Is nostalgia an emotion that's bitter, or sweet? Why are we so often pulled into memories of the past? This week on Hidden Brain, we talk about what prompts us to feel nostalgic, and the harms and benefits of this emotion. Plus, how Donald Trump employed nostalgia to win the 2016 presidential campaign.

Gender is one of the first things we notice about the people around us. But where do our ideas about gender come from? Can gender differences be explained by genes and chromosomes, or are they the result of upbringing, culture and the environment? This week, we delve into the debate over nature vs. nurture, and meet the first person in the United States to officially reject the labels of both male and female, and be recognized as "non-binary."

"Be the change you wish to see in the world." It's a popular quote that's made its way onto coffee mugs and bumper stickers — but it's not the easiest principle to live. On this week's Hidden Brain, we meet Royce and Jessica James, a couple who decided to raise their daughter in a gender-neutral way. It was far harder than they ever could have imagined.

We all know casual sex isn't about love. But what if it's not even about lust? Sociologist Lisa Wade believes the pervasive hookup culture on campuses today is different from that faced by previous generations. This week on Hidden Brain, we revisit a favorite episode exploring what this culture means for those who choose to participate, and for those who opt out.

Ignorance is bliss, but knowledge is power...right? In this episode of Hidden Brain, we explore why we sometimes avoid information that's vital to our well-being.

We all have regrets. By some estimates, regret is one of the most common emotions experienced in our daily lives. This week we'll hear listeners' stories of regret, and talk with psychology professor Amy Summerville. She runs the Regret Lab at Miami University in Ohio. Summerville says regret doesn't always have to be a negative force in our lives. Sometimes, it can be a hopeful emotion.

Several weeks ago, white supremacists took to the streets of Charlottesville, Virginia, in a demonstration that left many Americans asking a lot of questions. Who are we as a nation? What do we stand for, and what do we tolerate? The United States goes further than many other countries to protect speech — even hate-filled speech like that used in Charlottesville. In this episode, we look at how people use free speech arguments, and why the motivations behind these arguments may not be apparent — even to the people making them.

At one time or another, many of us feel stuck: in the wrong job, the wrong relationship, the wrong city – the wrong life. Psychologists and self-help gurus have all kinds of advice for us when we feel rudderless. This week on Hidden Brain, we conclude our You 2.0 series with a favorite episode exploring a new idea from an unlikely source: Silicon Valley.

In the latest in our You 2.0 series, we bring you a favorite conversation with Harvard researcher Dan Gilbert. He tells us why we're bad at predicting our future happiness, how that affects our decision making, and why we are actually happier after making a decision that feels irrevocable.

Many of us have heard that we should think positively and visualize ourselves achieving our goals. But researcher Gabriele Oettingen finds this isn't actually the best advice. Instead, she says, we should use her strategy — which she calls WOOP.