This post is the first of the new Sim­ple Sci­ence cat­e­gory. This thread fea­tures research top­ics that are mainly focused on intu­itive research facts/insight detected in the most impor­tant and well known vir­tual com­mu­ni­ties. How­ever, research on com­plex net­works is very inter­dis­ci­pli­nary thus we do not exclude to extend our find­ings to other than social networks.

Since we want an audi­ence as broad as pos­si­ble and the con­tent to be as read­able as pos­si­ble, we will not use strong sta­tis­ti­cal tools, but instead we adopt the basic and under­stand­able ones. In spe­cial cases where more advanced math­e­mat­i­cal meth­ods are needed, we pro­vide ade­quate and clear explanations.

Twit­ter is one of the most used micro blog­ging plat­form. Every day, more than 400 mil­lion short mes­sages (140 char­ac­ters, called tweets) are posted in user’s pro­files. The com­mu­ni­ca­tion in Twit­ter is per­formed by adding in the text a user’s ref­er­ence pre­fixed by a @ char­ac­ter (for instance @lpttwer). Indeed, words that begin with # have a spe­cial mean­ing and rep­re­sent a hash­tags (for exam­ple #sim­ple­science). In the last years, hash­tags have turned out to be a very pow­er­ful and effec­tive way of tag­ging con­tent, search­ing or detect­ing trend­ing top­ics in this vir­tual community.

Because of that, we are con­cerned in under­stand­ing how the way users employ hash­tags is chang­ing, and in par­tic­u­lar how the hash­tags’ length is changed in the last months.

Aver­age Hash­tags length over time

The plot on the left con­tains the aver­age hash­tags length as a func­tion of time. We base our find­ings on a set of more than 1.2 bil­lions tweets, col­lected between August 2011 and Octo­ber 2012 (aver­aged by weeks). It is clear from the fig­ure that the aver­age length has increased in the last 18 months. One of the pos­si­ble expla­na­tion of this phe­nom­ena is that the widely use of hash­tags in online com­mu­ni­ca­tions has lim­ited the unused words and con­se­quently, users have to choose longer hash­tags (maybe com­pounds words).

Stan­dard devi­a­tion of Twit­ter Hash­tags Length

How­ever, this pic­ture of the sit­u­a­tion is far from being complete. In fact, we see that the stan­dard devi­a­tion of the hash­tags lengths (plot on the right) has increased too as time pass by. This cap­tures another impor­tant fea­ture of the hash­tags’ dynam­ics. Not only the aver­age length is becom­ing big­ger, but also the vari­a­tion of the lengths com­pared to the aver­age is chang­ing, mean­ing that the longer hash­tags increase faster than shorter ones.