Effects of oxytocin on recollections of maternal careand closeness
Jennifer A. Bartza,1, Jamil Zakib, Kevin N. Ochsnerc, Niall Bolgerc, Alexander Kolevzona, Natasha Ludwiga,
and John E. LydondaDepartment of Psychiatry, Mount Sinai School of Medicine, New York, NY 10029; bDepartment of Psychology, Harvard University, Cambridge, MA 02138;
Department of Psychology, Columbia University, New York, NY 10027; and dDepartment of Psychology, McGill University, Montreal, QC, Canada H3A 2T5c

Although the infant–caregiver attachment bond is critical to survival, little is known about the biological mechanisms supporting
attachment representations in humans. Oxytocin plays a key role inattachment bond formation and maintenance in animals and thus
could be expected to affect attachment representations in humans.
To investigate this possibility, we administered 24 IU intranasal oxytocin to healthy male adults in a double-blind, placebo-controlled,
crossover designed study and then assessed memories of childhood
maternal care and closeness—two features of the attachment bond.
We found that the effects of oxytocin were moderated by the attachment representations people possess, with less anxiously attached individuals remembering their mother as more caring andclose after oxytocin (vs. placebo) but more anxiously attached individuals remembering their mother as less caring and close after
oxytocin (vs. placebo). These data contrast with the popular notionthat oxytocin has broad positive effects on social perception and are
more consistent with the animal literature, which emphasizes oxytocin’s role in encoding social memories and linking those memories
to the reward value of the social stimulus.
neurohypophyseal hormones
differences Syntocinon|| social cognition | social memory | individualA

ccording to attachment theory (1–3), infants develop affective bonds with their caregivers, which arise from an attachment behavioral system that promotes the infant’s survival byfacilitating caregiver closeness and protection. A core feature of
the attachment system is the notion of internal working models,
which are thought to contain information about close others’ reliability and availability to meet one’s needs for security, as well asaffective and motivational information about regulating the self in
relation to signiﬁcant others. These attachment representations
are formed in the infant–caregiver relationship but continue tooperate throughout the lifespan and are adjusted to incorporate
new close relationship experiences. The attachment behavioral
system plays an important role in guiding interpersonal perceptions, expectations, and behaviors, but it is also signiﬁcant from an
evolutionary perspective—the attachment bond is thought to be
essential for species survival because it fosters caregiver protection, thereby allowing the infant to survive to maturity and reproduce (2). Although critical to survival, little is known about
the biological mechanisms supporting attachment representations
in humans.
One candidate suggested by animal research is oxytocin, a mammalian hormone that acts as a neuromodulator in the brain. Oxytocin is produced in the hypothalamus and released into thecirculatory system, where it is involved in facilitating uterine contractions during parturition and milk ejection during lactation (4).
Oxytocin also is released directly into the brain, where it has beenshown to play a critical role in attachment bond formation andmaintenance in animals (5–8). A working hypothesis is that social
contact triggers the release of oxytocin; oxytocin then orients attention to social stimuli and facilitates the encoding of social
memories along with the hedonic value of the social stimulus (viainteractions with the dopamine system) so that attachment bonds

www.pnas.org/cgi/doi/10.1073/pnas.1012669107

are formed with social but not nonsocial objects (6, 9). On the basisof the physiological role oxytocin plays in childbirth and animal
attachment data, it often is assumed that oxytocin is involved inhuman attachment representations. This idea has not been tested
empirically, however.
We investigated whether oxytocin is involved in human attachment representations by manipulating the availability of oxytocin
in the brain and assessing the effects of oxytocin on recollections ofchildhood maternal care and closeness—two key features of theattachment bond. Although it is popularly thought that oxytocin
has broad positive effects on social perception and function inhumans (e.g., refs. 10–12), we theorized that if oxytocin is involved
in linking social stimuli (mother) and hedonic information (warm,
affectionate, “makes me feel better,” close), the effects of oxytocin
on recollections of maternal care and closeness should depend on
the attachment representations people possess. Rather than positively biasing maternal recollections for everyone, oxytocin should
bias these recollections in a positive or negative direction, depending on the nature of one’s attachment style.
One critical factor then that should moderate the effects of oxytocin on maternal recollections is chronic concerns about theavailability of close others, or attachment anxiety (1, 2). Attachment
anxiety is theorized to be rooted in early experiences with a caregiver
who inconsistently responds to the infant’s bids for protection andnurturance; in response, the infant becomes anxious, preoccupied
with securing the caregiver’s love and attention, and fearful ofabandonment. The attachment representation formed as a function of the infant–caregiver relationship then becomes an “interpretative ﬁlter” through which new relationships are meaningfully
understood and construed (2, 3, 13), although it is clear that subsequent interpersonal experiences can modify people’s attachment representations. [Indeed, a recent meta-analysis found that
infant and adult attachment styles are typically only moderately
correlated (Pearson r = 0.27), indicating that there is both stability
and change in attachment representations over time (14).] In thisway, attachment anxiety becomes a more general interpersonal
orientation characterized by worry, hypervigilance to attachmentrelated cues, and chronic feelings of unmet attachment needs. Thispattern of attachment can be contrasted with that of more securely
attached individuals who, through repeated experiences with a responsive caregiver, come to expect that close others can generally be
relied upon in times of need.
We hypothesized that oxytocin would positively bias recollections of maternal care and closeness for less anxiously attachedindividuals because it should bring to mind their positive caregiving experiences and expectancies—that is, feelings of adequate
caregiver responsivity and closeness. By contrast, oxytocin should
negatively bias recollections of maternal care and closeness for

Author contributions: J.A.B. designed research; J.A.B., A.K., and N.L. performed research;
J.A.B. and N.B. analyzed data; and J.A.B., J.Z., K.N.O., N.B., and J.E.L. wrote the paper.
The authors declare no conﬂict of interest.
*This Direct Submission article had a prearranged editor.
1

To whom correspondence should be addressed. E-mail: jennifer.bartz@mssm.edu.

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Edited* by Shelley E. Taylor, University of California, Los Angeles, CA, and approved October 28, 2010 (received for review August 26, 2010)

more anxiously attached individuals because it should bring tomind the caregiver’s inconsistencies and unpredictability, consistent with their chronic concerns about separation and abandonment.
To investigate the effects of oxytocin on recollections of maternal care and closeness in childhood, and to test whether attachment anxiety moderates those effects, we conducted a randomized, double-blind, placebo-controlled, crossover trial inwhich adult male participants received 24 IU intranasal oxytocin
or a matching placebo on two occasions (3–5 wk apart). Individual
differences in attachment anxiety and avoidance were assessed atbaseline, and recollections of maternal care and closeness inchildhood were assessed at both testing sessions after oxytocin/
placebo administration (Materials and Methods). We then calculated the change in maternal recollections as a function of drug by
subtracting placebo day ratings from oxytocin day ratings on themeasures of maternal care and closeness; thus, positive values onthese change indices indicate increased perceptions of care andcloseness for oxytocin vs. placebo, and negative values indicate decreased perceptions of care and closeness for oxytocin vs. placebo.
Results
Our primary dependent variables were change (oxytocin minus
placebo) in (i) maternal care ratings and (ii) maternal closenessratings. To test our hypotheses we conducted regression analyses
with mean-centered attachment anxiety, mean-centered avoidance, the anxiety × avoidance interaction, and drug administration order (coded: placebo ﬁrst = −0.5; oxytocin ﬁrst = +0.5) as
predictors of each change score. With the regression model set
up in this way, the intercept estimates the main effect of drug forthe typical person. Results showed no main effect of oxytocin onchange in maternal care ratings [b = 0.02, t(26) = 0.22, nonsigniﬁcant (ns)] or change in maternal closeness ratings [b =−0.03, t(26) = −0.17, ns]. This suggests that in contrast to theprediction that would be made on the basis of one popular view,
oxytocin did not positively bias recollections of maternal careand closeness in childhood for the typical person.
However, as hypothesized, attachment anxiety interacted withoxytocin administration. Speciﬁcally, attachment anxiety signiﬁcantly predicted change in maternal care ratings for oxytocin vs.
placebo [b = −0.12, t(26) = −2.16, P < 0.05] and change inmaternal closeness ratings for oxytocin vs. placebo [b = −0.45,t(26) = −2.95, P < 0.01]. As depicted in Figs. 1 and 2, less anxiously attached individuals remembered their mother as morecaring (Fig. 1, left side) and remembered being closer to theirmother (Fig. 2, left side) when they received oxytocin comparedwith when they received placebo, whereas the opposite was true formore anxiously attached individuals, who remembered theirmother as less caring (Fig. 1, right side) and remembered being lessclose to their mother (Fig. 2, right side) after oxytocin vs. placebo.
Neither avoidance nor the anxiety × avoidance interaction predicted change in maternal care (all ts < 1.7) or change in maternalcloseness (all ts < 1.4) ratings.†
Additional analyses indicate that oxytocin did not simply bias
participants’ current beliefs about themselves and/or their close
relationships more generally. Regression analyses like thosedescribed above revealed no effects of drug, attachment anxiety,attachment avoidance, or the anxiety × avoidance interaction onchange in self-esteem (all ts < 1), current attachment (all ts ≤ 1),or perceptions of closeness to participants’ closest current relationship partner (all ts < 1). Moreover, these observations†

There was a signiﬁcant effect of drug administration order on change in maternal closeness ratings [b = −0.79, t(26) = −2.29, P < 0.05] but not on change in maternal careratings (t < 0.5). Importantly, additional analyses showed no order × attachment anxiety
interaction (t < 0.5), indicating that the effect of attachment anxiety on change inmaternal closeness ratings does not depend on drug administration order.

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Fig. 1. Scatter plot displaying the association between participants’ attachment anxiety score (mean-centered) and change in recollections ofmaternal care after oxytocin (OXT) [vs. placebo (PL)], with predicted regression line. The dotted curves indicate 95% conﬁdence intervals (CIs).
Higher numbers on the care change index (y axis) indicate an increase in carerecollections in the oxytocin condition; lower numbers on the care change
index indicate a decrease in care recollections in the oxytocin condition;a change score of zero indicates no change in recollections of maternal careacross drug conditions. Higher numbers on the attachment anxiety scale (xaxis) indicate greater attachment anxiety. Predicted values are shown only
for observed levels of attachment anxiety. The predictive equation whenother variables are set to their mean value is as follows: change in maternalcare = 0.02 – 0.125 (mean-centered attachment anxiety). The effect of attachment anxiety predicting change in maternal care ratings was signiﬁcantat P < 0.05, two-tailed.

cannot be explained by the nonspeciﬁc effects of oxytocin onstate mood: paired-samples t tests comparing change in statemood (i.e., postoxytocin/placebo mood ratings vs. baseline moodratings) in the oxytocin and placebo conditions showed no effects
of drug on change in anxiety, anger, depression, confusion, fatigue, or vigor (all ts < 1, ns). Finally, the percentage of participants guessing they received oxytocin did not differ by drug
condition [54.84% receiving placebo and 45.16% receiving oxytocin; c2(2, n = 62) = 1.42, ns], indicating that participants were
unaware of whether they had received oxytocin or placebo.
Discussion
Little is known about the biological mechanisms supporting attachment representations in humans. One potential candidate is
the neuromodulator oxytocin, which regulates attachment bondformation and maintenance in animals. We investigated oxytocin’s
involvement in human attachment representations by manipulating the availability of oxytocin and measuring recollections ofmaternal care and closeness in childhood—two key features of
the attachment bond. In contrast to the popular view that oxytocin
exerts broad positive effects on social perception and behavior inhumans (10–12, 15), we did not ﬁnd that oxytocin positively biased
maternal recollections in all cases. Rather, we found that theeffects of oxytocin on maternal recollections were critically moderated by individual differences in attachment anxiety. Speciﬁcally,
less anxiously attached individuals remembered their mother as
more caring and remembered being closer to their mother in childhood after oxytocin (vs. placebo) administration, whereas more anxiously attached individuals remembered their mother as less caring
and remembered being less close to their mother in childhood
after oxytocin (vs. placebo) administration. These observations are
Bartz et al.

striking given that maternal recollections like those assessed here
are thought to be fairly stable (16). Importantly, oxytocin biased
neither peoples’ current beliefs about themselves or their mood,ruling out the possibility that such effects on participants’ current
state could have distorted their childhood memories. The fact thatoxytocin had a polarizing rather than a main effect on maternal
recollections suggests that oxytocin plays a more nuanced role inattachment representations than previously thought. Indeed, theseﬁndings are more consistent with the animal literature, in which it
has been suggested that oxytocin is involved in encoding social
memories and linking those memories to the reward value of social
stimuli (6, 9).
One question is whether oxytocin increases people’s ability toaccurately recollect their relationship with their mother duringchildhood. Although there is some evidence that oxytocin facilitates accurate memory for faces in humans (17–19), we cannot
conclusively say whether oxytocin increases people’s accuracy
here because we do not have information about participants’attachment style to their mother in childhood, which would beneeded for a true index of accuracy.
An alternative possibility is that oxytocin triggers a motivatedrecall, setting in motion a biased search for information that iscongruent with people’s current chronic interpersonal beliefs andexpectations (20). In contrast to the social memory studies referred
to above, which focused on relatively “cold” aspects of cognition(stranger’s faces) (21), we asked participants to recollect one of themost signiﬁcant relationships in their life—their relationship with
their mother. Moreover, attachment representations contain information about the identity of the caregiver but, more signiﬁcantly, cognitive, affective, and motivational information related tothe caregiver’s ability to meet one’s most basic needs for security.
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Fig. 2. Scatter plot displaying the association between participants’ attachment anxiety score (mean-centered) and change in recollections ofmaternal closeness after oxytocin (OXT) [vs. placebo (PL)], with predicted
regression line. The dotted curves indicate 95% conﬁdence intervals (CIs).
Higher numbers on the closeness change index (y axis) indicate an increase incloseness recollections in the oxytocin condition; lower numbers on thecloseness change index indicate a decrease in closeness recollections in theoxytocin condition; a change score of zero indicates no change in recollections of maternal closeness across drug conditions. Higher numbers on theattachment anxiety scale (x axis) indicate greater attachment anxiety. Predicted values are shown only for observed levels of attachment anxiety. The
predictive equation when other variables are set to their mean value is asfollows: change in maternal closeness = −0.03 − 0.446 (mean-centered attachment anxiety). The effect of attachment anxiety predicting change inmaternal closeness ratings was signiﬁcant at P < 0.05, two-tailed.

Given that we are tapping these “hot” aspects of cognition, there ismore opportunity for chronic affective and/or motivational interpersonal biases to come into play as people recollect on theseearly experiences (22, 23). We suspect that oxytocin may work inthe brain in ways that increase activation of the attachment systemand the reward centers associated with attachment, so that it produces an attachment-congruent memory search in which participants selectively remember information about their mother that is
consistent with their current chronic attachment style, in this way
biasing recollections. Future research will be needed to fully answer
the bias vs. accuracy question because both mechanisms are consistent with the data.
Another point worth discussing is that oxytocin did not change
participants’ current attachment level. Although it is possible thatmeasurement issues (e.g., assessing general rather than motherspeciﬁc attachment after oxytocin/placebo) may have undermined
our ability to detect an effect of oxytocin on change in current
attachment, this null effect is in fact consistent with the activation
hypothesis. Consider an analogy to cognitive priming of an attitude like “politicians are untrustworthy.” Such an attitude is available in memory (for those who hold the attitude), but it can also
be primed—for example, by showing people a picture of former
US President Nixon, a notoriously untrustworthy politician.
Priming does not typically alter the extremity of the attitude; rather,priming activates the attitude so that it is more readily applied ina situation involving the attitude object, in the example above biasing people’s evaluation of an unknown politician (see ref. 24 forfurther discussion about attitude extremity vs. strength). Similarly,
oxytocin may serve as a prime that increases the activation ofchronic attachment representations so that they more readily guidepeople’s memory search about their early experiences of maternalcare and closeness. Future research incorporating implicit measures of attachment accessibility could explore this hypothesis.
One last question is whether attachment in general, or motherspeciﬁc attachment, moderates the effects of oxytocin on maternal recollections. As noted, attachment representations arerooted in the infant–caregiver relationship but are revised overthe lifespan to incorporate other signiﬁcant relationships (2, 3).
Attachment in adulthood is thus complex, reﬂecting one’s pastand current relationship with parents, as well as those with romantic partners, and even close friends. Although a detailed discussion is beyond the scope of this article, theory (3) and empirical
work (25) suggest that attachment representations are hierarchically organized, with episodic memories of speciﬁc attachment
interactions at the bottom, representations of relationship “kinds”
in the middle, and more general attachment representations at the
top. Given the complexity of attachment in adulthood, it is standard to measure a person’s global attachment style (3) as we did,and data suggest that global and relationship-speciﬁc measures tap
distinguishable constructs that are modestly correlated (26). Given
the small correlations between explicit measures of global attachment and mother-speciﬁc attachment, it would seem unlikely that
our signiﬁcant effect for global attachment anxiety was due solely
to chronic mother-speciﬁc representations.
Finally, it should be noted that participants in this study weremen. Future research is needed to conﬁrm whether these ﬁndings generalize to women.
In closing, these data suggest caution when hypothesizing
about the effects of oxytocin for different individuals or as an intervention. On one hand, we found that oxytocin exacerbatedchronic concerns about closeness and the reliability of close others
that characterize attachment anxiety. On the other hand, lessanxious participants clearly showed a beneﬁcial response to oxytocin, remembering their relationship with their mother in childhood in a more positive light. Oxytocin is popularly dubbed the“hormone of love,” but these data suggest that oxytocin is not an
all-purpose attachment panacea.

Materials and Methods
Participants. Participants were 31 men aged 19–45 y (mean, 27.06 y; SD, 7.05 y;
median, 25 y) who were medication free and conﬁrmed to be mentally andphysically healthy by a study psychiatrist. We focused on men only in thisstudy because of possible risks associated with administering oxytocin to
women (i.e., inducing labor and unknown effects on a developing fetus).
The study was approved by the Mount Sinai School of Medicine Institutional
Review Board, and all participants gave informed consent before participation. Participants were compensated $120.
Procedures. Participants ﬁrst underwent a brief interview with a study psychiatrist to conﬁrm eligibility. Eligible participants completed a series of selfreport questionnaires including the Experience in Close Relationships scale(ECR) (27), a widely used and highly reliable self-report measure of adultattachment. Baseline mood was also assessed at this point with the Proﬁle ofMood States (POMS) (28).
Participants then self-administered 24 IU intranasal oxytocin [Syntocinon(Novartis), imported from Switzerland] or a matching placebo under the supervision of study personnel. The placebo was custom-designed by a commercial compounding pharmacy to match drug minus the active ingredient.
To maintain the blind, drug and placebo were transferred to generic bottles.
Drug/placebo administration order was counterbalanced, and participantsand experimenters were blind to drug condition (the Mount Sinai School of
Medicine pharmacy oversaw packaging, storage, and dispensation of study
drug and placebo, maintained drug accountability, and assigned randomization codes to study participants). As described in Results, participants wereunable to discern whether they had taken active drug or placebo when
queried at the end of each testing session.
Approximately 90 min after oxytocin/placebo administration, and after
completing the POMS again and another measure unrelated to this study (seeref. 29 for a detailed description of this measure), we assessed recollectionsof maternal care with the Parental Bonding Instrument (PBI) (30) and recollections of maternal closeness with the Inclusion of Other in the Self
scale (IOS) (31). To address the speciﬁcity of the effects of oxytocin, we also
assessed self-esteem (32), current attachment (33), and IOS for “closest
current relationship.” Finally, at the end of the testing session, participants
were asked to guess whether they had received oxytocin or placebo thatday. Participants returned 3–5 wk later, received the alternate compound,and underwent identical procedures (with the exception of the psychiatricinterview and baseline questionnaires).
Materials. The ECR (27), which was modiﬁed from 36 to 29 items to reduce
item redundancy, assesses attachment anxiety (i.e., sensitivity to and anxiety
about rejection/abandonment) and attachment avoidance (i.e., discomfort
with and desire to avoid closeness). Participants indicate on a seven-point
scale how much they agree or disagree with each item in terms of how they“generally feel in important close relationships in [their] life” (e.g., family
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members, romantic partners, and close friends). After reverse scoring items
for which lower numbers reﬂected greater attachment anxiety or avoidance,
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relationship closeness; scores range from 1 to 7, with higher numbers
reﬂecting greater closeness. To be consistent with the PBI, the IOS was
similarly framed in terms of how participants remember their relationshipwith their mother during their ﬁrst 16 y.
The Rosenberg Self-Esteem Scale (32) is a widely used self-report measureof self-esteem.
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the secure, preoccupied, avoidant-dismissive, and avoidant-fearful attachment styles. Participants rate the extent to which they resembled each of thefour styles in their close relationships on a scale from 0 (“not at all”) to 4(“completely”). Scores for attachment anxiety and avoidance can be calculated by subtracting dismissive from preoccupied ratings and subtracting
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observe a change in current attachment within a 3-h period if we assessedattachment using identical attachment measures before vs. after oxytocin.
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the extent to which each item describes “how they feel right now” on ascale from 0 (not at all) to 4 (extremely).
ACKNOWLEDGMENTS. We thank Julian Beale, Cara Settipani, Katherine
Remy, Ana Tryfon, David Grodberg, and Khalid Khan for research assistance.
The Beatrice and Samuel A. Seaver Foundation provided ﬁnancial support.
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