More Americans are finding certain behaviors morally acceptable that are nevertheless still widely considered unacceptable. In other words, approval (though still low) of these behaviors has been creeping up:

While a select few actions remain deeply taboo for much of the country, there has been an increasing shift to moral acceptability for some of these over time. Such actions include suicide (which 19% of Americans call “morally acceptable”), polygamy (16%) and cloning humans (15%).

Will they follow the route of once-disapproved-but-now-widely-approved behaviors such as premarital sex or gay/lesbian relationships? Or will they continue to remain in the dungeon like—and the low score of the following may surprise you, as it did me—adultery, which remains in the approval basement?:

On the other hand, “married men and women having an affair” has remained at the bottom of a list of 19 moral behaviors Gallup has measured, with only 8% considering it morally acceptable.

Not only is adultery at the bottom of the list, but I would wager it’s the most highly disapproved behavior that is most widely engaged in.

Or is it? Researchers have long had trouble gauging exactly how much hanky-panky is going on within marriage, but there are indications that it’s less widespread than commonly thought:

Taken together, in any given year, it looks like the actual likelihood of your relationship suffering from cheating is low — probably less than a 6 percent chance.

But over the course of your entire relationship, the chances of infidelity may rise to as much as 25 percent. Twenty-five percent — over the course of an entire relationship — is a far cry from the 50 percent number we hear from many so-called professionals and services trying to sell you something.

And to put cheating into perspective too, the relationship (or one of the people in the relationship) needs to be lacking in something.

Well, that’s a pretty low bar. Who isn’t lacking in something?

Another interesting fact is that these days, adultery is the only behavior on the list that is considered highly unacceptable (approval under 20%) by Americans 18-29; only 10% in that age group say it’s okay. That figure is similar to the disapproval rates in other age groups.

Most Americans now have no problem with out-of-wedlock births, at least in the moral sense (I’d guess there’s more practical disapproval than moral disapproval at this point, but the survey didn’t ask about that). This Gallup article from 2013 tracks some of the changes in a host of areas since around 2000, and it has been huge.

But most of the more recent changes in a 2014 poll have been among Democrats rather than Republicans. In other words, those who perceive that Democrats have moved more to the left, at least on the social dimension, are correct. The right has stayed surprisingly stable:

In the 12 years Gallup has asked this overall question, Democrats have become significantly more tolerant on many issues, while independents generally show a smaller shift in the same direction and Republicans’ views have changed little. The percentage of Democrats who say an issue is morally acceptable has increased for 10 issues, including abortion, sex between an unmarried man and woman, extramarital affairs, cloning humans, divorce, cloning animals, suicide, research using stem cells from human embryos, polygamy, and gay and lesbian relations.

In some cases, the change among Democrats has been substantial. For example, in 2003, 52% of Democrats said having a baby outside of wedlock was morally acceptable, and 40% of Republicans and 61% of independents agreed. This year [2014], 72% of Democrats, a 20-percentage-point increase, say it is morally acceptable. Meanwhile, Republicans have seen no change, with 40% still saying it is morally acceptable, although a higher 50% viewed it as morally acceptable last year. Independents have also not seen a change, with 60% saying having a baby out of wedlock is morally acceptable this year.

Republicans are slightly more accepting of gay and lesbian relations, sex between an unmarried man and woman, and divorce than they were in 2001, when these questions were first asked. Independents’ views on the first two issues (but not divorce) also have seen small shifts, but neither group has seen changes as drastic as those among Democrats.

I find that exceptionally interesting. However, we don’t know whether Republicans have toed the line, or whether those who used to call themselves Republicans but who shifted to the more accepting point of view have shifted their political allegiance to Democrat as well, leaving the more socially conservative within the Republican camp.

Generally, the changes have been among the old as well as among the young, so it’s not just the relentless drumbeat of the left in the school system that’s causing the shift.

If you were to track approval/disapproval of these things over a much longer time frame, my guess is that you would detect a slow increase (such as is now occurring with polygamy, for example) and then a sudden surge of approval, until it reaches a critical mass and the behavior is no longer considered a problem. That’s what probably happened with birth control, which now has the highest acceptance of all: in 2014, 90% had no moral problem with it.

Will acceptance of polygamy follow a similar sharply upward trajectory, or will it go the way of adultery, which has hardly changed in its approval figures over recent years?

[Neo-neocon is a writer with degrees in law and family therapy, who blogs at neo-neocon.]