Has your B.S. detector gotten rusty?

It’s understandable. We’ve been isolated for so long, interacting in narrow circles, often of like-minded people. We’re unprepared for the assault of someone spewing false information right to our face. But detecting B.S.—shorthand for a coarser version of what my grandmother called hogwash—is a crucial skill, also known as critical thinking, as we head back out into the world.

John Petrocelli is a social psychologist and professor of psychology at Wake Forest University, in Winston-Salem, N.C. He researches the causes and consequences of B.S., to help us improve our ability to detect and dispose of it. His studies have found that people tend to spread B.S. when they feel obligated to have an opinion about something they know little about—and when they feel they aren’t going to be challenged on it. He has a new book coming out later this month, called “The Life-Changing Science of Detecting Bullshit.”

Dr. Petrocelli says that some B.S.—such as flattery or an opinion about something inconsequential, like a TV show—serves a purpose: It connects us. But B.S. can often be dangerous, such as when people spread false rumors about a person; repeat information about current events that is not based on truth; or sugarcoat facts in a way that leads us to make a poor decision. “Imagine if you were looking to buy a home and the people who lived there told you it was a great place to live, but it really wasn’t,” he says.

I spoke with Dr. Petrocelli about who spreads B.S., when we’re susceptible to it, and how we can confront it. Here are edited excerpts of our conversation.

What is B.S.?

Dr. Petrocelli: B.S. is when someone communicates something with little regard for the truth, genuine evidence or established knowledge. It can be intentional. For example, if someone is trying to persuade, fit in, embellish, confuse or simply hide the fact that they don’t know what they’re talking about, they might B.S. But I think a lot of times people do it unintentionally. They just have not been held accountable and they think they can say whatever comes to mind. It’s a quick and dirty, fast and loose way of communicating.

Is it different from lying?

Completely. The liar actually knows and cares about the truth. They need to know the truth so they can detract you from it. The B.S.er not only doesn’t know the truth, they don’t care about it. A B.S.er could accidentally be telling you the truth and not even know it.

Why do people do it?

One reason is simply the obligation to have an opinion. People feel they have to have an opinion about everything—not just about big important things but also little things, like should “Game of Thrones” have ended when it did? This type of B.S. helps people develop and maintain connections. It promotes communion. We do it to facilitate a social bond, to be likable and interesting.

People B.S. in a relationship when they tell each other what they want to hear to avoid conflict or hurt feelings. “Of course, my mother loves you.” They may also use it to help them get what they want—to conceal jealousy or their motivations or to avoid someone.

And a really big motivation is to promote one’s status—to get ahead, appear knowledgeable, competent, skilled or admired.

Why is it so difficult to detect?

People usually maintain social circles with people who are like-minded. This is where you get the echo chambers of life. When you’re communicating with someone who has opinions similar to your own, you never think they’re B.S. You agree with what they’re saying.

It’s easier to detect when it doesn’t align with your beliefs. Now you’re in a state of skepticism. And if you don’t think something is true, you’re much more likely to ask further questions.

How can we get better at detecting B.S.?

One of the best ways is to ask questions. First, take a moment and process what they’re saying. It’s to your advantage to get them to clarify the claim, so ask: “Is what you are saying X?” When you ask people to clarify, they’ll often take a step back and think. And a lot of times, they’ll dial back their claim. So the first question is: “What? What are you saying?”

What’s the next question?

“How? How do you know that’s true? How did you come to that conclusion?”

This forces the person, maybe for the very first time, to survey the available evidence. A lot of times, they haven’t thought their claim through. They just like the sound of it. Ask for their reasoning, the evidence.

“Why” is not a good question to ask. That leads people into the abstract, to talk about their values and the heady stuff. The “how” question gets them down to the concrete, real-world, practical things that we would call evidence.

Anything else to ask?

The other question should be: “Have you ever considered any alternatives?” The reason for this question is that if they say no, you know they probably haven’t thought through the thing very well.

You can ask yourself questions too. For example, you can ask yourself if there is evidence that disproves the person’s claim. And you can ask yourself if the other person is relying on anecdotal evidence. B.S.ers love to use anecdotal evidence.

Are there specific statements to look out for?

I would look for what we call pseudo-profound, proverbial clichés. The statements that people use as if they are logic incarnate. “The grass is always greener on the other side.”

Ask yourself if the person is using jargon. Or unclear language. Or platitudes like “it’s always darkest before the dawn.” These B.S. statements aren’t harmless. They imply what you should do in your decision-making. For example, what if you’re in a bad relationship and you’re being told to just hang on because it will get better. That can have a cost.

One clue: These nonsensical, prescriptive statements are not always true. Often, there is another equally catchy proverb that disputes them. For example: “You can’t teach an old dog new tricks.” You also hear the opposite: “You’re never too old to learn.”

Sometimes people we love B.S. us. How can we keep from offending them?

Don’t call B.S. unless you’re sure it’s B.S. And you don’t have to accuse the person of being a B.S.er. What you want to do with your line of questioning is help the person rethink or reason.

Be considerate. Consider the possibility that you’re the one who is confused. You could simply act confused and tell them you just want to understand. “I’m confused. You said A, but what about B? I am just trying to understand.” This works because people hate know-it-alls. But if they think you’re just confused they’ll be honest about what they’re thinking.

And be sure to deal with the claim they’re making and not the person. Don’t make it a character attack. If people feel attacked, it will shut down the conversation. You’ll never get to the bottom of it.

Write to Elizabeth Bernstein at elizabeth.bernstein@wsj.com or follow her on Twitter, Facebook or Instagram at EBernsteinWSJ