Baby schema modulates the brain reward system
in nulliparous women
Melanie L. Glockera,b,1, Daniel D. Langlebenc,d, Kosha Ruparela, James W. Lougheada, Jeffrey N. Valdeza,
Mark D. Griffina, Norbert Sachserb, and Ruben C. Gura,d
aBrain Behavior Laboratory andcCenter for Studies of Addictions, Department of Psychiatry, University of Pennsylvania, Philadelphia, PA 19104;
bDepartment of Behavioral Biology, University of Muenster, 48149 Muenster, Germany; anddPhiladelphia Veterans Administration Medical
Center, Philadelphia, PA 19104
Edited by Marcus E. Raichle, Washington University School of Medicine, St. Louis, MO, and approved April 10, 2009 (received for review November 17, 2008)
Ethologist Konrad Lorenz defined the baby schema (‘‘Kindchen-
schema’’) as a set of infantile physical features, such as round face
and big eyes, that is perceived as cute and motivates caretaking
behavior in the human, with the evolutionary function of enhanc-
ing offspring survival. The neural basis of this fundamental altru-
of brain response to pictures of children, but did not dissociate the
brain response to baby schema from the response to children.
Using functional magnetic resonance imaging and controlled ma-
nipulation of the baby schema in infant faces, we found that baby
schema activates the nucleus accumbens, a key structure of the
mesocorticolimbic system mediating reward processing and ap-
petitive motivation, in nulliparous women. Our findings suggest
that engagement of the mesocorticolimbic system is the neuro-
physiologic mechanism by which baby schema promotes human
caregiving, regardless of kinship.
caregiving ? functional MRI ? social cognition ? infant ? accumbens
large head, big eyes, high and protruding forehead, chubby
cheeks, small nose and mouth, short and thick extremities, and
plump body shape, that is perceived as cute and motivates
caretaking behavior in the human (1, 2). In a species whose
young depend on care, such bias could be evolutionary adaptive
and enhance offspring survival (3–5). The behavioral effects of
the baby schema have been experimentally confirmed (6–14),
with implications for infant-caretaker interactions (15, 16). In
ethological terms, baby schema is classified as a ‘‘releaser’’ (or
‘‘key stimulus’’ in the context of social communication), which is
defined as a set of specific stimulus features sufficient to
selectively elicit a particular pattern of behavior (2, 17). This
abstract concept accounts for the generalization of the human
response to baby schema: We not only respond positively to
infants, but also to the baby schema features in adults (18),
animals (12, 19), and even objects (20). Additional support for
the motivating force of the baby schema comes from film, toy,
and advertisement industries who capitalize on our nurturing
reaction [i.e., Walt Disney’s Mickey Mouse (21)].
Although the baby schema response is a fundamental social
(22), its underlying neural mechanism is not well understood.
Ethologists postulate that a releaser unlocks a hypothetical
neurophysiologic ‘‘releasing mechanism’’ to trigger the respec-
tive behavioral response (2, 17), providing an early articulation
of a putative brain-behavior relationship for the baby schema.
Imaging studies demonstrated a differential brain response to
child faces when compared to adult faces, with activation in
multiple brain regions, including reward-related areas, such as
the orbitofrontal cortex (23, 24). Together with the behavioral
studies on the motivating effects of the baby schema (7, 8, 10),
these findings suggest that the mesocorticolimbic system under-
lying reward processing and appetitive motivation may mediate
thologist Konrad Lorenz defined the baby schema (‘‘Kind-
chenschema’’) as a set of infantile physical features, such as
the baby schema response. However, the baby schema is an
abstract concept of infantile features that is distinct from chil-
dren as a semantic category (1, 2). Previous studies reported a
to children. We used functional MRI (fMRI) and controlled
manipulation of baby schema in infant faces to test the hypoth-
esis that baby schema activates the mesocorticolimbic system,
comprised of the dopaminergic midbrain, nucleus accumbens,
amygdala, and ventromedial prefrontal cortex (25).
The majority of baby schema features are in the head and the
face and most prior research has focused on these infant
characteristics (6, 7, 9, 11–13). Using anthropometric (26) and
morphing techniques, we manipulated photographs of 17 infants
[originals courtesy Katherine Karraker, West Virginia Univer-
sity; (11)] to produce high (round face, high forehead, big eyes,
small nose and mouth), low (narrow face, low forehead, small
eyes, big nose and mouth), and unmanipulated baby schema
portraits of each infant (Fig. 1). We previously demonstrated in
a sample of 122 undergraduate students that the high baby
schema infants are perceived as cuter and elicit stronger moti-
vation for caretaking than the unmanipulated and the low baby
schema infants (10). In the present study, 16 nulliparous female
participants viewed a pseudorandom sequence of these infant
faces while we measured their brain activity with event-related
blood oxygenation level-dependent (BOLD) fMRI at high field
(3 Tesla). During the session, participants rated the pictures for
cuteness (1 ? ‘‘not very cute,’’ 2 ? ‘‘cute,’’ 3 ? ‘‘very cute’’) with
a button press on a fiber-optic response pad (FORP Current
Repeated-measures ANOVA revealed a significant main ef-
fect of baby schema on participants’ cuteness ratings (F(2, 14)
? 60.00, P ? 0.001). The high baby schema infants were rated
as cuter than the unmanipulated and the low baby schema
infants (Bonferroni corrected pair-wise comparisons: high vs.
low P ? 0.001, high vs. unmanipulated P ? 0.001, unmanipu-
lated vs. low P ? 0.001), confirming the behavioral validity of
our paradigm (10).
Neuroimaging results showed that infant faces (versus cross-
hair) across baby schema levels activated the fusiform gyrus,
thalamus, cingulate gyrus, insula, and orbitofrontal cortex (see
Table 1 for a complete list of regions), in agreement with
previous reports on the perception of children’s faces (23, 24,
fMRI signal with increased baby schema revealed significant
J.W.L., and J.N.V. performed research; M.L.G., K.R., J.W.L., and M.D.G. analyzed data; and
M.L.G., D.D.L., K.R., J.W.L., N.S., and R.C.G. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
1To whom correspondence should be addressed. E-mail: firstname.lastname@example.org.
www.pnas.org?cgi?doi?10.1073?pnas.0811620106 PNAS ?
June 2, 2009 ?
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clusters of activation in 4 brain regions: the right nucleus
left precuneus (–24, –68, 30), and left fusiform gyrus (–42, –62,
–9 and –32, –52, –14; z threshold ? 3.1, cluster probability P ?
0.001) (Fig. 2A). A test for quadratic effects did not reveal
differences between the manipulated and unmanipulated faces,
cluster in the nucleus accumbens, which was significantly higher for
high baby schema compared to unmanipulated and low baby
schema infants (repeated-measures ANOVA F(2, 14)? 12.96, P ?
0.001, high vs. unmanipulated P ? 0.05, unmanipulated vs. low ns)
A psychophysiological interactions (PPI) analysis showed that
signal in the bilateral nucleus accumbens (left, z ? 4.98, –8, 12,
–8; right, z ? 4.67, 10, 12, –8) covaried with the signal in the left
0.0001, uncorrected) (Fig. 3). There was no covariation in the
precuneus and anterior cingulate regions.
Our results are unique in experimental demonstration that baby
schema modulates the mesocorticolimbic system. These findings
suggest a neurophysiologic mechanism by which baby schema
could promote human caregiving. The nucleus accumbens is a
key structure of the mesocorticolimbic system that is linked to
the anticipation of reward (25, 30, 31). Its activation suggests that
baby schema is a positive incentive that provides motivational
drive to caretaking behavior (10). By activating the nucleus
accumbens, baby schema could release approach behavior to-
ward infants (32, 33), which may reflect the urge to hold and
cuddle an infant, as described by Lorenz (1, 2). The striatum, of
which nucleus accumbens is part, has also been associated with
more complex altruistic and affiliative processes, such as mutual
cooperation (34), charitable donation (35, 36), and social bond-
ing (27, 29). The anterior cingulate cortex projects onto the
nucleus accumbens and is activated during reward-based deci-
sion making (37, 38).
Activation of the precuneus, an area associated with attention
(39), suggests that baby schema allocates increased attention
resources to infant faces, which might be reflected in the
attention-capturing effects of infant faces in behavioral tasks
(40). The fusiform gyrus is important to face perception (41, 42),
with a particular role in processing invariant facial features (43).
The fusiform gyrus may perceptually encode baby schema
features in a face and forward this information to the nucleus
accumbens for assignment of motivational value (33, 44). Sup-
port for this conclusion comes from our finding of covariation of
the BOLD fMRI signal between the fusiform gyrus and nucleus
accumbens. This is consistent with an emerging role of the
fusiform gyrus as a major entry node in the ventrally located
extended limbic and prefrontal face network (45–47). The more
dorsally located precuneus and anterior cingulate cortex may
also receive input from visual areas other than the fusiform
gyrus, such as the inferior occipital gyri or superior temporal
sulcus (45). This may explain why we did not observe signal
covariation between the fusiform gyrus and precuneus or ante-
rior cingulate regions.
From an evolutionary perspective, recruitment of ‘‘hard-
wired’’ motivational brain mechanisms in response to baby
schema in nonparents could be adaptive, as human ancestors
likely evolved as cooperative breeders, a social system charac-
terized by the spread of the caretaker role to group members
other than the mother (5). By engaging the mesocorticolimbic
system, baby schema could motivate caring for any infant by any
potential caregiver in a group, regardless of kinship. Our study
cannot determine to what extent the baby schema response is an
evolutionary-selected mechanism brought about by natural se-
lection, and the extent to which it is modulated by cultural
contributions. There is evidence that responsiveness to baby
schema occurs in children (48) as young as 4 months of age (49),
suggesting an evolutionary-shaped basis. However, responsive-
ness to infants is also modulated by experience and learning
(50–52). Such experiences, including exposure to media and
the individual reaction to baby schema.
Our study was limited to nulliparous women and the brain
response to baby schema in men, or women in other phases of
the life cycle, may differ. Some fMRI studies on the perception
of nonvisual infantile cues, such as vocalization, demonstrated
sex-dependent activation patterns in brain regions associated
with emotion and motivation (i.e., amygdala and anterior cin-
gulate cortex) (53, 54). Behavioral studies produced inconclusive
results (7, 8, 10–14), but when sex differences were found,
women were usually more responsive to baby schema than men
(7, 8, 10, 12). We recently found that baby schema in infant faces
induces stronger motivation for caretaking in women (10). This
would suggest a stronger mesocorticolimbic response in women,
who are the primary caregivers in most societies (4). However,
in the same study, there were no sex differences in the perception
of cuteness (10), suggesting that men and women may process
baby schema similarly.
Our findings may have also been influenced by perceptual
attributions to the baby schema other than cuteness (1, 2). For
example, in infants attractiveness and cuteness ratings are highly
correlated (55), and attractive infants are rated as more smart,
likeable, healthy, friendly, and cheerful (55, 56), effects that may
themselves be mediated by the baby schema. It is possible that
these attributions covaried with our manipulations of baby
schema in infant faces, contributing to the observed brain
response. While examining the perceptual consequences of the
baby schema in infant faces other than cuteness perception is
outside the realm of this study, this idea could be an interesting
topic for future research.
mouth), unmanipulated, and high (round face, high forehead, big eyes, small
nose and mouth) baby schema faces. (Modified from ref. 10, copyright Black-
well Verlag GmbH.)
www.pnas.org?cgi?doi?10.1073?pnas.0811620106 Glocker et al.
The behavioral generalization of the baby schema response to
the perception of adults, animals, and objects with baby schema
features (12, 18–21) suggests that our neurophysiological find-
ings may extend beyond the female-infant context. Involvement
of the brain substrates for appetitive motivation may explain the
success of high baby schema icons, such as the Teddy Bear (20)
and the Volkswagen Beetle in popular culture.
In conclusion, our findings offer a previously unrecorded
insight into the biological foundations of human caregiving and
provide a neurobiological explanation to why we feel the urge to
care for anything that resembles a baby.
Materials and Methods
Subjects were 16 nulliparous, right-handed women (14 Caucasian, 2 Asian)
contraceptives and 15 were single. All had experience with child care (i.e.,
baby sitting or having a younger sibling). Candidates with psychiatric, neuro-
protocol was approved by the University of Pennsylvania Institutional Review
Board. All subjects gave written informed consent before participating.
fMRI task stimuli were 51 infant faces parametrically manipulated for their
amount of baby schema. Using antropometric (26) and morphing techniques,
we manipulated photographs of 17 Caucasian infants [8 boys and 9 girls aged
7–13 months with a neutral facial expression on black background (10, 11)] to
(narrow face, low forehead, small eyes, big nose and mouth), and unmanipu-
lated baby schema portraits of each infant (see Fig. 1). Techniques and
procedures used to create the baby schema stimuli are reported in detail in
Glocker et al. (10). Briefly, we operationalized baby schema in infant faces
using facial features that comprise the baby schema (1, 2, 6, 9, 11, 13, 57): face
Table 1. Maximally activated voxels in brain regions that respond to infant faces versus crosshair across baby schema levels
Global maxima locationLocal maxima location Coordinatesb
2,530Thalamus (medial dorsal nucleus)
?6, ?15, 8
?2, ?27, ?2
?14, ?11, 8
?10, 12, ?2
?24, ?25, ?4
2, ?28, ?2
?34, 16, ?1
?48, 9, ?7
?30, 19, ?1
?32, 19, ?6
?36, 11, ?12
?2, 14, 51
4, 21, 38
12, 14, 47
?2, 26, 24
4, ?56, ?29
?36, ?51, ?16
?16, ?69, 9
?4, 3, 24
6, 1, 22
6, 9, 22
34, 19, ?6
28, 25, ?3
32, 21, ?3
38, 15, ?6
36, 11, 20
36, 4, ?5
?26, ?50, 39
?32, ?47, 41
?28, ?54, 39
?49, ?19, 47
?44, ?21, 45
?44, ?31, 40
?40, ?25, 40
?42, 0, 29
?46, 6, 33
?51, 8, 36
14, 12, 3
14, 13, ?4
12, 8, ?4
14, 16, ?1
12, 6, 3
28, ?64, 33
24, ?62, 40
36, ?43, 41
Thalamus (ventral lateral nucleus)
Lateral geniculate body
632Insula (BA 13)
Superior temporal gyrus (BA 22)
Inferior frontal gyrus (BA 47)
Inferior frontal gyrus (BA 13)
869Superior frontal gyrus (BA 6)
Cingulate gyrus (BA 32)
Superior frontal gyrus (BA 6)
Anterior cingulate (BA 24)
Fusiform gyrus (BA 37)
Cuneus (BA 30)
73 Cingulate gyrus (BA 24)
Cingulate gyrus (BA 24)
Anterior cingulate (BA 33)
1,078Inferior frontal gyrus (BA 47)
Insula (BA 13)
Inferior frontal gyrus (BA 47)
Insula (BA 47)
Insula (BA 13)
240 Precuneus (BA 7)
Inferior parietal lobule (BA 40)
Superior parietal lobule (BA 7)
265 Postcentral gyrus (BA 2)
Postcentral gyrus (BA 3)
Inferior parietal lobule (BA 40)
Postcentral gyrus (BA 2)
76Precentral gyrus (BA 6)
Inferior frontal gyrus (BA 9)
Middle frontal gyrus (BA 9)
Lateral globus pallidius
Lateral globus pallidius
244Precuneus (BA 7)
Superior parietal lobule (BA 7)
Inferior parietal lobule (BA 40)
aVolumes are given as number of active 3.0 ? 3.44 ? 3.44 mm voxels.
bCoordinates (X,Y,Z) in Talairach space.
Results are family-wise error corrected for multiple comparisons across the whole brain (spatial extent ? 50 voxels).
Glocker et al.PNAS ?
June 2, 2009 ?
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width, forehead height and eye, nose and mouth size. These features were
captured by 6 facial parameters: Absolute face width (fw) in pixels with head
length fixed at 500 pixels and 5 proportion indices: forehead length/face
nose width/face width (nw/fw), and mouth width/face width (mw/fw). Using
of 40 unmanipulated infant photographs [20 boys and 20 girls aged 7–13
months with a neutral facial expression (10, 11)] and calculated the mean
values of each facial baby schema parameter in this sample. Using morphing
software (Morph Age, eX-cinder; Face Filter Studio, Reallusion Inc.), we then
mean values (z-scores) for each facial parameter from the sample of the 40
unmanipulated infants served as a guide for our manipulations: to maintain
normal facial appearance (26), the range of manipulations for each facial
parameter was restricted to a z-score range of ?/–2 SD. Manipulated faces
were remeasured and the new facial parameter z-scores calculated. The total
baby schema content within an infant’s face was quantified as the average
facial parameter z-score. This resulted in 17 high (mean total baby schema
z-score ? 1.0, SD ? 0.2), 17 low (mean total baby schema z-score ? –1.1, SD ?
0.1), and 17 unmanipulated baby schema infant portraits (mean total baby
schema z-score ? 0, SD ? 0.3).
During fMRI scan acquisition, participants were presented with a pseudoran-
dom, event-related sequence (optseq2, http://surfer.nmr.mgh.harvard.edu/
presented for 3 s, followed by a variable interstimulus interval (6–18 s) during
which a crosshair-fixation point was displayed on a black background (total
and 3 ? ‘‘very cute’’) with a button-press using a fiber-optic response pad (FORP
Current Design, Inc.). No stimulus picture was presented twice. Total task dura-
tion was 11 min and 36 s.
BOLD fMRI was acquired with a Siemens Trio 3 Tesla system using a
ing parameters: repetition time/echo time ? 3,000/30 ms, field of view ? 220
mm, matrix ? 64 ? 64, slice thickness/gap ? 3/0 mm, 40 slices, effective voxel
resolution of 3.4 ? 3.4 ? 3 mm. To reduce partial voluming in orbital frontal
regions, the echoplanar sequence was acquired obliquely (axial/coronal).
Before time-series acquisition, a 5-min magnetization-prepared, rapid acqui-
sition gradient-echo T1-weighted image (MPRAGE, repetition time 1,620 ms,
echo time 3.87 ms, field of view 250 mm, matrix 192 ? 256, effective voxel
resolution of 1 ? 1 ? 1 mm) was collected for anatomic overlays of functional
data and to aid spatial normalization to a standard atlas space (58).
The fMRI data were subjected to quality control, preprocessing, and sta-
tistical analysis using FEAT (fMRI Expert Analysis Tool) version 5.63, part of
FMRIB’s Software Library. Subject-level preprocessing included slice-time cor-
rection, motion correction to the median image using trilinear interpolation,
high-pass temporal filtering (100 s), spatial smoothing (6 mm FWHM, isotro-
pic), and scaling using mean-based intensity normalization. The median func-
tional image was coregistered to the corresponding high-resolution T1-
weighted structural image and transformed into standard anatomical space
(T1 Montreal Neurological Institute template) using trilinear interpolation.
Transformation parameters were applied to statistical maps before group
analyses. The brain extraction tool was used to remove nonbrain areas.
Subject-level time-series analyses were carried out using FMRIB’s Improved
Linear Model with local autocorrelation correction (59). Voxels showing in-
creased BOLD signal as a function of baby schema level were tested with a
parametric statistical model (60) using orthogonal basis functions up to the
second order. The zero-order term modeled the mean (constant term) effect
of infant faces to the crosshair irrespective of the baby schema level. The
first-order term modeled a parametric linear increase in baby schema level
(?1, 0, 1) and a second-order term modeled a quadratic relationship [all
manipulated vs. unmanipulated baby schema (–1, 2, –1)]. The parametric
model used a stepwise forward-model selection approach with 3 sequential
analyses, each with the respective order terms serving as the covariates of
interest. All covariates were convolved with a canonical hemodynamic re-
sponse function before inclusion in the general linear model (GLM). Contrast
maps of the covariates of interest were entered into a group-level 1-sample
T-test. Group Z statistic maps were generated and corrected for spatial extent
using Monte Carlo simulation (AFNI AlphaSim, R.W. Cox, National Institute of
Health) with a minimum z threshold ? 3.1 and cluster probability ? 0.001.
Identified clusters were assigned anatomic labels using the Talairach Daemon
To further examine our finding in the mesocorticolimbic system, we ex-
the 3 baby schema levels were estimated using a second single-subject anal-
convolved with canonical hemodynamic response function and modeled,
along with their temporal derivative, in a standard GLM. Mean percent signal
change values were extracted from the significant cluster in the nucleus
accumbens, identified by the linear parametric model (first order) for off-line
schema was a within-subject factor and mean percent signal change the
ing Bonferroni corrections using SPSS (SPSS Inc.).
by the first-order term of the parametric model described above (precuneus,
anterior cingulate cortex, and nucleus accumbens). A whole-brain PPI analysis
precuneus (PCu; –24, –68, 30), left fusiform gyrus (FG; –42, –62, –9 and –32, –52, –14) and right nucleus accumbens (NAcc; 10, 12, –8; z threshold ? 3.1, cluster
probability P ? 0.001). (B) The mean BOLD percent signal change from baseline in the right nucleus accumbens was greatest for high baby schema, followed
by the unmanipulated and low baby schema infants (repeated-measures ANOVA F(2, 14)? 12.96, P ? 0.001, Bonferroni corrected pair-wise comparisons *P ?
0.05 and ***P ? 0.001). Error bars show SEM.
Brain response to baby schema. (A) Linear increase in activation with increasing baby schema in the left anterior cingulate cortex (ACC; –4, 24, 38), left
4.98, –8, 12, –8; right, z ? 4.67, 10, 12, –8) that covaried with the left fusiform
gyrus seed region within the context of increasing baby schema (P ? 0.0001,
www.pnas.org?cgi?doi?10.1073?pnas.0811620106 Glocker et al.
was implemented in the FMRIB Software Library using procedures described by
Friston et al. (61). Briefly, each subject’s mean preprocessed time-series (see
above) was extracted from the left fusiform gyrus region. This seed region was
identified as the peak cluster in the whole-brain linear model. Similarly, target
regions were identified functionally using this contrast, but at a more liberal
threshold (P ? 0.01, uncorrected) that allowed inclusion of bilateral ROIs for the
precuneus, anterior cingulate cortex, and nucleus accumbens.
Subject-level PPI regressors were generated using the following design
matrix: (i) physiological term (mean time series in the fusiform gyrus); (ii)
psychological term (contrast vector for increasing baby schema convolved
contrast vector); and (iv) effect of no interest regressor (unmanipulated baby
schema). The model vectors were orthogonalized such that the PPI regressor
did not correlate with the main effects or nuisance variables. Then, subject-
specific PPI GLM models were run using the PPI regressor and movement
within the context of the first-order term of the parametric model. Single-
subject PPI images were entered into a group level, 1-sample T-test and the
resulting z statistic image (Gaussianized T) was thresholded at P ? 0.0001,
ACKNOWLEDGMENTS. We thank Dr. Katherine Karraker from the Depart-
ment of Psychology at West Virginia University for providing the original set
of infant photographs. This research was supported by a stipend of the
‘‘Studienstiftung des deutschen Volkes’’ (German National Academic Foun-
of the University of Pennsylvania and National Institute of Health Grant
MH-60722 (to R.C.G.).
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no. 22 ?