On typical Sundays, Mr. Littman is accompanied by his friend Sipai Klein, who also gives out hugs. But because of Mother's Day, Mr. Klein could not be there yesterday. Mr. Littman said he was "not in touch" with his own parents, who live in Brooklyn. The subject causes a brief, sad lull before he charges on.

"How about a free hug?" he hollered at a man, woman and small boy dressed all in black. "How about not?" the boy shot back.

"I'm trying to cut down," said a banker from Kenya.

"Nothing's free," said another man, as he brushed past with his golden retriever.

[...]

"What's your name?" Mr. Littman asked.

"Langdon."

"My name's Jayson. Now we're not strangers."

They hugged.

"It felt O.K.," Mr. Bosarge said as he walked off. "It was kind of the half-body-contact hug versus the full frontal."

It was what Mr. Littman has termed the "duck hug," when a person ducks in and out. There is also the "three-tap hug" - a cautious, back-patting type. No matter what comes at him, Mr. Littman always seems to respond with the same calm, noninvasive embrace.