The assistant professor of Wooster College in Ohio Laura Sirot together with the graduate student Paul Joseph decided to research consequences of so called “Coolidge Effect”, the known fact of decrease in the quality of sperm in male mammals that occurs with the repeated exposure to the same female.
Vice versa, with an exposure to a new female the sperm counts improve, providing greater volumes and more active sperm, ejaculated at greater speeds. The research has been published by Evolutionary Psychological Science magazine. Researchers used movies and images of various females, known and novel, to measure how sperm counts change.
The scientists state that “human males ejaculate more quickly and invest more in ejaculates with novel females.”
As such, it makes sense that one-night-stands are known to be more productive for falling pregnant among women than sex with a long-term partner. By the same virtue, people who have sex for the first time after their wedding would have a higher chance to conceive.
One implication of this study is the aspect of male infertility in long-term partnerships and marriages, which might have been overlooked previously. Normally, to confirm that a man’s sperm is of a sufficient quality, he would be required to produce a sample, which is usually provided by involving some visual stimulation featuring unknown females. In this case, the quality of the sperm might be higher than standard, since the man has been exposed to a novel female.
It appears that male infertility might be under-diagnosed, thus the attention is on the woman, if the pair struggles to conceive. Learning more about this phenomena may help to avoid expensive treatments that couples have to undergo in order to have kids.