Female penguins mate with males who bring them pebbles to build egg
nests. Hummingbirds mate to gain access to the most productive flowers
guarded by larger males.
New research shows that even affluent college students who don't
need resources will still attempt to trade sexual currency for
provisions, said Daniel Kruger, research scientist at the University of
Michigan School of Public Health.
The exchange of resources for sex---referred to by scientists as
nuptial gifts---has occurred throughout history in many species,
including humans, Kruger said. The male of the species offers
protection and resources to the female and offspring in exchange for
reproductive rights. For example, an arranged marriage can be
considered a contract to trade resources.
However, the recent findings suggest that such behaviors are hard
wired, and persist no matter how much wealth, resources or security
that people obtain.
"It's remarkable to find these patterns in the students in the
study," Kruger said. "We have seen many examples where people do this
out of necessity, but we still see these tendencies in people who are
already well provided for."
In addition, there are predictable, sexual differences in the types
of exchanges attempted. Men are more likely to attempt to exchange
investment for sex, females were more likely to attempt to exchange sex
for investment, Kruger said.
For the study, researchers interviewed 475 U-M undergraduate
students to discover if they attempted exchanges in reproductively
relevant currencies outside of dating or formally committed
relationships, and if they were aware of attempts others tried with
them. While the study population was limited to students, these types
of exchanges happen all over the world in different cultures and
species, he said.
The majority of students were well aware of their own attempts to
trade reproductive currency, Kruger said. However, if they were in
committed relationships, they did not view the partnership as trading
in reproductive currencies, he said.
Overall, the strategy of attempting to exchange investment for sex
is only successful about 25 percent of the time, the paper found. Some
of the attempted trades included: tickets to the U-M versus Ohio State
game; studying assistance; laundry washed; a Louis Vuitton bag; and
voice lessons among other things.
Students in the study were 18-26 years old. For exchange attempts
made, 27 percent of men and 14 percent of women reported attempts to
trade investment for sex, 5 percent of men and 9 percent of women
reported attempts to trade sex for investment. Of exchange attempts
initiated by others, 14 percent of men and 20 percent of women reported
that someone else attempted to trade investment for sex with them, and
8 percent of men and 5 percent of women reported that someone else
attempted to trade sex for their investment.
A sample of older individuals, especially one that is more
representative of the general population, would likely report higher
frequencies of experiences, Kruger said. The assumption is an older
population would have more unmet needs and would be more sexually
In fact, Kruger said the findings were remarkable in that any
exchanges were reported at all, considering the subjects' youth and
affluence---in other words, they don't want for much yet they still
attempt these exchanges.
"The confirmation of hypothetical predictions regarding these
exchanges once again demonstrates the power of an evolutionary
framework for understanding human psychology and behavior," Kruger said.