Hahaha! The average four-year-old child laughs 300 times a day. By contrast, it takes more than two months for the average 40-year-old adult to laugh that many times. This week, we talk with behavioral scientist Jennifer Aaker of Stanford University about why so many of us fall off a “humor cliff” as we become adults. Plus, how we can inject more laughter into our lives, even during the most difficult of times.

More than a century ago, millions of people around the world died in a massive influenza pandemic. The so-called "Spanish flu" outbreak of 1918 revealed a truth about viruses: they don't just infect us biologically. They also detect fissures in societies and fault lines between communities. Historian Nancy Bristow says this remains true today, as we continue to grapple with the COVID-19 pandemic.This week, we revisit our 2020 conversation with Bristow, and consider what history can tell us about human behavior during public health crises.

Podcast hosts are used to being the ones asking the questions. This week, though, we’re going to flip that script, and put Shankar in the guest seat. We’ll hear a recent interview he did with Krys Boyd of the public radio show Think from KERA in Dallas. The discussion revolves around Shankar's latest book, Useful Delusions, and how self-deceptions can bind together marriages, communities, and even entire nations.

Stories help us make sense of the world, and can even help us to heal from trauma. They also shape our cultural narratives, for better and for worse. This week on Hidden Brain, we conclude our three-part series on storytelling with a look at the phenomenon of "honor culture," and how it dictates the way we think and behave.

We can’t go back and change the past. We can’t erase trauma and hardship. But what if there was a way to regain control of our personal narratives? In the second part of our series on storytelling, we look at how interpreting the stories of our lives — and rewriting them — can change us forever. Also, a note that this week's episode touches on themes of trauma and suicide. If you or someone you know may be having thoughts of suicide, please call or text the National Suicide Prevention Lifeline at 1-800-273-8255.

Why is my friend late? How does nuclear fission work? What occurs when I sneeze? We all need to understand why certain things happen. Some researchers think the drive to explain the world is a basic human impulse, similar to thirst or hunger. This week on Hidden Brain, we begin a three part series on why we tell stories. Psychologist Tania Lombrozo discusses how explanations can lead to discovery, delight, and disaster.

For generations, it was difficult, even dangerous, to express a sexual orientation other than heterosexuality in the United States. But in recent years, much has changed. This week, we revisit our 2019 episode about one of the most striking transformations of public attitude ever recorded. And we consider whether the strategies used by the LGBTQ community hold lessons for other groups seeking change.

Why do some companies become household names, while others flame out? How do certain memes go viral? And why do some social movements take off and spread, while others fizzle? Today on the show, we talk with sociologist Damon Centola about social contagion, and how it can be harnessed to build a better world.

We get messages all the time from listeners who say Hidden Brain has helped them to think differently about the world, and about themselves. As producers, nothing is more rewarding or gratifying. Today, we bring you a listener story that especially moved us. It’s a tale about two friends, and how our show played a small role in their dramatic story.

If you've taken part in a religious service, have you ever stopped to think about how people become believers? Where do the rituals come from? And what purpose does it all serve? This week, we bring you a 2018 episode with social psychologist Azim Shariff. He argues that we should consider religion from a Darwinian perspective, as an innovation that helped human societies to grow and flourish.