两三年前，伊利诺伊州大学（University of Illinois）健康经济学家雪莉•埃默里在Twitter上看到谈论“吸烟辣妹”的帖子，也有一些帖子谈论“熏制肋骨”、“抽大麻”，以及教皇选举会议的象征——“冒烟的烟囱”。如果她幸运的话，还能看到那些明显与香烟有关的帖子，例如“吸烟广场”或者仅仅是“吸烟”。
2011年9月，美国国家癌症研究所（National Cancer Institute）为埃莫里拨款720万美元，用于开展此项研究。就这样，她进入了Twitter学（Twitterology）这一纷繁的新领域，成为了同行中第一个吃螃蟹的人。
现在，她并不是孤军奋战。自Twitter于2006年创建以来，各路学者纷纷涌向这一微博平台——不是去发帖（尽管有些人也这么做了），而是去研究这些帖子。每天有2.25亿Twitter用户发表5亿条帖子，在学术界看来，Twitter拥有最为丰富，也许是前所未有的数据集¬¬。它就相当于一个实时数据的虚拟培养皿，吸引着各个学科的学者开展五花八门的研究。物理学家利用Twitter研究网络；心理学家则用它来研究自恋心理；语言学家用它来研究语言的地区差异。其中也有一些论文利用Twitter来跟踪牙痛、空气质量和公众对流感的忧虑——也有人研究Twitter在预测美国橄榄球联盟（NFL）比赛结果，诊断创伤后应激障碍，以及衡量全球幸福指数方面的潜力。总之，据学术刊物数据库Scopus的统计，已有约2,000篇期刊文章和3,000篇会议论文在研究Twitter（或至少在文章标题、关键词或摘要中包含Twitter一词）。《文献工作杂志》（Journal of Documentation）于2013年发表了一篇论文，其标题就是“人们研究Twitter时是在研究什么？对Twitter相关学术论文进行分类”。
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?