Exploring
the link between empathy and contagious
yawning
Matthew W. Campbell &
Frans B. M. de Waal
There is mounting experimental support for
the link between contagious yawning and empathy,
and we sought to test this link further. If
empathy is the mechanism of yawn contagion, then
yawn contagion should be susceptible to the same
social biases as other measures of empathy. One
example in people is prejudice, or the
in-group–out-group bias, in
which people empathize more with people seen as
belonging to the same group as themselves than
people seen as different. We tested whether
chimpanzees show an
in-group–out-group bias in
contagious yawning.
We studied two groups of chimpanzees (12 and
11 individuals in each) at the Yerkes National
Primate Research Center who had no visual
contact and had never seen each other. We
videotaped spontaneous yawns from chimpanzees in
both groups. We edited a sequence of yawns from
seven individuals in each group (yawn video) and
a sequence of neutral expressions from the same
individuals (control video). Thus, we had four
videos: familiar yawns, familiar control,
unfamiliar yawns, and unfamiliar control. Each
chimpanzee (N = 22) saw all 4 videos, with one
video per day. Chimpanzees yawned significantly
more when viewing yawns of their own group than
the yawns of the strange individuals or the
controls. Thus, chimpanzees showed an
in-group-out-group bias in contagious yawning,
which is further evidence that contagious
yawning is a measure of empathy.
Methodological
Problems in the Study of Contagious
Yawning
Matthew Campbell
Frans de
Waal
Living Links
Center, Yerkes National Primate Research Center,
Emory University, Atlanta, USA
The recent interest in
contagious yawning has raised several challenges
as the varied methods of testing contagious
yawning leave some unresolved issues. We do not
know how differences in key variables affect the
observed rates of yawning, and we highlight
these as in need of direct testing. Different
researchers analyze their results differently,
and we make some recommendations for more
rigorous, thorough, and informative analyses.
Ultimately, problems arise when authors compare
studies that used different methods and
different analyses, without acknowledging how
these differences may have affected the results.
In this case, authors make inappropriate
comparisons, which leads to conclusions that add
confusion to the literature. Our goal in raising
awareness of these issues is to generate new
experiments and improve discussion of existing
research. With its link to empathy, a more
standardized study of contagious yawning may be
a useful tool for a variety of
disciplines.
Contagious yawning has been linked in humans to
empathy, and such cognitively complex capacties
as self-recognition and theory-of-mind. There is
previous evidence from a small population (N=6)
that chimpanzees also display contagious yawning
(Anderson et al 2004). We tested a new method of
stimulating contagious yawning using a
three-dimensional computer animation program. We
created three distinct virtual chimpanzees,
which could be given motion and viewed from
different angles. The virtual chimpanzees were
then animated to yawn, hoot, tooth-clack, and
form play faces (all without sound). From these
animations we assembled two video stimulus sets,
a Yawn condition, consisting of repeated
10-second clips of the different yawn
animations, and a Control condition, consisting
of repeated 10-second clips of the other three
mouth-moving expressions. Twenty-four
chimpanzees at the Yerkes National Primate
Research Center were tested in 12 mutually
exclusive pairs, each of which saw each stimulus
video twice. Stimulus videos lasted 15 minutes
each, consisting of 90 separate clips, and we
observed the subjects for an additional 5
minutes to look for any buildup effect. We
tallied the number of yawns for each subject in
each condition from video recordings. Multiple
individuals yawned significantly more in the
Yawn condition than in the Control condition
(binomial tests). The chimpanzees seem to have
sufficiently identified with the animated
chimpanzees for an involuntary behavior to be
stimulated. Computer generated animations may
have a host of applications for the emotional
and cognitive testing of chimpanzees.
-Campbell
M et al. Computer animations stimulate
contagious yawning in
chimpanzees Proceed Royal Soc Biol
2009:276(1676):4255-4259
-Campbell
MW, de Waal F. Ingroup-Outgroup Bias in
Contagious Yawning by Chimpanzees Supports Link
to Empathy. Plos One. 2011;6(4):1-4
-Campbell
M, de Waal F. Methodological Problems in the
Study of Contagious Yawning; In Walusinski O
(ed): The Mystery of Yawning in Physiology and
Disease. Front Neurol Neurosci. Basel, Karger,
2010, vol 28, pp 120&endash;127
-Campbell
M, de Waal F. Chimpanzees empathize with
group mates and humans, but not with baboons or
unfamiliar chimpanzees. Proc. R. Soc. B 281:
20140013
