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Christmas causes more sex, followed by more September baby births

Previous studies have suggested that a September peak in birth rates is due to seasonal changes in human biology that lead to more pregnancies at the end of the year. But now, scientists are reporting that the mood and behavior of society shifts around the holidays, and people become more interested in sex.

The researchers found evidence of this heightened interest in intimacy by analyzing internet searches and social media posts, which enabled them to explore underlying desires and motivations. Luis M. Rocha is a professor at Indiana University’s School of Informatics and co-lead author of the study.

“The rise of the web and social media provides the unprecedented power to analyze changes in people’s collective mood and behavior on a massive scale,” said Rocha. “This study is the first ‘planetary-level’ look at human reproduction as it relates to people’s moods and interest in sex online.”

The study was focused on sex-related Google search terms in nearly 130 countries from 2004 to 2014. The experts also examined 10 percent of public Twitter posts from 2010 to 2014.

The research team found that the appeal of sex rises substantially during major cultural or religious celebrations. This observation is based upon a greater use of the word “sex” or other sexual terms in web searches. The study also revealed that the elevated interest in sex widely corresponded to an increase in births nine months later.

Furthermore, the effect was noted in two different cultures, with the biggest spike in sexual activity occurring during Christmas in Christian-majority countries and during Eid-al-Fitr in Muslim-majority countries.

Eid-al-Fitr, which marks the end of Ramadan, is of particular significance because the holiday does not fall on the same day each year. The measured effects, however, were found to shift accordingly.

The researchers ruled out the possibility that the sex trends are due to biological shifts which are affected by factors such as changes in daylight or temperature.

“We didn’t see a reversal in birth rate or online interest in sex trends between the Northern and Southern hemispheres – and it didn’t seem to matter how far people lived from the equator,” said Rocha. “Rather, the study found culture – measured through online mood – to be the primary driver behind cyclic sexual and reproductive behavior in human populations.”

Rocha said the findings of the study, which are published in the journal Scientific Reports, could help public health researchers identify the most effective dates to launch public awareness campaigns encouraging safe sex in developing countries.

By Chrissy Sexton, Staff Writer

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