Keith E Rice's Integrated SocioPsychology Blog & Pages

Aligning, integrating and applying the behavioural sciences

What is Romantic Love? #2

Women and genes
If resources are one key element women want from a relationship, what about the other key element: ‘good genes’?

The female’s drive to acquire ‘good genes’ in the making of her children is a critical driver in Sexual Selection (Darwin, 1871). Traits in the male which are seen as attractive to the female and thus will aid the male’s chances of mating and thus passing on his genes are considered ‘sexually selected’. The more men have these traits, the more they are considered desirable by women. After all, when the woman puts a minimum of 6 years into having a child, it’s important the children she produces are ‘attractive’ and thus have an increased likelihood of being able to pass on their genes in the competitive environment of human reproduction.

According to Ronad A Fisher’s (1930) Sexy Sons Hypothesis (aka Runaway Process), traits which one generation of females find attractive are also likely to be attractive to the next generation – hence the universals of attractiveness discussed on the previous page.  Therefore, if her sons inherit the traits that attracted her, the mother’s genes are more likely to be passed on because the sons from such a mating are more likely to have sex with more women than sons from a mating with a man with fewer or no such traits. As males with such traits are much more likely to be successful reproductively than those without, over generations they are likely to become more and more exaggerated – Fisher’s ‘runaway process’. Meredith Small (1993) has even proposed that penis size is a ‘runaway’ ‘in human males: “One characteristic among primates has been clearly targeted for possible selection by Fisherian female choice – male penis size. Primate males living in groups with many females and many males, groups in which promiscuity is the mating rule, have long penes…. Male chimps, in fact, use their penis for display toward oestrous females. Because a longer penis would give a female pleasure (note that the human male has the longest and thickest penis of any primate), female choice might have been a factor driving penis length to extremes among primates.” 

Anders Pape Möller (1992) and David Concar (1995), working separately but both from animal studies, have proposed that symmetry across the natural world is an indicator of ‘good genes’. In what is effectively an extension of Amotz Zahavi’s Handicap  Hypothesis  (1975), the theory is that producing symmetry is genetically expensive – effectively a handicap. Therefore, the more symmetrical someone is, the more superior their genes must be to those who are less symmetrical. Thus, women are attracted to males with symmetrical faces and bodies because symmetry is another indicator of physical robustness.

In humans Anthony Little, Coren Apicella  & Frank Marlowe (2007) found  evidence of the universal appeal of symmetry when they compared preferences for symmetry in both the UK and the Hazda, a hunter- gatherer tribe in Tanzania. Both groups preferred symmetrical faces – the Hazda more so!

‘Real life’ tends to support this contention: most (though not all) male movie stars and pop stars who attract large female fan followings tend to have very symmetrical faces.

A potential explanation for the effect of symmetry in males on females is offered by Martin Lalumière, Grant Harris & Marnie Rice (1999). They note that first born males are often more symmetrical than their younger brothers. The researchers propose that this might be the result of the hostile reaction of the pregnant woman’s immune system to the male foetus releasing testosterone – the damaging effect becoming stronger with each successive son. Lalumière, Harris & Rice did not find this reducing symmetry effect in younger sisters – presumably because female foetuses do not release testosterone to trigger the hostile immune reaction.

Randy Thornhill, Steven Gangestead & Randall Comer (1995) proposed that there may be a link between symmetry and intelligence. In a study at the New Mexico University they found orgasms were 40% more common in women whose male partners had highly symmetrical faces and bodies. The researchers assumed that symmetry made the men more exciting. However, they then found that symmetrical men scored better on IQ tests. (Geoffrey Miller (1998) contends that intelligence and the corresponding large size of the human brain is a sexually-selected Fisherian runaway process – a concept supported by Susan Blackmore (1999) who holds that ideas (memes) forced the development of the human ‘big brain’.)

The material discussed so far provides generalised biological explanations for attractiveness and its relationship to sexual reproduction…but nothing so far reviewed explains why people become attracted to that ‘one special one’.

However, the concept of pheromones may do.

Pheromones are biochemical substances that act like hormones but are released into the air rather than the bloodstream. They have no odour and are not consciously detectable but they carry messages from one individual to another of the same species and impact on their behaviour. Sex pheromones are just one type of pheromone. They carry information about the transmitting person’s genotype; this is (subconsciously) decoded by the receiving person. The transmitter whose genetically based immunity to disease differs most from the receiver’s is most likely to be most attractive. as the resultant children from such a mating are more likely to be strong, healthy and resistant to disease.

Quite how humans detect each other’s pheromones is not fully understand. Many animals have a vomeronasal organ (VNO), which perceives the substance and then leads them to mate. Some anatomists don’t think humans have a VNO; others think they’ve found pits inside our nostrils related to the olfactory bulb that might be VNOs.

In 1986 Winnifred Cutler, a biologist and behavioural endocrinologist, co-discovered pheromones in our underarms (Winnifred Cutler et al; George Preti et al). She and her team of researchers found that once any overbearing underarm sweat was removed, what remained were the odourless materials containing the pheromones.

Cutler’s original studies in the ’70s (Winnifred Cutler, Celso Garcia & Abba Kreiger, 1979; Cutler, Garcia & Kreiger, 1980) showed that women who have regular sex with men have more regular menstrual cycles than women who have sporadic sex. Regular sex delayed the decline of oestrogen and made women more fertile. This led the research team to look for what the man was providing in the equation. By 1986 they realized it was pheromones.

Martha McClintock is another researcher who has spent years researching what we now call pheromones. She (Kathleen Stern & Martha McClintock, 1998) found that women who work with men have shorter menstrual cycles. McClintock suggestsd that male pheromones resetting a woman’s biological clock would have adaptive value. Women who ovulate more often when men are present are likely to have more offspring and this would increase the genetic strain that has this characteristic response ­to male presence. (However, at other times a short menstrual cycle would be a disadvantage because of the drain on resources.)

The concept of pheremones does offer an explanation for why people may be strongly attracted to members of the opposite sex whom they would not normally find physically attractive or may not even like in terms of ‘personality characteristics’. It may offer an explanation as to why, when other desirable factors are present, we choose one person over others. However, the mechanisms of pheromones and just how much they influence human mating behaviour are, as yet, poorly understood. Attributing choice of sexual partner to pheromones is undoubtedly a highly reductionistic explanation which many people would feel uncomfortable with. After all, choice of partner being driven by a poorly-understood biological mechanism is rather a long way from the lofty ideal of seeking your ‘soulmate’!

Men, genes and flaws in Evolutionary theory
Human children are effectively completely dependent on their mothers until about the age of 5. Even after that age, the child places considerable demands on the mother’s time. Clearly it is to the mother’s advantage if the parenting is shared with the child’s father. Therefore, long-term commitment from the man is critical from the viewpoint of most women – which helps explain why many women are very choosy about who they have sex with (as discussed on the previous page).

However, from a purely Evolutionary perspective, the best reproductive strategy for a man is to have sex with as many women as possible. From the Evolutionary perspective, it is self-defeating for a man to stay with one woman since he limits his reproductive opportunities. Yet, many men do stay with long-term partners and are faithful to them.

It could be argued that being in a committed relationship gives a man a steady supply of sex ‘on tap’ – without always going through the dangers of competing with other men for available women (intra-sexual selection). However, the idea of sex ‘on tap’ is something of a myth as William H James (1981) has shown: the rate of coitus among partnered/married couples tends to decline so that by the end of the first year it is around 50% of what it was at the start of their relationship – the so-called ‘Honeymoon Effect’.

Evolutionary theory can’t really explain why a man would limit himself to one woman when it is clearly not his best reproductive strategy. It takes no account of emotions or affiliative desires. In this sense at least Evolutionary theory is only an expression of BEIGE and cannot address the needs and wants of PURPLE and higher vMEMES.

Moreover, human biology provides a contradiction to the Evolutionary meme that men are programmed to have sex with multiple women to spread their genes. From the work of Sue Carter & Sue & Lowell Getz (1993), we know that monogamous mammals like prairie voles produce vast amounts of the hormones oxytocin (females) and vasopressin (males) durng sex while promiscuous mammals don’t. Carter & Getz associated these hormones with the prairie voles being monogamous. Compared to most mammals, humans are relatively monogamous and humans produce oxytocin and vasopressin (from the posterior pituitary gland) in large quantities during sex – particularly orgasmic sex. A number of researchers – eg: Thomas Insel et al (1998) – have built on Carter & Getz’ work to associate sex in humans producing oxytocin and vasopressin with the bonding effect ‘good sex’ has. Thus vasopressin released in men during sex makes men more likely to want to bond with their female partner which goes against the Evolutionary stereotype of men always being ready to mate with the next available woman.

Evolutionary theory also can’t explain why ever more effective means of contraception have been developed since they inhibit the spread of genes. Also, if romantic love is truly only about promulgating genes, then both  heterosexual couples who choose not to have children and homosexual couples are deviant by this concept.

However, Evolutionary theory can explain why female looks and body shape are important to men who are prepared to commit themselves a single woman. Shape and symmetry can also be seen as indicators of ‘good genes’ to men too. If a man is going to commit to one woman, attractiveness becomes important as an indicator that the woman is likely to produce attractive children who, in turn, are more likely to have reproductive success as adults. Interestingly, John Cartwright (2000) found that women with symmetrical breasts are more fertile than more asymmetrically-breasted women. This is yet more evidence of the relationship between body symmetry and reproductive fitness.

Evidence shows clearly that human sexual urges, while biologically-driven, are mediated by social and emotional factors. For example, Elizabeth Pillsworth, Martie Haselton & David Buss (2004) questioned  202 female university students about how sexy they felt that day, both in relation to their partner and to other attractive men. They were also questioned as to where they were in their menstrual cycle. They found that sexual desire peaked around ovulation for women with partners but not women without partners. Moreover, the women with partners experienced a greater increase in desire for their partner than they did for other men.

Falling in love
Picking up from Pillsworth, Haselton & Buss, unless people are content to acknowledge only Evolutionary/biological factors in the formation of relationships, there have to be other elements in the process we call ‘falling in love’.

Elaine Hatfield & G William Walster’s (1981) 3 Factor Theory of Love offers a socio-biological and very plausible explanation of this process,. They argue that 3 components need to be present for ‘love’ to occur:-

  1. Cultural exposure 
    Abraham Tesser & Delroy Paulhus (1976) argue that our culture provides us with a model of love – as discussed earlier, in Western society we are bombarded with the memes of romantic love. Thus, the more  we are exposed to such ideas, the more likely we are to want to find love – or at least be open to it
  2. Physiological (sympathetic system) arousal
    Through experiments with expectations created about physiological arousal Stanley Schacter & Jerome Singer (1962) concluded that all emotional experiences are preceded by a generalised state of arousal. The nature of the subjective experience is determined – labelled – by the individual’s cognitive assessment based on external situational cues or internal imaginative processes. So, for example, the symptoms of fear – fast beating heart, fast breathing, ‘butterflies’ in the stomach, dilated pupils, etc – are also very similar to the symptoms of excitement. Schacter & Singer argue it is how we think about the experience of the physiological arousal that determines how we label (meta-state) it.
  3. An appropriate love object
    Someone with us whom we would find sexually attractive.

Hatfield & Walster’s 3 Factor Theory of Love – graphic copyright © 2001 Psychology Press Ltd

A commonplace experience of how the 3 Factor Theory works is when young people go ‘clubbing’. Memes are everywhere in the Western media that we should find that ‘one special person’ and that clubs are a great place to meet potential partners – cultural exposure. The club setting is designed to be physiologically arousing – with pounding dance music, flashing lights and lots of alcohol. The arousal from loud music and pulsing lights, as found in most clubs, is known to stimulate the RED vMEME to express itself with immediate effect (Clare W Graves, 1971/2002). With attractive members of the opposite sex often dressed to please and sometimes provocatively, it fits Hatfield & Walter’s theory entirely that males and females pair up at the end of a night’s clubbing – even if the pairing is only temporarily.

The importance of memetic influence is demonstrated in several studies – eg:-…

  • James Averill & Phylis Boothroyd (1977) found that the more people believed in ‘love at first sight’, the more likely they were to experience it.
  • Robin Simon, Donna Eder & Cathy Evans (1992) provide an interesting example of such a cultural model of love at work amongst adolescent girls. Their study was conducted over 3 years at a school in the mid- western United States. Data was collected via participant observation, audio and video recording and in-depth group interviews. Most of the time the focus was on the naturally occurring conversations amongst the girls. 5 norms were identified from analysis of the data:-
    – Romantic relationships should be important but not everything in life
    – Romantic feelings can be held only for someone of the opposite sex
    – Romantic feelings for a boy who is already attached are not permissible
    – Romantic feelings should be held only for one boy at a time
    – Loyalty is critical

Support for the importance of physiological arousal in the process is demonstrated in several pieces of research – most notably the classic natural experiment by Donald Dutton & Arthur Aaron in 1974.  In this study, an attractive female or male experimenter approached men as they crossed either a high and narrow, rickety suspension bridge or a low safe bridge at a popular tourist site, Capilano Canyon,  in North Vancouver, British Columbia. Whenever an unaccompanied male began to walk across either bridge, he was approached by a male or female assistant, who introduced themselves as a psychology researcher and asked the men to write an imaginative story in response to a picture while standing on the bridge. The assistant also told the man that if he wanted to receive information about the study’s results, he could just call them. Dutton & Aron found that men who were approached by a woman on the suspension bridge told stories with the highest sexual imagery of all the experimental groups. These men were also more likely to call the assistant, regardless of sex, but the female research assistant got the most calls. The video below is a partial replication of Dutton & Aaron’s study.


One of the criticisms of this theory is that it assumes people fall in love pretty much instantly when many couples report they fall in love gradually. However, this criticism itself may be too simple as the 3 factors may coalesce over time. A personal anecdote, told me by one of my 6th Form students, illustrates this. A female friend  of the 6th Former had a very, very close male friend. Although other 6th Formers teased them that they should be a couple and they themselves had pondered it together (exposure), they had discounted the notion. However, the girl’s closest female friend’s father was dying from cancer. The girl was at the friend’s house as the father slipped away. Distressed and in a highly emotional state (arousal), the girl called her male friend. When he (love object) arrived at the house, also in a highly emotional state, the girl flung herself at him in tears and began kissing him. From that moment on, they were a couple.

Liking and loving
The anecdote above raises the issue of the difference between liking and loving – and also when does one become the other?

Zick Rubin (1970; 1973) is one researcher who has looked at this, devising a Love Scale and a Liking Scale in an attempt to draw a clear distinction between the 2 concepts.

He found that couples who scored high on the Love Scale revealed their feelings  through their body  language. They spend a lot of time gazing into each other’s eyes. They are also likely to sit and stand closer together and to discourage other people from intruding on their intimacy by turning their bodies towards each other. They jointly experienced feelings of exclusiveness and absorption. Love, according to Rubin, includes attachment, caring for the other’s well-being and intimacy with shared thoughts and feelings.

As for the Liking Scale results, Rubin found that…

  • couples do not always like each other to the same degree as they love each other
  • women like men more than men like women
  • men love in context of sexual relationship
  • women experience intimacy and attachment in a wider variety of relationships

Robert J Sternberg & Susan Grajek (1984) tested for a correlation between Rubin’s Love and Liking scales. The results showed:-

  • for lover +0.72
  • for best friend +0.66
  • for mother +0.73
  • for father +0.81

These strong correlations suggest that Rubin’s scales do not distinguish well between liking and loving.

Sternberg & Grajek also found that men love and like their lover more than their mother, father, sibling or best friend. On the other hand women tend to love their lover and best friend equally but like the best friend most. Love for one member of the family predicts the amount of love for another. However, it does not predict love for a lover or best friend.

Ellen Berscheid & Elaine Walster (1978) propose 2 different forms of love: ‘companionate love’ and ‘romantic love’.

Companionate Love
Berscheid & Walster see companionate love as having more depth and feeling than ‘liking’ but with less of the passion that characterises romantic love; sex is not as important as in romantic love. It is based on mutual rewards with emotions steady and positive and it leaves more time for other relationships. There is a comforting familiarity between the partners which deepens over time. Rubin (1974) describes it as “…a close, caring friendship which is deep and lasting involving positive emotions, similarity, reciprocal liking and respect. Each is concerned about the other’s happiness and welfare.”

Romantic Love (aka Passionate Love)
Berscheid & Walster perceive romantic love as characterised by intense, mixed and sometimes conflicting emotions eg:-

  • joys vs anxiety
  • excitement vs deep despair
  • tenderness vs sexual desire

Berscheid & Walster also note that the intensity of romantic love is often diluted over time, drifting into more of a companionate love.

Bernard Murstein (1980) describes romantic love as an intense overwhelming emotional state in which the partners are thinking about the other constantly and wanting to be with them. He also notes that they are often unrealistic in their judgements about the other.

Arthur Aron, Edward Melinat & Elaine Aron, in a 1997 study at the University of East  Carolina, found that over  half of the students surveyed  admitted to various kinds of  dangerous  behaviour ‘in the name of  love’, including:-

  • having unsafe sex
  • giving up aspects of their personality
  • deceiving their parents
  • driving under the influence of alcohol or in bad weather conditions

A minority appeared ready to  sacrifice whatever it takes – career,  family relationships, individual  identity – for the sake of love.

Some of these behaviours can be seen as symptomatic of a PURPLE/RED vMEME harmonic where the desire to belong with the love object (PURPLE) is so great it liberates RED to indulge in to-hell-with-the-consequences actions.

Berscheid & Walster’s distinctions are supported by Helmutt Lamm, Ulrich Wiesmann & Karsten Keller (1998). The researchers had students  write down how they could tell  whether they liked  someone, loved  someone or were in love with  someone.  They found liking was characterised by a desire for proximity, trust was essential for loving and arousal was key to being in love.

Biology clearly plays a major part in driving romantic love. For example, the feelings of intense joy and excitement Berscheid & Walster refer to – which Michael Liebowitz (1983) likens to a ‘cocaine rush’ – can be linked to surges in the hormone adrenaline and the neurotransmitter dopamine. The anxiety and despair the researchers reference can be related to lowered levels of another neurotransmitter serotonin, corresponding to state of ‘neediness’.

The critical roles of vasopressin and oxytocin in the bonding effect of sex have been discussed above but other hormones play important roles too.

Testosterone, of course, is associated with male sex drive (amongst other things). Testosterone levels tend to drop in men who are monogamous, leading to reduced sex drive. Testosterone levels also decrease with age and it is not uncommon for older men to experience impotency. Obviously, these factors can have a negative effect on a couple’s ‘love life’. However, as humans seem to be innately programmed to respond to difference – see NLP+ Communication Model and The Process of Change – arousal can be increased by presenting something markedly different (eg: sex games), leading to increased testosterone levels and thus greater potency. As Buss (2000) notes, novelty is particularly important for men.

A woman’s cycle is regulated by the hormones oestrogen and progesterone – oestrogen being highest at the time of ovaluation and progesterone highest during the pre-menstrual interval. Oestrogen levels rise during sex and fat is involved in converting circulating oestrogen into testosterone which amplifies a woman’s arousal. This may help explain why larger women often have a higher sex drive than smaller women. Older, post-menopausal women often experience a higher sex drive too as oestrogen levels decrease while testosterone (secreted by the adrenal glands) increases. Women who have sex regularly tend to have higher levels of oestrogen than women who don’t.

Another key hormone is dehydroepiandrosterone (DHEA). It is also released from the adrenal glands and is associated with increased sex drive in women. In the immediate build up to and during orgasm, levels of DHEA increase from 3-5 times their level outside of sexual activity.

Neurologically sex is reflected in increased activity in the anterior cingulate cortex, the basil ganglia, the hypothalamus and the amygdala. Amongst several other functions, the anterior cingulate cortex and the basil ganglia are associated with addiction to pleasurable stimuli!


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