Do thoughts of partner infidelity increase semen quality in men?

New research published in the journal Evolutionary Psychology investigated whether men produce higher quality ejaculate in response to thoughts of their partner’s infidelity.

It is not unusual for female mammals — including human women — to copulate with several males. The sperm from males then compete within the female to fertilize the eggs.

“Sperm competition theory can be used to generate the hypothesis that men alter the quality of their ejaculates as a function of sperm competition risk (such as risk of a partner’s infidelity),” said study author Todd K. Shackelford of Oakland University.

A higher quality ejaculate would increase the chances of success in competition with rival sperm.

The study examined whether men would produce better ejaculate after imagining their romantic partner had cheated on them. The 45 participants were between the ages of 18 to 33 years and had been in a relationship from 6 to 123 months.

But the researchers failed to find sufficient evidence for their hypothesis.

“Men did not produce higher quality masturbatory ejaculates in the sperm competition (infidelity) condition relative to the control condition,” Shackelford said.

“Despite the null results of the current research, there is evidence for psychological and physiological adaptations to sperm competition in humans,” he added.

For example, previous research has found that men orgasm faster and ejaculate more semen when masturbating to unfamiliar women.

“Methodological limitations may have produced the null results,” Shackelford added.

In the study, the men wore condoms to capture their sperm. However, this may have resulted in reduced sexual arousal. The researchers also noted that imagining a partner’s infidelity might not be enough to affect men.

“It is important to empirically test hypotheses, rather than assume they are either true or false,” Shackelford said.

The study, “Do Men Produce Higher Quality Ejaculates When Primed With Thoughts of Partner Infidelity?” was authored by Michael N. Pham, Nicole Barbaro, Andrew M. Holub, Christopher J. Holden,
Justin K. Mogilski, Guilherme S. Lopes, Sylis C. A. Nicolas, Yael Sela, Todd K. Shackelford, Virgil Zeigler-Hill, and Lisa L. M. Welling.