Transcript THE SCIENCE OF LOVE: IS THERE SUCH A THING?

FOR BETTER OR WORSE?
HOW WE PICK OUR PARTNERS
Glenn Wilson PhD, Gresham College, London
PARTNER PRIORITIES
Physical attractiveness is valued
by both men and women but
women place more importance on
traits relevant to resource
provision (wealth, status,
dominance, creativity, generosity).
For men, the priority is fertility
(youth and beauty). Hence tradeoffs are not uncommon.
Mrs Merton: “Debbie, what was it that first
attracted you to millionaire Paul Daniels?”
PARENTAL INVESTMENT
Females are more picky about partners because
they invest more in parenthood. Eggs are
scarcer than sperm and the costs of
squandering them high (Trivers, 1972).
Hence men favour short-term strategies while
women look for commitment. Men are also
more inclined to be visually aroused and
promiscuous.
Males compete with each other for access to
fertile females and enterprising courtship is
usually required.
Data from Symons & Ellis, 1989.
A SCIENCE OF PARTNER MATCHING?
Many superstitious and bogus theories:
 Astrology
 Palm-reading
 Biorhythms
 Numerology
Opposites attract is a popular lay theory but has
little supporting evidence.
Similarity (“birds of a feather”) is best supported.
People gravitate towards, and are happier with,
those who are like themselves.
A COMPATIBLE PAIR: SHARED TASTES
MATCHED COUPLES DO BETTER
Couples who are similar in body build and
whose physical attractiveness is roughly
equivalent are more likely to get together
and to stay together.
Couples matched on certain personality
traits like agreeableness, conscientiousness
and openness are also more likely to stay
together (Rammstedt & Schupp, 2008),
though other traits (extraversion &
emotional instability) do not show
assortative mating.
Prospects bleak?
ESTABLISHED AREAS OF HOMOGAMY
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Age (albeit males slightly older)
Race and religion
Socioeconomic status/IQ/education
Anthropometrics (e.g., height, weight)
Physical attractiveness
Personality (but only certain traits)
Attitudes/leisure interests/habits
Sex drive & permissiveness
TYPICAL GENDER DIFFERENCES
Where men and women differ significantly
on a trait, relationships work best if a couple
replicates that difference.
Tall men marry tall women but not as tall as
themselves; short men marry women even
shorter. Reversals of this tend to be unstable.
With personality, couples are happier when
traditional differences are present (he
tougher, she more sensitive).
Both partners are happier if the male is
slightly older (3-5 yrs).
AGE RANGES OF PREFERRED PARTNERS
Men generally prefer younger women; women prefer
older men (Data from Kenrick & Keefe,1992).
COUPLES WHERE MAN IS OLDER ARE MORE FERTILE
From Fieder & Huber (2007)
THE COMPATIBILITY QUOTIENT (CQ)
Comprises 25 items covering areas known through research to be
important for relationship success.
Answered independently by two individuals.
Each item offers 5 response categories arranged on scale such
that those further removed are less compatible.
A total discrepancy score is calculated between the responses of
the two people.
This “raw score” is
converted to a CQ
based on a normal
curve of M = 100,
SD = 15 (c.f. IQ)
TYPICAL ITEM
What is your view of pornography?
1. Disgusting
2. Prefer to avoid
3. OK sometimes
4. Harmless fun
5. A great turn-on
(Answers 1 and 5 are most incompatible; those adjacent much
less so. CQ scores are derived from total discrepancy summed
across all items and applied to the normal curve).
MEANING OF CQ SCORES
145+ Freak identity: Typical of test-retest reliability
(same person doing the test twice) or identical
twins.
130-144 Extremely compatible: Exceptionally high
degree of similarity. <2% of couples.
115-129 Very compatible: <20% of couples.
100-114 Above average: Might work but issues to be
dealt with.
85-99 Below average: Warning bells sounding.
70-84 Rather incompatible: Loud warning bells.
<70 Incompatible: Don’t even think about it!
Validity of the CQ was established by showing that couples have
higher CQs than randomly paired individuals and that happily
married couples have higher CQs than those less contented.
POSSIBLE APPLICATIONS OF CQ
Locating someone compatible that you have not yet met
e.g., through dating websites.
Assessing prospects for long-term happiness with a new
partner in early stages of courtship.
Diagnosing problematic areas in prenuptial or marriage
guidance counselling.
Assigning airline seating, holiday or dormitory-type
accommodation.
SPEED-DATE CHOICES
CQ scores predict desire to pursue a relationship after a
brief (3-min) speed-date encounter and even immediate
(first 30 sec.) attraction.
Mean CQs:
Mutually attracted couples:
108.0
Couples wanting to meet again:
107.7
Not attracted:
101.2
Couples not wanting to meet again: 102.7
Effects driven mainly by female preferences. Women seem to be
better at detecting compatible long-term partners, or is it that men
are just thinking short-term? (Wilson, Cousins & Fink, 2006).
EXPLANATIONS FOR THE
SIMILARITY EFFECT
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Propinquity – we meet & marry people who are
similar because they work/live nearby.
Sharing activities – “those who play together stay
together”.
Egotism – preferring people who agree with us on
controversial issues and who remind us of ourselves.
Genetic similarity – attraction to those who share
our own genes.
Imprinting – modelling partner on opposite-sex
parent.
I LIKE YOU – YOU’RE LIKE ME
People with alliterative first names (e.g. Barry & Barbara) pair off
more than chance.
Same surname marriages also exceed chance: (e.g., Smith/Smith 198,
Jones/Jones 125, Smith/Jones 62).
People given arbitrary codes similar to our own birth-date are judged
more likeable.
(Jones et al, 2004)
GENETICS OF PARTNER CHOICE
Rushton & Bons (2005) studied 174 MZ and
148 DZ twin pairs as well as their best friends
and spouses.
MZ twins chose partners (& friends) more
similar to those of their co-twins than did DZ
twins (esp. with respect to heritable traits).
Variation in partner choice estimated as 34%
genetic, 12% shared environment (e.g., family
values) 54% unique environment (e.g., being
at the right place/right time).
Argued that choosing genetically similar
partners helps perpetuate one’s own genes.
GENETIC SEXUAL ATTRACTION
When close family members are reunited after being raised separately
they often experience immediate and powerful sexual attraction.
These siblings, Patrick & Susan Stubing live together in Germany and
have two children despite having been jailed for incest. They did not
meet until their 20s, hence no Westermarck Effect.
COUSIN MARRIAGE
Cousin marriage is forbidden in many places
although the genetic overlap (25%) is less
problematic than with siblings (50%).
Darwin married his cousin Emma shortly after
returning from his Beagle voyage.
CHILDHOOD IMPRINTING OF SEX TARGETS
Cross-fostering studies (Kendrick et al, 1998) reveal importance of
mother-image. Lambs raised by a goat mother (left) and kids raised
by a sheep mother (right) fancy the “wrong” species when grown up
(esp. true for males, who depend more on visual “targets”.)
THE OEDIPUS EFFECT
Hawaiians of mixed race tend to marry into ethnic
group of opposite-sex parent (Jedlicka 1980).
Daughters of older men choose older partners (Zei et
al, 1981).
Women fall in love with men of eye colour more
similar to their father than their mother (Wilson &
Barrett 1987).
Both men and women choose partners more similar
to their opposite-sex parent in both eye and hair
colour (Little et al, 2003).
Photos of wives are correctly matched by external
judges to mothers-in-law beyond chance
(Bereczkei et al 2004).
MATCHING PARTNER WITH PARENT
Partner preferences are affected by the quality of
parent-child relationships. Daughters with good
relationships with their father prefer men with similar facial
structure - those with bad relationships do not.
(Wiszewska et al, 2007).
ONE’S SPITTING IMAGE?
Resemblance between men’s wives and their mothers is greater when
the relationship with the mother was good (Bereczkei et al, 2004)
FAMILIAL SMELLS
The major histocompatibility complex (MHC) governs our immune
system and can be detected by smell.
Animals prefer to mate with individuals of dissimilar MHC, which
would serve to broaden the immune system of their offspring.
There is some evidence that this applies to humans but women vary
according to their breeding mode. They prefer dissimilar mates when
fertile and similar mates when needing family support (e.g., when
already pregnant).
Women are more affected
by smell than men, which
might be why they are
so fond of kissing – chance
to sample the chemicals.
(Havlicek & Roberts, 2009)
INSTINCTS THAT DESTABILISE MARRIAGE
A SEVEN YEAR ITCH?
There may be some truth to the idea of a
“seven year itch”. According to a UK
MORI poll, one in five wives wish they
were not married and one in seven
husbands. Peak discontent occurs in
years 6-9 of marriage, when a third of
people wish they were not married.
Cross-culturally, the peak for actual
divorce occurs earlier (around 4 years
into marriage, which might connect with
the period of time needed to raise an
infant.
DIVORCE DECLINING
Divorce rates depend on the strength of social pressures against. They
increased steeply in the Western world following the liberalisation of
divorce laws but are now declining because people are marrying later
or not at all.
Divorce rates: England & Wales
Data from Buckle et al, 1996.
LOVE-RAT GENES
Sexual novelty-seeking is more
striking in males than females
because of prenatal effects of
testosterone on the brain.
The evolutionary basis of the sex
difference is parental investment.
Specific genes that relate to
vasopressin levels are associated
with bonding deficits and marital
problems in men.
(Walum et al, 2000 .
FEMALE INFIDELITY
Women also have motives for
“extra-pair copulation”. e.g.,
fertility insurance (2-3% of
children apparently not sired by
official father) and mate retention
(keeping partner on his toes).
Twin studies (Cherkas et al, 2004)
show that variation in female
infidelity is 41% genetic. (22% of
sample reported infidelity to a
long-term partner).
SPERM COMPETITION
A clue that human females have a
natural capacity for infidelity comes
from comparisons among the apes.
Gorillas defend harems by strength,
hence their sperm does not need to
compete with rivals and their
testicles are small. Humans are
nearer to the chimpanzee pattern,
where female promiscuity promotes
selection of larger testicles.
In monogamous species (e.g.,
gibbons) males and females are the
same size.
MATE POACHING AND RETENTION
Mate poaching tactics:
Flaunting physical charms (esp. women),
advertising wealth, e.g., by expensive
gifts, getting the partner drunk (esp.
men), sense of humour, flattery,
befriending the couple and awaiting an
opportunity (both men and women).
Mate retention tactics:
Enhancing looks, flirtation, signals of
possession (esp. women), vigilance,
threatening rivals, concealing the mate
(esp. men) monopolising time, punishing
infidelity, being derogatory about
competitors (both).
JEALOUSY: HIS AND HERS
Jealousy has a different focus for men and women.
For men it is the act of penetration, hence the risk that they
will put resources into offspring not carrying their genes.
For women the main concern is that her partner will form an
alternative emotional attachment and thus transfer resources.
THE EVOLUTIONARY ARMS RACE
Both men and women have evolved cryptic tactics for
selecting, attracting, poaching, retaining and disposing of
mates.
These are overlapping, complex and equally devious.
Flirtation, for example, may be used either for matepoaching (stealing someone else’s partner) or mate
retention (keeping one’s own partner vigilant).
Strategies differ according the phase of a woman’s cycle
and whether a short encounter or long-term mate is
sought.
All are geared to maximising the chances that the
individual’s genes will be passed to the next generation.