This is Scientific American — 60-Second Science. I'm Karen Hopkin.
In the United States, there's a holiday that goes hand in hand with romance...so much so that nine months later, there's a spike in the number of babies born. Valentine's day? Wrong! It seems that people in the U.S. and in other predominantly Christian countries have been having some very merry Christmases indeed. That's according to a study in the journal Scientific Reports.
Scientists have long wondered why, in Western countries, birth rates spike in September and early October.
"The prevailing hypothesis for this phenomenon postulates that there is a biological adaptation to the solar cycles."
Luis Rocha of Indiana University co-led the study. He notes that nine months before this baby boomlet is the winter solstice. And when the days grow shorter and the night grows long, well, humans seem to turn to procreation for recreation.
"However this hypothesis was built on observations pretty much restricted to northern hemisphere countries and also culturally Christian countries."
And some data suggested there might be something cultural going on.
"So for instance in Israel, it was previously observed that communities associated with different religions have birth peaks at different times of the year."
To try to separate the cultural from the biological, Rocha teamed up with Joana Gonçalves-Sá of the Gulbenkian Institute of Science in Portugal. Together, they combed through data on a planetary level...comparing countries in the Northern and Southern hemispheres...and countries with predominantly different cultures, in this case Christian and Muslim.
But they didn't look at when babies are born. They looked to see when, during the year, people around the world Google the word "sex". Joana Sá:
"What we found, first, was that Google...searches for sex on google...are a very good proxy for sexual appetite and sexual, offline sexual interest. And when we looked at close to 130 countries around the world, what we saw is that each country has a particular signature with peaks and valleys of interest in sexual content."
Sá says that those patterns were most similar for countries that shared a similar culture...
"This means that if you live in a culturally Christian country, whether you live in the northern hemisphere or the southern hemisphere, you are more likely to have an increase in sexual appetite around Christmas. But if you live in a Muslim country, you are much more likely to conceive around Eid-Al-Fitr, than at a different, at another time of the year."
Now, if you're still wondering what's so special about these holidays...Rocha says interest in sex coincides with a particular mood...a finding he made with the help of Twitter.
"We collected close to 50 billion tweets and showed that, independently of the geography and independently of the particular culture, when we observed the surge of interest in sex we also observe the appearance of a particular mood that can best be classified as calm and happy and de-stressed mood that is maximized around Christmas for Christian countries and maximized at the end of Ramadan with Eid for Muslim countries."
All of which makes the following year's holiday family gathering just a little bit bigger.
Thanks for listening for Scientific American — 60-Second Science. I'm Karen Hopkin.
美国有一个假日和浪漫密切相关，以致于9个月后出生婴儿的数量会猛增 。情人节吗？不对！看来美国和其他主要基督教国家的圣诞节确实过得很愉快 。这是《科学报告》期刊上刊登的一篇研究所得出的结论 。
印第安纳大学的路易斯·罗查是该研究的共同领导者 。他注意到，这种“婴儿潮”爆发9个月以前是冬至 。当白天越来越短而夜晚越来越长时，人类似乎转向以生育为乐 。
为了将文化因素与生物因素分离，罗查与葡萄牙古尔本吉安科学所的乔安娜·孔卡尔夫塞合作 。他们一起梳理了全球范围的数据，对北半球国家和南半球国家进行了比较，还对文化存在较大差异的国家进行了比较，这项研究对比的是基督教和穆斯林国家 。
但是他们并没有研究婴儿的出生时间 。他们关注的是，在一年中，世界各地的人们何时会在谷歌上搜索“性”这个字 。乔安娜·塞表示，
“我们发现，首先人们在谷歌上搜索‘性'，是性欲和线下性兴趣的优秀代表 。当我们观察全球近130个国家的情况时，我们发现每个国家在性内容方面都有独特的高峰和低谷时间 。”
“这意味着，如果你生活在一个基础教文化国家，那无论你是居住在北半球还是南半球，你都更可能在圣诞节前后性欲高涨 。但是如果你生活在穆斯林国家，与一年中其他时间相比，你更可能在开斋节前后怀孕 。”
谢谢大家收听科学美国人——60秒科学 。我是凯伦·霍普金 。
1. go hand in hand with （两件事）密切相关地，同时并进地；
Industrial progress should go hand in hand with the development of agriculture.
2. team up with (与…)组队；(与…)协作；
The participants were encouraged to team up with others in the class to do the homework, and the entire team would get credit.
3. comb through 在(信息)中仔细搜寻；
Eight policemen then spent two years combing through the evidence.
4. coincide with (想法、利益等)一致，相符；
He gave great encouragement to his students, especially if their passions happened to coincide with his own.