One of these fascinating experiments, involving some 800 participants, used images of ladders to help show how levels of inequality can differ considerably from one society to another. The research team showed the participants five different ten-rung ladders. Each ladder represented a different society, with each ladder rung representing 10 percent of each society’s population. The top rung represented the richest 10 percent, the bottom the poorest.

Upon each rung, the researchers placed images of money bags to indicate the total net worth of households in each particular 10 percent. In the most equal of these five ladder societies, no one rung carried many more money bags than any other rung. In the most unequal ladder societies, just the opposite. In these unequal societies, the overwhelming bulk of the money bags sat on the ladders’ top-most rungs.

Northwestern’s Kouchaki and her colleagues then asked their experiment’s participants to choose the ladder image that best reflected the distribution of wealth in their own real-life society. They also asked these’s participants to rate how acceptable unethical behaviors — everything from cheating on exams to illegally downloading software — have become in their own real-life societies.

The bottom line from this particular experiment matched up with the findings from all the rest of this research effort: People who live in highly unequal societies feel “a lower sense of control” and look less askance at unethical behaviors, either from others or from themselves, than do people who live in distinctly more equal societies.

“Overall,” Kouchaki and her colleagues conclude, “our results suggest inequality changes ethical standards.”

Other recent psychological research has come to the same core conclusion.

“When are people more open to cheating?” asked the Canadian researchers Anita Schmalor, Adrian Schroeder, and  Steven Heine in a paper published earlier this year. “Economic inequality makes people expect more everyday unethical behavior.”

The longer we let inequality define our contemporary daily lives, this new research helps us understand, the more the unethical behavior all around us will seem to reflect just the way our world naturally works. Economic inequality, in effect, normalizes unethical behavior. The sun will always rise and set, we come to assume, on a deeply unequal world that no mere mortals can ever change.

We need, some observers of our fraying social fabric suggest, more people in public life noble enough to champion basic ethical norms. True, we do need those champions. But what we need even more: a world of distinctly more equal societies.