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“No man is an island entire of
itself.” — John Donne
John Donne’s sentiment that the self extends beyond our
individual boundaries applies to virtually every animal. Mammals in particular
depend on others for growth, development, effective foraging, safety, and
ultimately survival. The young are born helpless and depend on their mother for
nutrition, immune defense, thermoregulation, and protection from predation. If
a mother (or father in some birds and a few mammals) fails to recognize that
her young are cold, hungry, or exposed to danger, it’s likely that the
offspring will die. A mother’s ability to react appropriately to her newborn’s
needs is the difference between the newborn living and carrying on its parents’
genes or dying and reaching an evolutionary dead end.
Young mammals depend on their mothers for far more than
nuts-and-bolts survival. American psychologist Harry Harlow dramatically
illustrated this point in the late 1950s through an experiment that involved
separating monkeys from their mothers and offering two mother substitutes, one
made of cloth and the other of wire.1 Even when the wire mother was
the baby’s only source of milk, the young spent ten times as much time with the
cloth (nonnutritive) mother than with the wire (nutritive) mother. The
experiment revealed that mammalian offspring crave a mother’s touch, which is
better approximated by cloth than wire, and demonstrated that a primate mother
provides her newborns with far more than nutrition. Indeed, mammals raised with
adequate food, warmth, and protection but with diminished social contact became
fearful, anxious adults with impaired social and parenting skills.2, 3
Whereas an empathic understanding by the mammalian mother of
her young’s condition is critical for survival and, in turn, for evolutionary
success, the utility of a social bond between individuals extends into
adulthood and encompasses more than just the mother-to-offspring relationship.
Darwin intuited that an individual should “extend his social instincts and
sympathies to all the members of the same nation, though personally unknown to
him.”4 If we take “nation” to mean tribe or herd or social group,
Darwin is clearly stating that social cohesion, borne of mutually directed
feelings, facilitates survival of the group and its constituent individuals. In
essence, sociality benefits individual adult survival by providing protection
and by increasing opportunities to feed, mate, and successfully raise offspring
to reproductive age.
Membership in a social group brings benefits that scale with
the ability of the group to work together. Thus social cohesion, more than
simple sociality, most powerfully promotes survival. William James considered
that “a man’s Self is the sum total of all that he CAN call his, not only his
body and his psychic powers, but his … friends.”5 James’s idea of an
extended self depends on individuals reacting to the fortunes of others as they
would if the same fortune or misfortune befell oneself. To the extent that our
mood soars at a friend’s triumph as it does upon our own triumph or plummets in
reaction to harm befalling a friend, that friend is part of a Jamesian extended
self. Social cohesion increases as more group members consider more other group
members as part of their extended selves.
To Act, or Not to Act
At the core of social cohesion among mammals is the
communication of affective or emotional states between individuals. When
individuals respond to others’ emotional states as if they were their own, the
result is a bond, thereby building social cohesion within the larger group. The
communication of affect or emotion between individuals is empathy. Defined in
this way, empathy is an umbrella term that includes a large range of
interactions in which an emotional or affective response is elicited by the
emotional or affective state of another individual. Moreover, according to this
definition, empathy is neutral in that responding to another’s affective state,
mood, or emotion does not constrain the actions taken, if any, as a result. We
may hope that an individual reacts with helping behavior to a member of his or
her own species in distress—the social instincts and sympathies Darwin
suggested. Yet, inaction and even targeted cruelty aimed at exacerbating a victim’s
distress are also possible reactions.
The perception-behavior link, an automatic function that
links our behavior to the behavior of another, is critical to affective
communication between two individuals. Many of us are familiar with the phenomenon
of adopting the physical stance of a person or people with whom we are talking;
soon after one member of a group crosses his or her arms, another person does
the same.
Simply viewing another individual’s actions increases the
probability that the viewer will perform the same actions — even if the
individuals are strangers.6 Similarly, people in conversation with
each other modify their fundamental speech frequencies to more closely match
each other.7 These social adjustments make the actions of two interacting
people more similar to each other and serve as an affiliative signal, or a kind
of social glue. Passing a person who cheerfully smiles at us makes us more
likely to smile. We don’t reason through this process; it just happens.
Actions are not only the readout of affect. They also
influence affect—the interaction between emotions and outward expressions is
two-way.8 In other words, just as our emotions lead to actions, our
motor actions are “re-experienced” as affect. Affect and emotions are expressed
through voluntary muscles responsible for posture, facial expression,
breathing, and gaze, as well as autonomic processes such as a rise in heart
rate or perspiring, blanching, and blushing. Facial expressions’ influence upon
emotional experience is particularly strong in humans. People report emotions
commensurate with artificially arranged facial expressions.9 Feeling
happy makes us smile and smiling can make us feel happy, or at least happier.
When you’re feeling good and laughing with friends, just try to feel angry or
sad. As long as you keep your face in a smile or laugh, feeling an incongruent
emotion is nearly impossible. Deriving emotion from action, often termed
embodied emotion, is the essence of the Stanislavski system of method acting in
which the affects that emerge from movements provide the emotive force of a
performance.
The links between perception and
action and between action and affect set up a cascade whereby one person’s
perception by another’s actions ultimately results in the first person feeling
the second one’s mood. This cascade results in matching affects.10
The affect the viewer experiences is vicarious in nature, “caught” from the
other individual. The process by which one individual catches the affect or
emotion of another is called “emotional contagion,” and it is a fundamental
building block of more complex forms of empathy.
Aid and Abetment
Emotional contagion is required but not sufficient to elicit
empathically motivated helping. In humans, personal distress must be suppressed in order to move
from emotional contagion to helping, to choose action over immobility and panic. High levels of personal
distress are detrimental to helping.11 Suppressing personal distress
allows someone to focus on the other over the self and leads to empathic
concern, an other-oriented emotional
response elicited by and congruent with the welfare of an individual in
distress. The response’s congruence with the welfare of the other
precludes antisocial actions so that the action taken by someone
feeling empathic concern is always prosocial in nature.
By helping a distressed individual, a
helper resolves not only the distressed individual’s predicament but also his
or her own uncomfortable affective state, providing an internal reward.12
Thus, helping dissipates the distress of both the helper and the beneficiary.
That the helper benefits does not diminish the prosocial action or its effect.
The empathy-helping connection is so effective precisely because “empathy gives
individuals an emotional stake in the welfare of others.”
What Nonhumans Reveal
Empathy is an internal experience. The feeling of empathy may
drive behavior such as a facial expression. In humans, empathy may even drive
speech. Nonhuman animals, however, do not have the control over, and variety
of, facial expressions that humans possess. Therefore, probing a nonhuman
animal for the internal feeling of empathy has proved challenging.
Researchers have taken two basic
approaches. One has been to test for emotional contagion. A typical experiment
using rodents tests the influence of one rodent’s expression of either fear or
pain on another rodent’s behavior. The second approach asks whether, given the
opportunity, animals will engage in prosocial behavior, such as sharing food
(in primates) or working for the relief of another from foot shock or
confinement (in rodents). Mounting evidence suggests that emotional contagion
and prosocial behavior are present in nonhuman primates and rodents and likely
are widespread among mammals.
Preverbal humans and nonhuman
primates show prosocial behavior. For example, a useful paradigm to test for
helping behavior is to place an object out of the reach of an experimenter but
within reach of the test subject. The subject watches the experimenter try to
reach for the object unsuccessfully. The question is whether the subject will
hand the object to the experimenter even though the subject gains no reward by
doing so. In one study using this paradigm, chimps handed the object to the
experimenter in about 40 percent of the trials; human infants helped in about
60 percent of trials.13 The proportions of children (60 percent) and
chimps (50 percent) that helped at least once in ten trials were similar. The
subsets of children and chimps that had helped were then tested on the same
task but with physical obstacles placed between them and the object, adding to
the cost of helping. Just over half of the subjects of both species helped even
when helping required significant effort.
Since emotional contagion is
automatic, from perception to action to embodied emotional cascade, it is not surprising that chimps
and other primates also appear to experience empathy.12 Moreover,
because the pathways involved in linking perception to action to embodied
emotional cascade are shared across mammals and the perception-action model for
empathy does not depend on conscious deliberation or higher cognition, there is
no reason to expect that empathy and prosocial behavior are exclusive to
primates.12, 14 Indeed, emotional contagion has been documented in a
number of mammalian species, including rodents.15 A mouse that views
another mouse experiencing foot shock, for example, shows fear by freezing in
place.16 In another example, pairs of mice that receive a noxious
stimulus show more pain behavior than a single mouse that receives the same
noxious stimulus; this finding has been interpreted as emotional contagion of
pain.17
Overcome by Caring
Several years ago, we designed a behavioral helping test for
rats.18 In
this test, one rat is restrained in a plastic tube located in the center of an
arena while a second rat is free to roam in the arena. The restrainer door can
be opened only from the outside—only by the free rat. Within a few sessions,
most rats begin to open the door consistently, releasing the other rat. By the
final session, most rats open the restrainer door within just minutes. The fact
that rats opened the restrainer door repeatedly and consistently is remarkable
in light of rats’ strong preference to remain close to walls and avoid open
areas. The motivation to approach the trapped rat in the arena center evidently
is sufficient to overcome rats’ natural avoidance of open space.
The rats’ helping actions are
remarkable for another reason. We would expect that emotional contagion would
lead the free rat to experience at least some of the distress felt by the
trapped rat. The most common reaction of a rat to personal distress is freezing
or immobility such as that which occurs in response to foot shock. Yet rats in
the helping test do not freeze. Instead they act intentionally to open the
restrainer door.18
This behavior suggests that the helper rat recognizes that its distress is
vicarious in origin. In other words, the rat is able to attribute personally
felt distress to the trapped rat’s condition and distinguish that from its own
condition. Such recognition of the distinction between self and other is
unexpected in a rat.
The helping behavior test is not the
first scientific demonstration of helping, but it is the first tractable
paradigm for studying prosocial behavior in a mammal. Already, the test has
been used to demonstrate that helping is socially selective.19 Rats help a
stranger rat but only if that rat is from a familiar strain. In other words, an
albino rat that has never before seen a black-hooded rat will not help it.
However, an albino rat that has lived with a black-hooded rat will open the
restrainer door for black-hooded strangers. Remarkably, albino rats raised
since birth with black-hooded rats do not help other albino rats, although they
do help black-hooded strangers. This suggests that rats do not inherit genetic
instructions to help others of their own kind. Instead, they learn which
individuals to help from their social environment. The test result tells us
that environmental experiences trump genetics when it comes to targeting
helping, resolving one piece of the nature-nurture debate. Moreover, because
the fostering-from-birth experiment is easy to perform in rodents but would be
impossible in most other mammals, this result shows the power of an
experimental model for prosocial behavior in rodents.
The finding that rats help strangers
of a familiar type but not strangers of an unfamiliar kind may appear, at first
glance, to suggest a biological basis for a social bias, a kind of “strainism.”
However, the results are more consistent with a biological basis for “groupism”
through social experience. Humans readily form strong affiliations to groups
that are based on “minimal-group” criteria such as an arbitrary assignment to
one of two meaningless markers (e.g., red or blue wrist bands).20 The finding that
rats raised without experience with their own strain do not help strangers of
their own strain demonstrates that group affiliation, with respect to helping,
is fluid, based on experience, and not genetically determined.
Motivation to Help
We still need to understand more about the rat’s motivation
to help another in distress and to discover the underlying brain mechanisms
that support helping behavior. While the motivation for prosocial behavior
looks like empathic concern, a rat may open a restrainer door for other
reasons. One commonly raised possibility is that the rat finds some part of the
trapped rat’s behavior so aversive that it opens the door to terminate this
aversive experience.
Since rats do not open restrainer
doors for rats from unfamiliar strains, including strangers from their own
strain if they were fostered with a different one, escaping aversion is a
possible but unlikely motivation for door-opening in the helping behavior test.19 Nonetheless, empathic concern
must start with an individual showing distress. Because an individual’s
demonstration of distress is as critical to empathic concern as another’s
noticing and responding to that distress, biology has left little to chance.
Crying works—babies and others get attention when they need help. Facial
expressions and posture also work because they are universal, with
commonalities across populations and across species. Conversely, in the absence
of an individual displaying distress, nonhuman animals and young humans are
never moved to “help.” Some degree of attention-getting distress is necessary
to elicit empathic concern.
A second common theory is that rats may be motivated by a
desire to interact socially with the trapped rat. Social reward is a
fundamental underpinning of social behavior, and all rodent behavior involving
more than one individual is, at the very least, influenced by social reward.
Rats will opt to be together when given the opportunity. Using a modification
of the helping behavior test in which rats were repeatedly retrapped, a free
rat that could not release the trapped rat opted for physical proximity.21 In contrast, when
given the chance, rats continue to open the door for a trapped cagemate even
when subsequent interactions are prevented.18 This finding suggests that the
opportunity to play or interact with the trapped rat is not a requirement for
prosocial behavior.
More Than a Feeling
Not all humans show empathy or express helping behavior. We
aren’t alone: About 25 percent of the rats that we have tested in standard
conditions do not exhibit helping behavior. The predominant reason for not
helping appears to be an excessive amount of personal anxiety. Similarly,
bonobo apes who show more anxiety (measured by how much they scratch
themselves) and take longer to recover from a stressful event show less
consolation behavior toward other bonobos in distress.22 This
finding dovetails beautifully with research in humans suggesting that in order
to use empathy for helping or caring, an individual must overcome personal
distress, a process typically termed self- or down-regulation. People with a
specific genetic variation who show greater social anxiety also demonstrate
less helping behavior.23 This finding suggests that rather than
lacking empathy, many individuals who do not help may be unable to suppress the
anxiety associated with catching another’s feeling of distress.
In professions
that involve repeated exposure to human suffering, such as medicine, strong
down-regulation is highly adaptive in counteracting the development of burnout.
Physicians have a down-regulated response to noxious events that are common in
medical practice. For example, an image of a needle stick evokes a lower
assessment of pain intensity and unpleasantness by physicians than controls.24
Finally, human psychopaths appear to lack empathy and exhibit a callous
disregard for others’ suffering. Whether psychopathic individuals exist in
other mammalian species is an unanswered question.
Researchers are beginning to
elucidate the brain circuits that support empathy and empathic concern. A
particularly instructive approach has been to compare brain activation in
humans, using functional magnetic resonance imaging (fMRI), to compare when an
emotion is experienced by the self versus when it is experienced by another.
When one person views another in pain, the activated brain areas are similar
and overlapping, but not identical, to those activated by a personal experience
of pain.25 The overlapping regions of activation evoked by self- and
other-pain can breed confusion so that an individual experiences another’s
distress as their own. Conflation of the distress originating with the self and
the other may explain why vicarious distress can be as immobilizing as personal
distress. It appears that the prefrontal cortex allows us to make the
distinction between ourselves and others by promoting down-regulation.25
For example, the medial and dorsolateral prefrontal cortex was activated as
physician acupuncturists viewed images of needle insertions, an activation that
was not observed in control subjects.26 Moreover, the degree of
activation in the prefrontal cortex was inversely correlated to the ratings of
pain intensity made by the subjects so that those with the greatest prefrontal
activation judged the needle insertions with the lowest pain ratings.
These
studies show that viewing others’ pain engages ascending affective pathways,
while top-down regulation arising from the prefrontal cortex is critical to
stemming personal distress so that empathy can serve as a call for action.
Nonhuman animals are likely to employ similar brain circuits. Indeed, fear
contagion in mice appears to require the anterior cingulate cortex as well.16,25 A full elucidation of the similarities and differences in brain
circuits involved in empathy and down-regulation between humans and other
mammals is an exciting challenge for the future.
