Terry Gross

The National Sleep Foundation recommends an average of eight hours of sleep per night for adults, but sleep scientist Matthew Walker says that too many people are falling short of the mark.

"Human beings are the only species that deliberately deprive themselves of sleep for no apparent gain," Walker says. "Many people walk through their lives in an underslept state, not realizing it."

David Litt was 24 years old and just a few years out of college when he landed a job writing speeches for President Barack Obama — an experience he calls "surreal and completely terrifying."

Though he was initially assigned the speeches no one else wanted to write, Litt eventually became a special assistant to the president and senior presidential speechwriter. His duties included writing jokes for the short comedy routine Obama performed annually at the White House Correspondents' Association Dinners.

When filmmakers Ken Burns and Lynn Novick began research for a 10-part PBS documentary on the Vietnam War, they thought they knew the material. After all, Burns was of draft age in 1970, though his draft number was too high for him to be called to serve.

But as they began interviewing subjects and sorting through archival footage, Burns and Novick soon came to appreciate just how complicated the war was. "We went in, both of us, with this kind of arrogance about it, and immediately had that blown out of the water," Burns says. "We realized we knew nothing."

During Donald Trump's campaign for president, there were times at his rallies when he singled out one reporter for criticism. Katy Tur, who covered the Trump campaign for NBC News and MSNBC, remembers those instances vividly.

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