The Transportation Security Administration, starting last December, decided to try out the approach at about a dozen airports, including Logan. At each airport, it used six officers who had once been routine screeners, had received an extra four days of classroom training in observation and questioning techniques, and had three days of field practice.

T.S.A. officers do not have law enforcement powers, so if they observe someone suspicious, they can chat with the person but cannot conduct a more formal interrogation. That leaves them with the option of requiring the passenger to go through a more intense checkpoint search, as they did with the man at Dulles on Wednesday. Or if the suspicion is serious enough, they call the local police assigned to the airport to take over the inquiry.

In nine months — a period in which about seven million people have flown out of Dulles — several hundred people have been referred for intense screening, and about 50 have been turned over to the police for follow-up questioning, said John F. Lenihan, the transportation agency’s security director at Dulles.

Of those, half a dozen have faced charges or other law enforcement follow-up, he said, because the behavior detection officials succeeded in picking out people who had a reason to be nervous, generally because of immigration matters, outstanding warrants or forged documents.

“It is an extra layer of security that is on top of what we have,” Mr. Hawley said of the program.

But Rafi Ron, the former director of security at Ben-Gurion International Airport in Tel Aviv, who was a consultant who helped train the officers at Logan Airport, said that the agency’s system, while a welcome improvement to airport security, was still flawed. Most importantly, he said, too few of the passengers pulled aside were more formally questioned as in the Israeli system, and when questioning was done, it was handled by local police officers who might not have had the necessary behavioral analysis skills.

He cited the case of Richard Reid, known as the shoe bomber, who aroused suspicion when he arrived at Charles de Gaulle International Airport outside Paris, but was ultimately allowed to board after the police had questioned him.

“If you don’t do the interviews properly, you are missing what is probably the most important and powerful part of the procedure,” he said.