Why is your spouse so predictable? Connecting
mirror neuron system and self-expansion model
of love

Stephanie Ortigue

a

, Francesco Bianchi-Demicheli

b,

*

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.

0306-9877/$ - see front matter



c

2008 Elsevier Ltd. All rights reserved.

doi:10.1016/j.mehy.2008.07.016

* Corresponding author. Tel.: [phone]; fax: [phone].

E-mail address:

[e-mail]

(F. Bianchi-Demicheli).

Medical Hypotheses (2008) 71, 941–944

www.elsevier.com/locate/mehy

Introduction

Self-expansion model of love

Often we here couples refer to each other as the
better half or the completion of oneself therefore
indicating that there is an expansion of the self in
a beloved

[1–4]

. Inspired mostly by Eastern con-

ceptualizations of love, Aron and Aron’s model of
self-expansion of love suggests that humans have
a recurrent motivation to expand their self

[2]

.

The self-expansion model of love assumes that
the expansion of the self involves two phases:
expansion, then integration of each new expansion
by incorporating aspects (e.g., new skills, atti-
tudes, resources, behaviors) of another into the
self

[1–3,5]

. Whereas this theory sounds kind of

‘cliche

´’, a growing body of social and psychological

evidence reinforces it

[1,2,4,6,7]

. It is concordant

with several studies suggesting that intense life-
time achievements (e.g., love) are a central human
motivation to ‘‘expand the self’’

[1–4]

. On a more

cognitive level, self-expansion means that each
partner makes a decision to include another in his
or her self

[2]

. Critically, recent neuroimaging

studies provide further support in favor of this
self-expansion model of love by demonstrating a
recruitment of the self-related brain network in
people who are in love

[7,8]

. Among this network,

one brain area, the inferior parietal lobule and
notably the angular gyrus, received particular
attention since it is involved in various functions,
such as metaphors, abstract representation of pas-
sionate love, and integrations of abstract represen-
tation of the self

[7,9–14]

. Interestingly, increase

of activation in this part of the brain is correlated
with faster meaningful (vs. meaningless) cognitive
decision making in people who are in love in com-
parison

with

people

who

are

not

in

love

[6,7,15,16]

. According to a study done by Ortigue

et al., when participants in love are exposed to
non-conscious presentation of their partners’ name
before a word detection exercise, they perform
better than when they are exposed to the non-con-
scious presentation of just a neutral acquain-
tance’s name. This performance is positively
correlated with different measures of love and de-
sire for their partner (e.g., passionate love scale,
intensity, and percent of thoughts)

[7,16]

. It is

worth noting that people in love are faster to re-
spond to meaningful stimuli only, and not to any
types of stimulation. These findings suggest that
participants who are in love perform quicker in
the cognitive exercise because they make auto-
matic self-related mental associations when the

name of their so-called « better-half » is presented

[7]

. Love is not only an emotion and/or a motiva-

tion; it is also an integrated cognitive mechanism
that may automatically call for stored representa-
tion of positive reinforcement for the self and the
significant other

[7]

. This cognitive facilitation ef-

fect is enhanced by the interaction between the
self and the significant other. Because a key aspect
of a successful love relationship is the extraordi-
nary ease to understand the mental states and
intentions of the significant other (ability that oc-
curs often automatically; i.e., without explicitly
trying too hard), this may have critical implications
in a love relationship, notably for the social–com-
municative functioning. This facilitation effect of
love on intention understanding constitutes a
strong rational for the present mirror neuron sys-
tem hypothesis of love.

The mirror neuron system and social
cognition

The discovery of the mirror neuron system (MNS),
which includes a type of neurons (i.e., mirror neu-
rons) that are activated both by the execution and
the observation of object-related actions, recently
challenged social cognition and interpersonal rela-
tionships

[10,17–23]

. Although individual neurons

cannot easily be recorded from the putative areas
in the human brain, a growing body of studies sup-
ports the existence of a human mirror neuron sys-
tem in action observation, execution, as well as
in intention understanding

[12,17,20,21,24]

. Nota-

bly, neurophysiological recordings, including elec-
troencephalography

(EEG)

and

magnetoen-

cephalography (MEG) as well as functional MRI
(fMRI) studies indicate that MNS provides a plausi-
ble neurophysiological mechanism to many social
behaviors, such as action, imitation, empathy, sex-
ual arousal, and also intention understanding and
prediction

[10–14,17,20–27]

. In the past decade,

MNS thus opened an avenue towards the under-
standing of social interactions by highlighting the
way people observe others’ actions, interact, enter
and maintain social inter-personal relationships.
The functional properties of MNS suggest that the
understanding of intentions of others is based
mainly on a mechanism that directly matches the
sensory representation of the observed actions
with one’s own motor representations of those
same actions, representations of past self-related
experiences that are stored and integrated at a
higher order cognitive level

[17,24,25–27]

. Be-

cause MNS generates internal representations of
action outcomes common to one’s self and others,

942

Ortigue and Bianchi-Demicheli

it is likely to be involved in our capacity to under-
stand the actions, intentions and experiences of
other people

[17,24,25–27]

. Through this mirror

mechanism the observer, besides recognizing the
observed motor act, is also able to predict what
will be the final goal of the agent’s action

[17,23,24]

. In other words, the observer can under-

stand the intentions behind the agent’s action. This
suggests that the observer understands actions and
intentions of others by automatically expanding his
self through a mechanism of embodied simulation
(i.e., internal representations of body states asso-
ciated with actions and emotions; e.g., being in
someone else’s shoes that is active when one does
something

or

observes

someone

else

acting

[10,17,21,25,27]

.

In humans, the mirror neuron system has two

major components

[17]

. One is formed by the infe-

rior parietal lobule and the ventral premotor cor-
tex plus the caudal part of Broca’s area, the
other by the insula and anterior cingulate gyrus

[17,21,26,27]

. The main visual input to the MNS

originates from the posterior part of the superior
temporal sulcus

[17,21,26,27]

. Recent evidence

suggest that MNS, insula and some limbic structures
interact. Critically, recent data suggest that the
insular–cingular network of the MNS would play a
fundamental role in emotion recognition and
empathy, whereas the MNS’s fronto–parietal net-
work would rather be important to understand
intentions of others

[17,21,26,27]

.

Our hypothesis

Based on the above it is our hypothesis that the
mirror neuron system plays a curical role in love.
Even if it of course clear that being in love is not
a prerequisite to activate the MNS, we postulate
the existence of a shared network for both love
and embodied simulations. Thus, we hypothesize
that a significant relationship may exist between
the cerebral correlates of love and at least one of
the brain regions located within the mirror neuron
system. Based on the functional properties of MNS,
and the self-expansion model, a mechanism partly
sustained by the inferior parietal lobule (a part of
MNS), we further hypothesize that people who
are in love are faster at automatically understand-
ing intentions of their beloved (and themselves) in
comparison with a neutral person when deciding
intentions of others. Critically, we suggest that
the MNS facilitates the modelling of the behaviour
of the beloved through a mechanism of embodied
simulation — that is, internal representations of

body states associated with actions and emotions.
The similarities between the mirror matching pro-
cess and the ease to understand the other in a love
relationship suggest that exposure to love might af-
fect functional and neural mechanisms, thus facil-
itating

the

understanding

of

the

beloved’s

intentions. Embodied simulation could provide a di-
rect facilitator of experiential understanding of the
beloved. Based on these phenomenological, and
neurofunctional findings we suggest that the mirror
mechanisms are involved in the facilitation effects
of love for understanding and predicting intentions
of the significant other, and might further be ex-
tended to any types of love (e.g., passionate love;
maternal love).

Testing the hypothesis

Our mirror neuron system hypothesis of love sug-
gests a positive correlation between love and MNS’s
activation. If this hypothesis is correct, one could
expect that the phenomenological manifestation
of MNS in persons who are in love might be charac-
terized by a facilitation effect for understanding
and predicting the intentions of their beloved (as
it would be the case for their own intentions) in
comparison with a neutral person when deciding
intentions of others. Our provisional data from sev-
eral participants (38 healthy volunteers; 18–25 yrs
old) lend to support our prediction that under-
standing of other’s intentions is facilitated (faster
reaction times during a motor intention inference
task) in couples who are in love. More precisely,
people who are in love are faster in automatically
understanding/predicting intentions of their be-
loved (and themselves) in comparison with a con-
trol stimulus (p < 0.01), even if they don’t know
the stimuli category.

On a neural point of view, this facilitation effect

should positively correlate with the recruitment of
MNS. Reciprocally, a disruption of MNS activity
would preclude such a facilitation effect of the
experiential understanding of the beloved. Given
the physiological properties of mirror neurons,
and the present assumed link between the MNS
and love, it is highly plausible that dysfunctions
of the MNS could lead to deficits in the love rela-
tionships. Particularly, we assume that reduced
other’s intention understanding might be a core
deficit in people who have love-relationship issues
(e.g., ‘‘the fortune fool in love’’). Thus, we sug-
gest that the MNS is less activated in people with
love interaction impairment. For instance, based
on the convergent data set that indicates that the
mu rhythm can be a window to explore the human

Why is your spouse so predictable? Connecting mirror neuron system and self-expansion model

943

MNS activity

[12]

, we expect mu rhythm to be re-

duced in persons who are reported to be the so-
called serial ‘‘fortune fool in love’’. Thus the mu
suppression could conceivably be used as a reliable
indicator of the human MNS activity in love rela-
tionships. The systematic study of this mirror neu-
ron system hypothesis of love in neurological
patients with focal brain damage within MNS will
provide critical insights on the spatio-temporal
dynamics of love. Yet, concerning its subjective
character, love experience is difficult to access.
The tools of socio-cognitive neuroscience make it
possible to approach love and self-related experi-
ences not only by the analysis of subjective self-re-
ported questionnaires, but also by approaching the
automatic (non-conscious) mirror experiences of
love in healthy subjects, neurological patients
after a brain damage, and/or patients suffering
from chronic social and affective disorders, such
as autism.

Conclusion

We hypothesize here that the mirror neuron system
is involved in love, notably in the ease to predict
the beloved’s actions and intentions. Although
the psychology of love is now well admitted, the
systematic multidisciplicary study of our new and
potentially testable explanation of love might open
a new avenue towards the social mind and self
consciousness.

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Available online at www.sciencedirect.com

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