Today's Please Explain is all about accents in the English speaking world--how did Australians come to sound different than New Zealanders? Why do some people lose their accents quickly...while others can hold on to them for decades? NYU Professor of Linguistics Gregory Guy and North Carolina State University Distinguished Professor of English Walt Wolfram will discuss the various accents in the English-speaking world and even analyze some samples from volunteers!

The first silk textiles were created some 5000 years ago. This week's Please Explain is all about silk, and how fibers made by worms create versatile fabrics and have helped shape the culture of much of the world. Mark Norell, Chair of the Division of Paleontology at the American Museum of Natural History, who is currently finishing a book on the Silk Road, talks about the history of silk; Ingrid Johnson, professor of Textile Development and Marketing at the Fashion Institute of Technology; and Rebecca Robertson, Decorating and Home Editor for Martha Stewart Living join us to discuss how silk is produced, processed, used, and how it should be cared for.

This week’s Please Explain investigates a common phenomenon that’s mysterious to many of us: sneezing! Dr. Marjorie Slankard, Clinical Professor of Medicine at Columbia University Medical Center, and Director of the Allergy Clinic at New York Presbyterian Hospital, and Dr.Neil Kao, allergy and asthma specialist with the Allergic Disease and Asthma Center in Greenville, South Carolina, join us.

This week’s Please Explain is about computer worms and viruses. Richard Ford, from the Center for Security Science at the Florida Institute of Technology, and Lance Ulanoff, Editor in Chief of PC Magazine, tell us how viruses and worms are created, how they infiltrate individual computers, explain the damage they can wreak and how we can best protect our machines.

Salt is found on most dining tables and in most kitchens—but this ubiquitous household item has a long and curious history. It’s a flavor enhancer, an ice melter, has been used as a currency, and has shaped civilization. Mark Kurlansky, author of  Salt: A World History, and Dr. Sonia Angell, Director, Cardiovascular Disease Prevention and Control, New York City Health Department, explain what salt is, where it comes from, and discusses its influence on history and on our health.

SAT, PSAT, LSAT, MCAT, GMAT, GRE, NAEP, PISA...when did the nation become obsessed with standardized testing and what do these exams tell us? On this week's Please Explain, testing experts Howard Everson and David Rindskopf explain how these tests are put together and what they are supposed to evaluate. Dr. Everson is co-chair of the Technical Advisory Committee for the National Center for Education and the Economy, as well as the chair of the Technical Advisory Committee for Testing and Assessment for the New York State Education Department. Dr. Rindskopf is Distinguished Professor of Educational Psychology and Psychology at the City University of New York Graduate School.

This cold weather has caused many of us to pull out our wool sweaters for extra warmth, and for this week’s Please Explain we’re talking about wool—and the process of gathering and using wool, from the sheep to the sweater! Clara Parkes, author of The Knitters Book of Wool: The Ultimate Guide to Understanding, Using, and Loving this Most Fabulous Fiber and The Knitter's Book of Yarn: The Ultimate Guide to Choosing, Using, and Enjoying Yarn, and Dr. Christopher Lupton, Professor, The Bill Sims Wool and Mohair Research Laboratory, Texas AgriLife Research and Extension Center, join us to discuss the subject.

Our latest Please Explain is all about seafood—how it’s harvested, what sustainable fishing entails, and how fish gets from the sea to your plate. We're joined by Sheila Bowman,  senior manager of outreach and education, Monterey Bay Aquarium Seafood Watch, and Dr. Gina Solomon, who is both a medical doctor and a senior scientist with Natural Resources Defense Council.

Today's Please Explain looks at spying, the organizations that do it, and how it's carried out and why. We're joined by Thomas S. Blanton, from George Washington University National Security Archives, and Joseph Weisberg, former CIA operative and author of An Ordinary Spy.

President Obama's health care reform has been seen as too much intervention by some and not enough of an overhaul by others, but few people know exactly what the new law includes and how it changes health care and health insurance in this country. On this week's Please Explain, Washington Post correspondent T. R. Reid explains the ins and outs, the costs and the savings, of the 2010 Patient Protection and Affordable Care Act. He's the author of The Healing of America: A Global Quest for Better, Cheaper, and Fairer Health Care.

Harold McGee discusses and debunks myths about food and cooking for today's Please Explain. He’s the author of Keys to Good Cooking: A Guide to Making the Best of Foods and Recipes.

The New York City Marathon is this Sunday, and thousands of runners will be racing through all five boroughs. On today's Please Explain, we'll find out what’s involved with completing the marathon’s 26.2 miles. David Willey, Editor-in-Chief of Runner's World magazine and Charlie Butler, executive editor of Runner's World and co-author of The Long Run: A New York City Firefighter's Triumphant Comeback from Crash Victim to Elite Athlete, join us now to talk about how runners race, train, deal with injuries, and how regular people can start running for exercise.

Putting thing off until the last minute is a compulsion many people share. On this week’s Please Explain, Dr. George Ainslie, Professor of Psychiatry at University of Cape Town, in South Africa, and Dr. Joseph Ferrari, professor of psychology at DePaul University, tell us what causes us to procrastinate, how it affects productivity, and methods for ending procrastination. Dr. Ferrari is the author of Still Procrastinating? The No Regrets Guide to Getting It Done. Dr. Ainslie is the author of Breakdown of Will and Picoeconomics.

If you've ever wondered how long you should wait before asking for a second date, or if it's acceptable to split the check, or whether or not you should declare that you are in a relationship on Facebook, today's Please Explain will provide some answers. Thomas P. Farley and Diane Gottsman discuss the etiquette of dating.

Please Explain takes a look at LSD and psychedelic drugs. Dr. Nicolas Langlitz, assistant professor of Medical Anthropology at the New School, and Dr. Stephen Ross, Assistant Professor at NYU Medical Center, Departments of Psychiatry and In-Patient Service, explain how psychedelic drugs affect the brain, how hallucinogens work, and new research into therapeutic uses for psychedelic drugs.

Doling out 15 percent of the check to the waiter is standard, but how much should you tip cab drivers and hairdressers?  Today’s Please Explain is all about tipping. Milla Bloch and Diane Gottsman explain how much to give, to whom, and where tipping comes from.

Do you have different tipping methods based on service? Do you tip a cab driver the same way you tip a waitress or a hairdresser?

Current and former waiters: do you tip more generously than others?

Rubber is all around us: from sneakers to tires to basketballs. On today’s Please Explain, we'll find out where rubber comes from, how it’s created and used, and how it changed the world. We're joined by John Loadman, analytical chemist and author of  Tears of the Tree: The Story of Rubber--A Modern Marvel, and Joe Jackson, author of The Thief at the End of the World: Rubber, Power, and the Seeds of Empire.

Today’s Please Explain is all about the sport of roller derby, from its earliest roots to its modern day revival. Alex Cohen (aka Axles of Evil) and Jennifer Barbee, the authors of Down and Derby: The Insider's Guide to Roller Derby, stop by our show today. Alex Cohen is a skater and trainer, and also served as the derby consultant/choreographer for Drew Barrymore’s film "Whip It!"

Ever since Joseph Priestly discovered how to "impregnate water with fixed air" in the 18th century, carbonated beverages have been ubiquitous. Sodas have been used to cure diseases, fight alcoholism, and spread American culture around the globe. On this week's Please Explain, we’ll find out what soda is, what’s in it, and when it became so popular. We’re joined by Dr. Kelly Brownell, the co-founder and director of the Yale Rudd Center for Food Policy and Obesity, and Darcy O'Neil, beverage master and author of the book Fix the Pumps, a history of soda from the 18th century to the present.

Today’s Please Explain is all about breakfast cereal. Food historian Andy Smith, the author of Eating History: Thirty Turning Points in the Making of American Cuisine, among other books, joins us along with Edwin Chavey, aka Mr. Breakfast, director of the Mr. Breakfast Website and "The Cereal Project," a database of 1,200 cereals made in the United States, to explain what cereals are made of, how truthful health claims made about some are, and how there got to be so many varieties.