(NEXSTAR) — You may refer to the current president as “Biden,” the former president as “Trump,” and those before them as “Obama,” “Bush,” and “Clinton.” But what about the Democratic presidential nominee running against Trump? 

Did you immediately think “Kamala” rather than her surname “Harris”?

If so, you’re not alone. 

A 2018 study found that both men and women are twice as likely to refer to a male — versus a female — by their last name in certain fields, including politics. As an example, researchers pointed to the 2008 Democratic primary, where those appearing on television news were more likely to refer to then-nominees Barack Obama by his last name than Hillary Clinton by hers. 

The researchers explained that the tendency to refer to women by their first and last name, or only their first name, may be caused by a variety of reasons, like women’s last names traditionally changing when they get married. “Male” is also often viewed as the “assumed default” when speaking about someone, so using the woman’s first name can help clarify the person’s gender (e.g., using “Michelle” or “Michelle Obama” rather than Obama, which could be confused with her husband, Barack Obama). 

This trend was noted across various high-status fields, including science, technology, and literature. Even women doctors are twice as likely to be called by their first name than their male colleagues, a separate 2022 study found.

While researchers determined this inconsistency of using or not using surnames could contribute to a gender bias, using a woman’s first name over her surname could be beneficial, according to one of the study’s contributors. 

“We know the first name is kind of more associated with familiarity,” Stav Atir, who has a doctoral degree in social psychology from Cornell University, told TODAY. That can also make them appear “more approachable” but give them a “lower status” than men, Atir said.

The ability to make a candidate more relatable by using their first name has been a common campaign method by Democrats, Ashley Etienne, a political advisor who served on President Joe Biden’s 2020 presidential campaign and as Harris’ communications director, also told the outlet. 

While noting that using a female politician’s first name can be “a sign of disrespect,” Mirya Holman, an associate professor at the Hobby School of Public Affairs at the University of Houston, acknowledged it could prove beneficial for Vice President Harris in this campaign. 

Speaking with NPR, Holman explained that because domestic policies are at the forefront of this election season — parental leave, reproductive rights, climate policy — and women are often viewed as having an advantage on these topics, referring to Harris as “Kamala” may not be “a terrible thing for her and for getting enthusiasm up among Democratic voters.”

It can also help to distinguish Harris, Kelly Dittmar, an associate professor at the Center for American Women and Politics at Rutgers University, told The Washington Post. Clinton may have leaned into “Hillary” as a more specific means of distinguishing herself from her husband, President Bill Clinton, but for Harris, “it gives her something to lean into in terms of her distinct identity.”

Mispronouncing Kamala, though, can serve as a sign of disrespect, according to Holman.

Included are House Speaker Emerita Nancy Pelosi (D-Calif.), Rep. Marjorie Taylor Greene (R-Ga.), and former Rep. Liz Cheney — all women from the political sphere that you, most likely, referred to by their full name. Rep. Alexandria Ocasio-Cortez (D-NY) could also be included in this list, though she is most often referred to by her nickname, AOC.

There are also men who get the first name treatment, like Sen. Bernie Sanders (I-VT), or “Bernie,” and President Dwight D. Eisenhower, sometimes referred to as “Ike.”

Alternatively, some women in politics are more often referred to by their last or full name. As Axios reports, former Republican presidential candidate and once-governor of South Carolina Nikki Haley is more often referred to as “Haley.” South Dakota Governor Kristi Noem, Associate Justice of the Supreme Court Sonia Sotomayor, and Michigan Governor Gretchen Whitmer have also been frequently referred to by their surnames.

While experts say referring to a female presidential candidate — or any female of power in any field, from health care to science to literature — can diminish their standing and widen the gender gap, Harris’ campaign has not shied away from using “Kamala,” putting her first name on shirts, signs, and social media.

When it comes to her running mate, though, it’s Walz, not Tim.