Americans are now more accepting of socially liberal attitudes than ever before, but there's one area where public opinion remains mostly unchanged: marital infidelity.
"Americans today appear to have greater comfort with a host of issues or behaviors that were at one time subject to social stigma," Gallup's Andrew Dugan said in his analysis of the polls.
"And even among the most taboo behaviors," he continued. "There is evidence of changing moral judgments, at least in relation to suicide, cloning humans and polygamy."
Approval for all three of those topics — suicide, human cloning and polygamy — have been trending steadily upward since 2012, according to Gallup, though all of them remain below a 20 percent approval rating.
Wider acceptance for issues that were once considered taboo, as Gallup put it, may have something to do with society's broadening acceptance of social liberalism, according to Dugan.
"Americans' growing social liberalism is evident not only in how they describe their views on social issues, but also in changes in specific attitudes, such as increased support for same-sex marriage and legalizing marijuana," Jeffrey M. Jones wrote while discussing Gallup's recent poll on social ideology.
"These longer-term trends may be attributable to changing attitudes among Americans of all ages, but they also may be a result of population changes," he explained, "with younger, more liberal Americans entering adulthood while older, more conservative adults pass on."
Another explanation, according to The Christian Science Monitor's Husna Haq, may be “a certain social snowball effect” that has come about for the issues of same-sex marriage and marijuana legalization. A shift which, according to Haq, may also be related to "the rise in popularity of libertarianism," or a growing political emphasis on "autonomy and freedom of choice."
But no matter the cause for Americans' growing acceptance of previously taboo subjects, the trend doesn't apply across the board. According to Dugan, attitudes toward infidelity haven't changed in any significant way.
"Over the past 15 years, no more than 1 in 10 U.S. adults have ever judged extramarital trysts as moral," he explained. "This item has always ranked at the bottom of all issues tested in terms of moral acceptability."
Currently, 8 percent of Americans think that marital infidelity is "morally acceptable," compared to 15 percent for cloning humans, 16 percent for polygamy and 19 percent for suicide. In 2001, both cloning and having an affair were at 7 percent.
According to the most recent Pew data, infidelity is generally considered immoral globally, but the United States is still exceptional in its disapproval.
According to Pew, the median global percentage of those who say having an affair is morally unacceptable is 79 percent. In the United States, disapproval is at 84 percent.
"The nation's thoughts on extramarital affairs may be considered an island of stability amid this sea change," Dugan concluded. "Even as much of the country expands the institution of marriage to include gay and lesbian couples, there has been no redefining of the commitment a couple enters into when they get married."
JJ Feinauer is a writer for Deseret News National. Email: firstname.lastname@example.org, Twitter: jjfeinauer.