Political observers have probably spent more time dissecting Donald Trump’s speech patterns than any presidential candidate in recent history. Interest in the GOP nominee’s rhetorical tics has been, well, huge.

But over the course of a 25-year career in politics, Hillary Clinton’s linguistic evolution has been just as noteworthy. My research finds that as the Democratic nominee moved from first lady to U.S. senator to secretary of state, she spoke in an increasingly masculine way. In talking more “like a man,” Clinton has conformed to prominent gender norms in American politics.

How women perform “masculinity” in politics

Women rarely act “like women” to achieve power and influence in politics. Women aspiring toward political leadership are more often expected to adopt masculine styles of behavior in order to get their points across. A classic example is Margaret Thatcher, who was trained to lower her naturally high-pitched voice to communicate with more authority.

My analysis of Clinton’s rhetoric draws on research conducted by psychologist James Pennebaker of the University of Texas at Austin. Pennebaker and his colleagues have discovered that men and women tend to speak differently — not necessarily in the content or topics of their conversations, but in the use of seemingly unremarkable “function words,” such as pronouns and prepositions. We use function words to structure and connect our thoughts when communicating with others. For this reason, they reflect both the deeply social nature of communication as well as how individuals organize and orient themselves within the world.

In general, women tend to use pronouns (you, theirs), and especially first-person singular pronouns (I, me), more frequently than men. They also use common verbs and auxiliary verbs (is, has, be, go), social (friend, talk), emotional (relieved, safe, kind), cognitive (think, because), and tentative (guess, maybe) words at higher rates than men.

Men, on the other hand, tend to use first-person plural words (the royal “we”), articles (a, an, the), prepositions (of, to, under), big words (over six letters), words associated with anger (destroy, kill), and swear words ([redacted]) more frequently than women.

Here’s an example of how Clinton’s vocabulary has changed

Consider a pair of examples from interviews that Clinton gave, nearly 20 years apart.

In 1996, she was asked on CBS what she would have done differently in her push for health-care reform. In the excerpt below, the “feminine” words are in bold.

You know, if you look at Harry Truman, it just was very hard for him and it’s hard for anybody who tries to approach it. So, yes, I know I made mistakes and I know there are better ways I could have done things. And if I were to do it over again, I would try to present it better. I don’t know if we’d have a different outcome, but I certainly would try.

Fast forward to 2014, when she was asked a similar question in a CNN interview, this time about what she would have done differently during the 2011 attack on the U.S. diplomatic compound in Benghazi, Libya, that resulted in the death of Ambassador J. Christopher Stevens. This time, masculine words are in bold.

Well, that’s a difficult question, because our ambassadors are the personal representatives of the president of the United States. We send people who we believe have the understanding of the cultures and the political systems that they are working in. And it’s very hard to second-guess.

Particularly revealing are changes in Clinton’s use of pronouns — from a total of 20 in the 1996 excerpt (27 percent of all words in 1996) to nine in 2014 (17 percent). In 1996, Clinton said “I” eight times and “we” only once, indicating a more personal, feminine style. In 2014, however, Clinton did not say “I” even once, but said “we” or “our” three times. Her 2014 response is less tentative and self-conscious, but more complex and distant — all markers of masculine language.

Changes in Clinton’s style are evident not just in these two instances, but in 567 interview and debate transcripts I analyzed from 1992 through 2013.

Here’s how the analysis was done

In the graph below, I calculated a ratio of feminine to masculine words in each transcript and, weighted by the number of words per transcript, averaged these values by year. The blue line represents the general trend and the dotted lines represent election years in which Clinton actively campaigned for herself (2000, 2006, 2008) or Bill Clinton (1992, 1996). Higher values indicate more feminine speech; lower values indicate more masculine speech.

Over this period, Clinton’s speech became increasingly masculine. When she occupied a political office or took on a major policy initiative, her language shifted to a more masculine style. In 1992 and 1996, Clinton’s linguistic style was consistent with her more feminine role as the wife of a presidential nominee. But when she led the administration’s health reform policy in 1993–1994, Clinton’s language changed to suit the political environment, reflecting masculine norms of communication that dominate policymaking.

After 1994, Clinton performed more traditional duties of the first lady and her language followed suit, turning more feminine. As a candidate for the U.S. Senate, her language again shifted toward a masculine style, sustained throughout her time in Congress. As secretary of state, her language again conformed to the masculine expectations of her position.

Looking at her first presidential campaign, I find that for most of 2007, Clinton’s language is consistently more masculine. By late 2007, however, when she was trailing far behind Barack Obama on measures of likability, Clinton’s language became more feminine, particularly in interviews.

The findings above are consistent with Regina Lawrence and Melody Rose’s analysis of Clinton’s campaign strategy: Clinton, in response to her likability problem, deviated from her dominant, masculine strategy in late 2007 into early 2008 in order to present herself to voters as a warmer, more feminine candidate. This shift in strategy marks an interesting point of disruption in Clinton’s language as well.

I do not find similar changes in the language of male politicians. For instance, John Kerry has taken on many of the same roles as Clinton. Between 2004 and 2015, the ratio of feminine to masculine words in Kerry’s interviews remains flat around 1.8.

I analyzed only transcripts from natural language sources — interviews and debates — not speeches or other formal addresses. This means that Clinton’s language became more masculine even outside the formal boundaries of the institutions she served. So, too, Clinton’s language changed even when the topic of conversation did not.

Women must change themselves to succeed in “male” political roles

For these reasons, Clinton’s words are almost certainly more calculated than those of her male colleagues and opponents who — by virtue of their gender — fit the prototype of a political leader.

Clinton’s career testifies to the conformities — and perhaps even contortions — that women undergo to achieve power and influence in a profession still mostly dominated by men and by a male model.

Though the times may be changing, the powerful voice in politics still speaks with a masculine style.

Jennifer Jones is a Ph.D. candidate in the department of political science at the University of California at Irvine.