On Saturday, Nikki Adams received an official-looking letter in her East Anchorage mailbox.

The return address was for an entity called the "Alaska State Voter Program," and the envelope bore an official-looking seal featuring an eagle swooping over a ballot box.

Inside, she found a letter that horrified her.

"WHAT IF YOUR FRIENDS, YOUR NEIGHBORS, AND YOUR COMMUNITY KNEW WHETHER YOU VOTED?" it began.

The letter said low voter turnout was a chronic and worsening problem.

"This year, we're taking a new approach," it continued. "We're sending this mailing to you, your friends, your neighbors, your colleagues at work and your community members to publicize who does and does not vote."

To make good on that threat, the names of 11 people -- some of whom Adams knew personally -- were listed below, along with their addresses and a tally of whether they had voted in the last three statewide elections.

There was a big question mark under the 2014 spot.

The letter let Adams know that the senders intended to mail an updated chart after the Nov. 4 election.

"I was outraged," said Adams, a full-time student who grew up in Alaska. "This is like a violation of privacy. It's not anybody's business whether or not I voted."

Whom a person votes for is always supposed to remain private. But whether someone voted has long been a matter of public record, said Gail Fenumiai, director of the Alaska Division of Elections.

Increasingly, political groups across the country are utilizing publicly available voter lists and other databases to send mailings that use what researchers call "social pressure" to get people to vote.

The most forceful threaten to expose an individual's voting record, or lack thereof, to peers. This election cycle, the "voter shaming" mailings have made their way to Anchorage.

It's not clear how the groups target who receives them, though presumably they want to motivate voters they believe will support their candidates or issues to get to the polls.

It's also not clear how the Opportunity Alliance PAC customized the letter sent to Adams and others in Anchorage to include the names, addresses and voting records of people she actually knew.

Another recipient of the Opportunity Alliance PAC mailing said the only thing the 11 people listed on her letter had in common was that they were her friends on Facebook, which seemed creepy to her.

Creepy or not, researchers say the technique works.

Letters like the one being delivered to mailboxes in Anchorage are among the most effective ways to mobilize voters, said Costas Panagopoulos, a political science professor at Fordham University in New York who studies voting behavior and motivation.

Political scientists examined the way social pressure could be used to influence voter behavior and found that shame was an effective motivator to get people to the polls, he said.

In the election cycles since the first major studies on the topic came out in 2008, groups have translated those findings to real get-out-the-vote campaigns, mailing letters and fliers that sometimes imitate the very letters social science researchers originally sent out as part of their experiment, Panagopoulos said.

The reason shame is such an effective motivator is deeply ingrained in human psychology, he said.

People are predisposed to want to at least seem socially engaged. If you see voting as a "pro-social activity," having people whose opinions you care about know you don't vote could be embarrassing.

"We want to appear to be good citizens," he said.

For all its utility, the technique also causes backlash.

News reports from the 2012 and 2014 election cycles describe angry reactions from recipients of "voter shaming" mailers in states like Colorado and Arkansas. Many see it as an invasion of privacy.

"People have a visceral reaction to these types of mailers," Panagopoulos said. "One reason is they may not be very aware that their voting history is a matter of public record."

Groups and individuals can buy access to a statewide voter list, which contains the names, residence addresses, mailing addresses, voting district and precinct, party affiliation and 10 years of voting participation and registration dates for Alaska voters, said Fenumiai. Whom a person voted for or against is always private and is not part of the statewide voter list. Other states keep similar lists, which are generally considered public information.

The voter-shaming mailers don't appear to be in violation of the law, she said.

"There are no limitations on what the list can be used for," said Fenumiai.

The Division of Elections has received complaints anyway.

"(Callers) are being told that legislative changes would be required to stop the voter list from being used like this," Fenumiai wrote.

Anchorage residents have reported receiving at least three versions of mailers that use individual data from the voter list, mailed by groups from across the political spectrum.

The mailer Adams received did not come from any official state source -- there is no "Alaska State Voter Program" -- despite its appearance.

Two separate mailers sent to Anchorage residents bill themselves as "voter report cards" or "voter audits" and remind recipients that whether you vote is public record by including personalized voter data.

One was sent by America Votes, a progressive group with national partners like the AFL-CIO and American Federation of Teachers.

The other was sent by the Koch brothers-backed conservative nonprofit Americans for Prosperity.

The "audit" and "report card" mailers differ from the Opportunity Alliance PAC letters in that they don't threaten to expose a person's voting record to a list of peers.

They represent a softer sort of social pressure that may not be as effective as the type of letter that angered Nikki Adams.

"Very few things have been proven to be as effective as the heavy-handed social pressure mailer," Panagopoulos said.

In fact, research shows they are roughly as effective as the far more resource-intensive door-to-door, get-out-the-vote visits, he said.

For Adams, none of that matters.

"It feels like, if you don't do this we're going to tattle on you," she said.