Contagious yawning and psychopathy
Brian K. Rundle ⁎, Vanessa R. Vaughn, Matthew S. Stanford
Baylor University, Department of Psychology and Neuroscience, One Bear Place 97334, Waco, TX 76798, United States
Received 25 March 2015
Received in revised form 18 May 2015
Accepted 19 May 2015
Available online xxxx
Psychopathy is characterized by a general antisocial lifestyle with behaviors including being selﬁsh, manipula-
tive, impulsive, fearless, callous, possibly domineering, and particularly lacking in empathy. Contagious yawning
in our species has been strongly linked to empathy. We exposed 135 students, male and female, who completed
the Psychopathic Personality Inventory-Revised (PPI-R), to a yawning paradigmintended to induce a reactionary
yawn. Further, we exposed males to an emotion-related startle paradigm meant to assess peripheral amygdalar
reactivity. We found that scores on the PPI-R subscale Coldheartedness signiﬁcantly predicted a reduced chance
of yawning. Further, we found that emotion-related startle amplitudes were predictive of frequency of conta-
gious yawning. These data suggest that psychopathic traits may be related to the empathic nature of contagious
yawning in our species.
© 2015 Elsevier B.V. All rights reserved.
1. Yawning and psychopathy
Yawning is a stereotyped behavior that, in our evolutionary history,
has clear, deep roots as evidenced by its proliferation in mammals as
well as many other vertebrates (Argiolas and Melis, 1998; Lehmann,
1979). It is clearly characterized by long inspiration followed by a
shorter expiration (Argiolas and Melis, 1998). While literature con-
cerning the pharmacology and functional anatomy of yawning is not
lacking (Argiolas and Melis, 1998; Guggisberg, Mathis, Schnider, and
Hess, 2010; Nahab, Hattori, Saad, and Hallett, 2009), the primary facet
of yawning of interest is the phenomena of contagious yawns, speciﬁ-
cally within the context of psychopathology.
Contagious yawns, which are spurred by yawn, thinking, hearing,
reading, or observing another conspeciﬁc(orotherspecies),have
been linked to empathy (Lehmann, 1979; Platek, Critton, Myers,
and Gallup, 2003; Platek, Mohamed, and Gallup, 2005). They are
even documented in other familiar animals such as Pan Troglodytes
and Canis Familiaris and have been linked to empathy (Campbell
and de Waal, 2011; Romero, Konno, and Hasegawa, 2013). The anat-
omy and pharmacology of yawning and its contagious nature are be-
ginning to be investigated, with oxytocin playing a large role as well
as the posterior cingulate cortex (PCC), precuneus, bilateral thala-
mus, and parahippocampal gyrus (PHG) (Platek et al., 2005; Sanna,
Argiolas, and Melis, 2012). Interestingly, Schürmann et al. (2005)
found that the mirror-neuron system is not directly activated in
contagious yawning, suggesting that the action is automatic and
not imitated. Norscia and Palagi (2011) found that people show a
large susceptibility to contagious yawns when elicited by a related
individual in terms of occurrence and frequency of yawns. For
strangers, they found that people show a marked latency period of
contagious yawns, strongly suggesting a component of familiarity
involved with the contagion.
Variations in susceptibility to contagious yawning are already
known to occur in certain populations. Age is known to affect the likeli-
hood of contagious yawning; as age increases, contagious yawning de-
creases (Bartholomew and Cirulli, 2014). Further, children on the
autism spectrum are less likely to demonstrate contagious yawning
(Giganti and EspositoZiello, 2009; Senju et al., 2007), which is speculat-
ed to have a strong relationship to the empathetic deﬁcits seen in this
Empirical support for yawning having its evolutionary roots in
empathic behavior is growing (Campbell and de Waal, 2011).
Psychopathic traits, then, become a curious angle in which to view
contagious yawning in our species. Psychopathy is characterized
by a general antisocial lifestyle including being selﬁsh, manipula-
tive, impulsive, fearless, callous, domineering, and particularly lack-
ing in empathy (Hare, 2003; Weber, Habel, Amunts, and Schneider,
2008). The disorder is typically assessed via the Psychopathic Check
List-Revised (PCL-R) developed by Hare (2003) or the Psychopathic
Personality Inventory (PPI-R) developed by Lilienfeld and Widows
(2005). Psychopathy and its close relative Antisocial Personality Disorder
are found overwhelmingly in males (Cale and Lilienfeld, 2002). Addi-
tionally, psychopathy carries speciﬁc brain abnormalities including
structural and functional impairments of the orbitofrontal–ventromedial
prefrontal cortex as well as the amygdala (Gao, Glenn, Schug, Yang, and
Raine, 2009; Weber et al., 2008).
Personality and Individual Differences 86 (2015) 33–37
E-mail address: Brian_rundle@baylor.edu (B.K. Rundle).
0191-8869/© 2015 Elsevier B.V. All rights reserved.
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The PPI-R operationalizes two discrete components within psychop-
athy: a primary (affective) and secondary (behavioral) facet (Hare,
2003; Lilienfeld and Widows, 2005), where the primary facet encom-
passes features including cruelty, lack of affect and empathy, while the
secondary facet encompasses features such as impulsivity and aggres-
sion. Psychopaths demons trate an overall small bu t marked decrea se
in the ability to recognize emotion in others (Kosson, Suchy, Mayer,
and Libby, 2002; Wilson, Juodis, and Porter, 2011), which is also
associated with decreased amygdalar function, particularly with
fearful faces (Jones, Laurens, Herba, Barker, and Viding, 2009).
Kosson et al. (2002) showed a slight overall decreased ability to rec-
ognize emotion, but a large deﬁcit in recognizing disgust in others
when the task involved non-verbal responses. It has also been
shown that psychopaths fail to exhibit a conditioned response to aver-
sive Pavlovian conditioning (Flor, Birbaumer, Hermann, Silvio, and
Patrick, 2002), which suggests deﬁciencies in amygdala-dependent
What sets psychopathy apart from its close relatives Conduct Disor-
der and Antisocial Personality Disorder is its distinct emotional compo-
nent. That is, psychopathy involves a prevalent emotional proﬁle
consisting of a considerable reduction in or lack of empathy (Frick,
O'Brien, Wooton, and McBurnett, 1994; Hare, 2003). Psychopathy has
also been found to be inversely related to the ability to perceive emotion
(in both male and females) and managing emotion (only in men)
(Lishner, Swim, Hong, and Vitacco, 2011).
Given the nature of psychopathy and yawning discussed herein, the
current study aims to examine the relationship between contagious
yawning and psychopathic traits. This will be examined both by a yawn-
ing paradigm designed by the current researchers (modeled after Platek
et al., 2005) as well as an emotion-related startle paradigm (ERS) previ-
ously used in Anderson, Stanford, Wan, and Young (2011).Affectivepo-
tentiation of the acoustic startle reﬂex (by Electromyograph [EMG] and
Galvanic skin response [GSR]) is one of the most prominent psycho-
physiological measures of amygdalar responsiveness (Davis, 1989;
Lang, Bradley, and Cuthbert, 1990; LeDoux, Iwata, Cicchetti, and Reis,
1988). Psychopaths reliably demonstrate an impairment of potentiation
of the startle reﬂex (Patrick, Bradley, and Lang, 1993), while healthy
controls reliably potentiate with negative affective valence and attenu-
ate the fearresponse with positive affective valences (Lang et al., 1990).
What's more, Patrick et al. (1993);Patrick (1994) connected the lack
of potentiated startle in psychopathy to the emotional facet of the
PCL-R (Hare, 2003) while the behavioral facet was found to be unre-
lated. Further, given the growing evidence that contagious yawning
and empathy are evolutionarily related, a connection between
psychopathy and yawning maintains sufﬁcient precedence. To
our knowledge, such an examination has not been done in high
psychopathic trait individuals, nor have contagious yawning been
addressed using ERS. In our case, we expect to ﬁnd a connection
between psychopathic traits and a decreased susceptibility to conta-
In these experiments, a total of 135 college male and female
participants were selected based on their completion of the PPI-R
(Lilienfeld and Widows, 2005). Psychopathic traits were operation-
alized as a spectrum and no arbitrary cut-off was used for high and
lowtraits unless noted. The PPI-R has three primary factors: Fearless
Dominance (FD)/Self-Centered Impulsivity (SCI; behavioral and in-
terpersonal aspects), and Coldheartedness (CD; social emotional
2.1. Experiment one: yawn
For the yawning paradigm, one hundred and thirty ﬁve univer-
sity students, males (n = 57) and females (n = 78), were used.
All participants completed the same yawning paradigm intended
to induce a reactive yawn. Participants were excluded from the
analyses if they resisted yawning or did not pay attention to the
2.1.2. Yawn paradigm
Videos of individual males and females unknown to any partici-
pants were selected to provide 7-10 second videos of a yawn, a
laugh, or a neutral face. This paradigm follows the methods listed
in Platek et al. (2005), a method shown to induce yawns. Partici-
pants viewed a series of video blocks. Each block consisted of three
videos (yawning, neutral-face, and smile) in random order. To be
clear, each video block did not contain the videos from one individ-
ual, but rather a pseudo-random and exhaustive selection of yawns,
laughs, or neutrals from a pool of videos recorded from strangers.
Each individual video was 7–10 s long and, thus, each block was
24–33 s long (with a one second interval between each video in
the video block). Ten seconds of a blank black screen separated
each block and participants viewed 20 blocks.
Participants were instructed to sit in a padded chair in a dimly lit,
radiofrequency anechoic chamber (Raymond EMC Enclosures Ltd.
Ottawa). Participants sat in front of a computer monitor and wore
noise canceling headphones. They were asked to relax for one minute's
time. They were told that they would be watching a movie of different
people's expressions that they need to remain comfortably seated, and
to keep their attention on the screen. Further, if they felt the need to ad-
just themselves, laugh, cough, yawn, or blink, that they were allowed to
do so as long as their attention remained on the screen and that they
would return to a still, comfortable position.
Facial EMG was recorded from the orbicularis oculi muscle of the
participant's right eye. A pair of Ag–AgCl electrodes (Biopac Systems
Inc., Goleta, CA, USA) was placed one centimeter below the eyelid,
with one directly below the pupil and the other one centimeter to the
right of the ﬁrst. A third electrode was placed directly in the middle of
the forehead to serve as a ground. Prior to placing the electrodes, skin
was prepared with an isopropyl alcohol rub and a mildly abrasive gel
(NuPrep) to improve surface conductance. Signa gel brand saline gel
was used as a conducting medium and impedances were kept below
5kΩ. Hardware used to collect EMG signals wasBioPac MP150 data ac-
quisition hardware using a sampling rate of 2000 Hz and a 10–500 Hz
bandpass ﬁlter. EMG data were rectiﬁed and integrated witha time con-
stant of 10 ms.
GSR was also obtained. Electrodermal activity was recorded by se-
curing Ag–AgCl to the index and ring ﬁnger of the participants. Skin
was prepped by removing surface oils with isopropyl alcohol followed
by the application of isotonic NaCl electrode paste. Hardware used to
collect GSR data was BioPac MP150 data acquisition hardware using a
sampling rate of 2000 Hz and a 0.5–1 Hz bandpass ﬁlter. For both
EMG and GSR, data was recorded with AcqKnowledge 4.1 Software
(BioPac Systems Inc.).
Unlike Platek et al. (2005), we were simply interested in in-
observation of the participant were utilized. That is, a clear physio-
logical characterization of a yawn was necessary for the behavior
to be considered a full yawn. This was in order to distinguish related
behaviors such as sighs and heavy inspirations as well as to validate
video observations. Electrophysiologically, we deﬁned a yawn as
sustained EMG impedance paired with a delayed GSR (see Fig. A.1
34 B.K. Rundle et al. / Personality and Individual Differences 86 (2015) 33–37
for an example). All full, validated yawns during the time of the
yawning video were counted.
2.2. Experiment two: startle
Males from the ﬁrst experiment (n = 57) also participated in an
emotional related startle paradigm. Participants were excluded
from the analysis if they were unable to perform any part of the
yawning or startle paradigm sufﬁciently or if they had already
participated in an emotion-related startle paradigm before. Only
males were used in this experiment due to its pilot nature and
the more complex variations in startle potentiation in females
(see Anderson et al., 2011).
2.2.2. Eyeblink startle
An eyeblink startle paradigm established by Anderson et al. (2011)
was used to measure emotion-modulated startle. Affective pictures
from the International Affective Picture System (IAPS; Lang, Ohman,
and Vaitl, 1988) were utilized. The images have standardized ratings
of affective valence and arousal level (Lang and Greenwald, 1988).
An equal number of positive, negative, and neutral pictures were used
(45 total). The particular set of images used in the current paradigm
were selected from a pool previously used in a study by Larson,
Ruffalo, Nietert, and Davidson (2005), which had veriﬁed test–retest re-
liability in measuring emotion-modulated startle. Anderson et al.
(2011) describes picture selection and exclusion criteria for theIAPS im-
ages used in this study.
Participants were instructed to sit in a padded chair in a dimly lit,
radiofrequency anechoic chamber (Raymond EMC Enclosures Ltd.
Ottawa), which is designed to minimize unnecessary electromagnetic
waves that would potentially interfere with equipment recordings. Par-
ticipants put on noise-canceling headphones, through which the startle
burst was delivered. They sat in front of a computer monitor and were
instructed to relax for one minute. Participants then were instructed
to keep their full attention on the screen during the entire presenta-
tion and were informed that they were going to hear a burst of
white-noise through their earphones, which is to be ignored. Pic-
tures were presented pseudo-randomly in a single block of 60 im-
ages. The order of the pictures was such that no two pictures were
Pictures were on screen for 6 s and followed by a 2 second interstim-
ulus interval which consisted of a white plus sign (+) in the middle of a
black screen for the participantto focus. Thirtyof the pictures contained
a white noise burst, which lasted 50 ms at 100 dB. Startle probes were
assigned randomly to images with an equal number of probes
assigned to each valence category. There were ﬁfteen images per va-
lence category with ten paired with the startle probe, which was de-
livered either 3 s or 5 s after the onset of the image. Software used to
present the startle paradigm was Superlab 4.0 (Cedrus Corporation,
San Pedro, CA, USA).
EMG was used to measure the magnitude of the startle response
with the same preparation as mentioned in the yawning paradigm.
Blink magnitudes were deﬁned as smoothed EMG signal, recorded as
baseline to peak differences for each startle probe. In order to establish
a baseline, the mean orbicularis oculi EMG reading during the 25 ms
prior onset of the noise was used; amplitude peaks of interest were de-
ﬁned as the maximum amplitude between 40 ms and 120 ms after the
onset of the noise.
2.2.3. Statistical analyses
For the yawing paradigm, logistic regression was performed on
the overall scale and subscales of the PCL-R on a dichotomous out-
come, namely “yawn”or “no yawn”. Further, startle amplitudes
were linearly regressed on frequency of yawning in order to assess
the relationship between emotion-related startle potentiation and
yawning susceptibility. Yawning frequency was recorded for demo-
It is important to note that prior to analysis, raw peaks were
standardized within subjects due to the high variability of blink am-
plitude variation. Further, a regression analysis was performed with
the difference score (DS), deﬁned as the mean peak amplitude for
neutral stimuli less the mean peak amplitude for negative stimuli
(see Anderson et al., 2011). Lower numerical values of DS would
suggest more potentiated reactions to negative stimuli. Higher nu-
merical values would suggest less potentiation to negative stimuli,
as the mean peak amplitude for negative stimuli would be a smaller
3.1. Experiment one
The mean age for the participants in this study was 18.89, SD = 1.13.
In terms of observed yawns (133) within the paradigm, the modal num-
ber of yawns was zero followed by 1, 2, and 3 yawns respectively
(Fig. A.2).All yawns included in the analyses met the physiologically de-
ﬁned parameters. Individuals with highly atypical Inconsistent
Responding scores (an internal validation measure to the PPI-R) were
removed from the analyses. As well, the invalid participants (listed in
experiment 2) were also excluded. Females were more likely than
males to yawn during the paradigm, but a statistically signiﬁcant gender
effect was not shown, β=0.432,p= .249. Next, a test looking at sus-
ceptibility to yawn by high and low traits on the overall score of the
PPI-R showed β=−0.008, p= 0.154. Sub-factor tests showed
β=−0.15, p= 0.129 for Fearless Dominance; Self-Centered Impul-
sivity showed β=−0.001, p= 0.923; and β=−0.062, p= 0.020
for Coldheartedness. Estimates and Standard Errors are summated
in Table A.1.
Diagnostic clinical signiﬁcance for psychopathy is the 65th percen-
tile and above. Though arbitrary, we evaluated the difference be-
tween clinically signiﬁcant scores and non-signiﬁcant scores. The
average number of yawns for a low-trait individual on the CD scale
was M= 3.36, SD = 3.72, while the average number of yawns for in-
dividuals high on CD traits was M= 1.96, SD = 3.11. An independent
samples t-test was performed between high and low trait partici-
pants on the Coldheartedness sub-factor and number of yawns
showing, t(121) = 2.184, p= .031; CI(95%) = .132 bμb2.680,
3.2. Experiment two
EMG data during the startle paradigm were analyzed. When
the DS between the mean peak of neutral pictures and negative
pictures was examined using a regression analysis (see experiment
2), the values were notably predictive of yawning frequency
(β=−1.110, pb.001). Thus, the lower the startle response, the
less likely a participant was to yawn in response to the yawning
4.1. Experiment one
While psychopathy is not simply the lack of empathy, endorsement
of the CD subscale is strongly indicative of damped empathic affect. The
theory that contagious yawning in our species is largely mediated by
empathy is supported by the signiﬁcant difference between genders
on probability of yawning (63.5% of women yawned compared to
53.1% of males), as females tend to score higher on measures of em-
pathy than males (Rueckert, Branch, and Doan, 2011). Further, as previ-
ously discussed, psychopathy is almost exclusively diagnosed in males.
35B.K. Rundle et al. / Personality and Individual Differences 86 (2015) 33–37
It is expected that a higher percentage of females would yawn dur-
ing the paradigm; however, since there was no statistical difference
between genders, a gender effect on likelihood to yawn can be easily
controlled. This difference merely shows that the paradigm itself
maintains a level of validity consistent with the existing literature
that would be expected. It is true that this is an indirect expectation
by means of empathy; to our knowledge, no conclusive evidence between
gender and contagious yawning has been established (Baenninger,
Binkley, and Baenninger, 1996).
When evaluating the all subscales, only CD yielded signiﬁcant re-
sults. This is not surprising considering that the grouping variables
SCI or FD do not wholly capture the emotional component (or lack
thereof) of psychopathy and tend to focus on behavioral and
interpersonal factors. A difference between groups suggests that
increased CD is associated with decreased susceptibility to a conta-
gious yawn. Further, when considering the overall PPI-R score,
which includes all subscales,
a strong trend towards signiﬁcance is
seen, which is likely mediated by Coldheartedness. When compared
to other sub-factors, FD and SCI, Coldheartedness clearly maintains
the largest affective component on the PPI-R (Lilienfeld and
In line with theory and previously shown between genders, in-
creased empathy is associated with increased susceptibility to conta-
gious yawning (Platek et al., 2003). Using psychopathy as a predictor
of susceptibility of contagious yawning may, then, be a viable avenue
of research simply by virtue of the interpersonal and emotional abnor-
malities associated with psychopathy. The results of this experiment
lend support to the theory that empathy and contagious yawning
are related in our species and may work together to accomplish
4.2. Experiment two
Though only males were exposed to the startle paradigm as part of a
separate study, yawning data were collected on all participants. A re-
gression analysis showed that the difference between the negative
and neutral mean potentiation was predictive of yawning frequency.
Experiment 2 provides physiological data and a predictive parametric
measure for future study. In this case, the lower the yawning suscepti-
bility, the lower the difference between neutral and negative startle re-
sponse (resulting in an overall higher numerical value). The negative
correlation between the neutral-negative difference and yawning fre-
quency shows that the higher the frequency of yawns, the greater the
difference between the neutral-negative difference (resulting in a
more negative numerical value). Thus, the greater the measured psy-
chopathic traits, the lower the startle potentiation and, therefore, the
lower difference value between neutral and negative. On the other
hand, individuals with lower levels of psychopathic traits showed
greater startle potentiation, which produces a greater difference
The relationship between startle potentiation and emotional dysreg-
ulation is well studied. Aside from the psychopathy-related research
currently presented, startle potentiation is seen in emotional disorders
involvingincreased (and dysregulated) emotional disposition including
anxiety and depression (see Ballard et al., 2014). The available research
gives sufﬁcient pretense to the data collected in these experiments. Our
data suggest that one's level of psychopathic traits and startle reactivity
are related to one's susceptibility to contagious yawning. That is to say,
a well-established physiological measure of psychopathic traits is
also highly associated with the susceptibility to contagious yawning.
The less emotion-related startle reactivity observed, the lower the
susceptibility to contagiously yawn. Both independent variables have
a strong relationship to empathic behavior and emotional regulation,
and taken together, provide insight into thecomplex nature of yawning
and social interaction. While no conclusion can be drawn at this time,
these data are steps forward in elucidating the function of contagious
yawning in our species. Further, this invites inquiry into amygdalar re-
activity as measured by ERS and the PCC, precuneus, thalamus, and
PHG, involved in empathy and self-referent processing (Platek et al.,
2005). Platek et al. suggests these areas may be related to the general
sensory aspects of face-processing.
To our knowledge, no experiments showing the relationship be-
tween startle potentiation, psychopathy, and yawning have been
published. It is, however, established the relationship between psy-
chopathy and startle as well as the relationship between yawning
and empathy (Norscia and Palagi, 2011). Though pilot in nature,
our data suggests that startle potentiation to negative stimuli may
predict one's susceptibility to contagious yawning. In line with the
theories presented on yawning and startle, it is reasonable to expect
that low startle potentiation is related to yawning susceptibility, as
affect is highly considered in both realms of research.
There is also an evolutionary justiﬁcation for the results found here-
in. While psychopathic traits are not the direct inverse of empathetic
traits, both are constructs that seem to capture polarized behaviors.
Coldheartedness refers to a dearth of social emotion (Lilienfeld and
Widows, 2005). That is, it is an inconsideration of the emotional state
of others. Our results, then, ﬁt well into the evolutionary model that
contagious yawning in our species is a function of empathy, as we
have shown that those who are characteristically lacking in empathy
are less susceptible to a contagious yawn when prompted in a paradigm
known to induce contagious yawning in normal individuals (Platek
et al., 2003).
The results of these two experiments are clear indicators that psy-
chopathy is a robust, multifaceted disposition, where a strict interpreta-
tion of an overall PPI-R score is not necessarily a predictive one. Rather,
attention to subscales and, of course, clinical evaluations are clearly
more appropriate for predictability. While gender effects between
yawning susceptibility may exist, the gender effect is controlled in the
current study. Of course, the use of females in the startle-yawn par-
adigm would be important in future studies, as psychopathy is not a
sex-dependent phenomenon (Anderson et al., 2011). The emotional
component of the PPI-R is likely the most relevant to the experi-
ments herein. While the overall measure is possibly too broad a
measure for these purposes, it nonetheless lends support to the de-
veloping idea that psychopathy, empathy, and contagious yawning
Machiavellian Egocentricism, Rebellious Nonconformity,Blame Externalization, Care-
free Nonplanfulness,Social Inﬂuence,Fearlessness,Stress Immunity,and Coldheartedness.
Standard estimates of factors on contagious yawning.
Predictor βStandard error
Total PCL-R −0.008 0.005
FD −0.015 0.010
SCI −0.001 0.009
Note. PCL-R= Psychopathic check list-revised; FD = Fearless Dominance; SCI = Self Cen-
tered Impulsivity; CD = Coldheartedness; DS = Difference Score of neutral peaks minus
The outcome variable is not dichotomous. The DS predicts frequency of yawning.
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Fig. A.1. Physiologically deﬁned contagious yawn.
Fig. A.2. Contagious yawning frequency observed in participants.
37B.K. Rundle et al. / Personality and Individual Differences 86 (2015) 33–37