Creepy, crawly, slithery, slippery. Lacking the charm of a cat, the gaiety of a bird, the loyalty of a dog, the grace of a horse. Man's worst friend, you might say. Just plain yuk.

But snakes are more, and less, than that. They have the ability to freak people out, so thoroughly and lastingly that some folks will go to extraordinary lengths to avoid even seeing one.

When their kids begin to head for the reptile house at the zoo, the fraidies will suddenly get headaches and suggest and ice cream.

Before they begin to read a magazine, they will ask their spouses to "scout" the thing to be sure no pictures of snakes are lurking. Before they sit down to catch their favorite TV show, they will call the station and ask if any snakes are about to jump from the tube.

To this kind of hard case, snake phobia has always been something one just had to live with, like air pollution alerts. But an assistant professor of psychology at Catholic University has spent the spring trying to change that. To judge from "graduation ceremonies" last week, he has succeeded beyond everyone's expectations, including his own.

Ronald Shectman is his name, and measuring fear, then "desensitizing" the person who has it, is his game.

Shectman's primary method is "relaxation therapy." He stands before a group of people who are scared stiff of snakes. He gradually talks that their fear is only in their minds.

The payoff is supposed to be that the scaredies will come closer to a snake at the end of the program than they would at the beginning. But Shecthan found that, in many cases, the "students" had come so far that many were willing to touch and hold a snake, despite lifelong reluctance.

Otelia Hebert was typical.

Like all Shectman's subjects, she had heard of the program through a newspaper ad Shectman placed, asking for volunteers. She cam with few expectations and lots of stark terror.

"You have not idea how bad it was," said Hebert, a social workers for the District government who lives in Southeast Washington. "If I came across a picture of a snake in a magazien, I'd start screaming and throw it on the floor. I figured I was so bad, I had nothing to lose."

Now it was a Saturday morning at C.U., and what was this? Was that Otelia Hebert actually holding a 3 1/2-foot-long boa constrictor? You know it.

Granted, it took 10 minutes of "relaxation" and another 20 of deep sighs and false starts before she could approach the snake. But now she was exultant.

Joan Kramer, of Sterling, Va., had been mortally flipped by snakes ever since, as a fifth grader, she watched a boy slip a garter snake down her sister's back.

"I've always wanted to get over it," said Kramer, as she reached gingerly toward the big boa. "Now I want to get over it for my son. I don't want him to be afraid."

Finally, Kramer was able to put one index finger on the snake, who seemed good and bored by it all. Then two fingers. Then a whole hand. Some of her classmates applauded.

Kramer looked more relieved than happy. "I feel a little better," she said, although she looked shaken.

Beside her, Roberta Liebman of Chevy Chase was still mustering her courage. Finally, she flicked out an index finger, not unlike the way a snake flicks his tougue. Sighs, cheers, laughter. "I feel I need to go home and go to bed for a week," said Liebman.

Such a mix of elation and emotional release came as no surprise to Shectman or Tom Colyer, his graduate assistant.

When they applied last fall for a grant from the National Institute of Mental Health to run the experiment, they knew they were dealing with what Shectman called "a very concentrated, specific kind of fear" - one that would defy simple measurement or cure.

Their program had three phases.

In the first, a snake was placed in a cage at the end of a corridor. Participants were asked to come as close to him as they could. Their closet approach point was measured in feet and inches.

Participants would "qualify" if they could not bring themselves to reach inside the snake's cage and pet him with a gloved hand. Fifty-eight Washingtoninas - including a priest, a Capitol Hill bigwig and a 70-year-old woman who had lived on a farm all her life - couldn't handle it.

They underwent six weeks of training and relaxation thereapy. Then came a follow-up, two weeks later, in which the subjects were remeasured - same corridor, same snake.

The final episode was "graduation," a purely voluntary hour not part of the formal program in which subjects could try to touch an honest-to-goodness snake.

Larry and Cheryl Gritton, a young, snake-loving couple from Landover, provided "the boys," as they called them. Each Gritton stood at the front of a classroom as graduation began. Each held a boa. When the "graduates" felt ready, Shectman asked them to begin coming forward toward the snakes, classroom row by classroom row.

As they came, Gritton explained that his two boas were not poisonous, and never had been. "You're lucky to be in this area of the country in that respect," Gritton said. "Only copperheads are poisonous here."

Snakes are "passive, not aggressive," Gritton assured the class. "They're primitive; they're not that inquisitive." As if one cue, each boa lazily began to wrap himself arounda Gritton arm. The class shuddered.

But all were in touching range 20 minutes later. Another 10 minutes, and all had hurdled the barrier that had stood in front of them for so long.

"I did it! Did you see me?

"I expected it to be scalier."

"What's the botom like?"

"I need a shower!"

It's like riding a bike."

And so one.

Ron Shectman knows he has not cooked up some miracle cure. He advised his class to reinforce their achievements by arranging to be around snakes in the near future, at the zoo or in the woods. "It's the best way to be sure it'll 'take,'" he said.

Meanwhile, Shectman plans another snake program this fall. He admits he will be better prepared for it.

It seems that, a few weeks ago, the big boa got loose outside Shectman's office. After much frantic searching, he was found inside an air conditioner. Shectman reached in and yanked him out.

"I probably wouldn't have been able to do it so easily seven weeks ago," Shectman said.