A few years ago, there was a piece on “This American Life” about a “living history” museum outside Indianapolis that tried to give patrons a more immediate sense of what it was like to live under slavery. So tourists would actually role-play the part of slaves, yelled at and berated by a historical reenactor playing the part of a slave master. Judging by the audio, he played the part very well — so well that he would make some tourists cry, even throw up.

Producer Alix Spiegel also interviewed the tourists, all but one of whom claim that they would have fought slavery if they have lived through the times. If they were black, they would have risen up against the slave owner. If they were white, they would have been part of the Underground Railroad ferrying escaped slaves to freedom.

But, of course, when the tourists were put into role-playing situations, they didn’t do anything of the sort. They cringe at the master’s threats, they shuffle along obediently. At one point, the actors playing the masters deliberately leave the “slaves” unguarded. Nobody tries to escape.

I thought about that episode a lot after watching the powerful and harrowing “12 Years a Slave,” which is effective in so many ways at making the audience understand what it was like to be an African-American slave.

The film is rough to watch, no question, but there’s such an artistry to Steve McQueen’s direction and John Ridley’s screenplay that makes the film such a powerful experience. This isn’t just about the lashes on the back, but the damage done to the self,  that sense of terror and powerlessness that Solomon Northup (Chiwetel Ejiofor) feels. As movie audiences, we’re trained to root for the underdog, cheering him on as he rises up against his oppressors. But when Solomon beats and whips the sadistic carpenter played by Paul Dano, all I could do was cringe. Don’t do that, I silently urged Solomon. Don’t.

Why is “12  Years a Slave” so effective at putting us in that mindset? Looking back, you can see John Ridley’s script as a series of betrayals, of false kindnesses offered, of real kindnesses that are then pulled back out of fear. In a way, these are almost worse than the flat-out cruelty the slaves suffer at the hands of someone like Michael Fassbender’s drunken, arrogant “n—–breaker,” or his psychopathic wife (Sarah Paulson). At least you know where you stand with the man who is whipping you.

The movie begins with a seeming act of generosity — Northup is hired by two friendly white men (Taram Killam and Scoot McNairy) to play for their traveling show at a more-than-fair wage. They wine and dine him, treat him as an equal, carrying him upstairs to bed, even tuck him in, Killam’s character positively paternal as he gently says “there’s nothing more we can do for him.”

This sequence is shown in flashback, as a chained Solomon begins to piece together the events that led up to him being kidnapped. But it’s key what scene is missing — the scene where we see Killam and McNairy turning over Solomon to the slave traders. That moment is wiped from the record — all we see from them, all Solomon can remember, is kindness. And now look where he is.

Then Solomon meets the two slave traders who good-cop, bad-cop him. One viciously beats him, the other offers him food and takes away his blood-soaked clothes. But the second is no kinder than the first — taking away the clothes removes the last vestiges of Solomon’s old life (“Rags and tatters, rags and tatters”). Now the only place the name Solomon Northup lives is in Solomon’s mind.

On the ship to Louisiana, one slave gets stabbed for trying to stop a rape. Another, Solomon’s closest ally, spots his master when they get to port and leaves Solomon behind without a backwards glance.

Again and again, kindness and cruelty becomeconfused with each other.

-There’s the white mistress who, greeting the mother whose children have been stripped from her, says “Your children will soon be forgotten.” She’s trying to console the mother by saying that.

-Master Ford (Benedict Cumberbatch) is the kindliest slave owner you can imagine, inviting Solomon onto the porch to play music, listening to his ideas, treating him as a man. But only to a point — in the end, Ford is too weak-willed to acknowledge the truth, that Solomon is an educated free man.

–When Solomon beats Paul Dano’s character, Ford’s overseer tells him to stay put, that if he leaves the plantation, “I can’t protect you.” So Solomon waits, trembling with fear. The overseer does save Solomon from a lynching — but then leaves him hanging, his toes grazing the muddy ground, all day long. Kindness.

–When Master Epps (Michael Fassbender) can’t pay his debts, Solomon goes to a kindly judge as collateral, who pays him well and lets him play violin for the house, a link back to his old life. But when Solomon goes back to Epps, he’s treated even harsher for the kindness. In the end, Solomon destroys his violin — a link to the old life is just too painful.

–Solomon confides in the former overseer (Garret Dillahunt), Armsby, who agrees to get a letter to his family back North. Then Armsby, of course, turns Solomon in in the hopes of getting a job as an overseer — a job that he just confessed eats away at a man’s soul. I don’t think he’s lying about feeling that way — Armsby is one of several white characters who you sense feels trapped in the slave system as well.

And then there’s perhaps the ultimate perversion of kindness, when the abused Patsy begs Solomon to drown her in the river, to free her from the rape and physical abuse from Epps and his wife. Solomon is horrified, and refuses. But later, Patsy is brutally whipped, McQueen waiting until the last possible moment to show us, graphically, the wounds. As the women dab ointment on Patsy’s savaged back, her eyes lock with Solomon’s. And he knows. He should have done her that kindness.

By the time Brad Pitt shows up as the Canadian carpenter Bass, who actually speaks up about how unjust slavery is, I found myself feeling nervous about Solomon confiding in him about his true situation, asking him to send a letter home describing his circumstances. After everything that had happened before, didn’t part of you think Bass would betray him too? There’s been some quibbling about casting someone as recognizable as Pitt in the role, but there’s something canny about seeing Pitt, such a picture of heroism and confidence in so many movies, playing someone who is moral, but still very scared of doing something so small to help a slave. The fear that slavery propagates lives deeps in the bones.

Slavery was an institution, a way of life, an economy that much of America depended on. But beyond laws and business transactions, what keeps such a cruel institution going? As we see in “12 Years a Slave,” it’s a million tiny moments between people, a million instances where one person treats another as less than human, as property. Everyone’s notion of right and wrong, kindness and cruelty, gets horribly warped in the process. And “12 Years a Slave” eloquently destroys every argument ever made that slavery is “in the past,” and that America needs to “move on.” A country doesn’t just briskly move on from that kind of widespread moral perversion.