How and why scholars cite on Twitter
Jason Priem and Kaitlin Light Costello
School of Information and Library Science,
University of North Carolina at Chapel Hill
CB #3360, 100 Manning Hall, Chapel Hill, NC
priem@email.unc.edu, kaitcost@email.unc.edu
ABSTRACT

Scholars are increasingly using the microblogging service
Twitter as a communication platform. Since citing is acentral practice of scholarly communication, weinvestigated whether and how scholars cite on Twitter. We
conducted interviews and harvested 46,515 tweets from asample of 28 scholars and found that they do cite on
Twitter, though often indirectly. Twitter citations are part ofa fast-moving conversation that participants believe reflects
scholarly impact. Twitter citation metrics could augment
traditional citation analysis, supporting a “scientometrics
2.0.”
Keywords

Twitter, citation, scholarly communication, bibliometrics,
social media.
INTRODUCTION AND LITERATURE REVIEW

Twitter (http://www.twitter.com/), which was established in2006 as a way to communicate online in 140 characters orless, is a popular microblogging service. Although Twitter
is often used for personal communication (Java et al.,2007), several studies have uncovered increasing use ofTwitter for work-related purposes. For instance, Zhao andRosson found that using Twitter in the workplace “canenhance colleagues’ efforts toward future collaboration atwork,” (2009, p. 10) while Golbeck et al. recently reported
growing professional use of Twitter by members of the US
Congress (2010).
The professional impact of Twitter may be particularly
pronounced for scholars (Letierce, 2010), given that sharing
information is a central component of their work.
Moreover, since one of the chief modes of scholarly
communication is citation, bibliometrics – particularly
citation analysis – could be a useful lens for examining
scholars’ behavior on Twitter. Although bibliometricians
and scientometricians have not yet focused their research on
Twitter, the field is increasingly engaged in measuringscholarly activity on the web (Thelwall, 2003). Cronin(2005) calls for greater investigation into the various types
of web-based invocation, suggesting that this will promotea finer-grained image of influence. More recently, Grothand Gurney (2010) show the practical potential of thisASIST 2010, October 22–27, 2010, Pittsburgh, PA, USA.
Copyright Jason Priem 2010.

approach, analyzing the bibliometric properties of academic
chemistry blogs. Given Twitter’s increasing popularity withscholars (Young, 2009), it is timely to extend their workfrom blogging to microblogging, and apply citation analysis
to examining scholars’ communication on Twitter. Priemand Hemminger (2010) call for investigation into Twitter
citations as part of a “scientometrics 2.0” that mines social
media for new signals of scholarly impact.
Before embarking on this full-scale bibliometric analysis,
however, we must first determine whether Twitter is suitedto this approach. In particular, it is important to understand:

Do scholars cite on Twitter?
If so, what do citations look like on Twitter?
Do citations on Twitter carry impact?

Thelwall (2003) used mixed methods to investigate
qualitative properties of a small sample of scholarly links
on the open web. This study takes a similar approach to
examining citation on Twitter.
METHODS

We recruited 28 academics – defined as faculty, postdocs or
doctoral students – using Twitter at least weekly. We used asnowball sampling method, starting with a seed of 3
academics working in the fields of science, social science,and humanities, respectively; as we added participants, weasked them to tweet an invitation to our study. The final
sample contained 7 scientists, 14 social scientists, and 7
humanists. To better understand the complexities of citingon Twitter, we used a mixed-methods approach. The
qualitative component consisted of semi-structured, 30- to
45-minute interviews. After these were recorded andtranscribed, we used open coding to isolate and describe
themes found across the interviews.
For the quantitative component, we harvested the last 3,200tweets (the maximum Twitter makes available) from 26 of
the participants. In the resulting set of 46,515 tweets,15,091 (34%) contained hyperlinks. We selected the 100
most recent such tweets from each participant, yielding asample of 2,483 tweets (three participants had fewer than
100 link-containing tweets); after discarding tweets withbroken links, we were left with a coding sample of 2,322.
The content of the resources linked to by these tweets wasanalyzed by the first author, using codes listed in Table 1.
The second author independently coded a sample of 500

tweets for the more subjective categories; intercoder
reliability was determined to be acceptable for thesecategories using Cohen’s kappa.
Category oflink target

Codes

Cohen’skappa

Resource typePeer-reviewed,
Link to peer-reviewed,
Not peer-reviewed.80

Description

Yes or No.76

Open accessYes or No

N/A

Date

Date string

N/A

Table 1. Categories for content analysis of resources
linked to from tweets.

RESULTS AND DISCUSSION
Twitter citations

We defined Twitter citations as direct or indirect links froma tweet to a peer-reviewed scholarly article online. It is
important to note that Twitter citations differ fromtraditional print citations in that they are not typicallyoffered in support of an argument:[Ronnie] I would compare tweeting a scholarly article tobringing it up in a seminar or a classroom situation. It’s about
pointing people in the direction of things that they would findinteresting, rather than using it as evidence for something.

We separated Twitter citations into first- and second-ordercitations depending on the presence of an intermediatewebpage between the tweet and target resource, as
described in Figure 1.
In both citation types, there is a clear connection between
one tweet to exactly one peer-reviewed article, presentation,or other resource. However, in the case of second-ordercitations, another webpage acts as an intermediary. Often
this middle page is a blog post or news article describing
and linking to the resource, or it might be a page on a social
bookmarking service like CiteULike. Some intermediary
pages do not hyperlink directly to the resource; instead,they describe its content and typically contain some partial
metadata like authors and journal name. This is common in
popular-press articles reporting on new study findings.
Scholars do not necessarily follow second-order citations
all the way to the resources themselves. However, as longas intermediary webpages provide at least an abstract-leveldescription, our participants often viewed them as
equivalent:[Terrance] So I think that if the blog is written relatively well,I tend to take their word for it, with a grain of salt, because
reading the paper itself I might not be able to get anything
extra from it anyways.

Figure 1: Types of twitter citations.
In our sample of tweets containing hyperlinks, 6% were
Twitter citations. Of these, 52% were first-order links and48% were second-order. Among second-order intermediary
pages, 69% contained a hyperlink to the cited resource; theremainder included descriptions and metadata.
Participants gave two main reasons for tweeting secondorder citations. First, it fit their workflow better:[Julio] I tweet resources and information that I see. I use
Google Reader as my RSS reader. I read several hundred
blogs each day, and will look for information that might beinteresting to the people I know who are following me onTwitter.

Second, it helped them get around paywalls to articles:[Armando] I’m much more likely, if I see an article that I
think is really interesting, to blog about it myself and post alink to that or to link to someone else’s blog about it. Because
you can provide a little more substance that way, even topeople who do not have access to it behind the paywall.

The quantitative data support this interview finding. While
56% of first-order links were open access, only 25% of
second-order links were free to access. This significant
difference (p < .001, χ² = 12.86) suggests that scholars may
prefer to link directly to the article when it is open accessbut will resort to second-order links to bypass paywall
restrictions. Participants were attracted to open-accessarticles for Twitter citations; Ben said “I would certainly bemuch more likely to link to things if they were more readily
available.”
Citing in conversation

In interviews, participants emphasized that they saw citingon Twitter as part of a dynamic, ongoing conversation:[Ronnie] When I send out a tweet, it’s part of being in an inthe-moment conversation, more like a hallway conversation at

a conference as opposed to being in front of the room andpresenting a paper.

Because scholars on Twitter typically follow people both inand out of their particular subfields, these conversations andthe citations that accompany them often afford a moreinterdisciplinary perspective:[Terrance] When you are discussing research you are not justdiscussing your specific project, you are discussing how thisrelates to other areas of research.... Reading other articles,posting them on Twitter, having discussions with other people
really helps; it helps you form these thought processes.

Two manifestations of conversation on Twitter are“retweets,” (forwards of another user’s tweet; boyd, 2010),
and “@replies,” (tweets addressed to a specific user;
Honeycutt and Herring, 2008). We found that 8% ofTwitter citations were @replies, and 19% were retweets. In
the entire sample of tweets containing links, 8% were@replies, while 40% were retweets. The significant
difference in retweet percentage between general links andTwitter citations (p < .001, χ² = 24.28) indicates that theTwitter citations are more likely than other links to beoriginal, rather than retweets.
SpeedGroth (2010) observes that citations on blogs are faster thancitations in traditional media. Given the relative ease ofcomposing tweets, we hypothesized that Twitter citations
would have even greater immediacy.
Our quantitative sample bore this out. As shown in Figure
2, the number of Twitter citations decays rapidly; 39% of
citations refer to articles less than one week old, and 15% of
citing tweets refer to articles published that same day.
Several participants discussed this speed as an advantage of
citing on Twitter:[Tyrone] If I find an interesting reference in the literature,people will only know about it after one year, maybe, after I
have actually published it. However if I tweet it people willknow about it immediately, as soon as possible.
ImpactVaughn and Shaw looked at mentions of scholarly literatureon blogs and found that “the nature of the intellectual
impact is unclear” (2008, p. 9). For citation analysis basedon Twitter to be useful, any such lack of clarity surrounding
impact should be resolved. We explored this question in ourinterviews.
Tameka saw using Twitter as “crowdsourcing reading theprofessional literature and telling about what is interesting.”
Much of the value was associated with trusting what Greg
called the “curatorial skill” of the people citing resources:[Julio] I won’t have time to look at everything. But I trust [thepeople I follow] and they trust me to contribute to theconversation of what to pay attention to. So yes, Twitter
definitely helps filter the literature.

Figure 2: Delay between resource publication andTwitter citation (log-log scale).
In addition to acting as a filter, Twitter can also be a net for
catching useful citations that scholars might not otherwise
be exposed to; as Derrick said, “it’s kind of like I have a
stream of lit review going.” Zhao and Rosson describe thisfunction of Twitter as a “people-based RSS feed” (2009, p.
5). Our interviews suggest that these citations can have asignificant effect on scholars’ thinking:[Carmella] It is like having a jury preselect what will probablyinterest you…. Occasionally there will be something thatpeople will link to, and it will change what I think, or what
I’m doing, or what I’m interested in.

Participants also discussed their desire to cite content thatwould impact the work of other scholars:[Elaine] I’m trying to spread knowledge in some ways [when Itweet an article]. Like, hey, if this isn’t part of the canon you
are reading, then you should be reading it.

Our participants did not tend to search for content to cite on
Twitter; instead, Twitter citations trace the intellectual
landscape of their everyday scholarship:[Clayton] It’s not necessarily that I am going out to look forthings to post to Twitter, it’s that I am doing my regular sort ofacademic work and I see something that might be of interest toother academics, or practitioners.

Scholars are conscious of their role as filters and theexpectations of their audience. They modify their citing
behavior based on responses from their followers:[Tyrone] I will tweet it if I find it interesting to my followers,
to what my followers expect I will tweet. And then… when [itis retweeted], I understand that people expect me to keep
tweeting about it.

Although Twitter citations are different from traditional
citations, our interview data indicate that scholars see
Twitter as a legitimate conduit of scholarly impact.
CONCLUSION

This study examined scholars’ attitudes and practices
relating to Twitter citation, focusing on a sample of 28
academics. We found that these scholars use Twitter to cite
articles, but that these citations differed from theirtraditional manifestations. While half of Twitter citations
link directly to a resource, many link through anintermediary which in turn links to or describes the target
resource. Twitter citations are also uniquely conversational,
reflecting a broader discussion crossing traditional
disciplinary boundaries. Twitter citations are much fasterthan traditional citations, with 40% occurring within one
week of the cited resource’s publication. Finally, while
Twitter citations are different from traditional citations, ourparticipants suggest that they still represent and transmit
scholarly impact.
This study has implications for scholars of both social
media and scholarly communication. Twitter citations
could be a valuable component of “scientometrics 2.0,”
offering faster, broader, and more nuanced metrics ofscholarly communication to supplement traditional citation
analysis. For example, up-to-date metrics including Twitter
citations might augment a tenure or promotion portfolio.
Twitter citations could also be automatically harvested andanalyzed to inform real-time article recommendationengines.
One limitation of this study is the snowball sampling
method. Although this approach is valuable for an
exploratory study and permitted access to our target
population, it hinders the generalizability of our results.
Future work could use individual articles as the unit ofanalysis, appraising the Twitter citation distribution acrossarticles. Investigators here could follow the lead ofresearchers like Vaughn and Shaw (2008), who examinedcorrelations between web citations and their traditionalcounterparts. These types of bibliometrics-based
approaches could yield valuable results when applied toTwitter.
ACKNOWLEDGMENTS

The authors would like to thank Dr. Barbara Wildemuthand Dr. Bradley Hemminger for their valuable comments
on early versions of this article.
REFERENCES

boyd, d., Golder, S., & Lotan, G. (2010). Tweet, tweet,
retweet: Conversational aspects of retweeting on Twitter.
In Proceedings of the Forty-Third Hawai’i International
Conference on System Sciences (pp. 1-10). Los Alamitos,
CA: IEEE Computer Society.

Cronin, B. (2005). The Hand of Science: Academic Writing
and Its Rewards. The Scarecrow Press, Inc.
Golbeck, J., Grimes, J. M., & Rogers, A. (2010). Twitter
use by the U.S. Congress. Journal of the American
Society for Information Science and Technology, article
preprint doi:10.1002/asi.21344
Groth, P., & Gurney, T. (2010). Studying scientificdiscourse on the Web using bibliometrics: A chemistry
blogging case study. Presented at the Web ScienceConference 2010, Raleigh, NC. Retrieved May 11, 2010,
from http://journal.webscience.org/308/
Honeycutt, C., & Herring, S. C. (2009). Beyond
Microblogging: Conversation and Collaboration via
Twitter. Proceedings of the Forty-Second Hawai’i
International Conference on System Sciences (pp. 1-10).
Los Alamitos, CA: IEEE Computer Society.
Java, A., Song, X., Finin, T., & Tseng, B. (2007). Why weTwitter: Understanding microblogging usage andcommunities. In Proceedings of the 9th WebKDD and 1stSNA-KDD 2007 workshop on Web mining and social
network analysis (pp. 56-65). San Jose, California: ACM.
doi:10.1145/1348549.1348556
Letierce, J., Passant, A., Decker, S., & Breslin, J. (2010).
Understanding how Twitter is used to spread scientificmessages. Presented at the Web Science Conference
2010, Raleigh, NC, USA.
Priem, J. & Hemminger, B. (2010). Scientometrics 2.0:
Toward new metrics of scholarly impact on the social
Web. First Monday 15(7).
Thelwall, M. (2003). What is this link doing here?
Beginning a fine-grained process of identifying reasonsfor academic hyperlink creation. Information Research,8(3).
Vaughan, L., & Shaw, D. (2008). A new look at evidenceof scholarly citation in citation indexes and from web
sources. Scientometrics, 74(2), 317-330.
Young, J. (2009, December 17). 10 High Fliers on Twitter.
The Chronicle of Higher Education. Retrieved fromhttp://chronicle.com/article/10-High-Fliers-onTwitter/16488/
Zhao, D., & Rosson, M. B. (2009). How and why people
Twitter: The role that micro-blogging plays in informal
communication at work. In Proceedings of the ACM 2009
International Conference on Supporting Group Work (pp.
243-252). Sanibel Island, Florida, USA: ACM.
doi:10.1145/1531674.1531