Thousands of high school students, many of them minors, have taken part in marches, walkouts, and other activism over the past month to encourage changes to gun policy. But the students, despite the depth of argument and maturity they’ve demonstrated under the national spotlight, don’t have the chance to advocate for gun reform in a voting booth — not until they turn 18, anyway.

Psychologist Laurence Steinberg cited student activism in the case he made in a recent New York Times op-ed for lowering the voting age from 18 to 16. Steinberg argued that the maturity needed to vote for public office is “cold cognition,” in which the brain slowly reasons through an issue.

“Studies of cold cognition have shown that the skills necessary to make informed decisions are firmly in place by 16. By that age, adolescents can gather and process information, weigh pros and cons, reason logically with facts and take time before making a decision. Teenagers may sometimes make bad choices, but statistically speaking, they do not make them any more often than adults do,” he wrote. “This psychological evidence is backed up by neuroscientific findings. Neuroimaging studies show that brain systems necessary for cold cognition are mature by mid-adolescence.”

Lowering the voting age would require a constitutional amendment, which can only be enacted two ways: a two-thirds vote among Congress and state legislatures, or through a convention of states called by two-thirds of state legislative bodies. While amending the Constitution to lower the voting age is a tall order, it has been done before. In 1971, Congress passed the 26th Amendment, which was then ratified by states and signed into law by President Richard Nixon, bringing the voting age down from 21 to 18.

Even before the federal voting age was lowered to 18, some states had already made the move. Georgia became the first state to lower its state and local voting age to 18 in 1943 during World War II. “Old enough to fight, old enough to vote,” was the slogan of reformers who watched young men march off to die in wars they didn’t have a say in.

But now, Congress members of both major parties are skeptical of lowering the voting age. In interviews with The Intercept, most lawmakers either said they haven’t thought enough about the idea or actively rejected the notion of lowering the voting age to 16.

Many of the lawmakers opposed to a change leaned on age-old arguments about maturity and responsibility — arguing that 16-year-olds are not mature enough to vote and that most are still dependents on their parents’ tax forms.

Hoover Institution Research Fellow David Davenport made a similar argument in a 2016 column. “Perhaps [the voting age] should also be a question of having a real stake in the process — such as serving in the military (age 18, or 17 with parental consent) or writing a check to the government to pay your taxes,” he wrote.

That’s the tack Rep. Darrell Issa, D-Calif., took.

“I don’t think a 16-year-old, who almost universally is a dependent, would by any stretch of the imagination be envisioned to be a voter,” Issa told us. All “entitlements,” including the age to consume alcohol, should be 18, he added.

Rep. Peter King, R-N.Y., agreed. “No, I think you need more maturity. … There’s enough people who don’t know what’s going on voting,” he said. “A person who is 16 years old does not have the worldly knowledge or ability to vote on something.”

“I think 18 is a fine age,” Maine’s Republican Sen. Susan Collins said.

Georgia Republican Sen. David Perdue let out a laugh when we asked him about the idea. “No, I think 18’s a good age,” he said.

“I haven’t thought about it,” offered South Carolina Republican Sen. Tim Scott.

But there are , in fact, a handful of countries around the world with a voting age of 16, including Austria, Brazil, and Ecuador. And the movement to lower the voting age is spreading. In March, Malta became the second European country to drop its voting age to 16. Late last year, the United Kingdom’s Labour Party officially endorsed lowering the voting age to 16, making a push to enfranchise 1.5 million additional British citizens. The change was patterned off voting in Scotland, where 16-year-olds have been able to vote in local and parliamentary elections since 2015.

Labour’s measure was blocked in Parliament, after it faced steep Conservative Party opposition. “It would be a great mistake to lower the voting age to 16. Most 16- and 17-year-olds do not have the level of political knowledge or maturity required,” Conservative MP Bernard Jenkin said in objection to the proposal. There may be a tactical reason for the partisan split: Far more young voters support the Labour Party than they do the Conservatives.

In the United States, Democrats have a similar advantage with younger voters. In 2016, 55 percent of millennials age 18 to 29 voted for Hillary Clinton, with just 37 percent of voters in that category voting for Donald Trump. (Notably, 8 percent of young voters opted for a third-party candidate or did not vote for a presidential candidate.) In 2008 and 2012, Barack Obama also enjoyed broad support among young voters in 2008 and 2012. Still, Democrats on Capitol Hill were skeptical of the proposition.

“If you can’t enter a binding contract, I don’t know whether the voting age should be any different than [for a binding contract],” Rep. Brad Sherman, D-Calif., argued, coming to the conclusion that 18 is just fine.

Rep. Steve Cohen, D-Tenn., answered the question by pointing to a more pressing issue: Russia. “I think we ought to concentrate on making sure our election system works in 2018 and 2020 from Russian interference,” he said. “I think 16 voting would not get anywhere, and we’ve got other serious priorities, defending democracy we need to pursue.”

“Voting age? I don’t know, I have to look at it. That’s a first one that I’ve heard,” Rep. Henry Cuellar, D-Texas, replied.

Sen. Richard Blumenthal, D-Conn., who had praised the activism of the Parkland students, was noncommittal. “I’d have to hear more about it,” he replied. “I think, in general, inclusiveness is a good idea.”

“I would have to think about whether we should lower the age to 16,” Sen. Jeanne Shaheen, D-N.H., replied. Massachusetts Democratic Sen. Ed Markey cited the significant constitutional threshold needed to amend the voting age and replied, “I don’t think we’ll be able to get that done in the near-term, just because of the fact that it has to pass supermajorities in the states and at the federal level.”

Maine’s Independent Sen. Angus King — whose home state of Maine is seeing a large-scale push for voting reform in the form of ranked-choice voting — was also skeptical. “I’m inclined to say 18 is good,” he replied. Montana Democratic Sen. Jon Tester declined to comment.

New York Rep. Carolyn Maloney offered modest support for the idea. “We need to get more young people involved, and I would support that,” she said.

Unlike most of his colleagues, Illinois Democrat Rep. Luis Gutiérrez, who is retiring, heartily endorsed the idea. He noted that he voted in his first election right after the voting age was lowered to 18.

“I got to vote in 1972 because they reduced it from 21 to 18. And they thought it was just going to upend the world, that it would be the worst thing in the world,” he said. “You know, I thought I was ready at 18. I think kids know a lot more today than I know when I was 18. And they mature a lot quicker. …We screwed this place up enough already. They should take the reins of the future. I like the idea. I’d be for it.”

At least one U.S. town has experimented with lowering the voting age, to considerable success. In 2013, Takoma Park, Maryland, lowered the age to vote in municipal elections to 16.

Takoma Park Council Member Terry Seamens, who was one of the original lawmakers to support lowering the age to 16, told The Intercept that youth voter turnout has grown every election since the original measure passed. “It’s been great,” he said about the results of lowering the voting age.

He fully supports moving the federal voting age to 16 as well. “Being able to participate in elections has really [piqued] the interests of the young people and they are out future,” Seamens said. “It’s great to get involved early.”