Is Pluto a planet? The world's astronomers met in Prague last week to vote on this question, and in a sort of cosmic game of "Survivor," they voted Pluto off the solar system.

For years, economists have taught their students a simple maxim: As employers hunt for workers, they want to get the best talent at the lowest price.

How the disaster starts does not matter: It could be a plane crashing into the World Trade Center, it could be the sea receding rapidly ahead of an advancing tsunami, it could be smoke billowing through a nightclub.

In 1935, researchers from Columbia University fanned out around the city of Allentown, Pa., and handed out leaflets ahead of local and state elections. What residents did not know was that they were part of an experiment in political persuasion -- an experiment whose results came to mind last week...

When freedom fighters in India inspired by Mahatma Gandhi turned violent in a clash with police in 1922, the nonviolent leader took personal responsibility, called off nationwide protests and starved himself for five days in a penitential fast. Gandhi was nearly alone in thinking an apology of such...

Antiwar liberals last week got to savor the four most satisfying words in the English language: "I told you so."

Here's a question with three different answers. The first answer is derived from arithmetic. The second comes from common sense. The third is based on psychology.

When the Rev. Martin Luther King Jr. called on America to open the doors of opportunity to people of color, the civil rights leader was making a moral argument.

When George W. Bush takes the podium tomorrow night to deliver his sixth State of the Union address, what are the chances he will say this? "The war in Iraq has been one gigantic mistake. I am sorry I got us into this mess. I am going to bring the troops home right away."

Whenever the United States goes to war, pro-war and antiwar advocates immediately reach for different history books. Hawks always equate the situation to a Hitler-Chamberlain standoff to show why hesitation can be fatal. Doves invariably pull the Vietnam War off the shelf to argue that plunging...

The 58 fans sitting before the big-screen television were watching the Super Bowl. Psychologist Emily Pronin was watching the fans.

So, Valentine's Day is two days away, but you know he isn't going to bring you any flowers. And instead of a cuddle and a kiss, you know she is going to dig up that old canard about your mother.

The perjury trial of I. Lewis "Scooter" Libby goes to the jury this week. The case speaks to several issues -- how the Bush administration deals with critics of the war in Iraq, and the games that Washington's reporters and politicians play with each other. As far as the jury is concerned, however,...

Let's say someone stuck a microphone in your face and gave you 45 seconds to say something meaningful to a billion people. Let's say, moreover, that this is the only chance you will ever have to directly address the entire world.

Two centuries ago, Napoleon Bonaparte sent his armies into Spain to overthrow a monarch who had once been a French ally. Napoleon, who believed he was touched by the hand of destiny, predicted his troops would be welcomed as liberators by ordinary Spaniards. He was wrong. The resulting Peninsular War from 1808 to 1814 seriously undermined French prestige, handed Napoleon a stinging defeat and produced a raft of unanticipated consequences that included the outbreak of deadly civil wars....

The conviction of I. Lewis "Scooter" Libby last week gave Americans a chance to pick at the scab of what has become a favored obsession -- the debate over the motives of the Bush administration in the run-up to the war in Iraq.

The NCAA men's college basketball championship game was on the line. People in office pools around the country were holding their breath. Louisville was down by four points with a few minutes left on the clock. A UCLA player stole a pass and raced down the court where, after being bumped by a...

If Democrats Hillary Clinton and Barack Obama ever took a break from fundraising to bone up on psychology, they might realize the need to talk up . . . John Edwards.

President Bush said last week that his thinking on the U.S. situation in Iraq was informed by an analogy: the October 2000 bombing of the USS Cole in Yemen. The lack of a sufficient American response to that and other al-Qaeda attacks, Bush said, led to the Sept. 11, 2001, attacks.

Economists have long known there are two reasons that people cheat on their taxes. One is that they are poor and need the extra cash so badly they are willing to risk getting caught. The other is that they are rich and have lots of "non-matchable" income -- mostly investment income not directly...

Like most people in Virginia, Donald Black was horrified by Seung Hui Cho's shooting rampage last week that left 33 people dead, including the shooter.

Four years ago tomorrow, President Bush landed on the USS Abraham Lincoln and dramatically strode onto the deck in a flight suit, a crash helmet tucked under one arm. Even without the giant banner that hung from the ship's tower, the president's message about the progress of the war in Iraq was u...

Here is a measure of the state of the war in Iraq: The number of Iraqis dying each month now rivals the total number of people who died in the Sept. 11, 2001, attacks.

Accountability is in the air in Washington. At one end of Pennsylvania Avenue, Paul Wolfowitz is struggling to save his job as president of the World Bank after getting caught arranging a sweetheart deal for his, well, sweetheart. A few blocks down the road, President Bush faces endless questions...

Like lunar and solar eclipses, there are some Washington phenomena that are so common they ought to have distinct names. Here is one: A public figure comes to be hated by large numbers of people. But the person cannot be prosecuted or punished, perhaps because his behavior did not involve a crime so...

It's almost June, which means we should soon start to hear the peal of wedding bells.

The ambitious immigration overhaul package that Congress is studying has drawn criticism from conservatives who say it offers amnesty to lawbreakers, and from immigration advocates who say it will not do enough to bring millions of people out of the shadows.

In the year 65, the Roman emperor Nero discovered that a group of nobles had hatched a conspiracy to kill him. The tyrant captured the suspects one by one and threatened them with torture; most confessed and implicated others. One of the conspirators, Epicharis, was publicly tortured -- her bones...

This year's National Basketball Association playoffs recently provided not one but two examples of a very interesting facet of human decision making. Even if you are not a sports fan, these moments tell you something about human nature.

A few days ago, Hamas fighters stormed Fatah strongholds in Gaza that were allied with Palestinian Authority President Mahmoud Abbas and effectively took control of one of the two pillars of the evolving Palestinian state. Fatah groups struck back in the West Bank, the other Palestinian pillar, and...

There are two ways to think about the staggering amounts of money given by special interest groups to politicians -- the type of contributions that were detailed for the last quarter in reports filed yesterday by presidential candidates and members of Congress.

Exhibit A: Sometime over the next few days, a San Francisco athlete will break baseball's most treasured record. Despite his achievement of hitting more home runs than anyone else in Major League Baseball, Barry Bonds will be greeted with rage, ridicule and vast amounts of spit -- because many pe...

In the face of mounting public and political opposition to the war in Iraq, recent reports from the White House suggest that President Bush remains serenely confident.

Why would David Vitter, a U.S. senator with four young children, have gotten involved with a seedy escort service? Why would Michael Vick, a gifted NFL quarterback, get mixed up with the sordid world of dog fighting? Why would Bill Clinton, a Rhodes scholar, six-time governor and president of the...

Long before word recently broke that white referees in the National Basketball Association were calling fouls at a higher rate on black athletes than on white athletes, and long before studies found racial disparities in how black and white applicants get called for job interviews, researchers no...

As big Labor Day sales roll around, computer stores will tell you about laptops that now come with biometric fingerprint readers. Car companies will talk about "variable air suspension" features that allow you to change the ride of a car, depending on terrain. And video game manufacturers will ha...

At the core of this fall's debate over Iraq lies one simple question: Can an increased number of U.S. troops subdue the Iraqi insurgency?

John Duffy lost 67 of his colleagues at the firm of Keefe, Bruyette & Woods six years ago during the Sept. 11, 2001, terrorist attacks. Among the dead was Duffy's son Christopher. The investment banking firm, located in the South Tower of the World Trade Center, was among the companies hit hardes...

Four years ago, during a speech in Manila, President Bush drew an analogy between the history of the Philippines and the history he was rewriting in Iraq.

Shortly after the Sept. 11, 2001, attacks, psychologist Jennifer Lerner conducted a national field experiment: She asked a random sampling of Americans how likely it was that they would be the victim of a terrorist attack in the next 12 months.

In the courts and in Congress, Sen. Larry Craig is fighting to withdraw his guilty plea to a misdemeanor charge that may suggest he tried to solicit sex from a man in June at a Minneapolis airport bathroom. Rather than resign yesterday, as the senator had promised and Republicans had hoped, Craig...

If you were Barack Obama, you would be scratching your head, too.

Last week, a gallon of gas at an Exxon station in the tony suburb of Bethesda cost $2.99.

Let's say there are 10 houses on your street and a giant pothole develops right in the middle of the block. Everyone benefits if the pothole gets fixed, but that might require multiple calls to municipal authorities and a lot of hassle. Since every resident benefits even if he or she does nothing...

When Columbia University sociologist Peter Bearman dived into the world of the white-gloved workers who open the front doors of expensive New York apartment buildings, he found that most people who applied for jobs as doormen never got one. Most doormen, however, had not applied for their jobs.

With just over five minutes to play in yesterday's game against the New York Jets, the Washington Redskins found themselves on their own 23-yard line facing a fourth and one. The team, which was ahead by just three points, elected to do what teams normally do in such situations: They played it safe...

If you consult the online encyclopedia Wikipedia, which is democratically created by Internet users, you will see a pattern emerge in the phrases used to describe the first female leaders of many countries.

What do the war in Iraq, your Christmas shopping and this week's Thanksgiving dinner have in common?

In the interest of promoting democracy, Pakistan's president, Gen. Pervez Musharraf, recently announced that he had to lock up most of his country's democracy activists. And because he wanted the Pakistani Supreme Court to independently rule on whether he could continue as president, Musharraf also...

Forget about buying low and selling high. If you are worried about the recent volatility in the stock market, perhaps you should let the weather be your guide.