Medical Hypotheses (2008) 71, 941 944
www.elsevier.com/locate/mehy
Why is your spouse so predictable? Connecting
mirror neuron system and self-expansion model
of love
a b,
*
Stephanie Ortigue , Francesco Bianchi-Demicheli
a
4D Brain Electrodynamics Laboratory, UCSB Brain Imaging Center, Institute for Collaborative
Biotechnologies, Sage Center for the Study of the Mind and Department of Psychology, Building 251,
room 3, University of California Santa Barbara, 93106 Santa Barbara, CA, USA
b
Psychosomatic Gynaecology and Sexology Unit, Emergency and Liaison Services, Geneva University
Psychiatric Center, 15 rue des Pitons; 1205 Geneva, Switzerland
Received 19 June 2008; accepted 3 July 2008
Summary The simulation theory assumes we understand actions and intentions of others through a direct matching
process. This matching process activates a complex brain network involving the mirror neuron system (MNS), which is
self-related and active when one does something or observes someone else acting. Because social psychology admits
that mutual intention s understanding grows in close relationship as love grows, we hypothesize that mirror
mechanisms take place in love relationships. The similarities between the mirror matching process and the mutual
intention s understanding that occurs when two persons are in love suggest that exposure to love might affect
functional and neural mechanisms, thus facilitating the understanding of the beloved s intentions. Congruent with our
hypothesis, our preliminary results from 38 subjects strongly suggest a significant facilitation effect of love on
understanding the intentions of the beloved (as opposed to control stimuli). Based on these phenomenological, and
neurofunctional findings we suggest that the mirror mechanisms are involved in the facilitation effects of love for
understanding intentions, and might further be extended to any types of love (e.g., passionate love, maternal love).
Love experiences are important not only to the beloved himself, but also to any societal, cultural, and institutional
patterns that relate to love. Yet, concerning its subjective character, love experiences are difficult to access. The
modern procedures and techniques of socio-cognitive neuroscience make it possible to understand love and self-
related experiences not only by the analysis of subjective self-reported questionnaires, but also by approaching the
automatic (non-conscious) mirror experiences of love in healthy subjects, and neurological patients with a brain
damage within the mirror neuron system. Although the psychology of love is now well admitted, the systematic study
of the automatic facilitation effect of love through mirror mechanisms might open a new avenue towards the social
mind and also self consciousness.
c
2008 Elsevier Ltd. All rights reserved.
*
Corresponding author. Tel.: [phone]; fax: [phone].
E-mail address: [e-mail] (F. Bianchi-Demicheli).
c
0306-9877/$ - see front matter 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.mehy.2008.07.016
942 Ortigue and Bianchi-Demicheli
name of their so-called « better-half is presented
Introduction
[7]. Love is not only an emotion and/or a motiva-
tion; it is also an integrated cognitive mechanism
Self-expansion model of love
that may automatically call for stored representa-
tion of positive reinforcement for the self and the
Often we here couples refer to each other as the
significant other [7]. This cognitive facilitation ef-
better half or the completion of oneself therefore
fect is enhanced by the interaction between the
indicating that there is an expansion of the self in
self and the significant other. Because a key aspect
a beloved [1 4]. Inspired mostly by Eastern con-
of a successful love relationship is the extraordi-
ceptualizations of love, Aron and Aron s model of
nary ease to understand the mental states and
self-expansion of love suggests that humans have
intentions of the significant other (ability that oc-
a recurrent motivation to expand their self [2].
curs often automatically; i.e., without explicitly
The self-expansion model of love assumes that
trying too hard), this may have critical implications
the expansion of the self involves two phases:
in a love relationship, notably for the social com-
expansion, then integration of each new expansion
municative functioning. This facilitation effect of
by incorporating aspects (e.g., new skills, atti-
love on intention understanding constitutes a
tudes, resources, behaviors) of another into the
strong rational for the present mirror neuron sys-
self [1 3,5]. Whereas this theory sounds kind of
tem hypothesis of love.
 cliché , a growing body of social and psychological
evidence reinforces it [1,2,4,6,7]. It is concordant
The mirror neuron system and social
with several studies suggesting that intense life-
cognition
time achievements (e.g., love) are a central human
motivation to   expand the self  [1 4]. On a more
The discovery of the mirror neuron system (MNS),
cognitive level, self-expansion means that each
which includes a type of neurons (i.e., mirror neu-
partner makes a decision to include another in his
rons) that are activated both by the execution and
or her self [2]. Critically, recent neuroimaging
the observation of object-related actions, recently
studies provide further support in favor of this
challenged social cognition and interpersonal rela-
self-expansion model of love by demonstrating a
tionships [10,17 23]. Although individual neurons
recruitment of the self-related brain network in
cannot easily be recorded from the putative areas
people who are in love [7,8]. Among this network,
in the human brain, a growing body of studies sup-
one brain area, the inferior parietal lobule and
ports the existence of a human mirror neuron sys-
notably the angular gyrus, received particular
tem in action observation, execution, as well as
attention since it is involved in various functions,
in intention understanding [12,17,20,21,24]. Nota-
such as metaphors, abstract representation of pas-
bly, neurophysiological recordings, including elec-
sionate love, and integrations of abstract represen-
troencephalography (EEG) and magnetoen-
tation of the self [7,9 14]. Interestingly, increase
cephalography (MEG) as well as functional MRI
of activation in this part of the brain is correlated
(fMRI) studies indicate that MNS provides a plausi-
with faster meaningful (vs. meaningless) cognitive
ble neurophysiological mechanism to many social
decision making in people who are in love in com-
behaviors, such as action, imitation, empathy, sex-
parison with people who are not in love
ual arousal, and also intention understanding and
[6,7,15,16]. According to a study done by Ortigue
prediction [10 14,17,20 27]. In the past decade,
et al., when participants in love are exposed to
MNS thus opened an avenue towards the under-
non-conscious presentation of their partners name
standing of social interactions by highlighting the
before a word detection exercise, they perform
waypeopleobserve others actions, interact, enter
better than when they are exposed to the non-con-
and maintain social inter-personal relationships.
scious presentation of just a neutral acquain-
The functional properties of MNS suggest that the
tance s name. This performance is positively
understanding of intentions of others is based
correlated with different measures of love and de-
mainly on a mechanism that directly matches the
sire for their partner (e.g., passionate love scale,
sensory representation of the observed actions
intensity, and percent of thoughts) [7,16]. It is
with one s own motor representations of those
worth noting that people in love are faster to re-
same actions, representations of past self-related
spond to meaningful stimuli only, and not to any
experiences that are stored and integrated at a
types of stimulation. These findings suggest that
higher order cognitive level [17,24,25 27]. Be-
participants who are in love perform quicker in
cause MNS generates internal representations of
the cognitive exercise because they make auto-
action outcomes common to one s self and others,
matic self-related mental associations when the
Why is your spouse so predictable? Connecting mirror neuron system and self-expansion model 943
it is likely to be involved in our capacity to under- body states associated with actions and emotions.
stand the actions, intentions and experiences of The similarities between the mirror matching pro-
other people [17,24,25 27]. Through this mirror cess and the ease to understand the other in a love
mechanism the observer, besides recognizing the relationship suggest that exposure to love might af-
observed motor act, is also able to predict what fect functional and neural mechanisms, thus facil-
will be the final goal of the agent s action itating the understanding of the beloved s
[17,23,24]. In other words, the observer can under- intentions.Embodiedsimulationcouldprovideadi-
stand theintentionsbehind the agent s action. This rect facilitator of experiential understanding ofthe
suggests that the observer understands actions and beloved. Based on these phenomenological, and
intentions of others by automatically expanding his neurofunctional findings we suggest that the mirror
self through a mechanism of embodied simulation mechanisms are involved in the facilitation effects
(i.e., internal representations of body states asso- of love for understanding and predicting intentions
ciated with actions and emotions; e.g., being in of the significant other, and might further be ex-
someone else s shoes that is active when one does tended to any types of love (e.g., passionate love;
something or observes someone else acting maternal love).
[10,17,21,25,27].
In humans, the mirror neuron system has two
Testing the hypothesis
major components [17]. One is formed by the infe-
rior parietal lobule and the ventral premotor cor-
Our mirror neuron system hypothesis of love sug-
tex plus the caudal part of Broca s area, the
gestsapositivecorrelationbetweenloveandMNS s
other by the insula and anterior cingulate gyrus
activation. If this hypothesis is correct, one could
[17,21,26,27]. The main visual input to the MNS
expect that the phenomenological manifestation
originates from the posterior part of the superior
of MNS in persons who are in love might be charac-
temporal sulcus [17,21,26,27]. Recent evidence
terized by a facilitation effect for understanding
suggestthat MNS,insulaandsome limbicstructures
and predicting the intentions of their beloved (as
interact. Critically, recent data suggest that the
it would be the case for their own intentions) in
insular cingular network of the MNS would play a
comparison with a neutral person when deciding
fundamental role in emotion recognition and
intentions of others. Our provisional data from sev-
empathy, whereas the MNS s fronto parietal net-
eral participants (38 healthy volunteers; 18 25 yrs
work would rather be important to understand
old) lend to support our prediction that under-
intentions of others [17,21,26,27].
standing of other s intentions is facilitated (faster
reaction times during a motor intention inference
task) in couples who are in love. More precisely,
Our hypothesis people who are in love are faster in automatically
understanding/predicting intentions of their be-
Based on the above it is our hypothesis that the loved (and themselves) in comparison with a con-
mirror neuron system plays a curical role in love. trol stimulus (p < 0.01), even if they don t know
Even if it of course clear that being in love is not the stimuli category.
a prerequisite to activate the MNS, we postulate On a neural point of view, this facilitation effect
the existence of a shared network for both love should positively correlate with the recruitment of
and embodied simulations. Thus, we hypothesize MNS. Reciprocally, a disruption of MNS activity
that a significant relationship may exist between would preclude such a facilitation effect of the
the cerebral correlates of love and at least one of experiential understanding of the beloved. Given
the brain regions located within the mirror neuron the physiological properties of mirror neurons,
system. Based on the functional properties of MNS, and the present assumed link between the MNS
and the self-expansion model, a mechanism partly and love, it is highly plausible that dysfunctions
sustained by the inferior parietal lobule (a part of of the MNS could lead to deficits in the love rela-
MNS), we further hypothesize that people who tionships. Particularly, we assume that reduced
are in love are faster at automatically understand- other s intention understanding might be a core
ing intentions of their beloved (and themselves) in deficit in people who have love-relationship issues
comparison with a neutral person when deciding (e.g.,   the fortune fool in love  ). Thus, we sug-
intentions of others. Critically, we suggest that gest that the MNS is less activated in people with
the MNS facilitates the modelling of the behaviour love interaction impairment. For instance, based
of the beloved through a mechanism of embodied on the convergent data set that indicates that the
simulation  that is, internal representations of mu rhythm can be a window to explore the human
944 Ortigue and Bianchi-Demicheli
[8] Aron A, Fisher H, Mashek DJ, Strong G, Li H, Brown LL.
MNS activity [12], we expect mu rhythm to be re-
Reward, motivation, and emotion systems associated with
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called serial   fortune fool in love  . Thus the mu
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