THE ROUGH GUIDE TO PSYCHOLOGYchasing every potential mate who passes by. When we’re in love, the rest
of the world fades to grey and all that matters is the object of our passion.
We’re enchanted by their every move, their every word, that smile, those
lips. Indeed, the experience can be so intense that psychologists have
even noted how the symptoms overlap with psychiatric conditions such
as mania and obsessive-compulsive disorder. Some people really are
madly in love.
As well as the rush of rewarding chemicals in the brain, falling in love
is also aided by a series of psychological illusions. Research shows, for
example, that heterosexual men are prone to interpret a woman’s smile
or laugh as a favourable response to them personally. A study in 2010
reported that men more prone to this bias tend to fall in love more
often. Yet further research shows that men claim to believe in love at
first sight more often than women. Again, this all makes evolutionary
sense. For male reproductive success, it’s less costly to suffer the tempo-
rary embarrassment of reading too much into a woman’s glance than it
is to regularly miss out on mating opportunities. By contrast, women
have to make a far greater personal investment in reproduction, so it’s
sensible for them to be more picky to ensure the potential father of their
offspring is really committed.
In search of human pheromones
In 1959 the biochemist Peter Karlson and entomologist Martin Luscher
coined the term “pheromone” to describe a chemical message passed
from one member of a species to another. Since then, the search
has been on for a human equivalent. The discovery of a substance,
released by one person and causing an involuntary reaction in
another, would be a revelation – especially if that reaction was one of
enhanced sexual interest. However, despite the dubious claims made
by various peddlers of love potions and the like, no human pheromone
has yet been definitively identified. That’s not to say there are no
plausible contenders. Two candidates are the testosterone deriva-
tive 4,16-androstadien-3-one (AND), found in men’s sweat, and the
oestrogen-like steroid estra-1,3,5(10),16-16-tetraen-3-ol (EST), found
in female urine. In a 2005 brain-imaging study, Ivanka Savic at the
Karolinska Institute found that the smell of AND triggered increased
activation in the anterior hypothalamus (known to be involved in
sexual behaviour) of heterosexual women and homosexual men, but
not heterosexual men. By contrast, it was the chemical EST that excited
this region in straight men.