Benefits of the Duchenne Smile and Positive Emotions. A Systematic Review

Abstract

Keywords: Duchenne smile, genuine smile, positive emotion

The Duchenne smile is the genuine smile characterized by the activation of the muscles around the eyes and mouth. It has been associated, in the specialized literature, with the experience of positive emotions. Through the present work, using a qualitative approach, we aimed to identify and systematize the studies carried out in the period 2010-2023 that investigated the relationship between the Duchenne smile and positive emotions. Following the application of specific keywords, 611 studies were identified, from which, after applying the inclusion-exclusion criteria, 8 studies were included in the review. A conclusion could not be drawn regarding the idea that the Duchenne smile is indisputably an indicator of positive emotions, but the data provide us with important information such as the following: the Duchenne smile is associated with experiencing positive emotions (happiness, joy, hope, contentment) and manifests itself in the context of affiliation and cooperation. It has an important role in triggering extended cognitive states (attentional ones) and can be performed voluntarily (in the presence/absence of a positive emotion), having the same health benefits as spontaneous smiling. In addition, the Duchenne smile increases the acceptance rate of feedback given by teachers in class. The relationship between the Duchenne smile and positive emotions is context dependent.

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10.24193/ed21.2024.27.09
Benefits of the Duchenne Smile and Positive
Emotions. A Systematic Review
Violeta Lupu-Merca, Sebastian Vaida

Educatia 21 Journal 27 (2024)
ISSN online: 2247-8671
Educatia 21 Journal, (27) 2024, Art. 09
doi: 10.24193/ed21.2024.27.09
Theoretical article
This is an open access article under the Creative Commons
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© 2024 Educatia 21 Journal.
Published by Educational Sciences Department, Babeș‐Bolyai University
Benefits of the Duchenne Smile and Positive Emotions. A Systematic Review
Violeta Lupu-Merca a*, Sebastian Vaida a
a Babeș-Bolyai University, Faculty of Psychology and Educational Sciences, Cluj-Napoca, România
*Corresponding author: sebastianvaida@psychology.ro
Abstract
Keywords:
Duchenne smile, genuine smile,
positive emotion
The Duchenne smile is the genuine smile characterized by the activation of the muscles around the eyes and
mouth. It has been associated, in the specialized literature, with the experience of positive emotions. Through
the present work, using a qualitative approach, we aimed to identify and systematize the studies carried out in
the period 2010-2023 that investigated the relationship between the Duchenne smile and positive emotions.
Following the application of specific keywords, 611 studies were identified, from which, after applying the
inclusion-exclusion criteria, 8 studies were included in the review. A conclusion could not be drawn regarding
the idea that the Duchenne smile is indisputably an indicator of positive emotions, but the data provide us with
important information such as the following: the Duchenne smile is associated with experiencing positive
emotions (happiness, joy, hope, contentment) and manifests itself in the context of affiliation and cooperation.
It has an important role in triggering extended cognitive states (attentional ones) and can be performed
voluntarily (in the presence/absence of a positive emotion), having the same health benefits as spontaneous
smiling. In addition, the Duchenne smile increases the acceptance rate of feedback given by teachers in class.
The relationship between the Duchenne smile and positive emotions is context dependent.
Zusammenfasung
Schlüsselworte:
Duchenne-Lächeln, ehrliches
Lächeln, positive Emotionen
Das Duchenne-Lächeln ist das echte Lächeln, das durch die Aktivierung der Muskeln um Augen und Mund
gekennzeichnet ist. In der Fachliteratur wird es mit dem Erleben positiver Emotionen in Verbindung gebracht.
Mit der vorliegenden Arbeit wollten wir mithilfe eines qualitativen Ansatzes die im Zeitraum 2010–2023
durchgeführten Studien identifizieren und systematisieren, die den Zusammenhang zwischen dem Duchenne-
Lächeln und positiven Emotionen untersuchten. Nach Anwendung spezifischer Schlüsselwörter wurden 611
Studien identifiziert, von denen nach Anwendung der Einschluss-/Ausschlusskriterien 8 Studien in die
Überprüfung einbezogen wurden. Es konnte keine Schlussfolgerung hinsichtlich der Vorstellung gezogen
werden, dass das Duchenne-Lächeln unbestreitbar ein Indikator für positive Emotionen ist, aber die Daten
liefern uns wichtige Informationen wie die folgende: Das Duchenne-Lächeln wird mit dem Erleben positiver
Emotionen (Glück, Freude, Hoffnung, Zufriedenheit) und manifestiert sich im Kontext von Zugehörigkeit und
Kooperation. Es spielt eine wichtige Rolle bei der Auslösung erweiterter kognitiver Zustände
(Aufmerksamkeitszustände) und kann freiwillig durchgeführt werden (bei Vorhandensein/Fehlen einer
positiven Emotion) und hat die gleichen gesundheitlichen Vorteile wie spontanes Lächeln. Darüber hinaus
erhöht das Duchenne-Lächeln die Akzeptanz des Feedbacks der Lehrer im Unterricht. Der Zusammenhang
zwischen dem Duchenne-Lächeln und positiven Emotionen ist kontextabhängig.
1. Introduction
The Duchenne smile has been the subject of much
research, especially in recent years since positive
psychology has seen considerable development. The
diversity of research on the Duchenne smile and the
domains in which it has been investigated (e.g., in the
field of emotions and facial recognition, the field of
social interactions, the neuro-physiological field, etc.)
have contributed to understanding the depth of this
concept and the importance that it can have in people's
lives. The researchers' concerns focused on how
people perceive the Duchenne smile and the
differences in perception between them, its
relationship with health, well-being in general, but
also in establishing to what extent a Duchenne smile
can or cannot be faked. One of the hypotheses most
used in research is the one that states that the
Duchenne smile is an indicator of positive emotions.
The Duchenne smile is the spontaneous smile, the
smile with "mouth to ears", the smile that can hardly
be faked, the smile that activates the muscles around
the eyes and mouth, the smile that is associated with
experiencing positive emotions (Ekman et al., 1990;
Frank & Ekman, 1993). The belief that this hypothesis
is true has led to the Duchenne smile being used in
several studies to identify positive emotions (Abel &
Kruger, 2010; Soussignan, 2002) in which various
concepts in relation to experiencing positive emotions
have been investigated. The most common emotion it
has been associated with is that of joy or happiness.
On the other hand, there are also studies that have

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Educatia 21 Journal, 27 (2024) Art. 09, Page | 95
claimed that the Duchenne smile can be achieved
voluntarily (Krumhuber & Manstead, 2009;
Krumhuber et al., 2014), can be used as a cultural tool
(Martin, et al., 2017) and that its appearance is also
present in the case of experiencing negative emotions
(Harris & Alvarado, 2005).
Smiling is associated with the idea of joy or
happiness, but to the same extent, smiling can also be
used to mask negative emotions such as fear, anger,
distress, disgust (Ekman, 2009). It is thus considered
to be "one of the most widely used signals used in
human communication" (Kraut & Johston, 1979, p.
1539). One of the reasons why smiling can easily be
used to mask other than positive emotions is that it is
the most easily voluntary facial expression (Ekman,
2009). Seen as an important tool of social
communication, the smile has been classified, in the
specialized literature, into several categories. Thus,
from the point of view of association or not with a
positive emotion, a distinction was made between the
genuine, true smile and the fake smile that does not
accompany positive emotions (Martin et al., 2017).
The smile typology was determined by calling on
different methods. The best known and most used is
the Facial Action Coding System (FACS) (Ekman,
2002), through which specialists can identify, based on
facial action units, movements of the muscles involved
in manifestation of facial expressions. Thus, in the
expression of a smile, the action units AU 6 (raising
the cheeks) and AU 12 (raising the corners of the
mouth) are activated. Starting from this method,
programs have been developed to accurately identify
the intensity and duration of certain expressions basic
facial recognition such as Noduls Face Reader which
has only 85-86% accuracy in facial emotion
recognition compared to FACS (Cross et al., 2022).
Another method used is facial electromyography
(EMG) which has the quality of capturing muscle
movement at the level of micro-expression that is not
visible to the naked eye (Wingenbach, 2022).
The importance of research on smiling is
supported by the results of studies that have provided
evidence that it has numerous benefits in various areas
of people's lives.
People who intentionally smile for one minute a
day improve their mood (Neuhoff & Schaefer, 2002).
This is of particular importance, as there are studies
that have shown that our emotional state has an
important impact on the immune system (D'Acquisto
et al., 2014). Smiling can therefore have a protective
role when people face situations laden with negative
emotionality (Ansfield, 2007). It appears that in mildly
depressed individuals, even a short-lived smile has the
ability to improve their negative moods in the long
term (Lin et al., 2015).
Today, the most widely used indicator that
differentiates between genuine and fake smiles is the
Duchenne marker, named after the well-known French
neurologist, Guillaume Benjamin Amand Duchenne
de Bologne (1862). He studied the movement of facial
muscles and observed that during the experience of
genuine joy, the zygomatic major muscle and the
orbicularis oculi contracted, which did not occur
during the display of fake joy and an inauthentic smile
associated with it (Ekman et al., 1990). The one who
coined this type of smile with the name of Duchenne
was Paul Ekman (1989).
The Duchenne smile was therefore most
associated with joy. Thus, in an experiment carried out
by Ekman et al. (1990), this type of smile was
displayed more often in the context of viewing
pleasant movies than during unpleasant ones, when the
comparison was made with other types of smiling. In
these contexts, smiling was observed taking into
account brain asymmetry measured by
electroencephalogram (EEG) and subjects' self-report
of their positive emotions. It was thus observed that
during the Duchenne smile, the left side of the
temporal and parietal region of the brain is mainly
activated, the activation of the left temporal side
occurring during the experience of positive emotions,
but it was not possible to specify what exactly the
activation of the parietal region of the brain reflects
(Ekman et al., 1990).
On the other hand, it has been shown that the
Duchenne smile can be produced deliberately even in
the absence of positive emotion (Gosselin et al., 2010).
Moreover, some research has found that the Duchenne
smile can occur even when negative emotions such as
stress, pain, or sadness are experienced (Harris &
Alvarado, 2005).
The Duchenne smile is assumed to be an indicator
of experiencing positive emotions (Messinger et al.,
2001). Researchers have questioned whether positive
emotions have the same adaptive purpose as negative
ones, which present specific behavioral tendencies
useful for survival (David & Szentágotai-Tătar, 2017).
Thus Broaden-and-Build Theory (Fredickson, 2001)
emerged as a response to traditional psychology that
has paid more attention to negative emotions and their
evolutionary role. This emphasizes the effect that
positive emotions have, in opposition to negative ones,

Violeta Lupu-Merca, Sebastian Vaida
Educatia 21 Journal, 27 (2024) Art. 09, Page | 96
on cognitive structures related to attention and
thinking, transformations that can further lead to
behavioral changes (Ayers et.al, 2014).
Contemporary theories of emotions (Ellis, 1994,
apud Dryden & Bond, 1994) claim that subjective
experiences, whether positive or negative, are not
generated by the life events we face, but by the way
we evaluate them, either consciously or
unconsciously, giving them a certain meaning,
emotions being able, in turn, to be evaluated and give
rise to other emotions (David & Szentágotai-Tătar,
2017).
2. Methodology
To carry out the systematic review, the PRISMA
(Preferred Reporting Items for Systematic Reviews
and Meta-Analyses) methodology was used, which,
although initially developed for research in the
medical field, was also successfully used in the field
of psychology (Bolier et al., 2013, apud. Tay et al.,
2021).
An online literature search was conducted using
two databases, Springer Link and Web of Science.
These databases were chosen after analyzing their
functions and content. They have been found to
represent data collections that can be used
appropriately for this type of approach and research
field, compared to others (Gusenbauer & Haddaway,
2020; Walden, 2021).
To refine the research, we used the Boolean search
type and created the following key word
combinations: ("Duchenne smile" OR "genuine smile"
OR "true smile" OR "authentic smile" OR "enjoyable
smile") AND ("positive emotions" OR “happiness”
OR “joy” OR “gratitude” OR “serenity” OR “interest”
OR “hope” OR “pride” OR “amusement” OR
“inspiration” OR “awe” OR “love”).
To identify the articles, the lexicon corresponding
to positive emotions exemplified in the Broaden-and-
Build Theory of positive emotions (Fredrickson, 1998)
was used. The intention was to review studies that
looked at other positive emotions in relation to the
Duchenne smile, apart from those that looked at the
emotions of happiness and joy.
3. Inclusion-exclusion criteria
We applied three inclusion criteria to identify
studies according to the objective of this review.
The first criterion followed the year of publication
of the article. We wanted to review articles from the
last ten years, to capture what was new on this topic,
but since approximately two years were affected by
the Covid 19 pandemic, we included three more years
in the research, the final period considered being 2010
-2023.
The next criterion considered the inclusion of
articles published only in scientific journals, not
books, and having a detailed analysis of the results.
The third criterion concerned the language in which
the article was written and, in this sense, only articles
written in English were chosen. Clinical trials, review
studies and meta-analyses were excluded. We decided
not to include reviews and meta-analyses, since these
presuppose the identification of primary research
specific to a topic (Pollock & Berge, 2018), or, by
selecting them, it would mean using secondary sources
of data, and the purpose of our research is not to carry
out an umbrella type review (Choi & Kang, 2023). We
also excluded studies that addressed the issue of
smiling in general, without a clear distinction between
Duchenne and non-Duchenne smiles or other types of
smiles. In addition, the articles that fall within the
scope of dental or aesthetic medicine, and the studies
that investigated the perception of the Duchenne smile
or the relationship of the Duchenne smile with other
concepts, were removed.
The title and abstract of articles were screened to
identify relevant articles meeting these criteria. When,
after reading the abstract, the article could not be
eliminated with certainty, the full text was analyzed.
There were no restrictions related to the number
of participants, their age, the type of design.
4. Results
After entering the keywords mentioned above, we
obtained a total of 611 studies. After removing
duplicates (394), 217 studies remained. 210 studies
were excluded because they were either unrelated to
the topic or did not meet the eligibility criteria.
Another study included in the bibliography of an
eligible article was identified and entered for analysis.
In total, 8 studies were fully and carefully analyzed
to extract the information necessary for our systematic
review. Figure 1 illustrates our approach through the
PRISMA diagram. The eight studies are illustrated in
Table 1.

Violeta Lupu-Merca, Sebastian Vaida
Educatia 21 Journal, 27 (2024) Art. 09, Page | 97
Table 1 Synthesis of the articles selected for the narrative review
regarding the relationship of the Duchenne smile with positive
emotions.
No
Article
1
Campos, B., Schoebi, D., Gonzaga, G. C., Gable, S. L.,
& Keltner, D. (2015). Attuned to the positive?
Awareness and responsiveness to others’ positive
emotion experience and display. Motivation and
Emotion, 39(5), 780–794.
https://doi.org/10.1007/s11031-015-9494-x
2
Gunnery, S. D., Hall, J. A., & Ruben, M. A. (2013).
The deliberate duchenne smile: Individual differences
in expressive control. Journal of Nonverbal
Behavior, 37(1), 29–41.
https://doi.org/10.1007/s10919-012-0139-4
3
Girard, J. M., Cohn, J. F., Yin, L., & Morency, L.-P.
(2021). Reconsidering the Duchenne smile:
Formalizing and testing hypotheses about eye
constriction and positive emotion. Affective
Science, 2(1), 32–47. https://doi.org/10.1007/s42761-
020-00030-w
4
Ergül, H. (2023). The case for smiling? Nonverbal
behavior and oral Corrective Feedback. Journal of
Psycholinguistic Research, 52(1), 17–32.
https://doi.org/10.1007/s10936-021-09807-x
5
Tuck, N. L., Adams, K. S., Pressman, S. D., &
Consedine, N. S. (2017). Greater ability to express
positive emotion is associated with lower projected
cardiovascular disease risk. Journal of Behavioral
Medicine, 40(6), 855–863.
https://doi.org/10.1007/s10865-017-9852-0
6
Johnson, K. J., Waugh, C. E., & Fredrickson, B. L.
(2010). Smile to see the forest: Facially expressed
positive emotions broaden cognition. Cognition &
Emotion, 24(2), 299–321.
https://doi.org/10.1080/02699930903384667
7
Mattson, W. I., Cohn, J. F., Mahoor, M. H., Gangi, D.
N., & Messinger, D. S. (2013). Darwin’s Duchenne: eye
constriction during infant joy and distress. PloS
One, 8(11), e80161.
https://doi.org/10.1371/journal.pone.0080161
8
Crivelli, C., Carrera, P., & Fernández-Dols, J.-M.
(2015). Are smiles a sign of happiness? Spontaneous
expressions of judo winners. Evolution and Human
Behavior: Official Journal of the Human Behavior and
Evolution Society, 36(1), 52–58.
https://doi.org/10.1016/j.evolhumbehav.2014.08.009
Figure 1. PRISMA diagram of the search and selection process.
Note: From Page MJ, McKenzie JE, Bossuyt PM, Boutron I,
Hoffmann TC, Mulrow CD, et al. The PRISMA 2020 statement:
an updated guideline for reporting systematic reviews. BMJ
2021;372:n71. doi: 10.1136/bmj.n71. For more information,
visit: http://www.prisma-statement.org/
5. Discussions
The Duchenne smile is the marker most used in
research to identify the experience of positive
emotions. However, the question has been raised
whether this assumption is correctly used and whether
when conducting such studies it is not necessary to
take into account the complexity of the context in
which a smile appears in general, and a Duchenne
smile in particular.
In the review of the specialized literature, we took
into account the way in which the Duchenne smile was
used and to what extent the authors of the studies
showed whether or not it is an indicator of positive
emotions. As we have seen, the essential element that
differentiates the Duchenne smile from other forms of
smiling is the activation of the eye muscles (lat.
Orbicularis oculi) which produces this expression of
raising the cheeks, narrowing the eyes and wrinkling
the skin around the eyes (Ekman et al ., 1990). Most
of the studies identified linked the Duchenne smile to
the expression of an emotion of happiness and joy.
However, it appears that this smiling time is also
associated with experiencing other positive emotions.
Thus, in the study by Johnson et al. (2010), the
occurrence of Duchenne smile during inductions of
positive, negative or neutral emotions was
investigated. Moreover, the authors, carrying out two
experimental studies, wanted to find out to what extent
the expansion of the cognitive repertoire as formulated
and supported by the Broaden-and-Build Theory
(Fredrickson, 2001) can be produced by facial
expressions specific to positive emotions. The study
used facial electromyography (EMG) as a method to
discriminate Duchenne from non-Duchenne smiles, as

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Educatia 21 Journal, 27 (2024) Art. 09, Page | 98
an alternative measure that the authors claimed was
more valid in capturing emotions not stated in subjects'
self-reports ( Johnson et al., 2010). It was found that
the frequency of Duchenne smiles among subjects was
higher during the induction of positive emotions than
when they were induced with negative or neutral
emotions, and this type of smile also correlated with
self-reports of positive emotions, such as hope and
contentment. In addition, the study showed that the
frequency of the Duchenne smile was associated with
attentional expansion, in a task of global processing of
visual stimuli, self-reports of positive emotions
expressed also at the facial level, being predictors in
this regard.
Given these results, however, we ask whether the
Duchenne smile can be deliberately produced and,
when it is, to what extent does it still express positive
emotion? In this sense, the study by Gunnery et al.
(2013) investigated the extent to which people can
voluntarily produce a Duchenne smile in different
social situations and if there are individual differences
in the ability to voluntarily produce this smile, the
experimental procedure took care to minimize the
effect of emotional and motivational factors. Subjects
participated in two types of tasks: a role-play task,
designed to measure the use of the deliberate
Duchenne smile in simulated social situations, and an
imitation task, designed to measure the ability to
produce the Duchenne smile. The results showed that
some of the participants were able to deliberately
produce a Duchenne smile in both tasks, which
indicated that such an expression of a positive emotion
can be deliberately achieved without the positive
emotion being experienced.
And in another study included in the review
(Girard et al., 2021), the authors reconsidered the
Duchenne smile hypothesis regarding the fact that it is
a specific indicator of genuine positive emotion. The
authors formulated and tested alternative hypotheses,
the results being the following: the hypothesis that the
Duchenne smile is triggered by positive emotions was
supported, 90% of the smiles produced while
experiencing a positive emotion involved narrowing
the eyes.
Although eye constriction was the main indicator
by which positive emotions were differentiated from
negative ones, however, the presence of this marker
explained only 27% of the variance of self-reported
positive emotions and only 32% of smile intensity. It
was thus shown that other dimensions such as smile
intensity and duration were better predictors of the
presence of positive emotions when eye muscle
movement was controlled for.
If the Duchenne smile can be produced voluntarily
and can have a role in social interactions, it remains to
be seen to what extent the same deliberate Duchenne
smile can have the benefits that arise from the
association of spontaneous smiling with positive
emotions.
In this sense, in the study by Tuck et al. (2017) the
Duchenne smile was used as an indicator of the ability
to express positive emotions. More precisely, the
subjects deliberately expressed ten basic emotions,
including that of happiness, the Duchenne smile being
identified by a special software that scores the
expressiveness according to the contraction of the
facial muscles, then calculating a positive
expressiveness score. After applying statistical
analyzes to test the associations between this score and
other variables measured in this study (demographic
data, atherosclerotic cardiovascular disease risk score,
emotion scale score, depression scale score, loneliness
and emotional intelligence) the authors found that
positive emotionality and the ability to voluntarily
express positive emotions were associated with
reduced risk of cardiovascular disease (CVD), even
after controlling for variables such as loneliness,
depression, and trait positive emotionality. These
results are consistent with those of an older study that
showed that regardless of whether an emotion is
experienced or not, the ability to deliberately express
it reduces the risk of CVD (Kraft & Pressman, 2012).
The study by Campos et al. (2015), even if its main
theme was to examine human emotional receptivity in
different social situations, it was chosen for analysis
because it aimed at the production of positive
emotions in these contexts, their identification being
achieved both by coding the manifested Duchenne
smiles, by Facial Action Coding System (FACS), as
well as in relation to the participants' self-reports of
their experiences. The authors demonstrated that
people are aware and responsive to others' emotions
when there is an opportunity for commitment in a
future relationship (Campos et al., 2015).
The results showed that the subjects were more
receptive to the positive emotions accompanied by the
Duchenne smile of others, compared to the positive
emotions that were not accompanied by this type of
smile. Only positive emotions (particularly
amusement) that displayed a Duchenne smile were
predictive of subsequent closeness between two
strangers.

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Based on the same argument as the one for which
I chose the previous article in the review, I also
included for analysis the studies of Crivelli et al.
(2015) and Ergul (2021).
Thus, the study conducted by Crivelli et al. (2015)
analyzed the controversy between Basic Emotion
Theory (Ekman & Friesen, 1969; Izard, 1971;
Tomkins, 1962) and Ecological Behavioral Theory
(Fridlun, 1994) whose assumptions we discussed in
the introductory part of this paper. The authors
observed the facial expressions of judo players in two
contexts: winning a match in a national junior
championship and instant victory in an international
competition. The second approach was carried out to
verify the results of the first study, in a more diverse
cultural context. Both situations had a high potential
for generating positive emotions.
What was predictive for the appearance of the
Duchenne smile was the moment of interaction of the
athletes (inferred from the movements of the arms and
hands in contact with the audience), this result coming
in support of the Behavioral Ecology Theory that sees
the smile as a tool of social interaction, and not an
expression of basic emotions (Fridlund, 1994).
Last but not least, the study conducted by Ergül
(2023) aimed to find out how often teachers smile
while giving students corrective feedback during
classes and whether the smile used is a genuine one.
Moreover, it was investigated to what extent the
genuine smile is a factor that can influence the
effectiveness of the corrective oral feedback. The
results showed that 64% of the smiles used by the
teachers during the corrective feedback were genuine.
Furthermore, when the genuineness of the smile was
taken into account it was found that the acceptance rate
of student feedback increased by 69.4%, with genuine
smiles significantly correlating with corrective oral
feedback compared to polite smiles (Ergül, 2023).
The last study selected for our analysis
investigated whether the Duchenne marker represents
the facial expression that signals both positive and
negative emotions in infants during parent-child play
using the face-to-face and still-face (Face-to-
Face/Still- Face [FFSF]) (Mattson et al., 2013). The
results of the study confirmed the hypothesis
formulated by Darwin according to which the
constriction of the eyes in babies is associated either
with more positive smiles or with a more negative
expressiveness of crying. Thus, the smile
accompanied by the narrowing of the eyes is more
intense and appears more often in situations that cause
positive emotions, than the simple smile, which does
not involve the constriction of the eyes. The study also
aimed at highlighting the role of eye constriction in the
emotional expressiveness of crying, in the inert face
condition of the mother and in a real distress situation,
namely the vaccination of children. As the authors of
the study also concluded, in infants, the Duchenne
smile signals the presence of a strong positive
emotion, but at the same time a Duchenne-type
expression can also indicate a negative emotion in
their case.
Is the Duchenne smile an indicator of positive
emotions? In an attempt to answer this question, we
selected and analyzed for the narrative systematic
review the studies in which the production of
Duchenne smiles either took place during the
experience of spontaneous positive emotions caused
by certain natural life situations, or appeared during
the induction of positive emotions in laboratory or
experimental situations. Articles that only investigated
the idea of perception and interpretation of these
smiles in different contexts without actually producing
the Duchenne smile, whether deliberate or not, were
removed. On the other hand, some of the present
studies did not entirely lack the investigation of
Duchenne smile perception, but since measuring the
frequency of smile production was one of their themes,
they were also taken into analysis.
Based on the results of these studies, we cannot yet
draw a clear conclusion regarding the idea that the
Duchenne smile is an indisputable indicator of positive
emotions, but the data provide us with important
information such as the following: Duchenne smile is
associated with experiencing positive emotions in
general , with those of happiness and joy, in particular.
However, the present studies have shown that this time
of smiling is also found when emotions such as hope
and contentment are experienced.
In addition, the Duchenne smile also occurs during
the experience of emotions that are manifested in the
context of affiliation and cooperation. Also, this type
of smile has an important role in triggering extended
cognitive states, without knowing the exact
mechanism in this regard.
On the other hand, emotions such as pride and awe
were not associated with the Duchenne smile, but on
the contrary, with the non-Duchenne smile. What has
also been established in both the present and older
studies is that the Duchenne smile can be produced
voluntarily, either in the presence or in the absence of
positive emotion, especially in tasks that do not

Violeta Lupu-Merca, Sebastian Vaida
Educatia 21 Journal, 27 (2024) Art. 09, Page | 100
involve more complex cognitive processing (e.g. when
participants are asked to imitate a smile, as opposed to
having to do so in a role play). Voluntary Duchenne
smiling may provide the same health benefits as
genuine smiling, individuals who have a good ability
to voluntarily express such smiles are likely to have
emotional self-regulation skills.
Related to the elements that differentiate a
Duchenne smile from a non-Duchenne smile and their
relationship with positive emotions, it was found that
although the constriction of the eyes through the
activation of the Orbicularis oculi muscle
corresponding to the facial action unit AU6 in the
FACS coding system is considered a differentiating
element between the two types of smiling, however
this expression was also encountered in situations
where no positive emotions were experienced. In
addition, it appears that intensity is a better predictor
of positive emotions.
Taking into account all these corroborated results
and data from other older studies, we can say that
research is still needed to discover the mechanisms
underlying these relationships between the Duchenne
smile and positive emotions.
The intensity of the smile must be taken into
account in such studies when differentiating between
Duchenne and non-Duchenne smiles. Some studies
have found in addition to spatial patterns, as
considered the Duchenne marker, and temporal
properties of emotional expressions that also
contribute to the differentiation between a
spontaneous and a deliberate smile, being associated
with the person's internal states, such as the duration
of a smile (Schmidt et al., 2006).
There are authors who recommend that we focus
our attention on what a Duchenne smile does rather
than what it expresses, without the intention of
detracting from the importance of its use for
identifying positive emotions, but considering that it is
insufficient to evaluate an emotion and label as such
(Krumhuber & Kappas, 2022).
A limitation of the present work arises from the
fact that the classification of positive emotions carried
out by Fredickson (2013) was used to identify the
studies. In the specialized literature, no agreement was
reached regarding a standard classification of positive
emotions, its use in the search process being possible
not to cover the whole spectrum of positive emotions
that could have been used as keywords.
Being an individual paper, it was not possible to
fulfill the requirement required by the methodology of
systematic reviews, namely the use of a minimum of
two people to select, preferably individually, the
articles for analysis, which may have influenced the
evaluation of their selection.
6. Conclusions
Is the Duchenne smile an indicator of positive
emotions? In an attempt to answer this question, we
selected and analyzed for the narrative systematic
review the studies in which the production of
Duchenne smiles either took place during the
experience of spontaneous positive emotions caused
by certain natural life situations, or appeared in during
the induction of positive emotions in laboratory or
experimental situations. Articles that only investigated
the idea of perception and interpretation of these
smiles in different contexts without actually producing
the Duchenne smile, whether deliberate or not, were
removed. On the other hand, some of the present
studies did not entirely lack the investigation of
Duchenne smile perception, but since measuring the
frequency of smile production was one of their themes,
they were also taken into analysis.
Based on the results of these studies, we cannot yet
draw a clear conclusion regarding the idea that the
Duchenne smile is an indisputable indicator of positive
emotions, but the data provide us with important
information such as the following: Duchenne smile is
associated with experiencing positive emotions in
general , with those of happiness and joy, in particular.
However, the present studies have shown that this time
of smiling is also found when emotions such as hope
and contentment are experienced.
In addition to their relationship with positive
emotions, it was found that although the constriction
of the eyes through the activation of the Orbicularis
oculi muscle corresponding to the facial action unit
AU6 in the FACS coding system is considered a
differentiating element between the two types of
smiling, however this expression was also encountered
in situations where no positive emotions were
experienced. Also, it appears that intensity is a better
predictor of positive emotions.
The Duchenne smile also appears in the interaction
between teachers and students, during which the
former provide corrective feedback, increasing the rate
of its acceptance by students. On the other hand, the
constriction of the eyes is a marker of distress found in
both children and adults.

Violeta Lupu-Merca, Sebastian Vaida
Educatia 21 Journal, 27 (2024) Art. 09, Page | 101
The intensity of the smile must be taken into
account in such studies when differentiating between
Duchenne and non-Duchenne smiles. Some studies
have found in addition to spatial patterns, as
considered the Duchenne marker, and temporal
properties of emotional expressions that also
contribute to the differentiation between a
spontaneous and a deliberate smile, being associated
with the person's internal states, such as the duration
of a smile (Schmidt et al., 2006).
There are authors who recommend that we focus
our attention on what a Duchenne smile does rather
than what it expresses, without the intention of
detracting from the importance of its use for
identifying positive emotions, but considering that it is
insufficient to evaluate an emotion and label as such
(Krumhuber & Kappas, 2022).
To conclude, taking into account all these
corroborated results and data from other older studies,
we can say that research is still needed to discover the
mechanisms underlying these relationships between
the Duchenne smile and positive emotions.
Authors note:
Violeta Lupu-Merca is a psychologist who
graduated from the Faculty of Psychology and
Educational Sciences within the Babeș Bolyai
University, Cluj-Napoca and is currently involved in
an MA in Clinical Psychology. Her interests are in the
area of clinical psychology and human development.
Sebastian Vaida is a PhD Lecturer in Psychology
at the University of Babeș-Bolyai interested in the
fields of social-emotional competences development,
psychology of advertising, adaptive learning and
IT&C applied to psychology.
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