ear position, the amount of visible eye white,
and tension in the chewing muscles can indicate dierent levels of
pain or fear in animals (Figure 1). It is important to remember that
the facial expressions of animals usually look dierent than those
of humans—joy might not be indicated by a smile (showing your
teeth is often a signal of stress in other primates), while sadness
is not accompanied by tears (pigs do not cry). In addition, prey
animals (including all farm animals) tend not to show emotions that
indicate pain or distress, as this might make them more vulnerable
to predators.
Another example of animal behaviour that is linked to emotions
involves vocalisations, such as grunts, bleats, and moos, which can
indicate stress in many species. We know this is true for humans,
too: imagine you are singing a song in front of many people; your
voice might get shaky if you are nervous or experiencing stage fright.
Researchers have found that the vocalisations of pigs, goats, and cows
also change and get less harmonious when these animals are under
stress, for example when they are isolated from the group, indicating
negative emotions [3].
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Krause and Nawroth Do Animals Experience Emotions?
Our decision-making is also influenced by the emotions we
experience. For example, we know that humans who are in a bad
mood tend to judge situations more negatively compared to humans
who are in a positive mood. We all know the saying about the glass
being either half full or half empty, depending on how you look at
it. Interestingly, this also appears to be the case for animals (Figure
1). Farm animals, such as pigs and horses, make more cautious
and pessimistic decisions after a negative event and more optimistic
decisions after a positive event [4], and sheep pay closer attention
to negative events when they are in a bad mood. However, we
must always keep in mind that behaviour in animal species can dier
depending on the situation, and we need to be cautious when we
interpret animal behaviour to assess emotions.
MEASURING THE PHYSIOLOGICAL COMPONENT OF
ANIMAL EMOTIONS
Physiological changes are central to emotions, as they play an
important role in preparing animals for potentially dangerous
situations. These changes include the activity of the nervous system
and the levels of certain hormones.
The autonomic nervous system regulates bodily functions including
AUTONOMIC
NERVOUS SYSTEM
(ANS)
Part of the nervous
system that acts largely
unconsciously and
regulates bodily
functions including
heart rate, blood
pressure, respiration,
and digestion.
heart rate, blood pressure, respiration, and digestion. Changes in
autonomic nervous system activity can be used to study emotions
in animal species. This is so because the two major subsystems
of the autonomic nervous system—the sympathetic (activating) and
SYMPATHETIC
NERVOUS SYSTEM
Part of the ANS that is
responsible for
preparing the body for
action, particularly in
situations threatening
survival. It increases
heart rate, constricts
blood vessels, and
raises blood pressure.
PARASYMPATHETIC
NERVOUS SYSTEM
Part of the ANS that is
responsible for
stimulation of activities
that occur when the
body is at rest,
especially after eating.
It decreases heart rate,
and increases intestinal
and gland activity.
parasympathetic (deactivating) systems—are directly connected to
the heart. Based on emotions and stress, the complex interaction
of these two subsystems causes variations in both heart rate and
HEART RATE
The number of heart
beats per minute.
the time between heartbeats, which is called heart rate variability
HEART RATE
VARIABILITY
It is a measure of the
variance in time
between the beats of
the heart and can be
aected by the
emotions and the stress
that we
currently experience.
[5]. But what exactly can these changes in heart rate and heart rate
variability tell us about emotions? Parasympathetic activity tells us
whether an animal experiences a situation as positive or negative,
whereas sympathetic activity tells us whether an animal experiences
low or high arousal, which means the level of attention and alertness
toward the environment. In our bear example, your experience of
the emotion of fear will be accompanied by an increased heartbeat
(high sympathetic activity) and less variability in your heart beats (low
parasympathetic activity). Researchers have found that animal and
human nervous systems react in similar ways in fearful situations. This
indicates that many emotions in animals physiologically mirror those
in humans.
Another physiological reaction to emotions in both humans and
animals involves changes in hormone concentrations. In stressful
HORMONES
Chemical messengers
that carry information
throughout the body.
They are produced by
glands and travel in the
bloodstream to tissues
and organs.
situations, an increase in a hormone called adrenaline immediately
reduces the blood supply to all organs that are not absolutely needed
in an emergency. At the same time, the blood flow to important
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Krause and Nawroth Do Animals Experience Emotions?
organs such as the brain, heart, and lungs is increased. The hormone
noradrenaline provides increased alertness, and cortisol provides
the energy to deal with stressful situations. Other hormones, such
as dopamine, serotonin, and oxytocin, play important roles in joy,
enthusiasm, and social bonding.
WHY SHOULD WE CARE IF ANIMALS EXPERIENCE
EMOTIONS?
From all this research, it seems that the similarities between human and
animal emotions might be closer than we would have expected a few
decades ago. Animals react to their environments much as humans
do. They respond emotionally to others and they evaluate situations
in a similar way, becoming stressed and anxious in times of danger.
While we may never know exactly how animals feel, studies have
found that there are definite behavioural and physiological similarities
in emotional expressions between humans and animals. We can thus
infer, with quite some confidence, that animals can feel emotions.
The more we discover about the behavioural and physiological
components of emotions in animals, the more we understand about
emotions, including our own ones, and how they aect the way we
behave in our world.
The evidence of emotions in animals might also encourage us to
re-think the environments in which we keep the animals that are
under our care—on farms, in zoos, or in our houses. If we can better
understand how animals interact and react to their environments,
we can ultimately improve these environments, and thus improve
human-animal relationships. It must be our ethical goal to decrease
the negative emotions these animals experience, as well as to increase
their experience of positive emotions.
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5. von Borell, E., Langbein, J., Després, G., Hansen, S., Leterrier, C., Marchant-Forde,
J., et al. 2007. Heart rate variability as a measure of autonomic regulation of
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cardiac activity for assessing stress and welfare in farm animals–a review. Physiol
Behav. 92:293–316. doi: 10.1016/j.physbeh.2007.01.007
SUBMITTED: 29 October 2020; ACCEPTED: 18 October 2021;
PUBLISHED ONLINE: 17 November 2021.
EDITED BY: Stuart Semple, University of Roehampton London, United Kingdom
CITATION: Krause A and Nawroth C (2021) Animal Emotions—Do Animals Feel as
We Do? Front. Young Minds 9:622811. doi: 10.3389/frym.2021.622811
CONFLICT OF INTEREST: The authors declare that the research was conducted in
the absence of any commercial or financial relationships that could be construed
as a potential conflict of interest.
COPYRIGHT © 2021 Krause and Nawroth. This is an open-access article distributed
under the terms of the Creative Commons Attribution License (CC BY). The use,
distribution or reproduction in other forums is permitted, provided the original
author(s) and the copyright owner(s) are credited and that the original publication
in this journal is cited, in accordance with accepted academic practice. No use,
distribution or reproduction is permitted which does not comply with these terms.
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CLUB DIVULGACIENCIA, AGES: 12–13
Members of Divulgaciencia are students from secondary school highly motivated in
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AUTHORS
ANNIKA KRAUSE
Annika is a behavioural biologist at the Leibniz-Institute for Farm Animal Biology,
and she investigates emotions in farm animals, especially pigs. With her studies, she
tries to understand how emotions are mediated by physiological and behavioural
processes and how personality may shape emotional experiences in animals. Her
research aims at a better understanding of the complexity of emotional states
in animals, which plays a significant role in improving farm animal conditions
and welfare. *krause@fbn-dummerstorf.de
CHRISTIAN NAWROTH
Christian is a trained biologist and a researcher at the Leibniz-Institute for Farm
Animal Biology, where he is currently working on a project that asks how
domestication and the selection for high milk yield has changed behaviour
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Krause and Nawroth Do Animals Experience Emotions?
and problem-solving abilities in goats. He is interested in how animals interact
with their physical and social environments, and his research focuses on the
mental capacities of farm (goats, horses, pigs, sheep) and zoo (great apes,
penguins) animals and how this knowledge can be used to improve the
animals’ conditions and human-animal interactions. *nawroth.christian@gmail.com;
orcid.org/0000-0003-4582-4057
†These authors have contributed equally to this work
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