Here’s an under-140-character musing for you: the hashtag can teach us something about gender. A male Twitter user might tag that observation with something like #linguistics, #gender, or maybe #hashtags. A female user is more likely to add something like #duh.

#Duh isn’t an inherently feminine response. It is, however, an example of an expressive hashtag—a hashtag that’s used not to tag a tweet (its original purpose), but to provide commentary. “A tag like #linguistics is meant to be searchable, to make conversation happen around a topic,” says Allison Shapp, a doctoral student in linguistics at NYU. For a study on gender differences in hashtag use, Shapp pulled together a library of tweets that included 1,633 hashtags, which she then divided into “traditional” tags (people, places, subjects, and events) and “expressive” tags (used to express feelings, tell jokes, or otherwise offer a personal take). About 59 percent of female users’ hashtags were expressive. Males’ hashtags, however, leaned dramatically in the other direction—77 percent were traditional.

The men in Shapp’s sample seem to be prioritizing function over expression—using tags to try to get their tweets seen. The women’s hashtags, by contrast, appear more playful. So while one man tweeted, “Free breakfast at #ikea,” a woman in a similar situation might joke (to borrow another tweet from Shapp’s sample), “Good morning y’all. #teamnosleep lol.”

Shapp’s finding echoes a broader observation that linguists have made about male versus female communication: namely, that women tend to be more expressive then men. This tendency plays out in a number of contexts. Studies have found that women do more diary-style blogging, while men’s blogs tend to feature more informational content; and that women are inclined to write with more personal pronouns, more emotive words, more abbreviations like lol, more emoticons, and more expressions such as ahhh, ugh, and grrr.

“The hashtag has become one more way to show emphasis,” says the linguist Deborah Tannen, a professor at Georgetown, who adds that this has “nothing to do with its original use to join a public conversation on a given topic.” According to Tannen, women’s preference for expressive hashtags is “similar to their using exclamation points, caps, and repetition of letters to show emphasis, and to the fact that women’s spoken intonation patterns tend to vary more than men’s.”

Being expressive isn’t a bad thing, of course. In this case, it’s allowing women to lead a set of changes that affect not just the way we all communicate but the way we live and work. “Women are less compelled to be traditional and conservative in their modes of expression,” says Alexandra King, a philosophy professor at suny Buffalo. “They can often be at the forefront of linguistic shifts.”

When it comes to Twitter, though, are women shifting the hashtag’s purpose, or partially defeating it? In its most simplistic form, Twitter is a tool for being seen and heard. And it’s not difficult to make a connection between purely expressive, even decorative, hashtags and tweets that aren’t likely to get noticed, much less retweeted. For example, a recent BBC analysis of how British politics are discussed on Twitter found not only that men were dominating the discussion, but that three-quarters of tweets with a hashtag mentioning one of the country’s political parties were from male users. Gender differences can also be seen in the main text of tweets: a study of tweets relating to Hurricane Irene found that words such as safe and praying were prevalent in women’s tweets, while men’s tweets were more likely to include timely or topical words like media, breaking, and Obama.

All of which may help explain why, although roughly equal proportions of American men and women use Twitter, women appear to trail male users in terms of influence. Back in 2009—admittedly an eon ago in social-media terms—a Harvard Business Review study found that both men and women were significantly more likely to follow men on Twitter. Today, men dominate lists of influential Twitter users, and recent analyses using the tool Twee-Q suggest that they are approximately twice as likely to be retweeted as women are. If you tweet and no one hears it, do you make a sound?