????兩三年前，伊利諾伊州大學(xué)（University of Illinois）健康經(jīng)濟學(xué)家雪莉?埃默里在Twitter上看到談?wù)摗拔鼰熇泵谩钡奶?，也有一些帖子談?wù)摗把评吖恰薄ⅰ俺榇舐椤?，以及教皇選舉會議的象征——“冒煙的煙囪”。如果她幸運的話，還能看到那些明顯與香煙有關(guān)的帖子，例如“吸煙廣場”或者僅僅是“吸煙”。

????多年來，埃默里一直在研究煙草廣告的影響。直到前不久，這項工作還意味著查看電視或廣播插播廣告，跟蹤尼爾森收視率（Nielsen Ratings）和地區(qū)吸煙率。但是2011年的一天晚上，她在瀏覽視頻網(wǎng)站Netflix時冒出了一個想法：如果她在上網(wǎng)，那么其他人也是一樣——而且他們很可能會在Twitter等社交平臺上發(fā)表自己對吸煙的看法。

????2011年9月，美國國家癌癥研究所（National Cancer Institute）為埃莫里撥款720萬美元，用于開展此項研究。就這樣，她進入了Twitter學(xué)（Twitterology）這一紛繁的新領(lǐng)域，成為了同行中第一個吃螃蟹的人。

????現(xiàn)在，她并不是孤軍奮戰(zhàn)。自Twitter于2006年創(chuàng)建以來，各路學(xué)者紛紛涌向這一微博平臺——不是去發(fā)帖（盡管有些人也這么做了），而是去研究這些帖子。每天有2.25億Twitter用戶發(fā)表5億條帖子，在學(xué)術(shù)界看來，Twitter擁有最為豐富，也許是前所未有的數(shù)據(jù)集??。它就相當(dāng)于一個實時數(shù)據(jù)的虛擬培養(yǎng)皿，吸引著各個學(xué)科的學(xué)者開展五花八門的研究。物理學(xué)家利用Twitter研究網(wǎng)絡(luò)；心理學(xué)家則用它來研究自戀心理；語言學(xué)家用它來研究語言的地區(qū)差異。其中也有一些論文利用Twitter來跟蹤牙痛、空氣質(zhì)量和公眾對流感的憂慮——也有人研究Twitter在預(yù)測美國橄欖球聯(lián)盟（NFL）比賽結(jié)果，診斷創(chuàng)傷后應(yīng)激障礙，以及衡量全球幸福指數(shù)方面的潛力?？傊瑩?jù)學(xué)術(shù)刊物數(shù)據(jù)庫Scopus的統(tǒng)計，已有約2,000篇期刊文章和3,000篇會議論文在研究Twitter（或至少在文章標(biāo)題、關(guān)鍵詞或摘要中包含Twitter一詞）?！段墨I工作雜志》（Journal of Documentation）于2013年發(fā)表了一篇論文，其標(biāo)題就是“人們研究Twitter時是在研究什么？對Twitter相關(guān)學(xué)術(shù)論文進行分類”。

????社交網(wǎng)站不大像是能夠令學(xué)術(shù)界動心的工具。那么，Twitter，一家要求每條留言最多為140個字節(jié)，把兩大流行歌星凱蒂?佩里（擁有5,560萬粉絲）和賈斯汀?比伯（擁有5,360萬粉絲）奉為最具影響力用戶的網(wǎng)站，是如何成為學(xué)術(shù)界眼中的香餑餑？

????在以傳染為主題的系列文章中，我和《財富》雜志(Fortune)的同事決定探究事物是如何蔓延的——從并購傳聞，到市場恐慌，再到“自拍”。作為該系列的最后一篇文章，我們決定追本溯源。畢竟，Twitter是當(dāng)今研究傳染力的首選工具之一，而剖析傳染這種社會流行病的最好方法，莫過于研究Twitter本身為何在其研究者中如此具有傳染力。

????A couple years ago, Sherry Emery, a health economist at the University of Illinois at Chicago, found herself reading tweets about “smoking hot girls.” Also about “smoking ribs,” “smoking weed,” and the “smoking chimney” of the papal conclave. If she got lucky, they’d be about “smoking squares” or just “smoking,” in an easily decoded context that referred to cigarettes.

????Emery has studied the impact of tobacco-related advertising for years. Until recently, that meant looking at TV and radio spots, tracking Nielsen Ratings and regional smoking rates. But then, one night watching Netflix in 2011, she had a thought: if she was on the web, so were many others—and they were likely leaving a trail of their attitudes towards smoking on social media platforms such as Twitter.

????In September 2011, the National Cancer Institute awarded her a $7.2 million grant to look into it—and so she went, a pioneer (in her line of work) into the brave new world of Twitterology.

????She’s hardly alone these days. Since Twitter was founded in 2006, academics have flocked to the micro-blogging platform—not to tweet messages (though some do that too), but to study them. With 225 million users issuing half a billion tweets per day, Twitter represents the richest dataset to hit academia….well, maybe ever—a virtual Petri dish of real-time data, attractive to scholars of all disciplines, for studies of all sorts. Physicists have used Twitter to study networks; psychologists to study narcissism; linguists to study regional language variation. There are research papers about what can be learned by using Twitter to track dental pain, air quality and public concern about flu outbreaks—as well as studies on Twitter’s potential to predict the outcome of NFL games, and diagnose post-traumatic stress disorder, and measure worldwide happiness. In all, some 2,000 journal articles and 3,000 conference papers have been written about Twitter (or have at least contained the word in their title, keywords or abstract), according to Scopus, a database of academic publications. There’s even a paper, published in 2013 in the Journal of Documentation, entitled, “What do people study when they study Twitter? Classifying Twitter related academic papers.”

????The social networking site is not the most likely of tools to have caught fire in the Ivory Tower. How did Twitter, a site that traffics in 140-character-or-less messages and that counts two pop stars—Katy Perry (with 55.6 million followers) and Justin Bieber (with 53.6 million)—as its most influential users, become so hot among the academic set?

????In this series on contagion, my FORTUNE colleagues and I set out to explore how things spread—from M&A rumors, to market panics, to the ‘selfie’. And for the final installment of this series, we decided to get especially meta. After all, how better to probe the anatomy of a social epidemic than to track how Twitter, one of the preferred tools for studying contagion these days, got so contagious among people studying it?