In this episode we sit down with psychology legend Richard Petty to discuss the Elaboration Likelihood Model, a theory he developed with psychologist John Cacioppo in the 1980s that unified the study of attitude change and persuasion and has since become one of the most robust models for explaining how and why some messages change people’s minds, some don’t, as well as what makes some stick and others fade in influence over time.

In this sprawling, strange, and mind-bending episode, Dr. Jud Brewer, a neuroscientist and addiction psychiatrist, discusses the biological origins of our bad habits and how we can change them using new techniques derived from his lab’s research.

Well, he tries to talk about that, but I keep interrupting him to try and solve the great mysteries of consciousness and the self. For instance, if you want to hear a neuroscientist quote Einstein — “No problem can be solved from the same consciousness that created it.” — then go from talking about worms and cigarettes to warning you to be careful with your brain or “you can go over the event horizon of the black hole of anxiety,” and the only way out is to add more information to the system to it can propel itself away from the worry black hole — this is the episode for you.

In Lori Gottlieb‘s new book, Maybe You Should Talk to Someone, she opens with a quote from James Baldwin that reads, “Nothing is more desirable than to be released from an affliction, but nothing is more frightening than to be divested of a crutch.”

It’s a book about therapy, what is is, what it isn’t, and how people do and do not change their behaviors. It’s intimate and human, gut-wrenching and inspiring, and full of science and drama and an honesty and candor that you rarely find in books like this.

Dinner parties used to be where you avoided politics. Now talking about politics at dinner parties is the norm.

Years ago, we avoided politics because we assumed the people at our table had diverse political identities, and we didn’t want to introduce a topic that might lead to an argument. Today, we assume our guests share a single identity, after all, why else would we have invited them?

Something has changed in the United States, and for many of us, it’s only at Thanksgiving dinner, a gathering where we don’t get to sort ourselves by political tribe, that we must face people who see the world differently than ourselves.

In 1835, at a tavern in Bavaria, a group of 120 people once met to drink from a randomized assortment of glass vials.

Before shuffling them, they divided the vials into two sets. One contained distilled water from a recent snowfall and the other a solution made by collecting 100 drops of that water and dropping into the pool a grain of salt, and then diluting a drop of the result into another 100 drops, again and again, 30 times in all.

They did this to test out a new idea in medicine called homeopathy, but it was the way they did it that changed things forever. By testing options A and B at the same time, but without telling sick people which option they would be getting, they not only debunked a questionable medical practice, they invented modern science and medicine.

About 200 years later a company in California tried something similar. A group of 700,000 people gathered inside a virtual tavern to share news and photos and stories both happy and sad. The company then used some trickery so that some people randomly encountered more happy things and others more sad things.

They did this to test out a new idea in networking called emotional contagion, but it was the way they did it that changed how many people felt about gathering online. By testing options A and B at the same time, but without telling people which option they would be getting, they not only learned if a computer program could make its users more happy or more sad, they created a backlash that resulted in a large-scale, world-wide panic.

Though we always learn something new when we perform an A/B test, we don’t always support the pursuit of that knowledge, which is strange, because without A/B testing we have to live with whatever option the world delivers to us, be it through chance or design. Should we use cancer drug A or B? Should we try gun control policy A or B? Should we try education technique A or B? It seems like our reaction to these questions would be to support testing A on half the people, B on the other, and then to look at which one works best and go with that moving forward, but as you will learn in this episode of the You Are Not So Smart Podcast, new research shows that a significant portion of the public does not feel this way, enough to cause doctors and lawmakers and educators to avoid A/B testing altogether.

Have you ever been in a classroom or a business meeting or a conference  and had a question or been confused by the presentation, and when the person running the show asked, “Does anyone have any questions?” or, “Does anyone not understand?” or, “Is anyone confused?” you looked around, saw no one else raising their hands, and then chose to pass on the opportunity to clear up your confusion?

If so, then, first of all, you are a normal, fully functioning human being with a normal, fully functioning brain, because not only is this common and predictable, there’s a psychological term for why most people don’t speak up in situations like these. It’s called pluralistic ignorance.