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What Does Sexual Orientation Orient? A Biobehavioral Model Distinguishing Romantic Love and Sexual Desire



Although it is typically presumed that heterosexual individuals only fall in love with other-gender partners and gay-lesbian individuals only fall in love with same-gender partners, this is not always so. The author develops a biobehavioral model of love and desire to explain why. The model specifies that (a) the evolved processes underlying sexual desire and affectional bonding are functionally independent; (b) the processes underlying affectional bonding are not intrinsically oriented toward other-gender or same-gender partners: (c) the biobehavioral links between love and desire are bidirectional, particularly among women. These claims are supported by social-psychological, historical, and cross-cultural research on human love and sexuality as well as by evidence regarding the evolved biobehavioral mechanisms underlying mammalian mating and social bonding.
What Does Sexual Orientation Orient? A Biobehavioral Model
Distinguishing Romantic Love and Sexual Desire
Lisa M. Diamond
University of Utah
Although it is typically presumed that heterosexual individuals only fall in love with other-gender
partners and gay–lesbian individuals only fall in love with same-gender partners, this is not always so.
The author develops a biobehavioral model of love and desire to explain why. The model specifies that
(a) the evolved processes underlying sexual desire and affectional bonding are functionally independent;
(b) the processes underlying affectional bonding are not intrinsically oriented toward other-gender or
same-gender partners; (c) the biobehavioral links between love and desire are bidirectional, particularly
among women. These claims are supported by social–psychological, historical, and cross-cultural
research on human love and sexuality as well as by evidence regarding the evolved biobehavioral
mechanisms underlying mammalian mating and social bonding.
As recent debates about same-gender marriage have made clear,
sexual orientation is about much more than sex. Although individ-
uals are typically classified as lesbian, gay, or bisexual on the basis
of their sexual desires, it is widely believed that sexual orientation
has an affectional component as well. The sexual and affectional
components are typically presumed to agree, meaning that indi-
viduals who sexually desire same-gender partners also fall in love
with same-gender partners (Bell, Weinberg, & Hammersmith,
1981; Money, 1988).
However, these components do not always agree. Research
conducted across different cultures and historical periods (includ-
ing present-day Western culture) has found that many individuals
develop passionate infatuations with same-gender partners in the
absence of same-gender sexual desires (Diamond, 2000a; Fader-
man, 1981; Jensen, 1999; Katz, 1976; Nardi, 1992; Rotundo, 1989;
W. L. Williams, 1992), whereas others experience same-gender
sexual desires that never manifest themselves in romantic passion
or attachment (Herdt, 1984; Whisman, 1996). For example, a
recent study of sexual-identity development found that one young
gay man described sex with his former girlfriend as “satisfying
physically, but not emotionally,” whereas another claimed that
although he had been in love with his high-school girlfriend,
“physically I didn’t want her” (Savin-Williams, 1998, p. 110).
How can this occur if sexual and affectional feelings are jointly
Researchers are ill equipped to answer this question because
little is known about the precise association between sexual and
affectional feelings and how each is influenced by sexual orienta-
tion. Most basic research on sexual orientation treats sexual desire
as the primary phenomenon to be explained, and same-gender
affectional feelings receive little theoretical or empirical attention
(Brown, 1995; DeCecco, 1990). This might be attributable to the
common assumption that sexual desire is a more basic, biologi-
cally mediated phenomenon than is romantic love and therefore
more amenable to scientific study.
Yet this assumption is outmoded. Research has demonstrated
that the distinct behaviors and intense feelings associated with
affectional bonds are governed not only by culture and socializa-
tion but also by evolved, neurochemically mediated processes that
are a fundamental legacy of humans’ mammalian heritage (Fisher,
1998; Hazan & Shaver, 1987; Nelson & Panksepp, 1998; Pank-
sepp, 1998; Uvna¨s-Moberg, 1997b). Just as sexual desire is a
species-typical phenomenon with both social and biological un-
derpinnings, so too is emotional affection. Thus, it is no longer
tenable to investigate the fundamental bases of same-gender sexual
desire without also considering the bases of same-gender affec-
tional bonding and whether the two phenomena are related.
I therefore develop a biobehavioral model of love and desire that
makes the following three claims. First, the evolved processes
underlying sexual desire and affectional bonding are functionally
independent. As a result, one can “fall in love” without experienc-
ing sexual desire. Second, the processes underlying affectional
bonding are not intrinsically oriented toward other-gender or
same-gender partners. As a result, individuals can fall in love with
partners of either gender, regardless of sexual orientation. Third,
the biobehavioral links between love and desire are bidirectional.
As a result, individuals can develop novel sexual desires—even
desires that contradict their sexual orientations—as a result of
falling in love.
These claims are supported by social–psychological, historical,
and cross-cultural research on human love and sexuality as well as
by evidence regarding the evolved biobehavioral mechanisms un-
derlying mammalian mating and social bonding. With regard to the
last source of evidence, it bears noting that the current understand-
ing of the neurobiological substrates of social bonding is based
An earlier version of this article was submitted to Cornell University in
1997 in partial fulfillment of the requirements for a doctoral degree in
Human Development, and I acknowledge Ritch Savin-Williams, Cindy
Hazan, and Anne Peplau for their comments on that version. Portions of
this article were also presented at the biennial meeting of the Society for
Research on Adolescence, Washington, DC, March 2000.
Correspondence concerning this article should be addressed to Lisa M.
Diamond, Department of Psychology, University of Utah, 390 South 1530
East, Room 502, Salt Lake City, Utah 84112-0251. E-mail: diamond@
Psychological Review Copyright 2003 by the American Psychological Association, Inc.
2003, Vol. 110, No. 1, 173–192 0033-295X/03/$12.00 DOI: 10.1037/0033-295X.110.1.173
predominantly on animal models (Panksepp, 1998), and the extent
to which these models generalize to humans remains unknown.
Although Nelson and Panksepp (1998) have noted that there is
considerable cross-species generality in the neural circuits under-
lying mammalian affiliation, Carter (1998) has noted that there is
considerable cross-species variation in the affective and behavioral
manifestations of these circuits. Thus, generalizations from ani-
mals to humans must be considered speculative pending future
A final caveat is necessary: In calling attention to the biological
substrates of love and desire, I do not mean to imply that biological
factors are more important than cultural factors in shaping these
experiences. On the contrary, research across many disciplines has
shown that human experiences of sexual arousal and romantic love
are always mediated by social, cultural, and interpersonal contexts,
and ignoring these contexts produces a distorted account of human
experience (Tolman & Diamond, 2001). However, ignoring the
biological underpinnings of human behavior produces a similarly
distorted account. As others have argued (Andersen, Cyranowski,
& Aarestad, 2000), human sexual and affectional experiences are
neither “mainly cultural” nor “mainly biological” but must always
be understood as products of powerful interactions between bio-
logical and social factors. This model’s focus on biobehavioral
mechanisms should not be mistaken for a dismissal of cultural
A Biobehavioral Model of Love and Desire
First, clarification of relevant terms is in order. Following Regan
and Berscheid (1995), sexual desire is defined as “a wish, need, or
drive to seek out sexual objects or to engage in sexual activities”
(p. 346). The terms romantic love,affectional feelings, and affec-
tional bonding denote the feelings of infatuation and emotional
attachment that are commonly associated with romantic relation-
ships (distinctions between infatuation and attachment are clarified
below). Finally, the term gender is used to refer to the categories
male and female to avoid confusion with sex as a reference to
sexual activity.
The model begins with the following assumption: Most individ-
uals possess a relatively stable tendency to seek sexual partners of
the same gender, the other gender, or both genders—this tendency
is denoted sexual orientation.
Although extensive debate remains
over whether sexual orientation really exists, whether it is a fixed
trait, and whether it is biologically based, these debates are not
engaged here. Rather, I assume that sexual orientation does exist,
that it is relatively stable (see Diamond, 2000b; Pattatucci &
Hamer, 1995), and that in some individuals it has some biological
component (evidence on this point is reviewed below). However,
sexual orientation is not presumed to be the sole factor determining
sexual attraction and behavior. Researchers have long noted that
human sexual responses are flexible and amenable to conditioning
(Bancroft, 1989; Cass, 1990; Money, 1988), and thus individuals
sometimes experience sexual desires that run counter to their
overall orientation (e.g., see Baumeister, 2000). With these as-
sumptions in place, the present model concerns itself with the
following question: Does sexual orientation fundamentally cir-
cumscribe the class of individuals with whom one can fall in love?
I posit that the answer is no, and the reasons are spelled out below.
Premise 1: Sexual Desire and Romantic Love Are
Functionally Independent
Although sexual desire and romantic love are often experienced
in concert, they are governed by different social–behavioral sys-
tems that evolved to serve different goals. As argued by Fisher
(1998), desire is governed by the sexual mating system, the goal of
which is sexual union for the purpose of reproduction. Romantic
love, however, is governed by the attachment or pair-bonding
system (Hazan & Shaver, 1987; Hazan & Zeifman, 1999), the goal
of which is the maintenance of an enduring association between
two individuals. Evolutionary theorists have argued that in the
environment in which humans evolved, highly dependent offspring
were far more likely to survive if they had the care of both parents
in the early years of life (Mellen, 1982), and the social–behavioral
system of pair-bonding accomplishes this aim by establishing a
robust emotional bond that keeps mates together past the initial
mating episode.
Obviously, not all human mating involves pair-bond formation.
Rather, the basic processes underlying mating and pair-bonding
are functionally independent. It has been argued that this is a
relatively recent mammalian adaptation (most pronounced in hu-
mans) that facilitated ecologically contingent flexibility in repro-
ductive strategies (Fisher, 1998). This functional independence
allows humans not only to mate without bonding but also to bond
without mating. Furthermore, humans can bond without experi-
encing the motivation to mate (i.e., sexual desire), under the right
conditions. These conditions appear to be high levels of proximity
and physical contact over sustained periods of time (Hazan &
Zeifman, 1994). Because sexual desire provides a powerful incen-
tive for such behaviors, it facilitates pair-bonding, but it is not a
precondition. Rather, high degrees of time, togetherness, and touch
can “stand in” for sexual desire in facilitating the development of
romantic love.
This premise has the following three implications. First, indi-
viduals should be capable of experiencing romantic love in the
absence of sexual desire. Second, individuals should be capable of
experiencing romantic love for individuals to whom they are not
typically sexually oriented. In other words, heterosexuals should
be capable of falling in love with same-gender partners, and
lesbian or gay individuals should be capable of falling in love with
other-gender partners. Third, these phenomena should be most
likely to occur in relationships containing unusually high proxim-
ity or physical contact over sustained periods of time.
Premise 2: Romantic Love Is Not Intrinsically Oriented to
Same-Gender or Other-Gender Partners
Whereas Premise 1 maintains that sexual orientation does not
necessarily circumscribe one’s experiences of romantic love,
Premise 2 specifies that love does not have an orientation of its
own. This premise is based on the hypothesized evolutionary
Because sexual orientation is used to denote an individual’s general
tendency to seek sexual–romantic partners of the same gender, the other
gender, or both genders, it would be more technically accurate to call this
sexual–romantic orientation or partner orientation. However, I continue to
use sexual orientation because of its widespread use and familiarity among
both scientists and laypeople.
origins of love and desire. As noted earlier, the evolutionary goal
of sexual desire is sexual reproduction,and therefore one can make
a plausible—albeit still controversial—argument that sexual de-
sires evolved to be intrinsically oriented toward other-gender part-
ners (as they are in the vast majority of cases, recently documented
by Laumann, Gagnon, Michael, & Michaels, 1994) in order to
selectively target individuals’ mating efforts toward appropriate
reproductive partners. According to this view, homosexual and
bisexual orientations represent (at least in some cases) intrinsic
deviations from this normative program.
Is there a similarly plausible evolutionary justification for in-
trinsic affectional orientations? As noted above, pair-bonding en-
hances reproductive success by keeping mates together long
enough to successfully rear their offspring past the initial, most
dangerous stage of life. Accordingly, we might expect the emo-
tions of pair-bonding—like sexual desires—to be intrinsically ori-
ented toward those who are the “right” gender to be reproductive
partners. Yet numerous psychologists, anthropologists, ethologists,
and evolutionary biologists have argued that although the powerful
emotions associated with pair-bonding are reproductively advan-
tageous, they did not originally evolve in the context of reproduc-
tive mating. Long before the evolutionary “problem” of keeping
reproductive mates together arose, mammals had already been
endowed with a potent social–behavioral system for social bond-
ing: infant–caregiver attachment, a system that originally evolved
to keep highly dependent mammalian infants in close proximity to
their caregivers (Bowlby, 1958, 1973a, 1973b, 1980, 1982). As
Gould and Vrba (1982) argued, natural selection does not gener-
ally result in the production of brand-new mechanisms to solve
evolutionary problems where existing ones will suffice. Thus, it
has been argued that the infant–caregiver attachment system was
exploited for the new purpose of maintaining enduring associa-
tions between adult reproductive partners (Hazan & Shaver, 1987;
Panksepp, 1998). In other words, adult pair-bonding appears to be
an exaptation—a system that originally evolved for one reason but
comes to serve another (Gould & Vrba, 1982).
The notion that romantic love is an adult “version” of the
powerful affectional bond between infants and their caregivers was
first systematically proposed and debated nearly 15 years ago
(Hazan & Shaver, 1987, 1994; Hazan & Zeifman, 1999; Shaver,
Hazan, & Bradshaw, 1988), and since that time it has arguably
become the predominant theoretical perspective underlying re-
search on adult romantic relationships. Yet the implications of this
perspective for conceptualizations of same-gender romantic love
have gone largely unnoticed: Specifically, if the mechanisms un-
derlying romantic love originally evolved to facilitate infant–
caregiver attachment (a hypothesis supported by the direct corre-
spondences, reviewed in depth below, between the feelings,
behaviors, and neurobiological substrates of infant–caregiver
bonding and adult romantic love), then intrinsic affectional orien-
tations—if they exist—must have evolved in the context of infant–
caregiver attachment rather than adult mating. Yet such orienta-
tions are implausible in the infant–caregiver context. Although
infant–caregiver attachment may not be wholly gender neutral
(given that most caregivers are female), infants do not become
selectively attached to other-gender versus same-gender caregiv-
ers, and it would be maladaptive if they did. Thus, there is no
plausible evolutionary basis for other-gender or same-gender ori-
entations to be coded into the biobehavioral processes underlying
affectional bonding.
This implies that although individuals might report stable ten-
dencies to fall in love with one gender or the other, such tendencies
have no intrinsic basis. Rather, they might reflect the fact that
adults typically only encounter the situational conditions that fa-
cilitate affectional bonding (sustained, heightened proximity and
physical contact) with individuals who are actual or potential
sexual partners. Yet once these situational conditions are in place,
individuals should be capable of falling in love with partners of
either gender.
Premise 3: The Links Between Love and Desire Are
Although love and desire are functionally independent, most
individuals perceive and experience powerful interconnections be-
tween these experiences. Many developmental psychologists have
suggested that these interconnections become established during
adolescence (Furman & Wehner, 1994; Hazan & Zeifman, 1994;
Laursen, 1996; Sullivan, 1953) such that reproductively mature
individuals end up being most likely and most motivated to bond
with potential reproductive partners. Processes of classical condi-
tioning may help establish these links, given that adolescents’
increasingly frequent and intimate other-gender interactions (Buhr-
mester, 1996; Laursen, 1996) provide them with repeated oppor-
tunities to experience affectional feelings in concert with newly
urgent sexual desires. Cultural norms also play a role, sending
strong messages regarding what types of feelings and behaviors
are appropriate with different social partners. Finally, these inter-
connections appear to have a neurobiological component: Animal
research has found that oxytocin, a neuropeptide hormone that is
critically implicated in mammalian affectional bonding, also facil-
itates mammalian sexual interest and behavior. Thus, overlap in
some of the biobehavioral mechanisms underlying sexual desire
and affectional bonding might contribute to the perceived links
between these experiences.
Although the overall psychobiological process through which
love and desire become interconnected during normal sociosexual
development has never been fully specified, there is tacit consen-
sus regarding the outcome of this process: a robust pathway
leading from sexual desire to infatuation–attachment, but not the
other way around. Although we are expected to form affectional
bonds with individuals we sexually desire, we are not expected to
develop novel sexual desires as a result of affectional bonding. It
is important to note that this notion of unidirectionality in the links
between love and desire has never been theoretically justified or
empirically tested. Premise 3 maintains that these links are not
unidirectional. Rather, the cultural practices, psychological asso-
ciations, and shared biobehavioral mechanisms that link love and
desire are more likely to foster bidirectional than unidirectional
pathways between these experiences, such that sexual desire can
facilitate affectional bonding, and affectional bonding can facili-
tate sexual desire.
This premise implies that individuals should be capable of
developing sexual desires as a result of falling in love, even desires
that run counter to their sexual orientation. Because such “cross-
orientation” desires emanate from the process of affectional bond-
ing, they should be relationship specific and may not generalize to
other partners. Premise 3 also implies that women should be more
likely than men to develop such affectionally based sexual desires.
This is because the cultural, psychological, and neurobiological
links between love and desire appear to be more robust among
women than among men. Women have been historically socialized
to restrict their sexual feelings and behaviors to intimate emotional
relationships—ideally marital ties—whereas males have not (Gag-
non & Simon, 1973), and women appear more likely than men to
have their first experiences of sexual arousal in interpersonal rather
than solitary contexts (Hyde & Jaffee, 2000). Women might also
have more extensive neurobiological interconnections between the
experiences of romantic love and sexual desire: Animal research
has demonstrated that oxytocin’s effects on both attachment and
sexual behavior are estrogen dependent and gender specific. If
bidirectionality between love and desire is based on just such
cultural, psychological, and neurobiological processes as
Premise 3 postulates, then it follows that women should be more
likely to report cross-orientation affectionally based sexual desires
than men.
Evidence for the Theory
Premise 1: Does Love Require Desire?
In considering whether sexual desire is a precondition for ro-
mantic love, one must first decide what type of romantic love
should be investigated. Numerous researchers accord with a basic
distinction between infatuation (also known as passionate love,
falling in love,orlimerence) and attachment (also known as
companionate love; Hatfield, 1987; Sternberg, 1986; Zeifman &
Hazan, 1997). In a self-report study of over 1,000 individuals,
Tennov (1979) found that infatuation was characterized by intense
desires for proximity and physical contact, resistance to separation,
feelings of excitement and euphoria when receiving attention and
affection from the partner, fascination with the partner’s behavior
and appearance, extreme sensitivity to his or her moods and signs
of interest, and intrusive thoughts of the partner. The same features
were noted by Hatfield and Sprecher (1986) as characteristics of
passionate love. In contrast, attachment or companionate love is
characterized by feelings of calm, security, mutual comfort seek-
ing, and deep affection (Hatfield, 1987; Hazan & Shaver, 1987;
Sternberg, 1986).
This basic distinction has been validated in numerous studies
assessing adults’ self-reported experiences in romantic and sexual
relationships (e.g., Hazan & Shaver, 1987; Hazan & Zeifman,
1994; Money, 1980; Sprecher & Regan, 1998). Research suggests
that infatuation and attachment are not simply different types of
love but rather different stages of love: Specifically, infatuation
represents an early-developing component of the bonding process.
For example, Sprecher and Regan (1998) collected relationship
descriptions from over 200 couples at various stages of relation-
ship development. They found that the longer couples had been
together, the fewer “passionate” and the more “companionate”
characteristics their relationship contained. The same phenomenon
was documented in a questionnaire study of over 100 couples by
Brezsnyak, Allen, Salz, Mattucci, and Hazan (1996). For example,
longer term couples reported less frequent hugging, cuddling,
sexual contact, mutual gazing into one another’s eyes, and intense
desires for physical proximity but were more likely to report
mutual provision of emotional security and comfort. Zeifman and
Hazan (1997) provided a plausible rationale for this sequence of
emotional experiences. They noted that the establishment of a
pair-bond requires extended proximity between partners over a
sustained amount of time, and the intense preoccupation of infat-
uation provides a potent motivator for such sustained proximity.
Of course, not all infatuations “make it” to the attachment stage,
and not all attachments are preceded by infatuation. The main
point is that if both passionate infatuation and companionate
attachment are parts of the social–behavioral system of pair-
bonding, and if the process of pair-bonding is functionally inde-
pendent from sexual desire, then sexual desire should not be a
precondition for either experience. Notably, this runs directly
counter to conventional wisdom on this topic. Sexual desire has
been found to be a more frequent and more prominent component
of the infatuation stage of love than the attachment stage (Aron &
Aron, 1991; Berscheid, 1985; Regan, 1998; Sprecher & Regan,
1998; Tennov, 1979), and therefore, many researchers have argued
that it is impossible to authentically experience infatuation without
desire (Lee, 1973; Money, 1997). Premise 1 maintains that this is
not the case.
Evidence for romantic love without desire. Extant empirical
data support this prediction. For example, Tennov’s (1979) ex-
haustive study of infatuation found that 61% of women and 35%
of men reported experiencing infatuation without feeling “any
need for sex” (p. 74). Even stronger evidence was provided by a
study by Hatfield, Schmitz, Cornelius, and Rapson (1988). They
hypothesized that if sexual desire were a necessary component of
infatuation, then the weakest experiences of infatuation should be
observed among prepubertal children, and the strongest experi-
ences should be observed among postpubertal adolescents, given
that the latter have undergone maturational surges in gonadal
hormones that produce notable increases in day-to-day sexual
desire (Udry & Billy, 1987; Udry, Talbert, & Morris, 1986). To
test this hypothesis, Hatfield et al. administered the Juvenile Love
Scale (based on the well-validated Passionate Love Scale; Hatfield
& Sprecher, 1986) to over 200 youths between 4 and 18 years of
age to measure the intensity of their infatuation experiences. Re-
spondents were asked to think about an other-gender boyfriend or
girlfriend for whom they had intense feelings (respondents were
not given the opportunity to nominate a same-gender friend) and to
rate their agreement with statements such as “I am always thinking
about X” or “When X hugs me my body feels warm all over.” The
intensity of respondents’ infatuation experiences were then corre-
lated with their degree of pubertal maturation (measured with
standardized assessments of physical development).
The results were unequivocal: Children of all ages were capable
of maximally intense infatuations, and the intensity of these expe-
riences was not associated with pubertal maturation. Although the
authors appropriately cautioned that their results could not reveal
whether the subjective experience of infatuation was fundamen-
tally the same for 4-year-olds as for 18-year-olds, these data
nonetheless provide evidence that sexual arousal is not the “spark”
that intensifies the preoccupation, separation distress, and height-
ened proximity seeking of infatuation.
Evidence for same-gender infatuations among heterosexuals.
There is also evidence that, as Premise 1 predicts, individuals can
become infatuated with partners of either gender, regardless of
sexual orientation. Documentation of same-gender infatuations
among heterosexuals provides more reliable evidence on this point
than documentation of other-gender infatuations among lesbian,
gay, or bisexual individuals, because cultural pressures might lead
lesbian, gay, or bisexual individuals to misreport or misperceive
experiences of other-gender affection (Savin-Williams, 1998).
Thus, the discussion below focuses on same-gender infatuations
among self-described heterosexuals.
There is extensive evidence of such infatuations. Anthropolo-
gists and historians have described unusually intimate, passionate,
platonic same-gender friendships among otherwise heterosexual
individuals in a variety of different cultures and historical periods,
dating as far back as ancient Greece (Blackwood, 1985; Brain,
1976; Faderman, 1981; Gay, 1985; Hansen, 1992; Katz, 1976;
Richards, 1987; Rotundo, 1989; Smith-Rosenberg, 1975; W. L.
Williams, 1992). These bonds often inspired their own unique
terms, such as romantic friendships (Faderman, 1981; Rotundo,
1989), bond friendships (Firth, 1967), mummy–baby friendships
(Gay, 1985), camaradia (Reina, 1966), or smashes (Sahli, 1979).
One 19th-century schoolmistress described smashes as
...anextraordinary habit which [schoolgirls] have of falling violently
in love with each other, and suffering all the pangs of unrequited
attachment, desperate jealousy etc. etc., with as much energy as if one
of them were a man. . . . If the “smash” is mutual, they monopolize
each other & “spoon” continually, & sleep together & lie awake all
night talking instead of going to sleep. (Sahli, 1979, p. 22)
W. L. Williams (1992) documented similarly intense but non-
sexual bonds between Native American men, and noted that early
Western explorers were surprised by how these men seemed to fall
in love with one another (Parkman, 1969; Trumbull, 1894). Brain
(1976) documented passionate friendships between young Bangwa
men in the Cameroon and reviewed reports of comparable male–
male ties in Melanesia (Malinowski, 1929), Samoa (Mead, 1943),
the Polynesian islands (Firth, 1967), and Guatemala (Reina, 1966).
According to these accounts, such relationships involved “affec-
tion of an extreme kind which...resembles more the passion of
heterosexual lovers than the calm friendship of equals” (Brain,
1976, pp. 3940).
Modern observers reading such descriptions often assume that
these relationships contained a subverted sexual element and that
if the participants had lived in a more permissive environment,
they would have pursued an openly sexual liaison. However, those
who study and document such relationships have argued against
this view, noting that the presumption of a necessary link between
same-gender affectional bonds and same-gender sexual desires is
historically and culturally specific (see especially D’Emilio &
Freedman, 1988; Faderman, 1981, 1993; Nardi, 1992). Although
some of these relationships might have involved sexual interest,
these authors maintained that this was not uniformly so.
Contemporary Western culture lacks a defined category for
platonic same-gender infatuations, yet they continue to occur and
have been most frequently documented between women (Dia-
mond, 2000a; Rothblum, 1993; Von Sydow, 1995). Oliker (1989)
noted that many contemporary women describe the beginning of a
same-gender best friendship with regard to “excitement, height-
ened energies, frequent thought about the other, invigorated self-
regard—in short, in terms of the ardent sensibilities of romantic
love” (p. 5). Similarly, Rubin (1985) directly likened new best
friendships among some women to “new loves” (p. 113), noting
that the two women often become obsessively intertwined. Von
Sydow’s (1995) interview study of older German women found
that a number of respondents (none of whom were sexually at-
tracted to women) described passionate adolescent same-gender
friendships that involved kissing, cuddling, dancing together, or
sleeping in the same bed. One woman remarked, “My first love
was a girl. .. . It was wonderful!” (p. 288) despite indicating that
she found the notion of same-gender sexual relationships
Contemporary passionate friendships may be more common
among women than among men because of differences in norma-
tive standards for male–male and female–female friendships. Both
W. L. Williams (1992) and Nardi (1992) noted that the contem-
porary West adheres to a particularly rigid notion of heterosexual
masculinity that precludes openly affectionate male–male bonds.
Thus, highly intimate and affectionate same-gender friendships are
more likely to engender suspicion of homosexuality when they
occur between men than when they occur between women (Der-
lega, Lewis, Harrison, Winstead, & Constanza, 1989). This was
not the case in 19th-century America (Hansen, 1992) or in the
non-Western cultures reviewed by Brain (1976), where passionate
friendships between men were more common.
Evidence for the importance of time, togetherness, and touch.
Obviously not all individuals form such bonds. If sexual desire is
not responsible for transforming a close friendship into an infatu-
ation, then what is? Premise 1 implies that because sustained
physical proximity plays a critical role in the process of pair-
bonding, same-gender infatuations among heterosexuals should be
most likely to develop when relationships contain heightened
levels of proximity or physical contact over sustained periods of
This is consistent with the available cross-cultural data. Descrip-
tions of passionate same-gender friendships frequently make ref-
erence to the extensive time that friends spend together, often in
close physical contact. For example, passionate friends are often
described as living with or near one another, sharing beds, being
“inseparable,” and engaging in frequent physical affection (Gay,
1985; Hansen, 1992; Katz, 1976; Richards, 1987; Rotundo, 1989;
Sahli, 1979; Smith-Rosenberg, 1975). The importance of time,
togetherness, and touch might also explain why same-gender af-
fectional bonds appear disproportionately likely to develop in
gender-segregated environments. Both Smith-Rosenberg (1975)
and Richards (1987) pointed out that men and women in 19th-
century America occupied distinctly separate occupational and
social spheres and suggested that this gender segregation facili-
tated same-gender bonding. Similar arguments were made by Sahli
(1979) and Gay (1985) with regard to the gender-segregated en-
vironments that gave rise to smashes and mummy–baby friend-
ships. Pleck and Pleck (1980) and D’Emilio and Freedman (1988)
further argued that the intense male–male bonding that has histor-
ically characterized the battlefield, the American frontier, and
numerous fraternal organizations is partially attributable to the fact
that these environments were “male-only” spaces.
A similar phenomenon can be identified in contemporary
gender-segregated colleges, boarding schools, sororities, athletic
teams, and fraternities (Golden, 1987; Von Sydow, 1995). Gender-
segregated environments obviously heighten individuals’ opportu-
nities for time, togetherness, and touch with one another, and thus
it is not surprising that they appear to facilitate the development of
same-gender infatuations and attachments. They also restrict indi-
viduals’ contact with other-gender individuals, whose sexual de-
sirability (at least to heterosexuals) might draw attention and
energy away from same-gender friends. Supporting this concep-
tualization, one of Von Sydow’s (1995) respondents noted that the
same-gender crushes she and her girlfriends routinely developed
“stopped when we started noticing the boys” (p. 288).
Such reports imply that the difference between same-gender
friendships and same-gender infatuations is one of degree rather
than kind, a notion that runs counter to the widespread belief that
falling in love involves an altogether different process than the
formation of a close friendship. Aron, Dutton, Aron, and Iverson
(1989) directly tested this proposition in a series of studies involv-
ing over 500 male and female undergraduates in which self-
reported elicitors of falling in love (i.e., developing a strong
attraction to someone) were compared with self-reported elicitors
of falling in friendship (i.e., going from not knowing much about
someone to developing very strong positive feelings for him or
her). A content analysis of the responses revealed that the most
common triggers for falling in love were exactly the same as those
for falling in friendship: reciprocal liking, propinquity, desirable
characteristics, and similarity.
These findings imply that the boundary between same-gender
friendship and infatuation might be relatively permeable. Of
course, it is certainly sensitive to conscious and unconscious
perceptions regarding the feelings and behaviors that are consid-
ered appropriate for each type of relationship. Modern Western
society is replete with implicit and explicit messages dictating that
heightened proximity seeking and frequent physical affection only
occur (and are only acceptable) with potential sexual–romantic
partners (Rothblum, 1997; W. L. Williams, 1992). These messages
undoubtedly constrain the type and degree of intimacy that indi-
viduals pursue with same-gender friends (O’Connor, 1992). In
cultures without such pervasive messages and in which same-
gender friends typically spend a great deal of time in close prox-
imity to one another, same-gender infatuations might be far more
likely to develop.
Areas requiring further study. More conclusive evidence for
the claim that sexual desire is not a prerequisite for infatuation
would be provided by research on the actual psychobiological
process of human affectional bonding, which has been the subject
of little systematic study (Diamond, 2001). For example, compre-
hensive, multimethod comparisons between new and established
couples and friendship dyads would allow researchers to ascertain
the affective and behavioral causes and consequences of pair-
bonding, chart their respective time courses, and identify their
potential underlying mechanisms. Longitudinal investigations
could discern whether extended proximity, physical affection, and
sexual contact facilitate (as research would appear to suggest) or
are facilitated by human attachment formation. Both are probably
true (Brennan, Wu, & Loev, 1998), but the question of whether
time, togetherness, and touch are truly necessary or sufficient
conditions for pair-bonding is an important and empirically an-
swerable question. Future research should also investigate condi-
tions other than gender segregation, such as psychological stress,
that facilitate same-gender bonding. The physiological arousal
associated with stress is well known to influence romantic attrac-
tion in humans (reviewed in Foster, Witcher, Campbell, & Green,
1998) and social bonding in animals (Carter, 1998; Carter &
DeVries, 1999). This is clearly a key area for future research.
Premise 2: Is Love Intrinsically Oriented?
Even if sexual desire is not a precondition for romantic love, one
might still posit that sexual orientation circumscribes romantic
love because it is coded into the pair-bonding process separately.
In other words, individuals might be intrinsically predisposed to
pair-bond with one gender or the other (or both). Premise 2
challenges this notion, maintaining that there is no plausible evo-
lutionary explanation for gender-based affectional orientations.
This is because the biobehavioral mechanisms underlying affec-
tional bonding originally evolved in the context of infant–
caregiver attachment, a context in which such orientations would
have been maladaptive.
Clearly, the cornerstone of this argument
is the notion that the processes underlying adult pair-bonding
originally evolved to facilitate infant–caregiver attachment, and
this notion cannot be tested directly. We can, however, critically
evaluate the degree of correspondence between the feelings, be-
haviors, and neurobiological substrates of infant–caregiver attach-
ment and adult pair-bonding. Although the existence of close
correspondences cannot prove, in and of itself, that romantic love
evolved in the context of infant–caregiver attachment, the absence
of such correspondences would directly contradict this claim.
Before reviewing the empirical data on this point, evidence for
the existence of intrinsic sexual orientations warrants a brief re-
view. Although this issue is theoretically and empirically distinct
from the issue of affectional orientations, it merits discussion
because it highlights the extent to which a plausible theoretical and
empirical case can be made for intrinsically oriented sexual desires
but not for intrinsically oriented affectional feelings.
Evidence regarding the orientation of sexual desire. Hetero-
sexually oriented sexual desires would clearly have been evolu-
tionarily adaptive, because they would have propelled individuals
to mate with other-gender partners, thereby facilitating successful
reproduction (Bailey, Dunne, & Martin, 2000). As noted earlier,
this would not require that individuals only experience desires
consistent with their sexual orientation. As long as individuals
Of course, the question of whether the caregiving system is gender
specific—that is, whether women are more biologically predisposed to
experience the powerful feelings of care and nurturance toward infants than
men—is obviously controversial. At the present time, there is no direct
evidence that this is the case among humans. However, as reviewed by
Panksepp (1998), animal research has revealed gender differences in the
oxytocinergic and opioid circuits that influence the onset and maintenance
of caregiving behavior in new parents. Many of these behaviors have been
shown to depend on interactions between these neural circuits and the
female gonadal hormones of estrogen, progesterone, and prolactin, all of
which undergo dramatic changes during pregnancy and parturition. How-
ever, the implications of the extant animal data for human behavior are as
yet unknown. Also, human caregiving is obviously subject to far more
conscious control and cultural shaping than is the case for other mammals.
Consequently, even if the neural circuits influencing caregiving are, in fact,
gender differentiated, this need not suggest that human females are neces-
sarily predisposed to be more willing or effective caregivers than human
males. Similarly, it is not known whether such gender differences might
have implications for gender differences in the propensity to form adult
romantic pair-bonds.
were generally oriented to seek sexual contact with other-gender
partners, a degree of flexibility in sexual arousal would incur no
evolutionary costs. This is supported by data on nonhuman pri-
mates indicating that periodic same-gender sexual activity never
completely supplants other-gender sexual activity and thus does
not hinder reproductive success (Nadler, 1990; Wallen & Parsons,
If heterosexual orientations did, in fact, evolve to facilitate
sexual mating, then they should be coded in our genes; correspond-
ingly, nonheterosexual orientations should also have a genetic
basis. Numerous studies have found support for this hypothesis.
For example, self-identified lesbian, gay, and bisexual individuals
are more likely to have lesbian, gay, and bisexual relatives than
would be predicted by chance (Bailey & Bell, 1993; Bailey &
Benishay, 1993; Bailey, Pillard, Neale, & Agyei, 1993; Pattatucci
& Hamer, 1995). Also, studies of unseparated twins have detected
significant concordance of self-reported sexual orientation in iden-
tical twins (usually around 50%) and greater concordance among
identical than fraternal twins (Bailey et al., 1993; Bailey & Pillard,
1991). The best and most reliable study to date examined
nearly 2,000 pairs of twins drawn from the Australian Twin
Registry (Bailey et al., 2000) and found concordances of 38% for
same-gender sexual desire in identical male twins, 30% for iden-
tical female twins, and no concordance in fraternal twins. Notably,
these concordance estimates are lower than those found in previ-
ous twin studies, which might stem from the fact that the Austra-
lian study recruited participants from a twin registry rather than
lesbian, gay, and bisexual publications (as in previous studies)
making it less subject to self-selection biases.
In summary, the genetic studies converge to suggest that the
orientation of some individuals’ sexual desires has some genetic
component, although there is no direct confirmation of this view.
Furthermore, it is not yet known what genes orienting sexual desire
might code for. Do they determine specific patterns of perinatal
hormonalization (L. Ellis, 1996), atypical features of brain anat-
omy (LeVay, 1993), or temperamental traits leading to gender-
typed social behaviors (Bem, 1996)? The end result might be
heterosexual, homosexual, or bisexual desires, but it is not clear
whether this result is functional or artifactual. In the final analysis,
the specific causal pathway is not germane to the model presented
here. The main point is that there is both a plausible evolutionary
basis for sexual desires to be oriented toward the other gender and
empirical evidence that same-gender desires are partly genetically
determined. Thus, it is reasonable and parsimonious to view sexual
desires as intrinsically oriented, with heterosexual orientations
overwhelmingly predominant and homosexual–bisexual orienta-
tions representing infrequent variations. The same cannot be said
with regard to pair-bonding. Unlike sexual desire, the emotions
underlying pair-bonding did not originally evolve to facilitate
mating, but infant–caregiver bonding. The evidence in support of
this claim is reviewed below, after a brief overview of the infant–
caregiver attachment system.
The evolution of infant–caregiver attachment. Attachment
theory (Bowlby, 1958, 1973a, 1973b, 1980, 1982) maintains that
because mammalian (and particularly primate) offspring require
substantial care and feeding after birth, the psychological mecha-
nism of attachment evolved to facilitate the formation of enduring,
survival-promoting bonds between mothers and their highly de-
pendent offspring.
This mechanism ensures that infants maintain
close proximity to their caregivers at all costs during the first few
years of life, thereby dramatically increasing their chances for
survival. The attachment system is driven by emotions. When
infants are too far from their caregivers, they experience distress
and signal the caregiver for attention. Once the caregiver is suffi-
ciently close, the infant feels calmed and can resume developmen-
tally appropriate behaviors such as exploration.
Although attachment is a species-typical, somewhat automatic
process, it is not instantaneous; rather, it takes 6–12 months of
regular contact for an infant to develop a basic, functional attach-
to his or her caregiver, a period of time that has been
described as “attachment-in-the-making” (Ainsworth, Blehar, Wa-
ters, & Wall, 1978, p. 24). During this period, the infant displays
an increasingly intense fixation on the adult with whom he or she
has the most extensive contact. By the end of this period, the
infant’s relationship with the caregiver is notably distinct from his
or her other social relationships. Although there is no single
marker that an attachment bond is in place, their core character-
istics involve heightened seeking of proximity and contact with the
attachment figure (accompanied by distinct physiological re-
sponses to such contact) and intense resistance to separation from
the attachment figure (again, accompanied by distinct physiolog-
ical responses to such separations). These characteristics have been
observed not only in humans (Ainsworth, 1967; Ainsworth et al.,
1978; Bowlby, 1973b, 1982; Field, 1985, 1994) but across a
variety of mammalian species, such as rats (Hofer, 1987, 1994),
guinea pigs (Graves & Hennessy, 2000), and nonhuman primates
(Berman, Rasmussen, & Suomi, 1994; Hoffman, Mendoza, Hen-
nessy, & Mason, 1995; Suomi, 1999).
Evidence for emotional–behavioral correspondences between
pair-bonding and infant–caregiver attachment. There is increas-
ing (albeit not universal) consensus and voluminous evidence from
human and animal research that adult pair-bonds and infant–
There is considerable diversity in the strength and long-term function-
ing of infant–caregiver attachments across different mammalian species.
The only other species showing infant–caregiver attachments as strong and
enduring as human attachments are Old World monkey and ape species
(Suomi, 1999).
It is important to note that there are stable individual differences in the
security of attachments formed between infants and caregivers (Ainsworth,
1967; Ainsworth et al., 1978; Weinfield, Sroufe, Egeland, & Carlson,
1999) and between adult romantic partners (Brennan & Shaver, 1995;
Crowell, Fraley, & Shaver, 1999; Hazan & Shaver, 1987; Simpson, 1990),
and these individual differences typically receive more theoretical and
empirical attention than normative processes of human attachment forma-
tion (Diamond, 2001; Marvin & Britner, 1999; Simpson & Rholes, 1998),
which are of greater interest here. Because this model focuses on the basic
establishment of an attachment bond and not the quality of that bond,
individual differences in attachment security are not discussed. As eluci-
dated by Hinde (1982) and Weiss (1982), the process of becoming attached
(which requires a certain amount of time in proximity to the potential
attachment figure) and the status of a relationship as an attachment bond
(which can be inferred from certain affective and behavioral characteristics
of the relationship) are independent of individual differences in the quality
of that bond (i.e., whether proximity to the attachment figure succeeds in
making the individual feel secure). As Bowlby (1956) demonstrated,
children reliably form robust, enduring attachments to abusive caregivers.
The quality of those bonds is undoubtedly low, but the bond still qualifies
as an attachment.
caregiver attachment involve the same basic emotions and behav-
iors. Among mammals that form reproductive pair-bonds (and not
all mammals do—see Insel, Young, & Wang, 1997), the behaviors
that characterize pair-bonding are the same as those that charac-
terize infant–caregiver attachment: selective proximity seeking,
visual tracking, grooming, huddling, and separation distress
(Carter, 1998; Carter, DeVries, & Getz, 1995; Mason & Mendoza,
1998). The same behavioral correspondences have been observed
between infant–caregiver attachment and adult pair-bonding in
humans (first systematically detailed by Hazan & Shaver, 1987).
For example, initial attachment formation between infants and
caregivers (attachment-in-the-making) is characterized by height-
ened attempts by the infant to gain proximity to the attachment
figure, marked distress during physical separations, increased
smiling, visual-motor orientation, and positive greeting responses
selectively directed to the attachment figure (Ainsworth, 1967;
Bowlby, 1982). As discussed earlier, analogous characteristics are
observed during adult infatuation: intense desires for proximity to
and physical contact with the partner, resistance to separation,
intrusive thoughts of the partner, and fascination with the partner’s
behavior and appearance (Hatfield, 1987; Tennov, 1979; Zeifman
& Hazan, 1997). Furthermore, the cues that have been shown to
trigger infatuation—propinquity and reciprocal liking—corre-
spond directly to the cues that target infants’ attachment behavior
toward the “right” caregiver: familiarity and responsiveness
(Hazan & Diamond, 2000).
Correspondences extend to the later phases of bonding, as well.
As the infant matures, short-term separations no longer provoke
extreme distress, but extended separations continue to be associ-
ated with marked behavioral and affective disruptions reminiscent
of depression (Ainsworth et al., 1978; Bowlby, 1982, 1988). The
same dynamics have been found to characterize adult romantic
relationships, evidenced by self-report data on proximity seeking,
contact seeking, and separation distress in long-term relationships
(Brezsnyak et al., 1996; Hazan & Zeifman, 1994); observational
studies of couples’ interactions before, during, and after stressful
experiences (Fraley & Shaver, 1998; Simpson, Rholes, & Nelli-
gan, 1992); and couples’ behavioral and affective responses to
brief and long-term separations from one another (reviewed in
Vormbrock, 1993).
Evidence for neurobiological correspondences between adult
pair-bonding and infant–caregiver attachment. Stronger evi-
dence for the shared evolutionary origin of adult pair-bonding and
infant–caregiver attachment is provided by research on the neu-
robiological substrates for these processes. It is important to note
that all of the extant data on this issue come from animal research,
and extrapolations to humans must obviously be conducted with
caution. Yet thus far, extant findings strongly support the notion
that infant–caregiver attachment bonds and adult pair-bonds are
mediated by the same neurobiological circuits. Initial research in
this area focused primarily on the role of endogenous opioids in
general affiliative behavior, but in recent years there has been
increasing attention to the neuropeptides oxytocin and vasopressin
in selective social bonding (such as infant–caregiver attachment
and pair-bonding). Both oxytocin and vasopressin are involved in
selective social bonding, yet because oxytocin appears to play a
uniquely important role for infant–caregiver attachment and adult
pair-bonding, I focus my review on oxytocin.
Oxytocin is a neuropeptide hormone produced in the hypothal-
amus that is released into circulation from the posterior pituitary;
oxytocin is also released directly into the brain from neurons in the
paraventricular nucleus. Brain oxytocin receptors are found
throughout the limbic system and in the brain stem, particularly in
areas associated with emotion, autonomic control, and reproduc-
tive and social behavior. Oxytocin is most well known for stimu-
lating the contractions of labor and facilitating milk letdown in
nursing mothers, but it is also involved in multiple processes of
mammalian attachment and affiliation over the life course. Studies
of animals (typically rats and prairie voles) have identified direct
effects of oxytocin on maternal feeding behavior, maternal–infant
bonding, and kin recognition (Carter, 1998; Nelson & Panksepp,
1996; Pedersen, Caldwell, Walker, & Ayers, 1994; Uvna¨s-
Moberg, 1994). Like endogenous opioids, oxytocin has powerful
conditioning effects that are implicated in the formation of stable
preferences for places, stimuli, and other animals. For example,
one study demonstrated that rats that had been conditioned to
prefer one experimental compartment to another were induced to
reverse this preference by pairing exposure to the nonpreferred
compartment with central injections of oxytocin (Liberzon, Tru-
jillo, Akil, & Young, 1997). Another study found that when
interactions with novel social partners were accompanied by oxy-
tocin infusion, rats showed enhanced social memory for these
interaction partners (Popik, Vetulani, & van Ree, 1992).
Such findings have been interpreted to suggest that oxytocin-
mediated conditioning effects may be an important mechanism—
along with opioid-mediated conditioning effects—through which
mammals form stable, intrinsically rewarding bonds to specific
social partners, most importantly the mother. Rats, for example,
normally show a strong preference for odors associated with their
mothers (Galef & Kaner, 1980), which is one of the indicators of
attachment, and administration of an oxytocin antagonist prevents
rats from developing this normative preference (Nelson & Pank-
sepp, 1996). Oxytocin also facilitates the mother’s attachment to
her infant. Central injections of oxytocin can induce adult ewes to
form strong social attachments to unfamiliar lambs (Keverne &
Kendrick, 1992), and administration of oxytocin antagonists to rats
extinguishes certain maternal behaviors such as pup retrieval (Ped-
ersen et al., 1994).
Proximity and physical contact may be important for initiating
these bonding processes. Oxytocin release in rats is facilitated by
multiple forms of social stimulation, including touch, warmth,
light pressure, and massage (Uvna¨s-Moberg, Bruzelius, Alster, &
Lundeberg, 1993; Witt, Winslow, & Insel, 1992), and may be
responsible for the comforting effects typically associated with
such contact. Uvna¨s-Moberg et al. (1993) found that in addition to
facilitating oxytocin release, physical vibration, warmth, and mild
electro-acupuncture were all capable of attenuating rats’ behav-
ioral reactivity to experimental stress. Moreover, after administer-
ing central injections of an oxytocin antagonist, physical stimula-
Vasopressin is a related neuropeptide that differs from oxytocin in only
two of nine amino acids, is synthesized in the same mammalian brain
regions as oxytocin, and has both analogous and antagonistic effects on
attachment and affiliative behaviors (Carter & DeVries, 1999). There has
been more extensive research on oxytocin than vasopressin, and thus in the
interests of space I focus only on oxytocin.
tion no longer produced these stress-attenuating effects. A later
study (Uvna¨s-Moberg, 1997a) established that chronic central in-
fusions of oxytocin in rats over a 5-day period produced sedation,
reductions in blood pressure, reductions in stress reactivity, and
reductions in stress hormone levels, and these effects persisted for
several weeks after oxytocin treatments were terminated. Further-
more, a study of rat pups separated from their mothers and litter-
mates found that central injections of oxytocin significantly re-
duced these pups’ distress vocalizations (Insel & Winslow, 1991).
On the basis of such findings, researchers such as Uvna¨s-Moberg
(1998) have postulated that the physiologically and psychologi-
cally soothing and rewarding effects of infant–caregiver attach-
ment would initially be conferred through direct physical contact
and mediated by the release of oxytocin and endogenous opioids.
Yet through conditioning processes, mental representations of
attachment figures—the affectional bond itself, as it were—may
become a signal for the release of these neurochemicals and
thereby confer the same physiological and psychological effects
originally elicited by direct physical contact (Knox & Uvna¨s-
Moberg, 1998; Uvna¨s-Moberg, 1998).
If the biobehavioral processes underlying romantic love origi-
nally evolved in the context of infant–caregiver attachment, as
Premise 2 suggests, then the oxytocinergic mechanisms reviewed
above should also underlie adult pair-bonding. There is extensive
evidence from animal studies that this is the case. Much of this
research has focused on prairie voles, which are one of the few
species of rodents to form enduring pair-bonds. Pair-bonding in
voles is typically studied by placing two “stranger” voles in an
experimental chamber under controlled conditions and later testing
whether the voles prefer one another’s company to that of other
voles. As with infants’ preferences for their mothers, oxytocin
appears to mediate these partner preferences. Female prairie voles
who were exposed to novel males just after receiving a central
oxytocin infusion subsequently displayed a preference for these
partners over other males (Cho, DeVries, Williams, & Carter,
1999), but when exposure to a novel male was paired with admin-
istration of an oxytocin antagonist, voles failed to form such a
preference (Insel & Hulihan, 1995; J. R. Williams, Insel, Har-
baugh, & Carter, 1994).
Also, as with the infant–caregiver context, physical contact
plays an important role in these effects, and its influence appears
to be mediated by oxytocin release. Prairie voles establish stable
preferences for partners more quickly if they have mated with the
partner (J. R. Williams, Catania, & Carter, 1992) or if they have
had extended nonsexual cohabitation and frequent physical contact
with the partner, and central injections of oxytocin facilitate this
process (J. R. Williams et al., 1994). Notably, the female voles in
this particular study had been ovariectomized, demonstrating that
gonadal hormones are not prerequisites for pair-bonding. Mason
and Mendoza (1998) therefore argued that it is the oxytocin release
provided by physical contact—and not necessarily sexual con-
tact—that facilitates pair-bonding between reproductive partners.
It is on the basis of such findings that researchers working in this
area (Carter, 1998; Carter & Keverne, 2002; Panksepp, 1998;
Panksepp, Nelson, & Bekkedal, 1997) generally maintain that
adult pair-bonding and infant–caregiver attachment share the same
neurobiological substrate, a conclusion that supports the notion of
a shared evolutionary origin for these two processes. This shared
evolutionary origin is the basis for Premise 2’s primary assertion,
that individuals do not possess intrinsic affectional orientations for
one gender or the other.
Evidence regarding the lack of affectional orientations. It is
practically impossible to find reliable evidence for or against this
assertion, given that most research on sexual orientation (and, most
importantly, all of the genetic research on sexual orientation) either
collapses assessments of sexual and romantic tendencies into a
single construct (e.g., Pattatucci & Hamer, 1995) or only assesses
the former (e.g., Bailey et al., 2000). The few studies that have
reported independent assessments of each dimension show that
individuals often experience disjunctures between the degree to
which they are sexually versus emotionally drawn to the same
gender (Diamond, in press-b; Weinberg, Williams, & Pryor, 1994).
It is not clear how to interpret such findings. On the one hand,
self-reported gaps between affectional and sexual “tendencies”
might be interpreted as evidence that independent affectional ori-
entations do exist and that they are independent of an individual’s
sexual orientation. On the other hand, they might reflect the fact
that when describing their patterns of affectional feelings, individ-
uals take into account their previous experiences and conscious
preferences regarding close relationships. For example, many het-
erosexual as well as lesbian or bisexual women have explicitly
acknowledged that although they are equally capable of emotion-
ally bonding with women and men, they prefer to develop affec-
tional bonds with women because women are more emotionally
responsive (Diamond, in press-b). Notably, many gay and bisexual
men report the same preference for emotional relationships with
women (Diamond & Dube´, 2002; Nardi, 1999; Savin-Williams,
1998). Consequently, differences between individualsself-
reported sexual and affectional tendencies cannot be interpreted as
reliable evidence for or against the existence of intrinsic affec-
tional orientations.
Given these ambiguities, it is instructive to revisit the animal
data. If mammalian pair-bonding is intrinsically heterosexually
oriented in the majority of cases (as appears to be true for their
sexual desires), then same-gender, nonsexual pair-bonds should be
exceedingly rare among mammalian species, and it should not be
possible to “induce” such pair-bonds on the basis of situational
factors. There are only a small number of studies that speak
directly to this question, but they converge to indicate that non-
sexual, same-gender pair-bonds are indeed observed in (heterosex-
ual) mammals, although such bonds do not appear to be as exclu-
sive or enduring as heterosexual reproductive pair-bonds. Same-
gender pair-bonds are most likely to occur in mammalian species
exhibiting communal or cooperative breeding, in which the care of
offspring is not managed exclusively by a male–female reproduc-
tive pair but is shared with a network of extended family members.
Notable examples include female-bondedprimate species
(Wallen & Tannenbaum, 1997; Wrangham, 1980), in which bonds
between female kin and affiliates are of preeminent importance in
fostering infant care and promoting reproductive success (re-
viewed in Carter & Keverne, 2002; Taylor et al., 2000). Female–
female bonds in such systems serve many attachment-like func-
tions, such as security and protection (Wallen & Tannenbaum,
1997), and they are typically manifested and maintained by the
same behaviors that characterize male–female pair-bonds: high
degrees of proximity seeking, physical contact, and mutual groom-
ing (Baldwin, 1985; Dunbar, 1996). Evidence that such bonds are
analogous to infant–caregiver attachments and adult reproductive
pair-bonds is provided by research on squirrel monkeys demon-
strating that females separated from their bonded female affiliates
show the same forms of physiological stress reactivity (specifi-
cally, activation of the hypothalamicpituitaryadrenocortical
axis) as have been classically observed when infants are separated
from caregivers and adults are separated from their pair-bonded
mates (Hennessy, 1997; Hennessy, Mendoza, & Kaplan, 1982).
Unfortunately, the biobehavioral mechanisms underlying
female–female bonds in such species (as well as mammals in
general) have remained largely unexplored (Carter & Keverne,
2002). Although researchers have argued that such mechanisms
are fundamentally derived from the same oxytocin and opioid
circuits governing infant–caregiver attachment and adult repro-
ductive pair-bonding (Keverne, Nevison, & Martel, 1999), very
few studies speak directly to this question. The most important
data on this topic come from a study on same-gender pair-bonding
in prairie voles (DeVries, Johnson, & Carter, 1997). Using the
classic partner-preference paradigm, this study showed that 24 hr
of cohabitation with a same-gender partner produced reliable so-
cial preferences for that partner in both male and female voles.
However, later introduction of a novel other-gender vole disrupted
these same-gender pair-bonds, suggesting that the motives and
rewards of mating may “trump” those of nonreproductive pair-
bonds in reproductively mature animals. This notably brings to
mind the aforementioned observation by one of Von Sydow’s
(1995) respondents that she and her friends stopped developing
same-gender infatuations once they started “noticing the boys.”
Interestingly, a subsequent study (DeVries & Carter, 1999) de-
tected gender differences in voles’ propensity to form same-gender
pair-bonds. Specifically, female voles formed such preferences
more quickly after cohabitation than males, and the females’
same-gender preferences were more robust over time. The authors
hypothesized that this may reflect the differential adaptive signif-
icance of affiliative bonding for male versus female reproductive
success, as noted above regarding female-bonded social systems.
These findings support the prediction that the biobehavioral
mechanisms underlying mammalian pair-bonding are not intrinsi-
cally oriented according to the same-gender–other-gender status of
one’s partner. Such orientations would not only be maladaptive for
infant–caregiver attachment, but they would be maladaptive for
communal or cooperative breeding systems, in which the neural
substrates for pair-bonding appear to be involved—at least to some
extent—in the formation of same-gender bonds. Rather, a more
plausible conceptualization of mammalian attachment was pro-
vided by Mason and Mendoza (1998), who argued that primate
attachment relies on dynamic action schemata. In other words,
primates are born with a complex, diffusely distributed, relatively
stable neurobiological structure equipping them to form filial
attachments. Yet although the selection of the attachment figure is
guided by certain species-characteristic dispositions, the attach-
ment schema is inherently “open” and opportunistic, ready to
assimilate what the environment affords. Although Mason and
Mendoza were speaking of the infantcaregiver context, this
model works just as well when considering same-gender
Areas requiring future study. Most of the evidence reviewed
above comes from animal studies, and thus a chief priority for
future research is to determine whether the neural circuits under-
lying mammalian attachment have the same types of influences on
human affect and behavior as have been identified in animals. For
example, what types of human social interactions facilitate oxyto-
cin release, and is there a direct relationship between the affective
quality of an interaction and the amount of oxytocin released
during the interaction? It is important that such research not be
limited to oxytocin. As others have noted (Taylor et al., 2000), a
number of neurochemicals other than oxytocin, brain opioids, and
gonadal hormones—such as serotonin, dopamine, prolactin, vaso-
pressin, and norepinephrine—also influence mammalian social
behavior, although they have not received as much sustained
investigation (see Bagdy & Arato, 1998; Insel & Winslow, 1998;
Panksepp, 1998; Panksepp et al., 1997; Schwarzberg, Kova´cs,
Szabo´, & Telegdy, 1981). Future research must investigate the
independent and interacting influences of these neurochemicals.
Another question for future investigation is the extent to which
most individuals perceive their affectional feelings to be oriented
in the same manner as their sexual feelings. As noted above, most
research on sexual orientation does not assess self-perceived ten-
dencies to bond affectionally with one gender or the other. Col-
lecting such assessments is important for determining whether, for
example, affectional feelings are more or less situationally variable
than sexual feelings and whether stable affectional tendencies
develop at different ages than sexual tendencies. Disjunctures
between sexual and affectional feelings also deserve attention.
Extant data suggest that such disjunctures often play a critical role
in shaping individuals’ judgments regarding their “true” sexual
identities (Diamond, in press-b), underscoring the importance of
integrating assessments of affectional feelings into research on
same-gender sexuality.
Premise 3: Can Love Lead to Desire?
Whereas Premises 1 and 2 emphasize distinctions between love
and desire, Premise 3 emphasizes the connections between these
experiences that are established and maintained by cultural prac-
tices (such as norms specifying that long-term pair-bonds are only
formed with sexual partners), psychological processes (such as
learned associations between love and desire), and shared neuro-
biological substrates (such as oxytocin and endogenous opioids).
Oxytocinergic links between love and desire are of particular
interest. In addition to mediating attachment-related feelings and
behaviors, oxytocin also mediates sexual behavior. Animal re-
search has found that exogenous administration of moderate
amounts of oxytocin stimulates females to seek out sexual activity
(Argiolas, Melis, Mauri, & Gessa, 1987; Floody, Cooper, & Al-
bers, 1998) and to show receptivity to sexual requests (Arletti &
Bertolini, 1985; Caldwell, Prange, & Pedersen, 1986; Gorzalka &
Lester, 1987). In fact, the highest circulating levels of oxytocin in
humans are detected during sex, and oxytocin has been implicated
in the experience of orgasm and the feeling of satiety that follows
sexual activity (Carmichael, Warburton, Dixen, & Davidson,
1994; Carter, 1992, 1998; Riley, 1988). Thus, oxytocin might be
critically implicated in the robust interconnections between love
and desire that become established and subsequently reinforced in
the years between puberty and adulthood.
It is important to note that conventional wisdom posits these
links to be unidirectional: That is, although one can fall in love
with an object of sexual desire, one is not expected to develop
novel sexual desires as a result of falling in love. Premise 3,
however, maintains that the cultural, psychological, and biobehav-
ioral pathways linking love and desire are bidirectional, such that
individuals can develop sexual desires as a result of affectional
bonding, even if such desires contradict their sexual orientation.
Given that these cross-orientation desires are dependent on the
emotional processes associated with pair-bonding, they should be
specific to the relationship in question.
Evidence for relationship-specific, cross-orientation desires.
There is evidence in support of this prediction. Scientific and
popular writings on sexual orientation are replete with accounts of
individuals whose same-gender desires revolve around specific
people they unexpectedly fell in love with rather than same-gender
partners in general (Cassingham & O’Neil, 1993; Golden, 1996;
Pillard, 1990; Savin-Williams, 1998; Whisman, 1996). Notably,
such reports are often greeted with skepticism. As Blumstein and
Schwartz (1993) noted, the conventional understanding of sexual
orientation maintains that it is impossible to have “only some”
same-gender attractions for “only some” special people, and that
individuals making such claims are consciously or unconsciously
misrepresenting their feelings in order to avoid the stigma of
homosexuality (p. 177). With enough time, such individuals are
expected to recant tales of relationship-specific desires and claim
lesbian, gay, or bisexual identities.
Certainly, some do. In the process of telling their “coming-out”
stories, many lesbian, gay, and bisexual individuals report that
although they initially thought their same-gender attractions were
restricted to one special person, they eventually realized this was
not so (e.g., Jensen, 1999; Stanley & Wolfe, 1980). Yet of course,
these accounts come from the most self-selected sample possible:
openly identified lesbian, gay, and bisexual individuals. A stronger
test of whether nonsexual affectional bonds can give rise to tem-
porary, relationship-specific sexual desires would be provided by
evidence that not only can heterosexual individuals develop such
desires in the context of same-gender affectional bonds but that
lesbian and gay individuals can also develop such desires in the
context of other-gender affectional bonds.
A recent longitudinal study of female sexual identity develop-
ment provides evidence for both of these phenomena. In this study,
approximately 80 nonheterosexual women were interviewed
shortly after coming out and then two additional times during the
next 5 years (Diamond, 1998, 2000b, in press-a, in press-b).
Consistent with prior research (Cassingham & ONeil, 1993;
Golden, 1987; Jensen, 1999), several of these women reported at
the initial interview that their first (and sometimes only) experi-
ences of same-gender desire were restricted to specific female
friends with whom they had developed unusually intense emo-
tional bonds. If all of these women were misrepresenting their true
feelings, one would expect them to eventually recant these expla-
nations once they became more comfortable with their lesbian or
bisexual identities.
This was not what happened. By the 5-year follow-up inter-
view, 7 women had gone back to identifying themselves as het-
erosexual, and 3 of these women were among the group that had
originally experienced their same-gender desires only in the con-
text of specific relationships (Diamond, 2000c, in press-a). These
women reported that once their special relationship ended, so did
their same-gender desires, and all expressed a degree of surprise
and sadness at the change. Even more interesting, 4 of the openly
identified lesbians in this sample reported having unexpectedly
fallen in love and become sexually involved with close male
friends in the 5 years since their first interview. As with
relationship-specific same-gender desires, these other-gender de-
sires caught women by surprise, and several expressed outright
embarrassment about them. All of these women explicitly stated
that they remained predominantly sexually attracted to women,
and that the men with whom they fell in love constituted
Of course, these cross-orientation, relationship-specific desires
were reported by only a small number of women, and the findings
require replication with more diverse samples. However, these
data suggest that although most individuals begin a romantic
relationship with feelings of sexual desire and end up experiencing
infatuation and attachment, this process can operate in the opposite
direction. Consequently, not all experiences of same-gender desire
or same-gender passionate attachment should be taken as defini-
tive indicators of intrinsic same-gender sexual orientations. Rather,
bidirectional links between the psychological and biobehavioral
processes underlying love and desire may render a range of same-
gender and other-gender sexual and romantic feelings possible at
different stages of life and under different circumstances.
Importantly, all of the evidence outlined above for bidirection-
ality is culled from research on women, raising the question of
whether love and desire are more bidirectional among women than
men. The present model suggests that this may be the case, given
that there appear to be more robust cultural, psychological, and
neurobiological links between love and desire among women than
men. For example, many societies actively constrain women’s
sexual activity to affectional contexts (Gagnon & Simon, 1973) or
deem that female sexual activity is only acceptable when it occurs
with a steady rather than a casual partner (reviewed in Hyde &
Durik, 2000). Men, in contrast, are typically granted considerably
more latitude in their sexual behavior. Furthermore, female social-
ization practices often focus on fostering communal orientations in
women, which might reinforce women’s perceptions that their
sexual desires are interpersonally based (Andersen et al., 2000).
Perhaps most intriguingly, animal research has demonstrated that
oxytocin’s effects on attachment and sexual behavior are estrogen
dependent and therefore highly gender specific (Caldwell, Walker,
Pedersen, Barakat, & Mason, 1994; Carter, 1992; McCarthy, Kow,
& Pfaff, 1992), suggesting potential gender differences in the
neurobiological connections between love and desire. For exam-
ple, research on rats has detected more extensive oxytocin circuits
in female than male brains, perhaps to facilitate oxytocin-
dependent caregiving behaviors (Panksepp, 1998), and some oxy-
tocin receptors have been found to be sexually dimorphic (De
Wied, Diamant, & Fodor, 1993). If bidirectionality is based on just
such cultural, psychological, and neurobiological connections be-
tween love and desire, then it follows that it should be more
pronounced among women than among men.
Evidence for gender differences in bidirectionality. It has long
been a truism that sex and love are more fused for women than for
men (Nichols, 1987), and apparently both men and women believe
this to be the case. Regan and Berscheid (1995) asked male and
female undergraduates what they thought caused male versus
female sexual desire, and found that the most widely endorsed
causes of male sexual desire were biological processes and a
physical “need” for sex. In contrast, the most widely endorsed
causes of female sexual desire were interpersonal experiences
related to romantic love. Research on lesbian and bisexual women
further supports a link between love and desire: Lesbian and
bisexual women frequently report feeling emotional same-gender
attractions before physical same-gender attractions, and physical
attractions often first develop in the context of an existing emo-
tional bond (Blumstein & Schwartz, 1993; Gramick, 1984; Rose &
Zand, 2000; Rose, Zand, & Cimi, 1993; Vetere, 1982; Whisman,
Women are also more likely than men to say that they become
attracted to—or fall in love with—the person and not the gender
(Blumstein & Schwartz, 1993; Golden, 1987; Savin-Williams,
1998) and appear more likely than men to engage in (and enjoy)
sexual behavior that runs counter to their established pattern of
sexual desire, that is, heterosexual women engaging in sexual
behavior with women (Davis, 1929/1972; Dixon, 1984, 1985;
Goode & Haber, 1977; Pillard, 1990) and lesbian women engaging
in sexual behavior with men (Bart, 1993; Chapman & Brannock,
1987; Clausen, 1999; Diamond, 2000b, in press-a, in press-b; Rust,
1992, 2000; Sophie, 1986; Weinberg et al., 1994). It is important
to note that intense emotional bonds are one of the most common
catalysts for such experiences. In such cases, women typically
report that their unusually strong emotional feelings spill over into
sexual desire (Bart, 1993; Cassingham & O’Neil, 1993; Clausen,
1999; Davis, 1929/1972; Diamond, 2000b, in press; Peplau &
Cochran, 1990; Peplau & Garnets, 2000; Pillard, 1990; Whisman,
Recently, Baumeister (2000) discussed such phenomena as ex-
amples of greater sexual plasticity among women than men. Yet he
portrayed the influence of affectional relationships on plasticity as
functionally equivalent to the influence of other situational and
social factors, such as education and societal permissiveness. The
common denominator linking such influences, in his analysis, was
their externality, because he emphasized that women’s sexual
responses, relative to men’s, are motivated more by external con-
text than by internal factors (p. 348). In a subsequent article on
gender differences in sex drive, Baumeister and colleagues
(Baumeister, Catanese, & Vohs, 2001) elaborated on the impor-
tance of extrinsic motivation for female sexuality, arguing that
“male desire aims at the sexual activity itself, whereas female
desire aims beyond it toward other outcomes and consequences”
(p. 263). They listed women’s need for a “relationship context” for
sex as a prime example of this phenomenon. This interpretation
may be apt, but it is incomplete: In addition to providing an
influential external context for sexual desire and activity, affec-
tional bonds might also shape the internal experience of desire by
activating the shared neurobiological substrates linking these two
subjective experiences.
Potential biobehavioral mechanisms underlying gender differ-
ences in bidirectionality. In considering this possibility, the dis-
tinction between proceptive and receptive sexual desire (Beach,
1976; Wallen, 1995) proves instructive. Proceptivity denotes the
urge to seek out and initiate sexual activity, whereas receptivity
denotes the capacity to become interested in sex on encountering
certain stimuli and is sometimes called arousability (Bancroft,
1989). This distinction is well known to those who study the sexual
behavior of nonhuman primates (Hrdy, 1987) but has received far
less attention in discussions of human sexuality, with a few notable
exceptions (Bancroft, 1989; Baumeister, 2000; Fisher, 1998;
Wallen, 1995). Research (as reviewed by Wallen, 1995) has found
that proceptive desire is directly mediated by gonadal hormones:
androgens in men and both androgens and estrogen in women.
Thus, the fact that women’s levels of circulating androgens are
substantially lower than those of men, coupled with the fact that
they only experience high estrogen levels a few days per month,
might partially explain (in concert with cultural factors) why
women generally experience fewer spontaneous sexual urges on a
day-to-day basis than men (Beck, Bozman, & Qualtrough, 1991;
Byers & Heinlein, 1989; Julien, Bouchard, Gagnon, & Pomerleau,
1992; Knoth, Boyd, & Singer, 1988; Laumann et al., 1994;
O’Sullivan & Byers, 1992) and fewer sexual fantasies (B. J. Ellis
& Symons, 1990; Leitenberg & Henning, 1995).
Yet notably, researchers have detected no direct relationship
between gonadal hormones and arousability (Abramson, Repczyn-
ski, & Merrill, 1976; Griffith & Walker, 1975; Hoon, Bruce, &
Kinchloe, 1982; Slob, Ernste, & van der Werff ten Bosch, 1991).
In fact, even hypogonadal men with castrate levels of testosterone
become readily aroused to erotic stimuli (Bancroft, Tennent, Lou-
cas, & Cass, 1974; Kwan, Greenleaf, Mann, Crapo, & Davidson,
1983). It is important to note that if the proceptive component of
women’s sexual desire is more quiescent than men’s because of
their different hormonal status, then a greater proportion of the
desires they do experience might be attributable to arousability,
and this might be the context in which pathways from love to
desire operate. Animal research suggests a possible role for oxy-
tocin in this regard. As noted above, studies of rats have found that
oxytocin administration facilitates both proceptive sexual interest
(Argiolas et al., 1987; Floody et al., 1998) and greater sexual
receptivity (Arletti & Bertolini, 1985; Caldwell et al., 1986; Gor-
zalka & Lester, 1987; Witt & Insel, 1991). However, oxytocin’s
effects on receptivity appear to be estrogen dependent (Arletti &
Bertolini, 1985; Caldwell et al., 1986; Gorzalka & Lester, 1987).
Perhaps, then, romantic love facilitates arousability via oxytocin
release, and perhaps this effect is disproportionally likely among
women because of its estrogen dependence. This does not, how-
ever, discount the influence of culture and socialization on sexual
feelings experienced within affectional contexts but rather sug-
gests that cultural influences might be facilitated by gender-
differentiated biobehavioral processes.
Areas requiring future study. The hypothesis that oxytocin
plays a role in mediating gender-differentiated bidirectional path-
ways between love and desire is admittedly speculative at the
current time, given how little is known about the role of oxytocin
in mediating both affectional and sexual feelings in humans. Fur-
thermore, although it might seem plausible to posit straightfor-
ward, dose-dependent associations between oxytocin levels and
emotional responses (such that low levels facilitate feelings of
comfort whereas high levels facilitate sexual desire), research on
animals suggests that it is not quite this simple. In rats, prolonged
exposure to high levels of oxytocin appears to induce feelings of
sexual satiety rather than arousal, and in male rats such exposure
promotes nonsexual rather than sexual physical contact (Witt et al.,
1992). Research on humans has shown that although high levels of
oxytocin are released during sexual activity, high levels are also
released during lactation, and most breast-feeding women report
declines rather than increases in sexual interest (Adler & Bancroft,
1983; Kayner & Zagar, 1983). Clearly, the context in which
oxytocin is released—both interpersonally and neurohormon-
ally—may be critically implicated in oxytocin’s subjective conse-
quences, and these issues must be carefully considered in future
research. We also do not know the extent to which oxytocin
functioning in humans is gender differentiated and whether this is
attributable to interactions between oxytocin and human gonadal
hormones. This question might be answered by studies investigat-
ing whether oxytocin functioning changes over the course of
adolescence as a function of pubertal changes in gonadal hor-
mones. One possibility is that maturationally dependent interac-
tions between oxytocin and gonadal hormones play a role in
linking perceptions and experiences of affectional and sexual feel-
ings during the adolescent years.
A promising paradigm for testing such possibilities involves
assessing oxytocin reactivity, or the degree to which exposure to
certain stimuli elicits increases in oxytocin release (manifested in
increased blood-plasma levels of oxytocin). Prior research on
individual differences in oxytocin reactivity (Light et al., 2000;
Turner, Altemus, Enos, Cooper, & McGuinness, 1999) suggests
fascinating directions for future study. For example, Turner et al.
(1999) measured women’s plasma levels of oxytocin after three
different episodes: pleasant massage, positive emotional imagery,
and negative emotional imagery. Some women showed consis-
tently greater oxytocin reactivity to the massage and positive
emotion inductions than others, and these women were also less
likely to report intrusive behavior in their close relationships (i.e.,
inappropriate self-disclosure, high attention seeking, and difficulty
spending time alone). One possible (albeit speculative) interpreta-
tion of this finding is that women with low oxytocin reactivity
experience disproportionately fewer affective rewards from their
social relationships as a result of their oxytocin response patterns
and that their intrusive behavior is a form of compensation. One
might then consider whether high oxytocin reactivity is associated
with a heightened capacity to form strong affectional bonds or
whether individual differences (and, of course, gender differences)
in oxytocin reactivity are related to the bidirectional links between
love and desire. Research pairing assessments of the quality of
individuals’ prior and current intimate relationships with experi-
mental measures of oxytocin reactivity would provide a fascinat-
ing new perspective on these questions.
The influence of situational factors such as environmental stress
on oxytocin release also requires further study. Oxytocin is re-
leased during mild to modulate stress and helps to reduce the
stress-related activity of the hypothalamic–pituitary
adrenocortical axis (Chiodera et al., 1991; Uvna¨s-Moberg, 1997b).
Considering both its conditioning and stress-reducing effects, oxy-
tocin release might account for the robust observation that attach-
ment formation is greatly facilitated by mild to moderate stress in
both primates (Mason & Mendoza, 1998) and humans (Simpson &
Rholes, 1994). Notably, the stress-reducing and mildly sedative
properties of oxytocin are stronger in females than males (Jezova,
Jurankova, Mosnarova, Kriska, & Skultetyova, 1996), suggesting
that stress-induced oxytocin release may play a more important
role for platonic attachment formation among women than among
men. This is consistent with Taylor et al.’s (2000) argument that
affiliation may constitute a fundamental component of mammalian
females’ biobehavioral responses to stress and that females there-
fore form such bonds more readily than males. Considering that
stress is also known to influence subjective experiences of attrac-
tion (Foster et al., 1998), the potential role of psychological stress
in facilitating gender-differentiated bidirectional pathways be-
tween love and desire is a promising area for future consideration.
Implications for Gender Differences in Sexuality and
Sexual Orientation
Clearly, the present model has numerous implications for con-
ceptualizing and explaining gender differences in sexuality, not all
of which have been addressed in depth above. For example, in
addition to the phenomenon of bidirectionality and the importance
of relational contexts for female sexual desire, this model has
implications for considering gender differences in sexual develop-
ment. Research has reliably demonstrated that interpersonal rela-
tionships exert a greater influence on female adolescents’ first
experiences of sexual desire and behavior than on males’ (e.g.,
Hyde & Jaffee, 2000; Udry & Billy, 1987). Previous explanations
of such gender differences have (appropriately) emphasized the
strong cultural messages instructing young women to confine their
sexuality to relational contexts. However, as noted earlier, the
present model implies that it should not be presumed that relational
contexts only function as external contexts. Rather, the emotions
associated with affectional bonding might reconstitute “internal”
experiences of sexual desire, potentially shaping girls’ subjective
experiences (and not just behavioral expressions) of sexual-
developmental transitions. This also has implications for interpret-
ing gender differences in sexual dysfunction, particularly gender
differences in the problem of low (or nonexistent) sexual desire
(Beck, 1995; Leiblum & Rosen, 2000). Sex therapists have long
acknowledged that this disorder involves a complex interplay of
cultural, interpersonal, and hormonal factors (Beck, 1995; Leiblum
& Rosen, 1988), and the present model might yield novel ways to
conceptualize how and why, for example, difficulties within a
romantic relationship might have a more powerful dampening
effect on women’s than men’s subjective experiences of sexual
Perhaps the most notable implication of the present model
concerns gender differences in the development and expression of
same-gender sexuality, which has received increasing attention in
recent years (Baumeister, 2000; Diamond & Savin-Williams,
2000; Peplau & Garnets, 2000; Peplau, Spalding, Conley, & Ve-
niegas, 1999; Savin-Williams & Diamond, 2000). For example,
women show greater variability than men in the age at which they
first become aware of same-gender attractions, the age at which
they consciously question their sexuality, and the age at which they
pursue their first same-gender sexual contact (Bell & Weinberg,
1978; D’Augelli & Hershberger, 1993; Fox, 1995; Herdt & Boxer,
1993; Sears, 1989; Weinberg et al., 1994). Many women experi-
ence these three “milestones” of sexual identity development si-
multaneously, late in life, in the context of an unexpected same-
gender affair (Cassingham & O’Neil, 1993; Kitzinger &
Wilkinson, 1995). Also, women place less emphasis on the sexual
component of their lesbian or bisexual identification, both during
and after the questioning process (Blumstein & Schwartz, 1993;
Cass, 1990; Esterberg, 1994; Nichols, 1990; Whisman, 1996), and
are more likely to report that their sexuality is fluid and chosen
versus fixed and biologically given (Esterberg, 1994; Golden,
1987, 1996; Rosenbluth, 1997; Whisman, 1996).
All of these findings are consistent with the notion that inter-
personal factors play a greater role in the development and expres-
sion of same-gender sexuality among women than among men. On
the basis of such differences, Peplau et al. (1999) recently pro-
posed that female same-gender sexuality might be fruitfully recon-
ceptualized in terms of intimate careers rather than early-
appearing, fixed traits. This conceptualization would model a
woman’s experiences of same-gender and other-gender sexual
desires as a function of her current and prior experiences in
same-gender and other-gender intimate relationships. This view
does not deny potential biological contributions to women’s same-
gender sexual desires but grants them notably less weight in
directing lifetime trajectories of intimate experience. The model
presented here is consistent with this perspective and points toward
some of the underlying mechanisms through which intimate ca-
reers might exert their influences.
Does this view imply that a woman’s participation in intimate
relationships can change her sexual orientation? The answer to this
question depends on how one defines sexual orientation. Cer-
tainly, same-gender sexual and affectional desires undergo some
change (Diamond, 2000b, in press-a; Pattatucci & Hamer, 1995;
Stokes, Damon, & McKirnan, 1997; Stokes, McKirnan, & Bur-
zette, 1993; Weinberg et al., 1994), yet such changes are usually
small in magnitude and do not typically involve the complete
disappearance of either same-gender or other-gender sexual or
affectional feelings. Thus, perhaps it is easier to develop novel
sexual desires (for either gender) than to extinguish them, a con-
clusion that is consistent with research on the development of
bisexual attractions and identities (Fox, 1995; Weinberg et al.,
A more perplexing issue concerns the long-term implications of
cross-orientation affectional bonds and relationship-specific sexual
desires. In some cases (as noted above), these experiences are
eventually interpreted as singular, temporary aberrations; in other
cases, they might be repeatedly reinforced and hence become
increasingly robust over time, eventually showing the same stabil-
ity traditionally expected of intrinsic same-gender desires (Cass,
1990). The inherent interconnectedness, plasticity, and develop-
mental sensitivity of the neural circuits involved in love and desire
may play a role in such phenomena. For example, Panksepp (1998)
suggested that such circuits may play a role in the mere-exposure
effect, whereby both animals and humans develop preferences for
stimuli to which they have been repeatedly exposed, especially if
the exposures were affectively positive (p. 259). Such processes
might help to explain why some women’s late-appearing, affec-
tionally based same-gender desires often prove to be notably
robust and stable (Cassingham & O’Neil, 1993). Perhaps repeated
participation in affectively positive same-gender intimacy (accom-
panied by the release of neurochemicals that facilitate condition-
ing) is capable of restructuring individuals’ romantic–sexual at-
tachment schemata, such that women who do not possess a genetic
orientation to the same gender might nonetheless develop
comparably stable and robust predispositions for same-gender
partners on the basis of multiple, affectively positive same-gender
This, of course, could also occur among men, and the specific
extent to which such phenomena might be gender-differentiated is
unknown. Clearly, much remains to be learned about the develop-
ment and expression of both female and male same-gender sexu-
ality. In this respect, perhaps the most important point highlighted
by the model I have presented is the simple fact that same-gender
sexuality has multiple components and multiple determinants. As
Bancroft (1990) noted, “the ‘state of being homosexual’ in our
society...isaconsequence (and not necessarily an end state) of
a multifactorial developmental process” (p. 101). Furthermore, this
process varies not only across but within men and women. It is
hoped that the present model will provide a useful framework for
future research delineating the diverse origins and implications of
same-gender and other-gender desires for men and women over
the life course.
Limitations of the Model
As noted repeatedly above, this model’s formulation of the
interacting biological underpinnings of human love and desire
relies heavily on research findings from animal studies, which is
perhaps its chief limitation. Given the extensive cross-species
variation that has been documented in parenting behavior, pair-
bonding behavior, sexual behavior, and also in the distribution and
functioning of oxytocin receptors (Tribollet, Dubois-Dauphin,
Dreifuss, Berberis, & Jard, 1992; Witt, 1997), definitive claims
regarding the specific neurobiological underpinnings of human
affect and behavior await future research. Another limitation con-
cerns the potential for reductionism. Philosophers have debated the
meaning of love for hundreds of years—is it really just a matter of
neurochemistry? The qualitative experience of romantic love
shows remarkable diversity across different cultures, different
individuals, and different relationships within a single individual’s
life: What accounts for such differences? The present model does
not address this complex question, and I have not systematically
discussed the multiple ways in which social and cultural factors
might interact with biological processes to influence subjective
experiences of sexual and affectional desire. However, the dispro-
portionate focus on biological rather than social determinants of
affect and behavior should not be interpreted as biological deter-
minism. Rather, it is intended to counterbalance the widespread
assumption that whereas sexual desires belong in the realm of
“nature,” affectional feelings belong in the realm of “culture.” I
fully acknowledge, however, that biological predispositions are in
constant interaction with environmental input (from individual
interpersonal experiences to overarching cultural norms) and that
all affective–behavioral outcomes must be viewed as products of
such interactions.
For example, as reviewed by Panksepp (1998), research on rats
has found that participation in sexual activity produces up to
threefold increases in male rats’ brain oxytocin levels, which might
function to facilitate subsequent pair-bonding and parenting (al-
though the duration of these changes and their specific behavioral
effects await future study). Such findings demonstrate that in the
realm of human social behavior, the nature–nurture dichotomy is
not only unpalatable but inaccurate. The available evidence sug-
gests that “the environment” (whether an entire society or a single
interpersonal relationship) is not simply layered on top of biolog-
ical processes but becomes fundamentally integrated into these
processes through direct experience (Money, 1988).
Given this fact, one might argue that it is too simplistic to view
sexual desire as intrinsically oriented by genetic factors. I share
this reservation. As noted above, although there is both a plausible
evolutionary basis for sexual desires to be heterosexually oriented
for most individuals, and empirical evidence that nonheterosexual
orientations are partially genetic, this does not prove that sexual
desires themselves are intrinsically gender coded. As noted above,
it is not yet clear what the genes in question code for. The present
model therefore takes a stronger stand for the absence of gender
coding in romantic love than the presence of gender coding in
sexual desire. Its strongest stand is that however sexual desires
come to be channeled in one direction or another—whether
through genes, perinatal hormonalization, or early learning—these
processes impose no de facto constraints on affectional bonding.
In critiquing the overemphasis on physical, mechanical aspects
of sexuality that characterized most basic research on sexual
orientation, DeCecco (1990) pointed out that such models are
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Received June 23, 2000
Revision received January 9, 2002
Accepted January 23, 2002
... Love and lust are essentially independent concepts related to distinctly separate neural biological material (Diamond 2003(Diamond , 2004. Love is an emotional state of not wanting to be separated from one another, which begins from emotional attachments between a mother and her babies and evolves into a strong attachment to an intimate partner. ...
... Love is an emotional state of not wanting to be separated from one another, which begins from emotional attachments between a mother and her babies and evolves into a strong attachment to an intimate partner. On the other hand, lust is an emotional state of longing for sexual activity for the purpose of reproduction (Aron and Aron 1986;Diamond 2003;Regan and Berscheid 1995;Rubin 1970). According to Fisher (1998) lust is governed by the sexual mating system, which is unrelated to bonding or long-term relationships, whereas love is governed by the pair-bonding system and attachment (Hazan and Shaver 1987;Hazan and Zeifman 1999). ...
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Prior research provides mixed evidence regarding the direction of the association between sexual and marital satisfaction. Whereas some studies suggest a bidirectional association, other studies fail to document one direction or the other. The current investigation used a 12-day diary study of 287 married individuals to clarify the nature of this association. Results from time-lagged mixed modeling revealed a significant positive bidirectional association. Both higher global sexual satisfaction one day and satisfaction with sex that occurred that day predicted higher marital satisfaction the next day; likewise, higher marital satisfaction one day significantly predicted higher global sexual satisfaction the next day and higher satisfaction with sex that occurred the next day. Both associations remained significant after controlling for participant’s gender/sex, neuroticism, attachment insecurity, self-esteem, stress, perceived childhood unpredictability and harshness, age of first intercourse, construal level, age, and length of marriage. We also explored whether these covariates moderated either direction of the association. Daily stress was the most reliable moderator, with three of the four interactions tested remaining significant after Bonferroni corrections. The bidirectional association between global sexual and marital satisfaction and the positive association between satisfaction with sex that occurred that day and marital satisfaction the next day were significantly stronger when individuals experienced high versus low stress. Although the exploratory nature of all moderation analyses suggests they should be replicated before drawing strong conclusions, these findings highlight the importance of sexual satisfaction to marital satisfaction and vice versa and point to the power of stress in strengthening these associations.
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Sexual orientation is a core aspect of human experience and understanding its development is fundamental to psychology as a scientific discipline. Biological perspectives have played an important role in uncovering the processes that contribute to sexual orientation development. Research in this field has relied on a variety of populations, including community, clinical, and cross-cultural samples, and has commonly focused on female gynephilia (i.e., female sexual attraction to adult females) and male androphilia (i.e., male sexual attraction to adult males). Genetic, hormonal, and immunological processes all appear to influence sexual orientation. Consistent with biological perspectives, there are sexual orientation differences in brain development and evidence indicates that similar biological influences apply across cultures. An outstanding question in the field is whether the hypothesized biological influences are all part of the same process or represent different developmental pathways leading to same-sex sexual orientation. Some studies indicate that same-sex sexually oriented people can be divided into subgroups who likely experienced different biological influences. Consideration of gender expression in addition to sexual orientation might help delineate such subgroups. Thus, future research on the possible existence of such subgroups could prove to be valuable for uncovering the biological development of sexual orientation. Recommendations for such future research are discussed.
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En este artículo se critica el capítulo 2 del libro "Atrapado en el cuerpo equivocado". Este capítulo se caracteriza por una fuerte omisión/Cherry picking de estudios y, en muchos casos, malinterpretación de los estudios que cita. Además de confundir la función de los estudios de gemelos. Es decir, el libro más que aclarar cosas o dar un conocimiento actualizado opta por generar más dudas mediante hipótesis ya desactualizadas
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Excitation transfer, the transfer of arousal from one emotion to another, might be a mechanism in the development of unusual sexual interests. In this pilot study, we investigated whether we could induce excitation transfer between various emotions and sexual arousal in a laboratory setting with 30 male volunteers. We induced low-level sexual arousal in four different emotional states (aggression/dominance, endearment, fear, disgust) and a neutral state. Sexual arousal was measured using penile plethysmography and self-report. Although there was no mean group effect, possibly due to large interindividual variations, 60% of the subjects showed more sexual arousal in response to sexual stimulation in at least one of the emotional states than in the neutral state. Excitation transfer was most prominent with aggression/dominance and least prominent with disgust. Genital excitation transfer was strongly related to lower penile reactivity and to higher self-reported erotophilia. This pilot study paves the way for further research into excitation transfer as a mechanism to increase the salience of stimuli that otherwise would not have been sexual in nature.
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Sexual and romantic orientations are often considered one and the same, and attitudes about engaging in sexual behavior are assumed to be predominantly positive. The current study explored the concordance between sexual and romantic orientations among allosexual and asexual adults as well as the frequency with which they identify as having a sex-positive, sex-neutral, or sex-averse attitude. As expected, allosexual adults were largely sex-positive (82%) and almost all (89%) had a romantic orientation that matched their sexual orientation. In contrast, we found that only 37% of asexual adults had concordant sexual and romantic orientations and that most asexual adults self-identify as either sex-neutral (41%) or sex-averse (54%). Further, we used a semantic differential task to assess sexual intimacy attitudes and how they varied for adults based on sexual attitude. Asexual adults, regardless of sexual attitude, had less positive attitudes overall than allosexual adults. Interestingly, aromantic asexual adults did not have more negative attitudes about sexual intimacy than romantic asexual participants. Although asexual adults held less positive attitudes about sex than allosexual adults, there was considerable heterogeneity within our asexual sample. The current study provides further insight into the concordance between romantic and sexual orientation, and the associations among sexual and intimacy attitudes for both allosexual and asexual adults. These findings will have implications for future research on how asexual adults navigate romantic relationships.
Nonverbal communication plays an instrumental role in the process of meeting someone in a potential romantic encounter, starting from determining if they are attractive, if they are interested in a relationship with us, and whether we would be compatible. In this chapter we highlight not just the nonverbal signs and signals of attraction, but attempt to articulate a deeper evolutionary derived meaning and reason for them. We examine the static features of faces and bodies that we find attractive, their relationship to health, fertility, and dominance (reproductive fitness), and then move to the dynamic nonverbal actions suggesting romantic interest, such as arousal and engagement, and finish by articulating those nonverbal markers that indicate attention, trust, and commitment. We hope this exploration of the static and dynamic characteristics of people will better illustrate how evolution can explain why and when people are attracted to each other.
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This study examined the effects of relationship status on response times to sexual and romantic stimuli during a memory task, which has not been studied before. Based on previous studies on sexual attitudes and behaviors, we hypothesized that response times to sexual stimuli would be faster in individuals who were in a relationship, compared to those who were not. We also hypothesized that the response times to sexual stimuli of individuals who were not in a relationship would be slower than their response time to romantic stimuli. A total of 348 college students memorized 27 sexual, romantic, and neutral sentences and were later asked to recognize them. The students’ response times to each sentence were recorded. The results of a 2 (gender) × 2 (stimulus type) × 2 (relationship status) ANOVA showed that response times to sexual sentences were faster in participants who were in a relationship, compared to those who were not. Furthermore, participants who were not in a relationship responded more slowly to sexual than to romantic sentences. Thus, our hypotheses were supported. Individuals’ relationship status influenced their response times to sexual and romantic stimuli even after controlling for the effects of gender.
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Low sexual desire in women partnered with men is typically presumed to be a problem—one that exists in women and encourages a research agenda on causation and treatment targeting women. In this paper, we present a distinct way forward for research on low sexual desire in women partnered with men that attends to a more structural explanation: heteronormativity. A heteronormative worldview assumes that relationships and structures are heterosexual, gender (usually conflated with sex) is binary and complementary, and gender roles fit within narrow bounds including nurturant labor for women. We propose the heteronormativity theory of low sexual desire in women partnered with men, arguing that heteronormative gender inequities are contributing factors. We outline four hypotheses and their predictions related to: inequitable divisions of household labor, blurring of partner and mother roles, objectification of women, and gender norms surrounding sexual initiation. We discuss some mechanisms—social, physiological, and otherwise—for the heteronormativity theory, especially related to stress, objectification, and nurturance. We close by noting some limitations of our paper and the ways that the heteronormativity theory of low sexual desire in women partnered with men provides a rigorous, generative, and empirical way forward.
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We examined whether heterosexual individuals’ self-reported sexual orientation could be influenced experimentally by manipulating their knowledge of the nature of sexual orientation. In Study 1 (180 university students, 66% female) participants read summaries describing evidence for sexual orientation existing on a continuum versus discrete categories or a control manipulation, and in Study 2 (460 participants in a nationally representative Qualtrics panel, 50% female) additionally read summaries describing sexual orientation as fluid versus stable across the life-course. After reading summaries, participants answered various questions about their sexual orientation. In Study 1, political moderates and progressives (but not conservatives) who read the continuous manipulation subsequently reported being less exclusively heterosexual, and regardless of political alignment, participants reported less certainty about their sexual orientation, relative to controls. In Study 2, after exposure to fluid or continuous manipulations heterosexual participants were up to five times more likely than controls to rate themselves as non-exclusively heterosexual. Additionally, those in the continuous condition reported less certainty about their sexual orientation and were more willing to engage in future same-sex sexual experiences, than those in the control condition. These results suggest that non-traditional theories of sexual orientation can lead heterosexuals to embrace less exclusive heterosexual orientations.
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Introduction to a collection of articles on MEN'S FRIENDSHIPS. When Montaigne described friendship as "souls that mingle and blend with each other so completely that they efface the seam that joined them," he was talking about his friendship with another man. .. The 11 articles in this collection are some of the first to explore the nature and meaning of friendship in men's lives.
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Lesbian dating and courtship were explored based on interviews with 38 predominantly white lesbians (ages 22-63) representing young adult, adult, and midlife age groups. Friendship was found to be the most widely used courtship script across all age groups, followed by the sexually explicit and romance scripts, with friendship and romance scripts being preferred. Unique aspects of lesbian dating cited by participants included freedom from gender roles, heightened intimacy/friendship, the rapid pace of lesbian relationship development, and the effects of prejudice. Friendship was found to be differentiated from romance by two main criteria: emotional intensity and sexual energy or contact. Verbal declarations of interest and nonverbal behaviors were the primary means of communicating sexual attraction. Few lesbians adhered to traditional gender roles in dating, and those who reported assuming the feminine reactive role nevertheless rejected the traditional notion that women should limit sexual contact. Overall, midlife lesbians were more purposive in their dating and more free from gender roles. Specifically, they were more concerned about the “attachment-worthiness” of a prospective partner and were significantly more likely than young adults to view dating as having a serious goal, to proceed at a rapid pace, to ask for a date, and to initiate physical intimacy.
Women's friendships - an under-explored topic? do married women have friends? friendship - a refuge for single women? elderly women and their friends is there something special about friendship? towards the future.